feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/object/src/write/coff/mod.rs

@@ -0,0 +1,10 @@
+//! Support for writing COFF files.
+//!
+//! Provides [`Writer`] for low level writing of COFF files.
+//! This is also used to provide COFF support for [`write::Object`](crate::write::Object).
+
+mod object;
+pub use self::object::*;
+
+mod writer;
+pub use writer::*;

vendor/object/src/write/coff/object.rs

@@ -0,0 +1,684 @@
+use alloc::vec::Vec;
+
+use crate::pe as coff;
+use crate::write::coff::writer;
+use crate::write::util::*;
+use crate::write::*;
+
+#[derive(Default, Clone, Copy)]
+struct SectionOffsets {
+    name: writer::Name,
+    offset: u32,
+    reloc_offset: u32,
+    selection: u8,
+    associative_section: u32,
+}
+
+#[derive(Default, Clone, Copy)]
+struct SymbolOffsets {
+    name: writer::Name,
+    index: u32,
+    aux_count: u8,
+}
+
+/// Internal format to use for the `.drectve` section containing linker
+/// directives for symbol exports.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum CoffExportStyle {
+    /// MSVC format supported by link.exe and LLD.
+    Msvc,
+    /// Gnu format supported by GNU LD and LLD.
+    Gnu,
+}
+
+impl<'a> Object<'a> {
+    pub(crate) fn coff_section_info(
+        &self,
+        section: StandardSection,
+    ) -> (&'static [u8], &'static [u8], SectionKind, SectionFlags) {
+        match section {
+            StandardSection::Text => (&[], &b".text"[..], SectionKind::Text, SectionFlags::None),
+            StandardSection::Data => (&[], &b".data"[..], SectionKind::Data, SectionFlags::None),
+            StandardSection::ReadOnlyData
+            | StandardSection::ReadOnlyDataWithRel
+            | StandardSection::ReadOnlyString => (
+                &[],
+                &b".rdata"[..],
+                SectionKind::ReadOnlyData,
+                SectionFlags::None,
+            ),
+            StandardSection::UninitializedData => (
+                &[],
+                &b".bss"[..],
+                SectionKind::UninitializedData,
+                SectionFlags::None,
+            ),
+            // TLS sections are data sections with a special name.
+            StandardSection::Tls => (&[], &b".tls$"[..], SectionKind::Data, SectionFlags::None),
+            StandardSection::UninitializedTls => {
+                // Unsupported section.
+                (&[], &[], SectionKind::UninitializedTls, SectionFlags::None)
+            }
+            StandardSection::TlsVariables => {
+                // Unsupported section.
+                (&[], &[], SectionKind::TlsVariables, SectionFlags::None)
+            }
+            StandardSection::Common => {
+                // Unsupported section.
+                (&[], &[], SectionKind::Common, SectionFlags::None)
+            }
+            StandardSection::GnuProperty => {
+                // Unsupported section.
+                (&[], &[], SectionKind::Note, SectionFlags::None)
+            }
+        }
+    }
+
+    pub(crate) fn coff_subsection_name(&self, section: &[u8], value: &[u8]) -> Vec<u8> {
+        let mut name = section.to_vec();
+        if !value.is_empty() {
+            name.push(b'$');
+            name.extend_from_slice(value);
+        }
+        name
+    }
+
+    pub(crate) fn coff_translate_relocation(&mut self, reloc: &mut Relocation) -> Result<()> {
+        use RelocationEncoding as E;
+        use RelocationKind as K;
+
+        let (mut kind, encoding, size) = if let RelocationFlags::Generic {
+            kind,
+            encoding,
+            size,
+        } = reloc.flags
+        {
+            (kind, encoding, size)
+        } else {
+            return Ok(());
+        };
+        if kind == K::GotRelative {
+            // Use a stub symbol for the relocation instead.
+            // This isn't really a GOT, but it's a similar purpose.
+            // TODO: need to handle DLL imports differently?
+            kind = K::Relative;
+            reloc.symbol = self.coff_add_stub_symbol(reloc.symbol)?;
+        } else if kind == K::PltRelative {
+            // Windows doesn't need a separate relocation type for
+            // references to functions in import libraries.
+            // For convenience, treat this the same as Relative.
+            kind = K::Relative;
+        }
+
+        let unsupported_reloc = || Err(Error(format!("unimplemented relocation {:?}", reloc)));
+        let typ = match self.architecture {
+            Architecture::I386 => match (kind, size) {
+                (K::Absolute, 16) => coff::IMAGE_REL_I386_DIR16,
+                (K::Relative, 16) => coff::IMAGE_REL_I386_REL16,
+                (K::Absolute, 32) => coff::IMAGE_REL_I386_DIR32,
+                (K::ImageOffset, 32) => coff::IMAGE_REL_I386_DIR32NB,
+                (K::SectionIndex, 16) => coff::IMAGE_REL_I386_SECTION,
+                (K::SectionOffset, 32) => coff::IMAGE_REL_I386_SECREL,
+                (K::SectionOffset, 7) => coff::IMAGE_REL_I386_SECREL7,
+                (K::Relative, 32) => coff::IMAGE_REL_I386_REL32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::X86_64 => match (kind, size) {
+                (K::Absolute, 64) => coff::IMAGE_REL_AMD64_ADDR64,
+                (K::Absolute, 32) => coff::IMAGE_REL_AMD64_ADDR32,
+                (K::ImageOffset, 32) => coff::IMAGE_REL_AMD64_ADDR32NB,
+                (K::Relative, 32) => match reloc.addend {
+                    -5 => coff::IMAGE_REL_AMD64_REL32_1,
+                    -6 => coff::IMAGE_REL_AMD64_REL32_2,
+                    -7 => coff::IMAGE_REL_AMD64_REL32_3,
+                    -8 => coff::IMAGE_REL_AMD64_REL32_4,
+                    -9 => coff::IMAGE_REL_AMD64_REL32_5,
+                    _ => coff::IMAGE_REL_AMD64_REL32,
+                },
+                (K::SectionIndex, 16) => coff::IMAGE_REL_AMD64_SECTION,
+                (K::SectionOffset, 32) => coff::IMAGE_REL_AMD64_SECREL,
+                (K::SectionOffset, 7) => coff::IMAGE_REL_AMD64_SECREL7,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Arm => match (kind, size) {
+                (K::Absolute, 32) => coff::IMAGE_REL_ARM_ADDR32,
+                (K::ImageOffset, 32) => coff::IMAGE_REL_ARM_ADDR32NB,
+                (K::Relative, 32) => coff::IMAGE_REL_ARM_REL32,
+                (K::SectionIndex, 16) => coff::IMAGE_REL_ARM_SECTION,
+                (K::SectionOffset, 32) => coff::IMAGE_REL_ARM_SECREL,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Aarch64 => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => coff::IMAGE_REL_ARM64_ADDR32,
+                (K::ImageOffset, _, 32) => coff::IMAGE_REL_ARM64_ADDR32NB,
+                (K::SectionIndex, _, 16) => coff::IMAGE_REL_ARM64_SECTION,
+                (K::SectionOffset, _, 32) => coff::IMAGE_REL_ARM64_SECREL,
+                (K::Absolute, _, 64) => coff::IMAGE_REL_ARM64_ADDR64,
+                (K::Relative, _, 32) => coff::IMAGE_REL_ARM64_REL32,
+                (K::Relative, E::AArch64Call, 26) => coff::IMAGE_REL_ARM64_BRANCH26,
+                _ => return unsupported_reloc(),
+            },
+            _ => {
+                return Err(Error(format!(
+                    "unimplemented architecture {:?}",
+                    self.architecture
+                )));
+            }
+        };
+        reloc.flags = RelocationFlags::Coff { typ };
+        Ok(())
+    }
+
+    pub(crate) fn coff_adjust_addend(&self, relocation: &mut Relocation) -> Result<bool> {
+        let typ = if let RelocationFlags::Coff { typ } = relocation.flags {
+            typ
+        } else {
+            return Err(Error(format!("invalid relocation flags {:?}", relocation)));
+        };
+        let offset = match self.architecture {
+            Architecture::Arm => {
+                if typ == coff::IMAGE_REL_ARM_REL32 {
+                    4
+                } else {
+                    0
+                }
+            }
+            Architecture::Aarch64 => {
+                if typ == coff::IMAGE_REL_ARM64_REL32 {
+                    4
+                } else {
+                    0
+                }
+            }
+            Architecture::I386 => {
+                if typ == coff::IMAGE_REL_I386_REL32 {
+                    4
+                } else {
+                    0
+                }
+            }
+            Architecture::X86_64 => match typ {
+                coff::IMAGE_REL_AMD64_REL32 => 4,
+                coff::IMAGE_REL_AMD64_REL32_1 => 5,
+                coff::IMAGE_REL_AMD64_REL32_2 => 6,
+                coff::IMAGE_REL_AMD64_REL32_3 => 7,
+                coff::IMAGE_REL_AMD64_REL32_4 => 8,
+                coff::IMAGE_REL_AMD64_REL32_5 => 9,
+                _ => 0,
+            },
+            _ => return Err(Error(format!("unimplemented relocation {:?}", relocation))),
+        };
+        relocation.addend += offset;
+        Ok(true)
+    }
+
+    pub(crate) fn coff_relocation_size(&self, reloc: &Relocation) -> Result<u8> {
+        let typ = if let RelocationFlags::Coff { typ } = reloc.flags {
+            typ
+        } else {
+            return Err(Error(format!("unexpected relocation for size {:?}", reloc)));
+        };
+        let size = match self.architecture {
+            Architecture::I386 => match typ {
+                coff::IMAGE_REL_I386_DIR16
+                | coff::IMAGE_REL_I386_REL16
+                | coff::IMAGE_REL_I386_SECTION => Some(16),
+                coff::IMAGE_REL_I386_DIR32
+                | coff::IMAGE_REL_I386_DIR32NB
+                | coff::IMAGE_REL_I386_SECREL
+                | coff::IMAGE_REL_I386_TOKEN
+                | coff::IMAGE_REL_I386_REL32 => Some(32),
+                _ => None,
+            },
+            Architecture::X86_64 => match typ {
+                coff::IMAGE_REL_AMD64_SECTION => Some(16),
+                coff::IMAGE_REL_AMD64_ADDR32
+                | coff::IMAGE_REL_AMD64_ADDR32NB
+                | coff::IMAGE_REL_AMD64_REL32
+                | coff::IMAGE_REL_AMD64_REL32_1
+                | coff::IMAGE_REL_AMD64_REL32_2
+                | coff::IMAGE_REL_AMD64_REL32_3
+                | coff::IMAGE_REL_AMD64_REL32_4
+                | coff::IMAGE_REL_AMD64_REL32_5
+                | coff::IMAGE_REL_AMD64_SECREL
+                | coff::IMAGE_REL_AMD64_TOKEN => Some(32),
+                coff::IMAGE_REL_AMD64_ADDR64 => Some(64),
+                _ => None,
+            },
+            Architecture::Arm => match typ {
+                coff::IMAGE_REL_ARM_SECTION => Some(16),
+                coff::IMAGE_REL_ARM_ADDR32
+                | coff::IMAGE_REL_ARM_ADDR32NB
+                | coff::IMAGE_REL_ARM_TOKEN
+                | coff::IMAGE_REL_ARM_REL32
+                | coff::IMAGE_REL_ARM_SECREL => Some(32),
+                _ => None,
+            },
+            Architecture::Aarch64 => match typ {
+                coff::IMAGE_REL_ARM64_SECTION => Some(16),
+                coff::IMAGE_REL_ARM64_ADDR32
+                | coff::IMAGE_REL_ARM64_ADDR32NB
+                | coff::IMAGE_REL_ARM64_SECREL
+                | coff::IMAGE_REL_ARM64_TOKEN
+                | coff::IMAGE_REL_ARM64_REL32 => Some(32),
+                coff::IMAGE_REL_ARM64_ADDR64 => Some(64),
+                _ => None,
+            },
+            _ => None,
+        };
+        size.ok_or_else(|| Error(format!("unsupported relocation for size {:?}", reloc)))
+    }
+
+    fn coff_add_stub_symbol(&mut self, symbol_id: SymbolId) -> Result<SymbolId> {
+        if let Some(stub_id) = self.stub_symbols.get(&symbol_id) {
+            return Ok(*stub_id);
+        }
+        let stub_size = self.architecture.address_size().unwrap().bytes();
+
+        let name = b".rdata$.refptr".to_vec();
+        let section_id = self.add_section(Vec::new(), name, SectionKind::ReadOnlyData);
+        let section = self.section_mut(section_id);
+        section.set_data(vec![0; stub_size as usize], u64::from(stub_size));
+        self.add_relocation(
+            section_id,
+            Relocation {
+                offset: 0,
+                symbol: symbol_id,
+                addend: 0,
+                flags: RelocationFlags::Generic {
+                    kind: RelocationKind::Absolute,
+                    encoding: RelocationEncoding::Generic,
+                    size: stub_size * 8,
+                },
+            },
+        )?;
+
+        let mut name = b".refptr.".to_vec();
+        name.extend_from_slice(&self.symbol(symbol_id).name);
+        let stub_id = self.add_raw_symbol(Symbol {
+            name,
+            value: 0,
+            size: u64::from(stub_size),
+            kind: SymbolKind::Data,
+            scope: SymbolScope::Compilation,
+            weak: false,
+            section: SymbolSection::Section(section_id),
+            flags: SymbolFlags::None,
+        });
+        self.stub_symbols.insert(symbol_id, stub_id);
+
+        Ok(stub_id)
+    }
+
+    /// Appends linker directives to the `.drectve` section to tell the linker
+    /// to export all symbols with `SymbolScope::Dynamic`.
+    ///
+    /// This must be called after all symbols have been defined.
+    pub fn add_coff_exports(&mut self, style: CoffExportStyle) {
+        assert_eq!(self.format, BinaryFormat::Coff);
+
+        let mut directives = vec![];
+        for symbol in &self.symbols {
+            if symbol.scope == SymbolScope::Dynamic {
+                match style {
+                    CoffExportStyle::Msvc => directives.extend(b" /EXPORT:\""),
+                    CoffExportStyle::Gnu => directives.extend(b" -export:\""),
+                }
+                directives.extend(&symbol.name);
+                directives.extend(b"\"");
+                if symbol.kind != SymbolKind::Text {
+                    match style {
+                        CoffExportStyle::Msvc => directives.extend(b",DATA"),
+                        CoffExportStyle::Gnu => directives.extend(b",data"),
+                    }
+                }
+            }
+        }
+        let drectve = self.add_section(vec![], b".drectve".to_vec(), SectionKind::Linker);
+        self.append_section_data(drectve, &directives, 1);
+    }
+
+    pub(crate) fn coff_write(&self, buffer: &mut dyn WritableBuffer) -> Result<()> {
+        let mut writer = writer::Writer::new(buffer);
+
+        // Add section strings to strtab.
+        let mut section_offsets = vec![SectionOffsets::default(); self.sections.len()];
+        for (index, section) in self.sections.iter().enumerate() {
+            section_offsets[index].name = writer.add_name(&section.name);
+        }
+
+        // Set COMDAT flags.
+        for comdat in &self.comdats {
+            let symbol = &self.symbols[comdat.symbol.0];
+            let comdat_section = match symbol.section {
+                SymbolSection::Section(id) => id.0,
+                _ => {
+                    return Err(Error(format!(
+                        "unsupported COMDAT symbol `{}` section {:?}",
+                        symbol.name().unwrap_or(""),
+                        symbol.section
+                    )));
+                }
+            };
+            section_offsets[comdat_section].selection = match comdat.kind {
+                ComdatKind::NoDuplicates => coff::IMAGE_COMDAT_SELECT_NODUPLICATES,
+                ComdatKind::Any => coff::IMAGE_COMDAT_SELECT_ANY,
+                ComdatKind::SameSize => coff::IMAGE_COMDAT_SELECT_SAME_SIZE,
+                ComdatKind::ExactMatch => coff::IMAGE_COMDAT_SELECT_EXACT_MATCH,
+                ComdatKind::Largest => coff::IMAGE_COMDAT_SELECT_LARGEST,
+                ComdatKind::Newest => coff::IMAGE_COMDAT_SELECT_NEWEST,
+                ComdatKind::Unknown => {
+                    return Err(Error(format!(
+                        "unsupported COMDAT symbol `{}` kind {:?}",
+                        symbol.name().unwrap_or(""),
+                        comdat.kind
+                    )));
+                }
+            };
+            for id in &comdat.sections {
+                let section = &self.sections[id.0];
+                if section.symbol.is_none() {
+                    return Err(Error(format!(
+                        "missing symbol for COMDAT section `{}`",
+                        section.name().unwrap_or(""),
+                    )));
+                }
+                if id.0 != comdat_section {
+                    section_offsets[id.0].selection = coff::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
+                    section_offsets[id.0].associative_section = comdat_section as u32 + 1;
+                }
+            }
+        }
+
+        // Reserve symbol indices and add symbol strings to strtab.
+        let mut symbol_offsets = vec![SymbolOffsets::default(); self.symbols.len()];
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            symbol_offsets[index].index = writer.reserve_symbol_index();
+            let mut name = &*symbol.name;
+            match symbol.kind {
+                SymbolKind::File => {
+                    // Name goes in auxiliary symbol records.
+                    symbol_offsets[index].aux_count = writer.reserve_aux_file_name(&symbol.name);
+                    name = b".file";
+                }
+                SymbolKind::Section if symbol.section.id().is_some() => {
+                    symbol_offsets[index].aux_count = writer.reserve_aux_section();
+                }
+                _ => {}
+            };
+            symbol_offsets[index].name = writer.add_name(name);
+        }
+
+        // Reserve file ranges.
+        writer.reserve_file_header();
+        writer.reserve_section_headers(self.sections.len() as u16);
+        for (index, section) in self.sections.iter().enumerate() {
+            section_offsets[index].offset = writer.reserve_section(section.data.len());
+            section_offsets[index].reloc_offset =
+                writer.reserve_relocations(section.relocations.len());
+        }
+        writer.reserve_symtab_strtab();
+
+        // Start writing.
+        writer.write_file_header(writer::FileHeader {
+            machine: match (self.architecture, self.sub_architecture) {
+                (Architecture::Arm, None) => coff::IMAGE_FILE_MACHINE_ARMNT,
+                (Architecture::Aarch64, None) => coff::IMAGE_FILE_MACHINE_ARM64,
+                (Architecture::Aarch64, Some(SubArchitecture::Arm64EC)) => {
+                    coff::IMAGE_FILE_MACHINE_ARM64EC
+                }
+                (Architecture::I386, None) => coff::IMAGE_FILE_MACHINE_I386,
+                (Architecture::X86_64, None) => coff::IMAGE_FILE_MACHINE_AMD64,
+                _ => {
+                    return Err(Error(format!(
+                        "unimplemented architecture {:?} with sub-architecture {:?}",
+                        self.architecture, self.sub_architecture
+                    )));
+                }
+            },
+            time_date_stamp: 0,
+            characteristics: match self.flags {
+                FileFlags::Coff { characteristics } => characteristics,
+                _ => 0,
+            },
+        })?;
+
+        // Write section headers.
+        for (index, section) in self.sections.iter().enumerate() {
+            let mut characteristics = if let SectionFlags::Coff {
+                characteristics, ..
+            } = section.flags
+            {
+                characteristics
+            } else {
+                match section.kind {
+                    SectionKind::Text => {
+                        coff::IMAGE_SCN_CNT_CODE
+                            | coff::IMAGE_SCN_MEM_EXECUTE
+                            | coff::IMAGE_SCN_MEM_READ
+                    }
+                    SectionKind::Data => {
+                        coff::IMAGE_SCN_CNT_INITIALIZED_DATA
+                            | coff::IMAGE_SCN_MEM_READ
+                            | coff::IMAGE_SCN_MEM_WRITE
+                    }
+                    SectionKind::UninitializedData => {
+                        coff::IMAGE_SCN_CNT_UNINITIALIZED_DATA
+                            | coff::IMAGE_SCN_MEM_READ
+                            | coff::IMAGE_SCN_MEM_WRITE
+                    }
+                    SectionKind::ReadOnlyData
+                    | SectionKind::ReadOnlyDataWithRel
+                    | SectionKind::ReadOnlyString => {
+                        coff::IMAGE_SCN_CNT_INITIALIZED_DATA | coff::IMAGE_SCN_MEM_READ
+                    }
+                    SectionKind::Debug
+                    | SectionKind::DebugString
+                    | SectionKind::Other
+                    | SectionKind::OtherString => {
+                        coff::IMAGE_SCN_CNT_INITIALIZED_DATA
+                            | coff::IMAGE_SCN_MEM_READ
+                            | coff::IMAGE_SCN_MEM_DISCARDABLE
+                    }
+                    SectionKind::Linker => coff::IMAGE_SCN_LNK_INFO | coff::IMAGE_SCN_LNK_REMOVE,
+                    SectionKind::Common
+                    | SectionKind::Tls
+                    | SectionKind::UninitializedTls
+                    | SectionKind::TlsVariables
+                    | SectionKind::Note
+                    | SectionKind::Unknown
+                    | SectionKind::Metadata
+                    | SectionKind::Elf(_) => {
+                        return Err(Error(format!(
+                            "unimplemented section `{}` kind {:?}",
+                            section.name().unwrap_or(""),
+                            section.kind
+                        )));
+                    }
+                }
+            };
+            if section_offsets[index].selection != 0 {
+                characteristics |= coff::IMAGE_SCN_LNK_COMDAT;
+            };
+            if section.relocations.len() > 0xffff {
+                characteristics |= coff::IMAGE_SCN_LNK_NRELOC_OVFL;
+            }
+            characteristics |= match section.align {
+                1 => coff::IMAGE_SCN_ALIGN_1BYTES,
+                2 => coff::IMAGE_SCN_ALIGN_2BYTES,
+                4 => coff::IMAGE_SCN_ALIGN_4BYTES,
+                8 => coff::IMAGE_SCN_ALIGN_8BYTES,
+                16 => coff::IMAGE_SCN_ALIGN_16BYTES,
+                32 => coff::IMAGE_SCN_ALIGN_32BYTES,
+                64 => coff::IMAGE_SCN_ALIGN_64BYTES,
+                128 => coff::IMAGE_SCN_ALIGN_128BYTES,
+                256 => coff::IMAGE_SCN_ALIGN_256BYTES,
+                512 => coff::IMAGE_SCN_ALIGN_512BYTES,
+                1024 => coff::IMAGE_SCN_ALIGN_1024BYTES,
+                2048 => coff::IMAGE_SCN_ALIGN_2048BYTES,
+                4096 => coff::IMAGE_SCN_ALIGN_4096BYTES,
+                8192 => coff::IMAGE_SCN_ALIGN_8192BYTES,
+                _ => {
+                    return Err(Error(format!(
+                        "unimplemented section `{}` align {}",
+                        section.name().unwrap_or(""),
+                        section.align
+                    )));
+                }
+            };
+            writer.write_section_header(writer::SectionHeader {
+                name: section_offsets[index].name,
+                size_of_raw_data: section.size as u32,
+                pointer_to_raw_data: section_offsets[index].offset,
+                pointer_to_relocations: section_offsets[index].reloc_offset,
+                pointer_to_linenumbers: 0,
+                number_of_relocations: section.relocations.len() as u32,
+                number_of_linenumbers: 0,
+                characteristics,
+            });
+        }
+
+        // Write section data and relocations.
+        for section in &self.sections {
+            writer.write_section(&section.data);
+
+            if !section.relocations.is_empty() {
+                //debug_assert_eq!(section_offsets[index].reloc_offset, buffer.len());
+                writer.write_relocations_count(section.relocations.len());
+                for reloc in &section.relocations {
+                    let typ = if let RelocationFlags::Coff { typ } = reloc.flags {
+                        typ
+                    } else {
+                        return Err(Error("invalid relocation flags".into()));
+                    };
+                    writer.write_relocation(writer::Relocation {
+                        virtual_address: reloc.offset as u32,
+                        symbol: symbol_offsets[reloc.symbol.0].index,
+                        typ,
+                    });
+                }
+            }
+        }
+
+        // Write symbols.
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            let section_number = match symbol.section {
+                SymbolSection::None => {
+                    debug_assert_eq!(symbol.kind, SymbolKind::File);
+                    coff::IMAGE_SYM_DEBUG as u16
+                }
+                SymbolSection::Undefined => coff::IMAGE_SYM_UNDEFINED as u16,
+                SymbolSection::Absolute => coff::IMAGE_SYM_ABSOLUTE as u16,
+                SymbolSection::Common => coff::IMAGE_SYM_UNDEFINED as u16,
+                SymbolSection::Section(id) => id.0 as u16 + 1,
+            };
+            let typ = if symbol.kind == SymbolKind::Text {
+                coff::IMAGE_SYM_DTYPE_FUNCTION << coff::IMAGE_SYM_DTYPE_SHIFT
+            } else {
+                coff::IMAGE_SYM_TYPE_NULL
+            };
+            let storage_class = match symbol.kind {
+                SymbolKind::File => coff::IMAGE_SYM_CLASS_FILE,
+                SymbolKind::Section => {
+                    if symbol.section.id().is_some() {
+                        coff::IMAGE_SYM_CLASS_STATIC
+                    } else {
+                        coff::IMAGE_SYM_CLASS_SECTION
+                    }
+                }
+                SymbolKind::Label => coff::IMAGE_SYM_CLASS_LABEL,
+                SymbolKind::Text | SymbolKind::Data | SymbolKind::Tls => {
+                    match symbol.section {
+                        SymbolSection::None => {
+                            return Err(Error(format!(
+                                "missing section for symbol `{}`",
+                                symbol.name().unwrap_or("")
+                            )));
+                        }
+                        SymbolSection::Undefined | SymbolSection::Common => {
+                            coff::IMAGE_SYM_CLASS_EXTERNAL
+                        }
+                        SymbolSection::Absolute | SymbolSection::Section(_) => {
+                            match symbol.scope {
+                                // TODO: does this need aux symbol records too?
+                                _ if symbol.weak => coff::IMAGE_SYM_CLASS_WEAK_EXTERNAL,
+                                SymbolScope::Unknown => {
+                                    return Err(Error(format!(
+                                        "unimplemented symbol `{}` scope {:?}",
+                                        symbol.name().unwrap_or(""),
+                                        symbol.scope
+                                    )));
+                                }
+                                SymbolScope::Compilation => coff::IMAGE_SYM_CLASS_STATIC,
+                                SymbolScope::Linkage | SymbolScope::Dynamic => {
+                                    coff::IMAGE_SYM_CLASS_EXTERNAL
+                                }
+                            }
+                        }
+                    }
+                }
+                SymbolKind::Unknown => {
+                    return Err(Error(format!(
+                        "unimplemented symbol `{}` kind {:?}",
+                        symbol.name().unwrap_or(""),
+                        symbol.kind
+                    )));
+                }
+            };
+            let number_of_aux_symbols = symbol_offsets[index].aux_count;
+            let value = if symbol.section == SymbolSection::Common {
+                symbol.size as u32
+            } else {
+                symbol.value as u32
+            };
+            writer.write_symbol(writer::Symbol {
+                name: symbol_offsets[index].name,
+                value,
+                section_number,
+                typ,
+                storage_class,
+                number_of_aux_symbols,
+            });
+
+            // Write auxiliary symbols.
+            match symbol.kind {
+                SymbolKind::File => {
+                    writer.write_aux_file_name(&symbol.name, number_of_aux_symbols);
+                }
+                SymbolKind::Section if symbol.section.id().is_some() => {
+                    debug_assert_eq!(number_of_aux_symbols, 1);
+                    let section_index = symbol.section.id().unwrap().0;
+                    let section = &self.sections[section_index];
+                    writer.write_aux_section(writer::AuxSymbolSection {
+                        length: section.size as u32,
+                        number_of_relocations: section.relocations.len() as u32,
+                        number_of_linenumbers: 0,
+                        check_sum: if section.is_bss() {
+                            0
+                        } else {
+                            checksum(section.data())
+                        },
+                        number: section_offsets[section_index].associative_section,
+                        selection: section_offsets[section_index].selection,
+                    });
+                }
+                _ => {
+                    debug_assert_eq!(number_of_aux_symbols, 0);
+                }
+            }
+        }
+
+        writer.write_strtab();
+
+        debug_assert_eq!(writer.reserved_len(), writer.len());
+
+        Ok(())
+    }
+}
+
+// JamCRC
+fn checksum(data: &[u8]) -> u32 {
+    let mut hasher = crc32fast::Hasher::new_with_initial(0xffff_ffff);
+    hasher.update(data);
+    !hasher.finalize()
+}

vendor/object/src/write/coff/writer.rs

@@ -0,0 +1,520 @@
+//! Helper for writing COFF files.
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::mem;
+
+use crate::endian::{LittleEndian as LE, U16Bytes, U32Bytes, U16, U32};
+use crate::pe;
+use crate::write::string::{StringId, StringTable};
+use crate::write::util;
+use crate::write::{Error, Result, WritableBuffer};
+
+/// A helper for writing COFF files.
+///
+/// Writing uses a two phase approach. The first phase builds up all of the information
+/// that may need to be known ahead of time:
+/// - build string table
+/// - reserve section indices
+/// - reserve symbol indices
+/// - reserve file ranges for headers and sections
+///
+/// Some of the information has ordering requirements. For example, strings must be added
+/// to the string table before reserving the file range for the string table. There are debug
+/// asserts to check some of these requirements.
+///
+/// The second phase writes everything out in order. Thus the caller must ensure writing
+/// is in the same order that file ranges were reserved. There are debug asserts to assist
+/// with checking this.
+#[allow(missing_debug_implementations)]
+pub struct Writer<'a> {
+    buffer: &'a mut dyn WritableBuffer,
+    len: usize,
+
+    section_num: u16,
+
+    symtab_offset: u32,
+    symtab_num: u32,
+
+    strtab: StringTable<'a>,
+    strtab_len: usize,
+    strtab_offset: u32,
+    strtab_data: Vec<u8>,
+}
+
+impl<'a> Writer<'a> {
+    /// Create a new `Writer`.
+    pub fn new(buffer: &'a mut dyn WritableBuffer) -> Self {
+        Writer {
+            buffer,
+            len: 0,
+
+            section_num: 0,
+
+            symtab_offset: 0,
+            symtab_num: 0,
+
+            strtab: StringTable::default(),
+            strtab_len: 0,
+            strtab_offset: 0,
+            strtab_data: Vec::new(),
+        }
+    }
+
+    /// Return the current file length that has been reserved.
+    pub fn reserved_len(&self) -> usize {
+        self.len
+    }
+
+    /// Return the current file length that has been written.
+    #[allow(clippy::len_without_is_empty)]
+    pub fn len(&self) -> usize {
+        self.buffer.len()
+    }
+
+    /// Reserve a file range with the given size and starting alignment.
+    ///
+    /// Returns the aligned offset of the start of the range.
+    ///
+    /// `align_start` must be a power of two.
+    pub fn reserve(&mut self, len: usize, align_start: usize) -> u32 {
+        if align_start > 1 {
+            self.len = util::align(self.len, align_start);
+        }
+        let offset = self.len;
+        self.len += len;
+        offset as u32
+    }
+
+    /// Write alignment padding bytes.
+    pub fn write_align(&mut self, align_start: usize) {
+        if align_start > 1 {
+            util::write_align(self.buffer, align_start);
+        }
+    }
+
+    /// Write data.
+    pub fn write(&mut self, data: &[u8]) {
+        self.buffer.write_bytes(data);
+    }
+
+    /// Reserve the file range up to the given file offset.
+    pub fn reserve_until(&mut self, offset: usize) {
+        debug_assert!(self.len <= offset);
+        self.len = offset;
+    }
+
+    /// Write padding up to the given file offset.
+    pub fn pad_until(&mut self, offset: usize) {
+        debug_assert!(self.buffer.len() <= offset);
+        self.buffer.resize(offset);
+    }
+
+    /// Reserve the range for the file header.
+    ///
+    /// This must be at the start of the file.
+    pub fn reserve_file_header(&mut self) {
+        debug_assert_eq!(self.len, 0);
+        self.reserve(mem::size_of::<pe::ImageFileHeader>(), 1);
+    }
+
+    /// Write the file header.
+    ///
+    /// This must be at the start of the file.
+    ///
+    /// Fields that can be derived from known information are automatically set by this function.
+    pub fn write_file_header(&mut self, header: FileHeader) -> Result<()> {
+        debug_assert_eq!(self.buffer.len(), 0);
+
+        // Start writing.
+        self.buffer
+            .reserve(self.len)
+            .map_err(|_| Error(String::from("Cannot allocate buffer")))?;
+
+        // Write file header.
+        let header = pe::ImageFileHeader {
+            machine: U16::new(LE, header.machine),
+            number_of_sections: U16::new(LE, self.section_num),
+            time_date_stamp: U32::new(LE, header.time_date_stamp),
+            pointer_to_symbol_table: U32::new(LE, self.symtab_offset),
+            number_of_symbols: U32::new(LE, self.symtab_num),
+            size_of_optional_header: U16::default(),
+            characteristics: U16::new(LE, header.characteristics),
+        };
+        self.buffer.write(&header);
+
+        Ok(())
+    }
+
+    /// Reserve the range for the section headers.
+    pub fn reserve_section_headers(&mut self, section_num: u16) {
+        debug_assert_eq!(self.section_num, 0);
+        self.section_num = section_num;
+        self.reserve(
+            section_num as usize * mem::size_of::<pe::ImageSectionHeader>(),
+            1,
+        );
+    }
+
+    /// Write a section header.
+    pub fn write_section_header(&mut self, section: SectionHeader) {
+        let mut coff_section = pe::ImageSectionHeader {
+            name: [0; 8],
+            virtual_size: U32::default(),
+            virtual_address: U32::default(),
+            size_of_raw_data: U32::new(LE, section.size_of_raw_data),
+            pointer_to_raw_data: U32::new(LE, section.pointer_to_raw_data),
+            pointer_to_relocations: U32::new(LE, section.pointer_to_relocations),
+            pointer_to_linenumbers: U32::new(LE, section.pointer_to_linenumbers),
+            number_of_relocations: if section.number_of_relocations > 0xffff {
+                U16::new(LE, 0xffff)
+            } else {
+                U16::new(LE, section.number_of_relocations as u16)
+            },
+            number_of_linenumbers: U16::default(),
+            characteristics: U32::new(LE, section.characteristics),
+        };
+        match section.name {
+            Name::Short(name) => coff_section.name = name,
+            Name::Long(str_id) => {
+                let mut str_offset = self.strtab.get_offset(str_id);
+                if str_offset <= 9_999_999 {
+                    let mut name = [0; 7];
+                    let mut len = 0;
+                    if str_offset == 0 {
+                        name[6] = b'0';
+                        len = 1;
+                    } else {
+                        while str_offset != 0 {
+                            let rem = (str_offset % 10) as u8;
+                            str_offset /= 10;
+                            name[6 - len] = b'0' + rem;
+                            len += 1;
+                        }
+                    }
+                    coff_section.name = [0; 8];
+                    coff_section.name[0] = b'/';
+                    coff_section.name[1..][..len].copy_from_slice(&name[7 - len..]);
+                } else {
+                    debug_assert!(str_offset as u64 <= 0xf_ffff_ffff);
+                    coff_section.name[0] = b'/';
+                    coff_section.name[1] = b'/';
+                    for i in 0..6 {
+                        let rem = (str_offset % 64) as u8;
+                        str_offset /= 64;
+                        let c = match rem {
+                            0..=25 => b'A' + rem,
+                            26..=51 => b'a' + rem - 26,
+                            52..=61 => b'0' + rem - 52,
+                            62 => b'+',
+                            63 => b'/',
+                            _ => unreachable!(),
+                        };
+                        coff_section.name[7 - i] = c;
+                    }
+                }
+            }
+        }
+        self.buffer.write(&coff_section);
+    }
+
+    /// Reserve the range for the section data.
+    ///
+    /// Returns the aligned offset of the start of the range.
+    /// Does nothing and returns 0 if the length is zero.
+    pub fn reserve_section(&mut self, len: usize) -> u32 {
+        if len == 0 {
+            return 0;
+        }
+        // TODO: not sure what alignment is required here, but this seems to match LLVM
+        self.reserve(len, 4)
+    }
+
+    /// Write the alignment bytes prior to section data.
+    ///
+    /// This is unneeded if you are using `write_section` or `write_section_zeroes`
+    /// for the data.
+    pub fn write_section_align(&mut self) {
+        util::write_align(self.buffer, 4);
+    }
+
+    /// Write the section data.
+    ///
+    /// Writes alignment bytes prior to the data.
+    /// Does nothing if the data is empty.
+    pub fn write_section(&mut self, data: &[u8]) {
+        if data.is_empty() {
+            return;
+        }
+        self.write_section_align();
+        self.buffer.write_bytes(data);
+    }
+
+    /// Write the section data using zero bytes.
+    ///
+    /// Writes alignment bytes prior to the data.
+    /// Does nothing if the length is zero.
+    pub fn write_section_zeroes(&mut self, len: usize) {
+        if len == 0 {
+            return;
+        }
+        self.write_section_align();
+        self.buffer.resize(self.buffer.len() + len);
+    }
+
+    /// Reserve a file range for the given number of relocations.
+    ///
+    /// This will automatically reserve an extra relocation if there are more than 0xffff.
+    ///
+    /// Returns the offset of the range.
+    /// Does nothing and returns 0 if the count is zero.
+    pub fn reserve_relocations(&mut self, mut count: usize) -> u32 {
+        if count == 0 {
+            return 0;
+        }
+        if count > 0xffff {
+            count += 1;
+        }
+        self.reserve(count * mem::size_of::<pe::ImageRelocation>(), 1)
+    }
+
+    /// Write a relocation containing the count if required.
+    ///
+    /// This should be called before writing the first relocation for a section.
+    pub fn write_relocations_count(&mut self, count: usize) {
+        if count > 0xffff {
+            let coff_relocation = pe::ImageRelocation {
+                virtual_address: U32Bytes::new(LE, count as u32 + 1),
+                symbol_table_index: U32Bytes::new(LE, 0),
+                typ: U16Bytes::new(LE, 0),
+            };
+            self.buffer.write(&coff_relocation);
+        }
+    }
+
+    /// Write a relocation.
+    pub fn write_relocation(&mut self, reloc: Relocation) {
+        let coff_relocation = pe::ImageRelocation {
+            virtual_address: U32Bytes::new(LE, reloc.virtual_address),
+            symbol_table_index: U32Bytes::new(LE, reloc.symbol),
+            typ: U16Bytes::new(LE, reloc.typ),
+        };
+        self.buffer.write(&coff_relocation);
+    }
+
+    /// Reserve a symbol table entry.
+    ///
+    /// This must be called before [`Self::reserve_symtab_strtab`].
+    pub fn reserve_symbol_index(&mut self) -> u32 {
+        debug_assert_eq!(self.symtab_offset, 0);
+        let index = self.symtab_num;
+        self.symtab_num += 1;
+        index
+    }
+
+    /// Reserve a number of symbol table entries.
+    pub fn reserve_symbol_indices(&mut self, count: u32) {
+        debug_assert_eq!(self.symtab_offset, 0);
+        self.symtab_num += count;
+    }
+
+    /// Write a symbol table entry.
+    pub fn write_symbol(&mut self, symbol: Symbol) {
+        let mut coff_symbol = pe::ImageSymbol {
+            name: [0; 8],
+            value: U32Bytes::new(LE, symbol.value),
+            section_number: U16Bytes::new(LE, symbol.section_number),
+            typ: U16Bytes::new(LE, symbol.typ),
+            storage_class: symbol.storage_class,
+            number_of_aux_symbols: symbol.number_of_aux_symbols,
+        };
+        match symbol.name {
+            Name::Short(name) => coff_symbol.name = name,
+            Name::Long(str_id) => {
+                let str_offset = self.strtab.get_offset(str_id);
+                coff_symbol.name[4..8].copy_from_slice(&u32::to_le_bytes(str_offset as u32));
+            }
+        }
+        self.buffer.write(&coff_symbol);
+    }
+
+    /// Reserve auxiliary symbols for a file name.
+    ///
+    /// Returns the number of auxiliary symbols required.
+    ///
+    /// This must be called before [`Self::reserve_symtab_strtab`].
+    pub fn reserve_aux_file_name(&mut self, name: &[u8]) -> u8 {
+        debug_assert_eq!(self.symtab_offset, 0);
+        let aux_count = (name.len() + pe::IMAGE_SIZEOF_SYMBOL - 1) / pe::IMAGE_SIZEOF_SYMBOL;
+        self.symtab_num += aux_count as u32;
+        aux_count as u8
+    }
+
+    /// Write auxiliary symbols for a file name.
+    pub fn write_aux_file_name(&mut self, name: &[u8], aux_count: u8) {
+        let aux_len = aux_count as usize * pe::IMAGE_SIZEOF_SYMBOL;
+        debug_assert!(aux_len >= name.len());
+        let old_len = self.buffer.len();
+        self.buffer.write_bytes(name);
+        self.buffer.resize(old_len + aux_len);
+    }
+
+    /// Reserve an auxiliary symbol for a section.
+    ///
+    /// Returns the number of auxiliary symbols required.
+    ///
+    /// This must be called before [`Self::reserve_symtab_strtab`].
+    pub fn reserve_aux_section(&mut self) -> u8 {
+        debug_assert_eq!(self.symtab_offset, 0);
+        self.symtab_num += 1;
+        1
+    }
+
+    /// Write an auxiliary symbol for a section.
+    pub fn write_aux_section(&mut self, section: AuxSymbolSection) {
+        let aux = pe::ImageAuxSymbolSection {
+            length: U32Bytes::new(LE, section.length),
+            number_of_relocations: if section.number_of_relocations > 0xffff {
+                U16Bytes::new(LE, 0xffff)
+            } else {
+                U16Bytes::new(LE, section.number_of_relocations as u16)
+            },
+            number_of_linenumbers: U16Bytes::new(LE, section.number_of_linenumbers),
+            check_sum: U32Bytes::new(LE, section.check_sum),
+            number: U16Bytes::new(LE, section.number as u16),
+            selection: section.selection,
+            reserved: 0,
+            high_number: U16Bytes::new(LE, (section.number >> 16) as u16),
+        };
+        self.buffer.write(&aux);
+    }
+
+    /// Return the number of reserved symbol table entries.
+    pub fn symbol_count(&self) -> u32 {
+        self.symtab_num
+    }
+
+    /// Add a string to the string table.
+    ///
+    /// This must be called before [`Self::reserve_symtab_strtab`].
+    pub fn add_string(&mut self, name: &'a [u8]) -> StringId {
+        debug_assert_eq!(self.strtab_offset, 0);
+        self.strtab.add(name)
+    }
+
+    /// Add a section or symbol name to the string table if required.
+    ///
+    /// This must be called before [`Self::reserve_symtab_strtab`].
+    pub fn add_name(&mut self, name: &'a [u8]) -> Name {
+        if name.len() > 8 {
+            Name::Long(self.add_string(name))
+        } else {
+            let mut short_name = [0; 8];
+            short_name[..name.len()].copy_from_slice(name);
+            Name::Short(short_name)
+        }
+    }
+
+    /// Reserve the range for the symbol table and string table.
+    ///
+    /// This must be called after functions that reserve symbol
+    /// indices or add strings.
+    pub fn reserve_symtab_strtab(&mut self) {
+        debug_assert_eq!(self.symtab_offset, 0);
+        self.symtab_offset = self.reserve(self.symtab_num as usize * pe::IMAGE_SIZEOF_SYMBOL, 1);
+
+        debug_assert_eq!(self.strtab_offset, 0);
+        // First 4 bytes of strtab are the length.
+        self.strtab.write(4, &mut self.strtab_data);
+        self.strtab_len = self.strtab_data.len() + 4;
+        self.strtab_offset = self.reserve(self.strtab_len, 1);
+    }
+
+    /// Write the string table.
+    pub fn write_strtab(&mut self) {
+        debug_assert_eq!(self.strtab_offset, self.buffer.len() as u32);
+        self.buffer
+            .write_bytes(&u32::to_le_bytes(self.strtab_len as u32));
+        self.buffer.write_bytes(&self.strtab_data);
+    }
+}
+
+/// Shortened and native endian version of [`pe::ImageFileHeader`].
+#[allow(missing_docs)]
+#[derive(Debug, Default, Clone)]
+pub struct FileHeader {
+    pub machine: u16,
+    pub time_date_stamp: u32,
+    pub characteristics: u16,
+}
+
+/// A section or symbol name.
+#[derive(Debug, Clone, Copy)]
+pub enum Name {
+    /// An inline name.
+    Short([u8; 8]),
+    /// An id of a string table entry.
+    Long(StringId),
+}
+
+impl Default for Name {
+    fn default() -> Name {
+        Name::Short([0; 8])
+    }
+}
+
+// From isn't useful.
+#[allow(clippy::from_over_into)]
+impl<'a> Into<Name> for &'a [u8; 8] {
+    fn into(self) -> Name {
+        Name::Short(*self)
+    }
+}
+
+/// Native endian version of [`pe::ImageSectionHeader`].
+#[allow(missing_docs)]
+#[derive(Debug, Default, Clone)]
+pub struct SectionHeader {
+    pub name: Name,
+    pub size_of_raw_data: u32,
+    pub pointer_to_raw_data: u32,
+    pub pointer_to_relocations: u32,
+    pub pointer_to_linenumbers: u32,
+    /// This will automatically be clamped if there are more than 0xffff.
+    pub number_of_relocations: u32,
+    pub number_of_linenumbers: u16,
+    pub characteristics: u32,
+}
+
+/// Native endian version of [`pe::ImageSymbol`].
+#[allow(missing_docs)]
+#[derive(Debug, Default, Clone)]
+pub struct Symbol {
+    pub name: Name,
+    pub value: u32,
+    pub section_number: u16,
+    pub typ: u16,
+    pub storage_class: u8,
+    pub number_of_aux_symbols: u8,
+}
+
+/// Native endian version of [`pe::ImageAuxSymbolSection`].
+#[allow(missing_docs)]
+#[derive(Debug, Default, Clone)]
+pub struct AuxSymbolSection {
+    pub length: u32,
+    /// This will automatically be clamped if there are more than 0xffff.
+    pub number_of_relocations: u32,
+    pub number_of_linenumbers: u16,
+    pub check_sum: u32,
+    pub number: u32,
+    pub selection: u8,
+}
+
+/// Native endian version of [`pe::ImageRelocation`].
+#[allow(missing_docs)]
+#[derive(Debug, Default, Clone)]
+pub struct Relocation {
+    pub virtual_address: u32,
+    pub symbol: u32,
+    pub typ: u16,
+}

vendor/object/src/write/elf/mod.rs

@@ -0,0 +1,9 @@
+//! Support for writing ELF files.
+//!
+//! Provides [`Writer`] for low level writing of ELF files.
+//! This is also used to provide ELF support for [`write::Object`](crate::write::Object).
+
+mod object;
+
+mod writer;
+pub use writer::*;

vendor/object/src/write/elf/object.rs

@@ -0,0 +1,841 @@
+use alloc::vec::Vec;
+
+use crate::write::elf::writer::*;
+use crate::write::string::StringId;
+use crate::write::*;
+use crate::{elf, pod};
+
+#[derive(Clone, Copy)]
+struct ComdatOffsets {
+    offset: usize,
+    str_id: StringId,
+}
+
+#[derive(Clone, Copy)]
+struct SectionOffsets {
+    index: SectionIndex,
+    offset: usize,
+    str_id: StringId,
+    reloc_offset: usize,
+    reloc_str_id: Option<StringId>,
+}
+
+#[derive(Default, Clone, Copy)]
+struct SymbolOffsets {
+    index: SymbolIndex,
+    str_id: Option<StringId>,
+}
+
+// Public methods.
+impl<'a> Object<'a> {
+    /// Add a property with a u32 value to the ELF ".note.gnu.property" section.
+    ///
+    /// Requires `feature = "elf"`.
+    pub fn add_elf_gnu_property_u32(&mut self, property: u32, value: u32) {
+        if self.format != BinaryFormat::Elf {
+            return;
+        }
+
+        let align = if self.elf_is_64() { 8 } else { 4 };
+        let mut data = Vec::with_capacity(32);
+        let n_name = b"GNU\0";
+        data.extend_from_slice(pod::bytes_of(&elf::NoteHeader32 {
+            n_namesz: U32::new(self.endian, n_name.len() as u32),
+            n_descsz: U32::new(self.endian, util::align(3 * 4, align) as u32),
+            n_type: U32::new(self.endian, elf::NT_GNU_PROPERTY_TYPE_0),
+        }));
+        data.extend_from_slice(n_name);
+        // This happens to already be aligned correctly.
+        debug_assert_eq!(util::align(data.len(), align), data.len());
+        data.extend_from_slice(pod::bytes_of(&U32::new(self.endian, property)));
+        // Value size
+        data.extend_from_slice(pod::bytes_of(&U32::new(self.endian, 4)));
+        data.extend_from_slice(pod::bytes_of(&U32::new(self.endian, value)));
+        util::write_align(&mut data, align);
+
+        let section = self.section_id(StandardSection::GnuProperty);
+        self.append_section_data(section, &data, align as u64);
+    }
+}
+
+// Private methods.
+impl<'a> Object<'a> {
+    pub(crate) fn elf_section_info(
+        &self,
+        section: StandardSection,
+    ) -> (&'static [u8], &'static [u8], SectionKind, SectionFlags) {
+        match section {
+            StandardSection::Text => (&[], &b".text"[..], SectionKind::Text, SectionFlags::None),
+            StandardSection::Data => (&[], &b".data"[..], SectionKind::Data, SectionFlags::None),
+            StandardSection::ReadOnlyData | StandardSection::ReadOnlyString => (
+                &[],
+                &b".rodata"[..],
+                SectionKind::ReadOnlyData,
+                SectionFlags::None,
+            ),
+            StandardSection::ReadOnlyDataWithRel => (
+                &[],
+                b".data.rel.ro",
+                SectionKind::ReadOnlyDataWithRel,
+                SectionFlags::None,
+            ),
+            StandardSection::UninitializedData => (
+                &[],
+                &b".bss"[..],
+                SectionKind::UninitializedData,
+                SectionFlags::None,
+            ),
+            StandardSection::Tls => (&[], &b".tdata"[..], SectionKind::Tls, SectionFlags::None),
+            StandardSection::UninitializedTls => (
+                &[],
+                &b".tbss"[..],
+                SectionKind::UninitializedTls,
+                SectionFlags::None,
+            ),
+            StandardSection::TlsVariables => {
+                // Unsupported section.
+                (&[], &[], SectionKind::TlsVariables, SectionFlags::None)
+            }
+            StandardSection::Common => {
+                // Unsupported section.
+                (&[], &[], SectionKind::Common, SectionFlags::None)
+            }
+            StandardSection::GnuProperty => (
+                &[],
+                &b".note.gnu.property"[..],
+                SectionKind::Note,
+                SectionFlags::Elf {
+                    sh_flags: u64::from(elf::SHF_ALLOC),
+                },
+            ),
+        }
+    }
+
+    pub(crate) fn elf_subsection_name(&self, section: &[u8], value: &[u8]) -> Vec<u8> {
+        let mut name = section.to_vec();
+        if !value.is_empty() {
+            name.push(b'.');
+            name.extend_from_slice(value);
+        }
+        name
+    }
+
+    fn elf_has_relocation_addend(&self) -> Result<bool> {
+        Ok(match self.architecture {
+            Architecture::Aarch64 => true,
+            Architecture::Aarch64_Ilp32 => true,
+            Architecture::Arm => false,
+            Architecture::Avr => true,
+            Architecture::Bpf => false,
+            Architecture::Csky => true,
+            Architecture::E2K32 => true,
+            Architecture::E2K64 => true,
+            Architecture::I386 => false,
+            Architecture::X86_64 => true,
+            Architecture::X86_64_X32 => true,
+            Architecture::Hexagon => true,
+            Architecture::LoongArch64 => true,
+            Architecture::M68k => true,
+            Architecture::Mips => false,
+            Architecture::Mips64 => true,
+            Architecture::Mips64_N32 => true,
+            Architecture::Msp430 => true,
+            Architecture::PowerPc => true,
+            Architecture::PowerPc64 => true,
+            Architecture::Riscv64 => true,
+            Architecture::Riscv32 => true,
+            Architecture::S390x => true,
+            Architecture::Sbf => false,
+            Architecture::Sharc => true,
+            Architecture::Sparc => true,
+            Architecture::Sparc32Plus => true,
+            Architecture::Sparc64 => true,
+            Architecture::Xtensa => true,
+            _ => {
+                return Err(Error(format!(
+                    "unimplemented architecture {:?}",
+                    self.architecture
+                )));
+            }
+        })
+    }
+
+    pub(crate) fn elf_translate_relocation(&mut self, reloc: &mut Relocation) -> Result<()> {
+        use RelocationEncoding as E;
+        use RelocationKind as K;
+
+        let (kind, encoding, size) = if let RelocationFlags::Generic {
+            kind,
+            encoding,
+            size,
+        } = reloc.flags
+        {
+            (kind, encoding, size)
+        } else {
+            return Ok(());
+        };
+
+        let unsupported_reloc = || Err(Error(format!("unimplemented ELF relocation {:?}", reloc)));
+        let r_type = match self.architecture {
+            Architecture::Aarch64 => match (kind, encoding, size) {
+                (K::Absolute, E::Generic, 64) => elf::R_AARCH64_ABS64,
+                (K::Absolute, E::Generic, 32) => elf::R_AARCH64_ABS32,
+                (K::Absolute, E::Generic, 16) => elf::R_AARCH64_ABS16,
+                (K::Relative, E::Generic, 64) => elf::R_AARCH64_PREL64,
+                (K::Relative, E::Generic, 32) => elf::R_AARCH64_PREL32,
+                (K::Relative, E::Generic, 16) => elf::R_AARCH64_PREL16,
+                (K::Relative, E::AArch64Call, 26) => elf::R_AARCH64_CALL26,
+                (K::PltRelative, E::AArch64Call, 26) => elf::R_AARCH64_CALL26,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Aarch64_Ilp32 => match (kind, encoding, size) {
+                (K::Absolute, E::Generic, 32) => elf::R_AARCH64_P32_ABS32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Arm => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_ARM_ABS32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Avr => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_AVR_32,
+                (K::Absolute, _, 16) => elf::R_AVR_16,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Bpf => match (kind, encoding, size) {
+                (K::Absolute, _, 64) => elf::R_BPF_64_64,
+                (K::Absolute, _, 32) => elf::R_BPF_64_32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Csky => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_CKCORE_ADDR32,
+                (K::Relative, E::Generic, 32) => elf::R_CKCORE_PCREL32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::I386 => match (kind, size) {
+                (K::Absolute, 32) => elf::R_386_32,
+                (K::Relative, 32) => elf::R_386_PC32,
+                (K::Got, 32) => elf::R_386_GOT32,
+                (K::PltRelative, 32) => elf::R_386_PLT32,
+                (K::GotBaseOffset, 32) => elf::R_386_GOTOFF,
+                (K::GotBaseRelative, 32) => elf::R_386_GOTPC,
+                (K::Absolute, 16) => elf::R_386_16,
+                (K::Relative, 16) => elf::R_386_PC16,
+                (K::Absolute, 8) => elf::R_386_8,
+                (K::Relative, 8) => elf::R_386_PC8,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::E2K32 | Architecture::E2K64 => match (kind, encoding, size) {
+                (K::Absolute, E::Generic, 32) => elf::R_E2K_32_ABS,
+                (K::Absolute, E::E2KLit, 64) => elf::R_E2K_64_ABS_LIT,
+                (K::Absolute, E::Generic, 64) => elf::R_E2K_64_ABS,
+                (K::Relative, E::E2KDisp, 28) => elf::R_E2K_DISP,
+                (K::Got, _, 32) => elf::R_E2K_GOT,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::X86_64 | Architecture::X86_64_X32 => match (kind, encoding, size) {
+                (K::Absolute, E::Generic, 64) => elf::R_X86_64_64,
+                (K::Relative, E::X86Branch, 32) => elf::R_X86_64_PLT32,
+                (K::Relative, _, 32) => elf::R_X86_64_PC32,
+                (K::Got, _, 32) => elf::R_X86_64_GOT32,
+                (K::PltRelative, _, 32) => elf::R_X86_64_PLT32,
+                (K::GotRelative, _, 32) => elf::R_X86_64_GOTPCREL,
+                (K::Absolute, E::Generic, 32) => elf::R_X86_64_32,
+                (K::Absolute, E::X86Signed, 32) => elf::R_X86_64_32S,
+                (K::Absolute, _, 16) => elf::R_X86_64_16,
+                (K::Relative, _, 16) => elf::R_X86_64_PC16,
+                (K::Absolute, _, 8) => elf::R_X86_64_8,
+                (K::Relative, _, 8) => elf::R_X86_64_PC8,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Hexagon => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_HEX_32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::LoongArch64 => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_LARCH_32,
+                (K::Absolute, _, 64) => elf::R_LARCH_64,
+                (K::Relative, _, 32) => elf::R_LARCH_32_PCREL,
+                (K::Relative, _, 64) => elf::R_LARCH_64_PCREL,
+                (K::Relative, E::LoongArchBranch, 16) => elf::R_LARCH_B16,
+                (K::PltRelative, E::LoongArchBranch, 16) => elf::R_LARCH_B16,
+                (K::Relative, E::LoongArchBranch, 21) => elf::R_LARCH_B21,
+                (K::PltRelative, E::LoongArchBranch, 21) => elf::R_LARCH_B21,
+                (K::Relative, E::LoongArchBranch, 26) => elf::R_LARCH_B26,
+                (K::PltRelative, E::LoongArchBranch, 26) => elf::R_LARCH_B26,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::M68k => match (kind, encoding, size) {
+                (K::Absolute, _, 8) => elf::R_68K_8,
+                (K::Absolute, _, 16) => elf::R_68K_16,
+                (K::Absolute, _, 32) => elf::R_68K_32,
+                (K::Relative, _, 8) => elf::R_68K_PC8,
+                (K::Relative, _, 16) => elf::R_68K_PC16,
+                (K::Relative, _, 32) => elf::R_68K_PC32,
+                (K::GotRelative, _, 8) => elf::R_68K_GOT8,
+                (K::GotRelative, _, 16) => elf::R_68K_GOT16,
+                (K::GotRelative, _, 32) => elf::R_68K_GOT32,
+                (K::Got, _, 8) => elf::R_68K_GOT8O,
+                (K::Got, _, 16) => elf::R_68K_GOT16O,
+                (K::Got, _, 32) => elf::R_68K_GOT32O,
+                (K::PltRelative, _, 8) => elf::R_68K_PLT8,
+                (K::PltRelative, _, 16) => elf::R_68K_PLT16,
+                (K::PltRelative, _, 32) => elf::R_68K_PLT32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Mips | Architecture::Mips64 | Architecture::Mips64_N32 => {
+                match (kind, encoding, size) {
+                    (K::Absolute, _, 16) => elf::R_MIPS_16,
+                    (K::Absolute, _, 32) => elf::R_MIPS_32,
+                    (K::Absolute, _, 64) => elf::R_MIPS_64,
+                    _ => return unsupported_reloc(),
+                }
+            }
+            Architecture::Msp430 => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_MSP430_32,
+                (K::Absolute, _, 16) => elf::R_MSP430_16_BYTE,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::PowerPc => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_PPC_ADDR32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::PowerPc64 => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_PPC64_ADDR32,
+                (K::Absolute, _, 64) => elf::R_PPC64_ADDR64,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Riscv32 | Architecture::Riscv64 => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_RISCV_32,
+                (K::Absolute, _, 64) => elf::R_RISCV_64,
+                (K::Relative, E::Generic, 32) => elf::R_RISCV_32_PCREL,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::S390x => match (kind, encoding, size) {
+                (K::Absolute, E::Generic, 8) => elf::R_390_8,
+                (K::Absolute, E::Generic, 16) => elf::R_390_16,
+                (K::Absolute, E::Generic, 32) => elf::R_390_32,
+                (K::Absolute, E::Generic, 64) => elf::R_390_64,
+                (K::Relative, E::Generic, 16) => elf::R_390_PC16,
+                (K::Relative, E::Generic, 32) => elf::R_390_PC32,
+                (K::Relative, E::Generic, 64) => elf::R_390_PC64,
+                (K::Relative, E::S390xDbl, 16) => elf::R_390_PC16DBL,
+                (K::Relative, E::S390xDbl, 32) => elf::R_390_PC32DBL,
+                (K::PltRelative, E::S390xDbl, 16) => elf::R_390_PLT16DBL,
+                (K::PltRelative, E::S390xDbl, 32) => elf::R_390_PLT32DBL,
+                (K::Got, E::Generic, 16) => elf::R_390_GOT16,
+                (K::Got, E::Generic, 32) => elf::R_390_GOT32,
+                (K::Got, E::Generic, 64) => elf::R_390_GOT64,
+                (K::GotRelative, E::S390xDbl, 32) => elf::R_390_GOTENT,
+                (K::GotBaseOffset, E::Generic, 16) => elf::R_390_GOTOFF16,
+                (K::GotBaseOffset, E::Generic, 32) => elf::R_390_GOTOFF32,
+                (K::GotBaseOffset, E::Generic, 64) => elf::R_390_GOTOFF64,
+                (K::GotBaseRelative, E::Generic, 64) => elf::R_390_GOTPC,
+                (K::GotBaseRelative, E::S390xDbl, 32) => elf::R_390_GOTPCDBL,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Sbf => match (kind, encoding, size) {
+                (K::Absolute, _, 64) => elf::R_SBF_64_64,
+                (K::Absolute, _, 32) => elf::R_SBF_64_32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Sharc => match (kind, encoding, size) {
+                (K::Absolute, E::SharcTypeA, 32) => elf::R_SHARC_ADDR32_V3,
+                (K::Absolute, E::Generic, 32) => elf::R_SHARC_ADDR_VAR_V3,
+                (K::Relative, E::SharcTypeA, 24) => elf::R_SHARC_PCRLONG_V3,
+                (K::Relative, E::SharcTypeA, 6) => elf::R_SHARC_PCRSHORT_V3,
+                (K::Relative, E::SharcTypeB, 6) => elf::R_SHARC_PCRSHORT_V3,
+                (K::Absolute, E::Generic, 16) => elf::R_SHARC_ADDR_VAR16_V3,
+                (K::Absolute, E::SharcTypeA, 16) => elf::R_SHARC_DATA16_V3,
+                (K::Absolute, E::SharcTypeB, 16) => elf::R_SHARC_DATA16_VISA_V3,
+                (K::Absolute, E::SharcTypeA, 24) => elf::R_SHARC_ADDR24_V3,
+                (K::Absolute, E::SharcTypeA, 6) => elf::R_SHARC_DATA6_V3,
+                (K::Absolute, E::SharcTypeB, 6) => elf::R_SHARC_DATA6_VISA_V3,
+                (K::Absolute, E::SharcTypeB, 7) => elf::R_SHARC_DATA7_VISA_V3,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Sparc | Architecture::Sparc32Plus => match (kind, encoding, size) {
+                // TODO: use R_SPARC_32 if aligned.
+                (K::Absolute, _, 32) => elf::R_SPARC_UA32,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Sparc64 => match (kind, encoding, size) {
+                // TODO: use R_SPARC_32/R_SPARC_64 if aligned.
+                (K::Absolute, _, 32) => elf::R_SPARC_UA32,
+                (K::Absolute, _, 64) => elf::R_SPARC_UA64,
+                _ => return unsupported_reloc(),
+            },
+            Architecture::Xtensa => match (kind, encoding, size) {
+                (K::Absolute, _, 32) => elf::R_XTENSA_32,
+                (K::Relative, E::Generic, 32) => elf::R_XTENSA_32_PCREL,
+                _ => return unsupported_reloc(),
+            },
+            _ => {
+                return Err(Error(format!(
+                    "unimplemented architecture {:?}",
+                    self.architecture
+                )));
+            }
+        };
+        reloc.flags = RelocationFlags::Elf { r_type };
+        Ok(())
+    }
+
+    pub(crate) fn elf_adjust_addend(&mut self, _relocation: &mut Relocation) -> Result<bool> {
+        // Determine whether the addend is stored in the relocation or the data.
+        let implicit = !self.elf_has_relocation_addend()?;
+        Ok(implicit)
+    }
+
+    pub(crate) fn elf_relocation_size(&self, reloc: &Relocation) -> Result<u8> {
+        let r_type = if let RelocationFlags::Elf { r_type } = reloc.flags {
+            r_type
+        } else {
+            return Err(Error("invalid relocation flags".into()));
+        };
+        // This only needs to support architectures that use implicit addends.
+        let size = match self.architecture {
+            Architecture::Arm => match r_type {
+                elf::R_ARM_ABS16 => Some(16),
+                elf::R_ARM_ABS32 | elf::R_ARM_REL32 => Some(32),
+                _ => None,
+            },
+            Architecture::Bpf => match r_type {
+                elf::R_BPF_64_32 => Some(32),
+                elf::R_BPF_64_64 => Some(64),
+                _ => None,
+            },
+            Architecture::I386 => match r_type {
+                elf::R_386_8 | elf::R_386_PC8 => Some(8),
+                elf::R_386_16 | elf::R_386_PC16 => Some(16),
+                elf::R_386_32
+                | elf::R_386_PC32
+                | elf::R_386_GOT32
+                | elf::R_386_PLT32
+                | elf::R_386_GOTOFF
+                | elf::R_386_GOTPC => Some(32),
+                _ => None,
+            },
+            Architecture::Mips => match r_type {
+                elf::R_MIPS_16 => Some(16),
+                elf::R_MIPS_32 => Some(32),
+                elf::R_MIPS_64 => Some(64),
+                _ => None,
+            },
+            Architecture::Sbf => match r_type {
+                elf::R_SBF_64_32 => Some(32),
+                elf::R_SBF_64_64 => Some(64),
+                _ => None,
+            },
+            _ => {
+                return Err(Error(format!(
+                    "unimplemented architecture {:?}",
+                    self.architecture
+                )));
+            }
+        };
+        size.ok_or_else(|| Error(format!("unsupported relocation for size {:?}", reloc)))
+    }
+
+    pub(crate) fn elf_is_64(&self) -> bool {
+        match self.architecture.address_size().unwrap() {
+            AddressSize::U8 | AddressSize::U16 | AddressSize::U32 => false,
+            AddressSize::U64 => true,
+        }
+    }
+
+    pub(crate) fn elf_write(&self, buffer: &mut dyn WritableBuffer) -> Result<()> {
+        // Create reloc section header names so we can reference them.
+        let is_rela = self.elf_has_relocation_addend()?;
+        let reloc_names: Vec<_> = self
+            .sections
+            .iter()
+            .map(|section| {
+                let mut reloc_name = Vec::with_capacity(
+                    if is_rela { ".rela".len() } else { ".rel".len() } + section.name.len(),
+                );
+                if !section.relocations.is_empty() {
+                    reloc_name.extend_from_slice(if is_rela {
+                        &b".rela"[..]
+                    } else {
+                        &b".rel"[..]
+                    });
+                    reloc_name.extend_from_slice(&section.name);
+                }
+                reloc_name
+            })
+            .collect();
+
+        // Start calculating offsets of everything.
+        let mut writer = Writer::new(self.endian, self.elf_is_64(), buffer);
+        writer.reserve_file_header();
+
+        // Calculate size of section data.
+        let mut comdat_offsets = Vec::with_capacity(self.comdats.len());
+        for comdat in &self.comdats {
+            if comdat.kind != ComdatKind::Any {
+                return Err(Error(format!(
+                    "unsupported COMDAT symbol `{}` kind {:?}",
+                    self.symbols[comdat.symbol.0].name().unwrap_or(""),
+                    comdat.kind
+                )));
+            }
+
+            writer.reserve_section_index();
+            let offset = writer.reserve_comdat(comdat.sections.len());
+            let str_id = writer.add_section_name(b".group");
+            comdat_offsets.push(ComdatOffsets { offset, str_id });
+        }
+        let mut section_offsets = Vec::with_capacity(self.sections.len());
+        for (section, reloc_name) in self.sections.iter().zip(reloc_names.iter()) {
+            let index = writer.reserve_section_index();
+            let offset = writer.reserve(section.data.len(), section.align as usize);
+            let str_id = writer.add_section_name(&section.name);
+            let mut reloc_str_id = None;
+            if !section.relocations.is_empty() {
+                writer.reserve_section_index();
+                reloc_str_id = Some(writer.add_section_name(reloc_name));
+            }
+            section_offsets.push(SectionOffsets {
+                index,
+                offset,
+                str_id,
+                // Relocation data is reserved later.
+                reloc_offset: 0,
+                reloc_str_id,
+            });
+        }
+
+        // Calculate index of symbols and add symbol strings to strtab.
+        let mut symbol_offsets = vec![SymbolOffsets::default(); self.symbols.len()];
+        writer.reserve_null_symbol_index();
+        // Local symbols must come before global.
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if symbol.is_local() {
+                let section_index = symbol.section.id().map(|s| section_offsets[s.0].index);
+                symbol_offsets[index].index = writer.reserve_symbol_index(section_index);
+            }
+        }
+        let symtab_num_local = writer.symbol_count();
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if !symbol.is_local() {
+                let section_index = symbol.section.id().map(|s| section_offsets[s.0].index);
+                symbol_offsets[index].index = writer.reserve_symbol_index(section_index);
+            }
+        }
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if symbol.kind != SymbolKind::Section && !symbol.name.is_empty() {
+                symbol_offsets[index].str_id = Some(writer.add_string(&symbol.name));
+            }
+        }
+
+        // Calculate size of symbols.
+        writer.reserve_symtab_section_index();
+        writer.reserve_symtab();
+        if writer.symtab_shndx_needed() {
+            writer.reserve_symtab_shndx_section_index();
+        }
+        writer.reserve_symtab_shndx();
+        writer.reserve_strtab_section_index();
+        writer.reserve_strtab();
+
+        // Calculate size of relocations.
+        for (index, section) in self.sections.iter().enumerate() {
+            let count = section.relocations.len();
+            if count != 0 {
+                section_offsets[index].reloc_offset = writer.reserve_relocations(count, is_rela);
+            }
+        }
+
+        // Calculate size of section headers.
+        writer.reserve_shstrtab_section_index();
+        writer.reserve_shstrtab();
+        writer.reserve_section_headers();
+
+        // Start writing.
+        let e_type = elf::ET_REL;
+        let e_machine = match (self.architecture, self.sub_architecture) {
+            (Architecture::Aarch64, None) => elf::EM_AARCH64,
+            (Architecture::Aarch64_Ilp32, None) => elf::EM_AARCH64,
+            (Architecture::Arm, None) => elf::EM_ARM,
+            (Architecture::Avr, None) => elf::EM_AVR,
+            (Architecture::Bpf, None) => elf::EM_BPF,
+            (Architecture::Csky, None) => elf::EM_CSKY,
+            (Architecture::E2K32, None) => elf::EM_MCST_ELBRUS,
+            (Architecture::E2K64, None) => elf::EM_MCST_ELBRUS,
+            (Architecture::I386, None) => elf::EM_386,
+            (Architecture::X86_64, None) => elf::EM_X86_64,
+            (Architecture::X86_64_X32, None) => elf::EM_X86_64,
+            (Architecture::Hexagon, None) => elf::EM_HEXAGON,
+            (Architecture::LoongArch64, None) => elf::EM_LOONGARCH,
+            (Architecture::M68k, None) => elf::EM_68K,
+            (Architecture::Mips, None) => elf::EM_MIPS,
+            (Architecture::Mips64, None) => elf::EM_MIPS,
+            (Architecture::Mips64_N32, None) => elf::EM_MIPS,
+            (Architecture::Msp430, None) => elf::EM_MSP430,
+            (Architecture::PowerPc, None) => elf::EM_PPC,
+            (Architecture::PowerPc64, None) => elf::EM_PPC64,
+            (Architecture::Riscv32, None) => elf::EM_RISCV,
+            (Architecture::Riscv64, None) => elf::EM_RISCV,
+            (Architecture::S390x, None) => elf::EM_S390,
+            (Architecture::Sbf, None) => elf::EM_SBF,
+            (Architecture::Sharc, None) => elf::EM_SHARC,
+            (Architecture::Sparc, None) => elf::EM_SPARC,
+            (Architecture::Sparc32Plus, None) => elf::EM_SPARC32PLUS,
+            (Architecture::Sparc64, None) => elf::EM_SPARCV9,
+            (Architecture::Xtensa, None) => elf::EM_XTENSA,
+            _ => {
+                return Err(Error(format!(
+                    "unimplemented architecture {:?} with sub-architecture {:?}",
+                    self.architecture, self.sub_architecture
+                )));
+            }
+        };
+        let (os_abi, abi_version, mut e_flags) = if let FileFlags::Elf {
+            os_abi,
+            abi_version,
+            e_flags,
+        } = self.flags
+        {
+            (os_abi, abi_version, e_flags)
+        } else {
+            (elf::ELFOSABI_NONE, 0, 0)
+        };
+
+        if self.architecture == Architecture::Mips64_N32 {
+            e_flags |= elf::EF_MIPS_ABI2;
+        }
+
+        writer.write_file_header(&FileHeader {
+            os_abi,
+            abi_version,
+            e_type,
+            e_machine,
+            e_entry: 0,
+            e_flags,
+        })?;
+
+        // Write section data.
+        for comdat in &self.comdats {
+            writer.write_comdat_header();
+            for section in &comdat.sections {
+                writer.write_comdat_entry(section_offsets[section.0].index);
+            }
+        }
+        for (index, section) in self.sections.iter().enumerate() {
+            writer.write_align(section.align as usize);
+            debug_assert_eq!(section_offsets[index].offset, writer.len());
+            writer.write(&section.data);
+        }
+
+        // Write symbols.
+        writer.write_null_symbol();
+        let mut write_symbol = |index: usize, symbol: &Symbol| -> Result<()> {
+            let st_info = if let SymbolFlags::Elf { st_info, .. } = symbol.flags {
+                st_info
+            } else {
+                let st_type = match symbol.kind {
+                    SymbolKind::Text => {
+                        if symbol.is_undefined() {
+                            elf::STT_NOTYPE
+                        } else {
+                            elf::STT_FUNC
+                        }
+                    }
+                    SymbolKind::Data => {
+                        if symbol.is_undefined() {
+                            elf::STT_NOTYPE
+                        } else if symbol.is_common() {
+                            elf::STT_COMMON
+                        } else {
+                            elf::STT_OBJECT
+                        }
+                    }
+                    SymbolKind::Section => elf::STT_SECTION,
+                    SymbolKind::File => elf::STT_FILE,
+                    SymbolKind::Tls => elf::STT_TLS,
+                    SymbolKind::Label => elf::STT_NOTYPE,
+                    SymbolKind::Unknown => {
+                        if symbol.is_undefined() {
+                            elf::STT_NOTYPE
+                        } else {
+                            return Err(Error(format!(
+                                "unimplemented symbol `{}` kind {:?}",
+                                symbol.name().unwrap_or(""),
+                                symbol.kind
+                            )));
+                        }
+                    }
+                };
+                let st_bind = if symbol.weak {
+                    elf::STB_WEAK
+                } else if symbol.is_undefined() {
+                    elf::STB_GLOBAL
+                } else if symbol.is_local() {
+                    elf::STB_LOCAL
+                } else {
+                    elf::STB_GLOBAL
+                };
+                (st_bind << 4) + st_type
+            };
+            let st_other = if let SymbolFlags::Elf { st_other, .. } = symbol.flags {
+                st_other
+            } else if symbol.scope == SymbolScope::Linkage {
+                elf::STV_HIDDEN
+            } else {
+                elf::STV_DEFAULT
+            };
+            let (st_shndx, section) = match symbol.section {
+                SymbolSection::None => {
+                    debug_assert_eq!(symbol.kind, SymbolKind::File);
+                    (elf::SHN_ABS, None)
+                }
+                SymbolSection::Undefined => (elf::SHN_UNDEF, None),
+                SymbolSection::Absolute => (elf::SHN_ABS, None),
+                SymbolSection::Common => (elf::SHN_COMMON, None),
+                SymbolSection::Section(id) => (0, Some(section_offsets[id.0].index)),
+            };
+            writer.write_symbol(&Sym {
+                name: symbol_offsets[index].str_id,
+                section,
+                st_info,
+                st_other,
+                st_shndx,
+                st_value: symbol.value,
+                st_size: symbol.size,
+            });
+            Ok(())
+        };
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if symbol.is_local() {
+                write_symbol(index, symbol)?;
+            }
+        }
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if !symbol.is_local() {
+                write_symbol(index, symbol)?;
+            }
+        }
+        writer.write_symtab_shndx();
+        writer.write_strtab();
+
+        // Write relocations.
+        for (index, section) in self.sections.iter().enumerate() {
+            if !section.relocations.is_empty() {
+                writer.write_align_relocation();
+                debug_assert_eq!(section_offsets[index].reloc_offset, writer.len());
+                for reloc in &section.relocations {
+                    let r_type = if let RelocationFlags::Elf { r_type } = reloc.flags {
+                        r_type
+                    } else {
+                        return Err(Error("invalid relocation flags".into()));
+                    };
+                    let r_sym = symbol_offsets[reloc.symbol.0].index.0;
+                    writer.write_relocation(
+                        is_rela,
+                        &Rel {
+                            r_offset: reloc.offset,
+                            r_sym,
+                            r_type,
+                            r_addend: reloc.addend,
+                        },
+                    );
+                }
+            }
+        }
+
+        writer.write_shstrtab();
+
+        // Write section headers.
+        writer.write_null_section_header();
+
+        let symtab_index = writer.symtab_index();
+        for (comdat, comdat_offset) in self.comdats.iter().zip(comdat_offsets.iter()) {
+            writer.write_comdat_section_header(
+                comdat_offset.str_id,
+                symtab_index,
+                symbol_offsets[comdat.symbol.0].index,
+                comdat_offset.offset,
+                comdat.sections.len(),
+            );
+        }
+        for (index, section) in self.sections.iter().enumerate() {
+            let sh_type = match section.kind {
+                SectionKind::UninitializedData | SectionKind::UninitializedTls => elf::SHT_NOBITS,
+                SectionKind::Note => elf::SHT_NOTE,
+                SectionKind::Elf(sh_type) => sh_type,
+                _ => elf::SHT_PROGBITS,
+            };
+            let sh_flags = if let SectionFlags::Elf { sh_flags } = section.flags {
+                sh_flags
+            } else {
+                match section.kind {
+                    SectionKind::Text => elf::SHF_ALLOC | elf::SHF_EXECINSTR,
+                    SectionKind::Data | SectionKind::ReadOnlyDataWithRel => {
+                        elf::SHF_ALLOC | elf::SHF_WRITE
+                    }
+                    SectionKind::Tls => elf::SHF_ALLOC | elf::SHF_WRITE | elf::SHF_TLS,
+                    SectionKind::UninitializedData => elf::SHF_ALLOC | elf::SHF_WRITE,
+                    SectionKind::UninitializedTls => elf::SHF_ALLOC | elf::SHF_WRITE | elf::SHF_TLS,
+                    SectionKind::ReadOnlyData => elf::SHF_ALLOC,
+                    SectionKind::ReadOnlyString => {
+                        elf::SHF_ALLOC | elf::SHF_STRINGS | elf::SHF_MERGE
+                    }
+                    SectionKind::OtherString | SectionKind::DebugString => {
+                        elf::SHF_STRINGS | elf::SHF_MERGE
+                    }
+                    SectionKind::Other
+                    | SectionKind::Debug
+                    | SectionKind::Metadata
+                    | SectionKind::Linker
+                    | SectionKind::Note
+                    | SectionKind::Elf(_) => 0,
+                    SectionKind::Unknown | SectionKind::Common | SectionKind::TlsVariables => {
+                        return Err(Error(format!(
+                            "unimplemented section `{}` kind {:?}",
+                            section.name().unwrap_or(""),
+                            section.kind
+                        )));
+                    }
+                }
+                .into()
+            };
+            // TODO: not sure if this is correct, maybe user should determine this
+            let sh_entsize = match section.kind {
+                SectionKind::ReadOnlyString | SectionKind::OtherString => 1,
+                _ => 0,
+            };
+            writer.write_section_header(&SectionHeader {
+                name: Some(section_offsets[index].str_id),
+                sh_type,
+                sh_flags,
+                sh_addr: 0,
+                sh_offset: section_offsets[index].offset as u64,
+                sh_size: section.size,
+                sh_link: 0,
+                sh_info: 0,
+                sh_addralign: section.align,
+                sh_entsize,
+            });
+
+            if !section.relocations.is_empty() {
+                writer.write_relocation_section_header(
+                    section_offsets[index].reloc_str_id.unwrap(),
+                    section_offsets[index].index,
+                    symtab_index,
+                    section_offsets[index].reloc_offset,
+                    section.relocations.len(),
+                    is_rela,
+                );
+            }
+        }
+
+        writer.write_symtab_section_header(symtab_num_local);
+        writer.write_symtab_shndx_section_header();
+        writer.write_strtab_section_header();
+        writer.write_shstrtab_section_header();
+
+        debug_assert_eq!(writer.reserved_len(), writer.len());
+
+        Ok(())
+    }
+}

vendor/object/src/write/pe.rs

@@ -0,0 +1,849 @@
+//! Helper for writing PE files.
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::mem;
+
+use crate::endian::{LittleEndian as LE, *};
+use crate::pe;
+use crate::write::util;
+use crate::write::{Error, Result, WritableBuffer};
+
+/// A helper for writing PE files.
+///
+/// Writing uses a two phase approach. The first phase reserves file ranges and virtual
+/// address ranges for everything in the order that they will be written.
+///
+/// The second phase writes everything out in order. Thus the caller must ensure writing
+/// is in the same order that file ranges were reserved.
+#[allow(missing_debug_implementations)]
+pub struct Writer<'a> {
+    is_64: bool,
+    section_alignment: u32,
+    file_alignment: u32,
+
+    buffer: &'a mut dyn WritableBuffer,
+    len: u32,
+    virtual_len: u32,
+    headers_len: u32,
+
+    code_address: u32,
+    data_address: u32,
+    code_len: u32,
+    data_len: u32,
+    bss_len: u32,
+
+    nt_headers_offset: u32,
+    data_directories: Vec<DataDirectory>,
+    section_header_num: u16,
+    sections: Vec<Section>,
+
+    symbol_offset: u32,
+    symbol_num: u32,
+
+    reloc_blocks: Vec<RelocBlock>,
+    relocs: Vec<U16<LE>>,
+    reloc_offset: u32,
+}
+
+impl<'a> Writer<'a> {
+    /// Create a new `Writer`.
+    ///
+    /// The alignment values must be powers of two.
+    pub fn new(
+        is_64: bool,
+        section_alignment: u32,
+        file_alignment: u32,
+        buffer: &'a mut dyn WritableBuffer,
+    ) -> Self {
+        Writer {
+            is_64,
+            section_alignment,
+            file_alignment,
+
+            buffer,
+            len: 0,
+            virtual_len: 0,
+            headers_len: 0,
+
+            code_address: 0,
+            data_address: 0,
+            code_len: 0,
+            data_len: 0,
+            bss_len: 0,
+
+            nt_headers_offset: 0,
+            data_directories: Vec::new(),
+            section_header_num: 0,
+            sections: Vec::new(),
+
+            symbol_offset: 0,
+            symbol_num: 0,
+
+            reloc_blocks: Vec::new(),
+            relocs: Vec::new(),
+            reloc_offset: 0,
+        }
+    }
+
+    /// Return the current virtual address size that has been reserved.
+    ///
+    /// This is only valid after section headers have been reserved.
+    pub fn virtual_len(&self) -> u32 {
+        self.virtual_len
+    }
+
+    /// Reserve a virtual address range with the given size.
+    ///
+    /// The reserved length will be increased to match the section alignment.
+    ///
+    /// Returns the aligned offset of the start of the range.
+    pub fn reserve_virtual(&mut self, len: u32) -> u32 {
+        let offset = self.virtual_len;
+        self.virtual_len += len;
+        self.virtual_len = util::align_u32(self.virtual_len, self.section_alignment);
+        offset
+    }
+
+    /// Reserve up to the given virtual address.
+    ///
+    /// The reserved length will be increased to match the section alignment.
+    pub fn reserve_virtual_until(&mut self, address: u32) {
+        debug_assert!(self.virtual_len <= address);
+        self.virtual_len = util::align_u32(address, self.section_alignment);
+    }
+
+    /// Return the current file length that has been reserved.
+    pub fn reserved_len(&self) -> u32 {
+        self.len
+    }
+
+    /// Return the current file length that has been written.
+    #[allow(clippy::len_without_is_empty)]
+    pub fn len(&self) -> usize {
+        self.buffer.len()
+    }
+
+    /// Reserve a file range with the given size and starting alignment.
+    ///
+    /// Returns the aligned offset of the start of the range.
+    pub fn reserve(&mut self, len: u32, align_start: u32) -> u32 {
+        if len == 0 {
+            return self.len;
+        }
+        self.reserve_align(align_start);
+        let offset = self.len;
+        self.len += len;
+        offset
+    }
+
+    /// Reserve a file range with the given size and using the file alignment.
+    ///
+    /// Returns the aligned offset of the start of the range.
+    pub fn reserve_file(&mut self, len: u32) -> u32 {
+        self.reserve(len, self.file_alignment)
+    }
+
+    /// Write data.
+    pub fn write(&mut self, data: &[u8]) {
+        self.buffer.write_bytes(data);
+    }
+
+    /// Reserve alignment padding bytes.
+    pub fn reserve_align(&mut self, align_start: u32) {
+        self.len = util::align_u32(self.len, align_start);
+    }
+
+    /// Write alignment padding bytes.
+    pub fn write_align(&mut self, align_start: u32) {
+        util::write_align(self.buffer, align_start as usize);
+    }
+
+    /// Write padding up to the next multiple of file alignment.
+    pub fn write_file_align(&mut self) {
+        self.write_align(self.file_alignment);
+    }
+
+    /// Reserve the file range up to the given file offset.
+    pub fn reserve_until(&mut self, offset: u32) {
+        debug_assert!(self.len <= offset);
+        self.len = offset;
+    }
+
+    /// Write padding up to the given file offset.
+    pub fn pad_until(&mut self, offset: u32) {
+        debug_assert!(self.buffer.len() <= offset as usize);
+        self.buffer.resize(offset as usize);
+    }
+
+    /// Reserve the range for the DOS header.
+    ///
+    /// This must be at the start of the file.
+    ///
+    /// When writing, you may use `write_custom_dos_header` or `write_empty_dos_header`.
+    pub fn reserve_dos_header(&mut self) {
+        debug_assert_eq!(self.len, 0);
+        self.reserve(mem::size_of::<pe::ImageDosHeader>() as u32, 1);
+    }
+
+    /// Write a custom DOS header.
+    ///
+    /// This must be at the start of the file.
+    pub fn write_custom_dos_header(&mut self, dos_header: &pe::ImageDosHeader) -> Result<()> {
+        debug_assert_eq!(self.buffer.len(), 0);
+
+        // Start writing.
+        self.buffer
+            .reserve(self.len as usize)
+            .map_err(|_| Error(String::from("Cannot allocate buffer")))?;
+
+        self.buffer.write(dos_header);
+        Ok(())
+    }
+
+    /// Write the DOS header for a file without a stub.
+    ///
+    /// This must be at the start of the file.
+    ///
+    /// Uses default values for all fields.
+    pub fn write_empty_dos_header(&mut self) -> Result<()> {
+        self.write_custom_dos_header(&pe::ImageDosHeader {
+            e_magic: U16::new(LE, pe::IMAGE_DOS_SIGNATURE),
+            e_cblp: U16::new(LE, 0),
+            e_cp: U16::new(LE, 0),
+            e_crlc: U16::new(LE, 0),
+            e_cparhdr: U16::new(LE, 0),
+            e_minalloc: U16::new(LE, 0),
+            e_maxalloc: U16::new(LE, 0),
+            e_ss: U16::new(LE, 0),
+            e_sp: U16::new(LE, 0),
+            e_csum: U16::new(LE, 0),
+            e_ip: U16::new(LE, 0),
+            e_cs: U16::new(LE, 0),
+            e_lfarlc: U16::new(LE, 0),
+            e_ovno: U16::new(LE, 0),
+            e_res: [U16::new(LE, 0); 4],
+            e_oemid: U16::new(LE, 0),
+            e_oeminfo: U16::new(LE, 0),
+            e_res2: [U16::new(LE, 0); 10],
+            e_lfanew: U32::new(LE, self.nt_headers_offset),
+        })
+    }
+
+    /// Reserve a fixed DOS header and stub.
+    ///
+    /// Use `reserve_dos_header` and `reserve` if you need a custom stub.
+    pub fn reserve_dos_header_and_stub(&mut self) {
+        self.reserve_dos_header();
+        self.reserve(64, 1);
+    }
+
+    /// Write a fixed DOS header and stub.
+    ///
+    /// Use `write_custom_dos_header` and `write` if you need a custom stub.
+    pub fn write_dos_header_and_stub(&mut self) -> Result<()> {
+        self.write_custom_dos_header(&pe::ImageDosHeader {
+            e_magic: U16::new(LE, pe::IMAGE_DOS_SIGNATURE),
+            e_cblp: U16::new(LE, 0x90),
+            e_cp: U16::new(LE, 3),
+            e_crlc: U16::new(LE, 0),
+            e_cparhdr: U16::new(LE, 4),
+            e_minalloc: U16::new(LE, 0),
+            e_maxalloc: U16::new(LE, 0xffff),
+            e_ss: U16::new(LE, 0),
+            e_sp: U16::new(LE, 0xb8),
+            e_csum: U16::new(LE, 0),
+            e_ip: U16::new(LE, 0),
+            e_cs: U16::new(LE, 0),
+            e_lfarlc: U16::new(LE, 0x40),
+            e_ovno: U16::new(LE, 0),
+            e_res: [U16::new(LE, 0); 4],
+            e_oemid: U16::new(LE, 0),
+            e_oeminfo: U16::new(LE, 0),
+            e_res2: [U16::new(LE, 0); 10],
+            e_lfanew: U32::new(LE, self.nt_headers_offset),
+        })?;
+
+        #[rustfmt::skip]
+        self.buffer.write_bytes(&[
+            0x0e, 0x1f, 0xba, 0x0e, 0x00, 0xb4, 0x09, 0xcd,
+            0x21, 0xb8, 0x01, 0x4c, 0xcd, 0x21, 0x54, 0x68,
+            0x69, 0x73, 0x20, 0x70, 0x72, 0x6f, 0x67, 0x72,
+            0x61, 0x6d, 0x20, 0x63, 0x61, 0x6e, 0x6e, 0x6f,
+            0x74, 0x20, 0x62, 0x65, 0x20, 0x72, 0x75, 0x6e,
+            0x20, 0x69, 0x6e, 0x20, 0x44, 0x4f, 0x53, 0x20,
+            0x6d, 0x6f, 0x64, 0x65, 0x2e, 0x0d, 0x0d, 0x0a,
+            0x24, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        ]);
+
+        Ok(())
+    }
+
+    fn nt_headers_size(&self) -> u32 {
+        if self.is_64 {
+            mem::size_of::<pe::ImageNtHeaders64>() as u32
+        } else {
+            mem::size_of::<pe::ImageNtHeaders32>() as u32
+        }
+    }
+
+    fn optional_header_size(&self) -> u32 {
+        let size = if self.is_64 {
+            mem::size_of::<pe::ImageOptionalHeader64>() as u32
+        } else {
+            mem::size_of::<pe::ImageOptionalHeader32>() as u32
+        };
+        size + self.data_directories.len() as u32 * mem::size_of::<pe::ImageDataDirectory>() as u32
+    }
+
+    /// Return the offset of the NT headers, if reserved.
+    pub fn nt_headers_offset(&self) -> u32 {
+        self.nt_headers_offset
+    }
+
+    /// Reserve the range for the NT headers.
+    pub fn reserve_nt_headers(&mut self, data_directory_num: usize) {
+        debug_assert_eq!(self.nt_headers_offset, 0);
+        self.nt_headers_offset = self.reserve(self.nt_headers_size(), 8);
+        self.data_directories = vec![DataDirectory::default(); data_directory_num];
+        self.reserve(
+            data_directory_num as u32 * mem::size_of::<pe::ImageDataDirectory>() as u32,
+            1,
+        );
+    }
+
+    /// Set the virtual address and size of a data directory.
+    pub fn set_data_directory(&mut self, index: usize, virtual_address: u32, size: u32) {
+        self.data_directories[index] = DataDirectory {
+            virtual_address,
+            size,
+        }
+    }
+
+    /// Write the NT headers.
+    pub fn write_nt_headers(&mut self, nt_headers: NtHeaders) {
+        self.pad_until(self.nt_headers_offset);
+        self.buffer.write(&U32::new(LE, pe::IMAGE_NT_SIGNATURE));
+        let file_header = pe::ImageFileHeader {
+            machine: U16::new(LE, nt_headers.machine),
+            number_of_sections: U16::new(LE, self.section_header_num),
+            time_date_stamp: U32::new(LE, nt_headers.time_date_stamp),
+            pointer_to_symbol_table: U32::new(LE, self.symbol_offset),
+            number_of_symbols: U32::new(LE, self.symbol_num),
+            size_of_optional_header: U16::new(LE, self.optional_header_size() as u16),
+            characteristics: U16::new(LE, nt_headers.characteristics),
+        };
+        self.buffer.write(&file_header);
+        if self.is_64 {
+            let optional_header = pe::ImageOptionalHeader64 {
+                magic: U16::new(LE, pe::IMAGE_NT_OPTIONAL_HDR64_MAGIC),
+                major_linker_version: nt_headers.major_linker_version,
+                minor_linker_version: nt_headers.minor_linker_version,
+                size_of_code: U32::new(LE, self.code_len),
+                size_of_initialized_data: U32::new(LE, self.data_len),
+                size_of_uninitialized_data: U32::new(LE, self.bss_len),
+                address_of_entry_point: U32::new(LE, nt_headers.address_of_entry_point),
+                base_of_code: U32::new(LE, self.code_address),
+                image_base: U64::new(LE, nt_headers.image_base),
+                section_alignment: U32::new(LE, self.section_alignment),
+                file_alignment: U32::new(LE, self.file_alignment),
+                major_operating_system_version: U16::new(
+                    LE,
+                    nt_headers.major_operating_system_version,
+                ),
+                minor_operating_system_version: U16::new(
+                    LE,
+                    nt_headers.minor_operating_system_version,
+                ),
+                major_image_version: U16::new(LE, nt_headers.major_image_version),
+                minor_image_version: U16::new(LE, nt_headers.minor_image_version),
+                major_subsystem_version: U16::new(LE, nt_headers.major_subsystem_version),
+                minor_subsystem_version: U16::new(LE, nt_headers.minor_subsystem_version),
+                win32_version_value: U32::new(LE, 0),
+                size_of_image: U32::new(LE, self.virtual_len),
+                size_of_headers: U32::new(LE, self.headers_len),
+                check_sum: U32::new(LE, 0),
+                subsystem: U16::new(LE, nt_headers.subsystem),
+                dll_characteristics: U16::new(LE, nt_headers.dll_characteristics),
+                size_of_stack_reserve: U64::new(LE, nt_headers.size_of_stack_reserve),
+                size_of_stack_commit: U64::new(LE, nt_headers.size_of_stack_commit),
+                size_of_heap_reserve: U64::new(LE, nt_headers.size_of_heap_reserve),
+                size_of_heap_commit: U64::new(LE, nt_headers.size_of_heap_commit),
+                loader_flags: U32::new(LE, 0),
+                number_of_rva_and_sizes: U32::new(LE, self.data_directories.len() as u32),
+            };
+            self.buffer.write(&optional_header);
+        } else {
+            let optional_header = pe::ImageOptionalHeader32 {
+                magic: U16::new(LE, pe::IMAGE_NT_OPTIONAL_HDR32_MAGIC),
+                major_linker_version: nt_headers.major_linker_version,
+                minor_linker_version: nt_headers.minor_linker_version,
+                size_of_code: U32::new(LE, self.code_len),
+                size_of_initialized_data: U32::new(LE, self.data_len),
+                size_of_uninitialized_data: U32::new(LE, self.bss_len),
+                address_of_entry_point: U32::new(LE, nt_headers.address_of_entry_point),
+                base_of_code: U32::new(LE, self.code_address),
+                base_of_data: U32::new(LE, self.data_address),
+                image_base: U32::new(LE, nt_headers.image_base as u32),
+                section_alignment: U32::new(LE, self.section_alignment),
+                file_alignment: U32::new(LE, self.file_alignment),
+                major_operating_system_version: U16::new(
+                    LE,
+                    nt_headers.major_operating_system_version,
+                ),
+                minor_operating_system_version: U16::new(
+                    LE,
+                    nt_headers.minor_operating_system_version,
+                ),
+                major_image_version: U16::new(LE, nt_headers.major_image_version),
+                minor_image_version: U16::new(LE, nt_headers.minor_image_version),
+                major_subsystem_version: U16::new(LE, nt_headers.major_subsystem_version),
+                minor_subsystem_version: U16::new(LE, nt_headers.minor_subsystem_version),
+                win32_version_value: U32::new(LE, 0),
+                size_of_image: U32::new(LE, self.virtual_len),
+                size_of_headers: U32::new(LE, self.headers_len),
+                check_sum: U32::new(LE, 0),
+                subsystem: U16::new(LE, nt_headers.subsystem),
+                dll_characteristics: U16::new(LE, nt_headers.dll_characteristics),
+                size_of_stack_reserve: U32::new(LE, nt_headers.size_of_stack_reserve as u32),
+                size_of_stack_commit: U32::new(LE, nt_headers.size_of_stack_commit as u32),
+                size_of_heap_reserve: U32::new(LE, nt_headers.size_of_heap_reserve as u32),
+                size_of_heap_commit: U32::new(LE, nt_headers.size_of_heap_commit as u32),
+                loader_flags: U32::new(LE, 0),
+                number_of_rva_and_sizes: U32::new(LE, self.data_directories.len() as u32),
+            };
+            self.buffer.write(&optional_header);
+        }
+
+        for dir in &self.data_directories {
+            self.buffer.write(&pe::ImageDataDirectory {
+                virtual_address: U32::new(LE, dir.virtual_address),
+                size: U32::new(LE, dir.size),
+            })
+        }
+    }
+
+    /// Reserve the section headers.
+    ///
+    /// The number of reserved section headers must be the same as the number of sections that
+    /// are later reserved.
+    // TODO: change this to a maximum number of sections?
+    pub fn reserve_section_headers(&mut self, section_header_num: u16) {
+        debug_assert_eq!(self.section_header_num, 0);
+        self.section_header_num = section_header_num;
+        self.reserve(
+            u32::from(section_header_num) * mem::size_of::<pe::ImageSectionHeader>() as u32,
+            1,
+        );
+        // Padding before sections must be included in headers_len.
+        self.reserve_align(self.file_alignment);
+        self.headers_len = self.len;
+        self.reserve_virtual(self.len);
+    }
+
+    /// Write the section headers.
+    ///
+    /// This uses information that was recorded when the sections were reserved.
+    pub fn write_section_headers(&mut self) {
+        debug_assert_eq!(self.section_header_num as usize, self.sections.len());
+        for section in &self.sections {
+            let section_header = pe::ImageSectionHeader {
+                name: section.name,
+                virtual_size: U32::new(LE, section.range.virtual_size),
+                virtual_address: U32::new(LE, section.range.virtual_address),
+                size_of_raw_data: U32::new(LE, section.range.file_size),
+                pointer_to_raw_data: U32::new(LE, section.range.file_offset),
+                pointer_to_relocations: U32::new(LE, 0),
+                pointer_to_linenumbers: U32::new(LE, 0),
+                number_of_relocations: U16::new(LE, 0),
+                number_of_linenumbers: U16::new(LE, 0),
+                characteristics: U32::new(LE, section.characteristics),
+            };
+            self.buffer.write(&section_header);
+        }
+    }
+
+    /// Reserve a section.
+    ///
+    /// Returns the file range and virtual address range that are reserved
+    /// for the section.
+    pub fn reserve_section(
+        &mut self,
+        name: [u8; 8],
+        characteristics: u32,
+        virtual_size: u32,
+        data_size: u32,
+    ) -> SectionRange {
+        let virtual_address = self.reserve_virtual(virtual_size);
+
+        // Padding after section must be included in section file size.
+        let file_size = util::align_u32(data_size, self.file_alignment);
+        let file_offset = if file_size != 0 {
+            self.reserve(file_size, self.file_alignment)
+        } else {
+            0
+        };
+
+        // Sizes in optional header use the virtual size with the file alignment.
+        let aligned_virtual_size = util::align_u32(virtual_size, self.file_alignment);
+        if characteristics & pe::IMAGE_SCN_CNT_CODE != 0 {
+            if self.code_address == 0 {
+                self.code_address = virtual_address;
+            }
+            self.code_len += aligned_virtual_size;
+        } else if characteristics & pe::IMAGE_SCN_CNT_INITIALIZED_DATA != 0 {
+            if self.data_address == 0 {
+                self.data_address = virtual_address;
+            }
+            self.data_len += aligned_virtual_size;
+        } else if characteristics & pe::IMAGE_SCN_CNT_UNINITIALIZED_DATA != 0 {
+            if self.data_address == 0 {
+                self.data_address = virtual_address;
+            }
+            self.bss_len += aligned_virtual_size;
+        }
+
+        let range = SectionRange {
+            virtual_address,
+            virtual_size,
+            file_offset,
+            file_size,
+        };
+        self.sections.push(Section {
+            name,
+            characteristics,
+            range,
+        });
+        range
+    }
+
+    /// Write the data for a section.
+    pub fn write_section(&mut self, offset: u32, data: &[u8]) {
+        if data.is_empty() {
+            return;
+        }
+        self.pad_until(offset);
+        self.write(data);
+        self.write_align(self.file_alignment);
+    }
+
+    /// Reserve a `.text` section.
+    ///
+    /// Contains executable code.
+    pub fn reserve_text_section(&mut self, size: u32) -> SectionRange {
+        self.reserve_section(
+            *b".text\0\0\0",
+            pe::IMAGE_SCN_CNT_CODE | pe::IMAGE_SCN_MEM_EXECUTE | pe::IMAGE_SCN_MEM_READ,
+            size,
+            size,
+        )
+    }
+
+    /// Reserve a `.data` section.
+    ///
+    /// Contains initialized data.
+    ///
+    /// May also contain uninitialized data if `virtual_size` is greater than `data_size`.
+    pub fn reserve_data_section(&mut self, virtual_size: u32, data_size: u32) -> SectionRange {
+        self.reserve_section(
+            *b".data\0\0\0",
+            pe::IMAGE_SCN_CNT_INITIALIZED_DATA | pe::IMAGE_SCN_MEM_READ | pe::IMAGE_SCN_MEM_WRITE,
+            virtual_size,
+            data_size,
+        )
+    }
+
+    /// Reserve a `.rdata` section.
+    ///
+    /// Contains read-only initialized data.
+    pub fn reserve_rdata_section(&mut self, size: u32) -> SectionRange {
+        self.reserve_section(
+            *b".rdata\0\0",
+            pe::IMAGE_SCN_CNT_INITIALIZED_DATA | pe::IMAGE_SCN_MEM_READ,
+            size,
+            size,
+        )
+    }
+
+    /// Reserve a `.bss` section.
+    ///
+    /// Contains uninitialized data.
+    pub fn reserve_bss_section(&mut self, size: u32) -> SectionRange {
+        self.reserve_section(
+            *b".bss\0\0\0\0",
+            pe::IMAGE_SCN_CNT_UNINITIALIZED_DATA | pe::IMAGE_SCN_MEM_READ | pe::IMAGE_SCN_MEM_WRITE,
+            size,
+            0,
+        )
+    }
+
+    /// Reserve an `.idata` section.
+    ///
+    /// Contains import tables. Note that it is permissible to store import tables in a different
+    /// section.
+    ///
+    /// This also sets the `pe::IMAGE_DIRECTORY_ENTRY_IMPORT` data directory.
+    pub fn reserve_idata_section(&mut self, size: u32) -> SectionRange {
+        let range = self.reserve_section(
+            *b".idata\0\0",
+            pe::IMAGE_SCN_CNT_INITIALIZED_DATA | pe::IMAGE_SCN_MEM_READ | pe::IMAGE_SCN_MEM_WRITE,
+            size,
+            size,
+        );
+        let dir = &mut self.data_directories[pe::IMAGE_DIRECTORY_ENTRY_IMPORT];
+        debug_assert_eq!(dir.virtual_address, 0);
+        *dir = DataDirectory {
+            virtual_address: range.virtual_address,
+            size,
+        };
+        range
+    }
+
+    /// Reserve an `.edata` section.
+    ///
+    /// Contains export tables.
+    ///
+    /// This also sets the `pe::IMAGE_DIRECTORY_ENTRY_EXPORT` data directory.
+    pub fn reserve_edata_section(&mut self, size: u32) -> SectionRange {
+        let range = self.reserve_section(
+            *b".edata\0\0",
+            pe::IMAGE_SCN_CNT_INITIALIZED_DATA | pe::IMAGE_SCN_MEM_READ,
+            size,
+            size,
+        );
+        let dir = &mut self.data_directories[pe::IMAGE_DIRECTORY_ENTRY_EXPORT];
+        debug_assert_eq!(dir.virtual_address, 0);
+        *dir = DataDirectory {
+            virtual_address: range.virtual_address,
+            size,
+        };
+        range
+    }
+
+    /// Reserve a `.pdata` section.
+    ///
+    /// Contains exception information.
+    ///
+    /// This also sets the `pe::IMAGE_DIRECTORY_ENTRY_EXCEPTION` data directory.
+    pub fn reserve_pdata_section(&mut self, size: u32) -> SectionRange {
+        let range = self.reserve_section(
+            *b".pdata\0\0",
+            pe::IMAGE_SCN_CNT_INITIALIZED_DATA | pe::IMAGE_SCN_MEM_READ,
+            size,
+            size,
+        );
+        let dir = &mut self.data_directories[pe::IMAGE_DIRECTORY_ENTRY_EXCEPTION];
+        debug_assert_eq!(dir.virtual_address, 0);
+        *dir = DataDirectory {
+            virtual_address: range.virtual_address,
+            size,
+        };
+        range
+    }
+
+    /// Reserve a `.xdata` section.
+    ///
+    /// Contains exception information.
+    pub fn reserve_xdata_section(&mut self, size: u32) -> SectionRange {
+        self.reserve_section(
+            *b".xdata\0\0",
+            pe::IMAGE_SCN_CNT_INITIALIZED_DATA | pe::IMAGE_SCN_MEM_READ,
+            size,
+            size,
+        )
+    }
+
+    /// Reserve a `.rsrc` section.
+    ///
+    /// Contains the resource directory.
+    ///
+    /// This also sets the `pe::IMAGE_DIRECTORY_ENTRY_RESOURCE` data directory.
+    pub fn reserve_rsrc_section(&mut self, size: u32) -> SectionRange {
+        let range = self.reserve_section(
+            *b".rsrc\0\0\0",
+            pe::IMAGE_SCN_CNT_INITIALIZED_DATA | pe::IMAGE_SCN_MEM_READ,
+            size,
+            size,
+        );
+        let dir = &mut self.data_directories[pe::IMAGE_DIRECTORY_ENTRY_RESOURCE];
+        debug_assert_eq!(dir.virtual_address, 0);
+        *dir = DataDirectory {
+            virtual_address: range.virtual_address,
+            size,
+        };
+        range
+    }
+
+    /// Add a base relocation.
+    ///
+    /// `typ` must be one of the `IMAGE_REL_BASED_*` constants.
+    pub fn add_reloc(&mut self, mut virtual_address: u32, typ: u16) {
+        let reloc = U16::new(LE, typ << 12 | (virtual_address & 0xfff) as u16);
+        virtual_address &= !0xfff;
+        if let Some(block) = self.reloc_blocks.last_mut() {
+            if block.virtual_address == virtual_address {
+                self.relocs.push(reloc);
+                block.count += 1;
+                return;
+            }
+            // Blocks must have an even number of relocations.
+            if block.count & 1 != 0 {
+                self.relocs.push(U16::new(LE, 0));
+                block.count += 1;
+            }
+            debug_assert!(block.virtual_address < virtual_address);
+        }
+        self.relocs.push(reloc);
+        self.reloc_blocks.push(RelocBlock {
+            virtual_address,
+            count: 1,
+        });
+    }
+
+    /// Return true if a base relocation has been added.
+    pub fn has_relocs(&mut self) -> bool {
+        !self.relocs.is_empty()
+    }
+
+    /// Reserve a `.reloc` section.
+    ///
+    /// This contains the base relocations that were added with `add_reloc`.
+    ///
+    /// This also sets the `pe::IMAGE_DIRECTORY_ENTRY_BASERELOC` data directory.
+    pub fn reserve_reloc_section(&mut self) -> SectionRange {
+        if let Some(block) = self.reloc_blocks.last_mut() {
+            // Blocks must have an even number of relocations.
+            if block.count & 1 != 0 {
+                self.relocs.push(U16::new(LE, 0));
+                block.count += 1;
+            }
+        }
+        let size = self.reloc_blocks.iter().map(RelocBlock::size).sum();
+        let range = self.reserve_section(
+            *b".reloc\0\0",
+            pe::IMAGE_SCN_CNT_INITIALIZED_DATA
+                | pe::IMAGE_SCN_MEM_READ
+                | pe::IMAGE_SCN_MEM_DISCARDABLE,
+            size,
+            size,
+        );
+        let dir = &mut self.data_directories[pe::IMAGE_DIRECTORY_ENTRY_BASERELOC];
+        debug_assert_eq!(dir.virtual_address, 0);
+        *dir = DataDirectory {
+            virtual_address: range.virtual_address,
+            size,
+        };
+        self.reloc_offset = range.file_offset;
+        range
+    }
+
+    /// Write a `.reloc` section.
+    ///
+    /// This contains the base relocations that were added with `add_reloc`.
+    pub fn write_reloc_section(&mut self) {
+        if self.reloc_offset == 0 {
+            return;
+        }
+        self.pad_until(self.reloc_offset);
+
+        let mut total = 0;
+        for block in &self.reloc_blocks {
+            self.buffer.write(&pe::ImageBaseRelocation {
+                virtual_address: U32::new(LE, block.virtual_address),
+                size_of_block: U32::new(LE, block.size()),
+            });
+            self.buffer
+                .write_slice(&self.relocs[total..][..block.count as usize]);
+            total += block.count as usize;
+        }
+        debug_assert_eq!(total, self.relocs.len());
+
+        self.write_align(self.file_alignment);
+    }
+
+    /// Reserve the certificate table.
+    ///
+    /// This also sets the `pe::IMAGE_DIRECTORY_ENTRY_SECURITY` data directory.
+    // TODO: reserve individual certificates
+    pub fn reserve_certificate_table(&mut self, size: u32) {
+        let size = util::align_u32(size, 8);
+        let offset = self.reserve(size, 8);
+        let dir = &mut self.data_directories[pe::IMAGE_DIRECTORY_ENTRY_SECURITY];
+        debug_assert_eq!(dir.virtual_address, 0);
+        *dir = DataDirectory {
+            virtual_address: offset,
+            size,
+        };
+    }
+
+    /// Write the certificate table.
+    // TODO: write individual certificates
+    pub fn write_certificate_table(&mut self, data: &[u8]) {
+        let dir = self.data_directories[pe::IMAGE_DIRECTORY_ENTRY_SECURITY];
+        self.pad_until(dir.virtual_address);
+        self.write(data);
+        self.pad_until(dir.virtual_address + dir.size);
+    }
+}
+
+/// Information required for writing [`pe::ImageNtHeaders32`] or [`pe::ImageNtHeaders64`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct NtHeaders {
+    // ImageFileHeader
+    pub machine: u16,
+    pub time_date_stamp: u32,
+    pub characteristics: u16,
+    // ImageOptionalHeader
+    pub major_linker_version: u8,
+    pub minor_linker_version: u8,
+    pub address_of_entry_point: u32,
+    pub image_base: u64,
+    pub major_operating_system_version: u16,
+    pub minor_operating_system_version: u16,
+    pub major_image_version: u16,
+    pub minor_image_version: u16,
+    pub major_subsystem_version: u16,
+    pub minor_subsystem_version: u16,
+    pub subsystem: u16,
+    pub dll_characteristics: u16,
+    pub size_of_stack_reserve: u64,
+    pub size_of_stack_commit: u64,
+    pub size_of_heap_reserve: u64,
+    pub size_of_heap_commit: u64,
+}
+
+#[derive(Default, Clone, Copy)]
+struct DataDirectory {
+    virtual_address: u32,
+    size: u32,
+}
+
+/// Information required for writing [`pe::ImageSectionHeader`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct Section {
+    pub name: [u8; pe::IMAGE_SIZEOF_SHORT_NAME],
+    pub characteristics: u32,
+    pub range: SectionRange,
+}
+
+/// The file range and virtual address range for a section.
+#[allow(missing_docs)]
+#[derive(Debug, Default, Clone, Copy)]
+pub struct SectionRange {
+    pub virtual_address: u32,
+    pub virtual_size: u32,
+    pub file_offset: u32,
+    pub file_size: u32,
+}
+
+struct RelocBlock {
+    virtual_address: u32,
+    count: u32,
+}
+
+impl RelocBlock {
+    fn size(&self) -> u32 {
+        mem::size_of::<pe::ImageBaseRelocation>() as u32 + self.count * mem::size_of::<u16>() as u32
+    }
+}

vendor/object/src/write/string.rs

@@ -0,0 +1,186 @@
+use alloc::vec::Vec;
+
+#[cfg(feature = "write_std")]
+type IndexSet<K> = indexmap::IndexSet<K>;
+#[cfg(not(feature = "write_std"))]
+type IndexSet<K> = indexmap::IndexSet<K, hashbrown::DefaultHashBuilder>;
+
+/// An identifier for an entry in a string table.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct StringId(usize);
+
+#[derive(Debug, Default)]
+pub(crate) struct StringTable<'a> {
+    strings: IndexSet<&'a [u8]>,
+    offsets: Vec<usize>,
+}
+
+impl<'a> StringTable<'a> {
+    /// Add a string to the string table.
+    ///
+    /// Panics if the string table has already been written, or
+    /// if the string contains a null byte.
+    pub fn add(&mut self, string: &'a [u8]) -> StringId {
+        assert!(self.offsets.is_empty());
+        assert!(!string.contains(&0));
+        let id = self.strings.insert_full(string).0;
+        StringId(id)
+    }
+
+    /// Return the id of the given string.
+    ///
+    /// Panics if the string is not in the string table.
+    #[allow(dead_code)]
+    pub fn get_id(&self, string: &[u8]) -> StringId {
+        let id = self.strings.get_index_of(string).unwrap();
+        StringId(id)
+    }
+
+    /// Return the string for the given id.
+    ///
+    /// Panics if the string is not in the string table.
+    #[allow(dead_code)]
+    pub fn get_string(&self, id: StringId) -> &'a [u8] {
+        self.strings.get_index(id.0).unwrap()
+    }
+
+    /// Return the offset of the given string.
+    ///
+    /// Panics if the string table has not been written, or
+    /// if the string is not in the string table.
+    pub fn get_offset(&self, id: StringId) -> usize {
+        self.offsets[id.0]
+    }
+
+    /// Append the string table to the given `Vec`, and
+    /// calculate the list of string offsets.
+    ///
+    /// `base` is the initial string table offset. For example,
+    /// this should be 1 for ELF, to account for the initial
+    /// null byte (which must have been written by the caller).
+    ///
+    /// Panics if the string table has already been written.
+    pub fn write(&mut self, base: usize, w: &mut Vec<u8>) {
+        assert!(self.offsets.is_empty());
+
+        let mut ids: Vec<_> = (0..self.strings.len()).collect();
+        sort(&mut ids, 1, &self.strings);
+
+        self.offsets = vec![0; ids.len()];
+        let mut offset = base;
+        let mut previous = &[][..];
+        for id in ids {
+            let string = self.strings.get_index(id).unwrap();
+            if previous.ends_with(string) {
+                self.offsets[id] = offset - string.len() - 1;
+            } else {
+                self.offsets[id] = offset;
+                w.extend_from_slice(string);
+                w.push(0);
+                offset += string.len() + 1;
+                previous = string;
+            }
+        }
+    }
+
+    /// Calculate the size in bytes of the string table.
+    ///
+    /// `base` is the initial string table offset. For example,
+    /// this should be 1 for ELF, to account for the initial
+    /// null byte.
+    #[allow(dead_code)]
+    pub fn size(&self, base: usize) -> usize {
+        // TODO: cache this result?
+        let mut ids: Vec<_> = (0..self.strings.len()).collect();
+        sort(&mut ids, 1, &self.strings);
+
+        let mut size = base;
+        let mut previous = &[][..];
+        for id in ids {
+            let string = self.strings.get_index(id).unwrap();
+            if !previous.ends_with(string) {
+                size += string.len() + 1;
+                previous = string;
+            }
+        }
+        size
+    }
+}
+
+// Multi-key quicksort.
+//
+// Ordering is such that if a string is a suffix of at least one other string,
+// then it is placed immediately after one of those strings. That is:
+// - comparison starts at the end of the string
+// - shorter strings come later
+//
+// Based on the implementation in LLVM.
+fn sort(mut ids: &mut [usize], mut pos: usize, strings: &IndexSet<&[u8]>) {
+    loop {
+        if ids.len() <= 1 {
+            return;
+        }
+
+        let pivot = byte(ids[0], pos, strings);
+        let mut lower = 0;
+        let mut upper = ids.len();
+        let mut i = 1;
+        while i < upper {
+            let b = byte(ids[i], pos, strings);
+            if b > pivot {
+                ids.swap(lower, i);
+                lower += 1;
+                i += 1;
+            } else if b < pivot {
+                upper -= 1;
+                ids.swap(upper, i);
+            } else {
+                i += 1;
+            }
+        }
+
+        sort(&mut ids[..lower], pos, strings);
+        sort(&mut ids[upper..], pos, strings);
+
+        if pivot == 0 {
+            return;
+        }
+        ids = &mut ids[lower..upper];
+        pos += 1;
+    }
+}
+
+fn byte(id: usize, pos: usize, strings: &IndexSet<&[u8]>) -> u8 {
+    let string = strings.get_index(id).unwrap();
+    let len = string.len();
+    if len >= pos {
+        string[len - pos]
+    } else {
+        // We know the strings don't contain null bytes.
+        0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn string_table() {
+        let mut table = StringTable::default();
+        let id0 = table.add(b"");
+        let id1 = table.add(b"foo");
+        let id2 = table.add(b"bar");
+        let id3 = table.add(b"foobar");
+
+        let mut data = Vec::new();
+        data.push(0);
+        table.write(1, &mut data);
+        assert_eq!(data, b"\0foobar\0foo\0");
+
+        assert_eq!(table.get_offset(id0), 11);
+        assert_eq!(table.get_offset(id1), 8);
+        assert_eq!(table.get_offset(id2), 4);
+        assert_eq!(table.get_offset(id3), 1);
+    }
+}

vendor/object/src/write/util.rs

@@ -0,0 +1,261 @@
+use alloc::vec::Vec;
+#[cfg(feature = "std")]
+use std::{io, mem};
+
+use crate::pod::{bytes_of, bytes_of_slice, Pod};
+
+/// Trait for writable buffer.
+#[allow(clippy::len_without_is_empty)]
+pub trait WritableBuffer {
+    /// Returns position/offset for data to be written at.
+    ///
+    /// Should only be used in debug assertions
+    fn len(&self) -> usize;
+
+    /// Reserves specified number of bytes in the buffer.
+    ///
+    /// This will be called exactly once before writing anything to the buffer,
+    /// and the given size is the exact total number of bytes that will be written.
+    fn reserve(&mut self, size: usize) -> Result<(), ()>;
+
+    /// Writes zero bytes at the end of the buffer until the buffer
+    /// has the specified length.
+    fn resize(&mut self, new_len: usize);
+
+    /// Writes the specified slice of bytes at the end of the buffer.
+    fn write_bytes(&mut self, val: &[u8]);
+
+    /// Writes the specified `Pod` type at the end of the buffer.
+    fn write_pod<T: Pod>(&mut self, val: &T)
+    where
+        Self: Sized,
+    {
+        self.write_bytes(bytes_of(val))
+    }
+
+    /// Writes the specified `Pod` slice at the end of the buffer.
+    fn write_pod_slice<T: Pod>(&mut self, val: &[T])
+    where
+        Self: Sized,
+    {
+        self.write_bytes(bytes_of_slice(val))
+    }
+}
+
+impl<'a> dyn WritableBuffer + 'a {
+    /// Writes the specified `Pod` type at the end of the buffer.
+    pub fn write<T: Pod>(&mut self, val: &T) {
+        self.write_bytes(bytes_of(val))
+    }
+
+    /// Writes the specified `Pod` slice at the end of the buffer.
+    pub fn write_slice<T: Pod>(&mut self, val: &[T]) {
+        self.write_bytes(bytes_of_slice(val))
+    }
+}
+
+impl WritableBuffer for Vec<u8> {
+    #[inline]
+    fn len(&self) -> usize {
+        self.len()
+    }
+
+    #[inline]
+    fn reserve(&mut self, size: usize) -> Result<(), ()> {
+        debug_assert!(self.is_empty());
+        self.reserve(size);
+        Ok(())
+    }
+
+    #[inline]
+    fn resize(&mut self, new_len: usize) {
+        debug_assert!(new_len >= self.len());
+        self.resize(new_len, 0);
+    }
+
+    #[inline]
+    fn write_bytes(&mut self, val: &[u8]) {
+        debug_assert!(self.len() + val.len() <= self.capacity());
+        self.extend_from_slice(val)
+    }
+}
+
+/// A [`WritableBuffer`] that streams data to a [`Write`](std::io::Write) implementation.
+///
+/// [`Self::result`] must be called to determine if an I/O error occurred during writing.
+///
+/// It is advisable to use a buffered writer like [`BufWriter`](std::io::BufWriter)
+/// instead of an unbuffered writer like [`File`](std::fs::File).
+#[cfg(feature = "std")]
+#[derive(Debug)]
+pub struct StreamingBuffer<W> {
+    writer: W,
+    len: usize,
+    result: Result<(), io::Error>,
+}
+
+#[cfg(feature = "std")]
+impl<W> StreamingBuffer<W> {
+    /// Create a new `StreamingBuffer` backed by the given writer.
+    pub fn new(writer: W) -> Self {
+        StreamingBuffer {
+            writer,
+            len: 0,
+            result: Ok(()),
+        }
+    }
+
+    /// Unwraps this [`StreamingBuffer`] giving back the original writer.
+    pub fn into_inner(self) -> W {
+        self.writer
+    }
+
+    /// Returns any error that occurred during writing.
+    pub fn result(&mut self) -> Result<(), io::Error> {
+        mem::replace(&mut self.result, Ok(()))
+    }
+}
+
+#[cfg(feature = "std")]
+impl<W: io::Write> WritableBuffer for StreamingBuffer<W> {
+    #[inline]
+    fn len(&self) -> usize {
+        self.len
+    }
+
+    #[inline]
+    fn reserve(&mut self, _size: usize) -> Result<(), ()> {
+        Ok(())
+    }
+
+    #[inline]
+    fn resize(&mut self, new_len: usize) {
+        debug_assert!(self.len <= new_len);
+        while self.len < new_len {
+            let write_amt = (new_len - self.len - 1) % 1024 + 1;
+            self.write_bytes(&[0; 1024][..write_amt]);
+        }
+    }
+
+    #[inline]
+    fn write_bytes(&mut self, val: &[u8]) {
+        if self.result.is_ok() {
+            self.result = self.writer.write_all(val);
+        }
+        self.len += val.len();
+    }
+}
+
+/// A trait for mutable byte slices.
+///
+/// It provides convenience methods for `Pod` types.
+pub(crate) trait BytesMut {
+    fn write_at<T: Pod>(self, offset: usize, val: &T) -> Result<(), ()>;
+}
+
+impl<'a> BytesMut for &'a mut [u8] {
+    #[inline]
+    fn write_at<T: Pod>(self, offset: usize, val: &T) -> Result<(), ()> {
+        let src = bytes_of(val);
+        let dest = self.get_mut(offset..).ok_or(())?;
+        let dest = dest.get_mut(..src.len()).ok_or(())?;
+        dest.copy_from_slice(src);
+        Ok(())
+    }
+}
+
+/// Write an unsigned number using the LEB128 encoding to a buffer.
+///
+/// Returns the number of bytes written.
+#[allow(dead_code)]
+pub(crate) fn write_uleb128(buf: &mut Vec<u8>, mut val: u64) -> usize {
+    let mut len = 0;
+    loop {
+        let mut byte = (val & 0x7f) as u8;
+        val >>= 7;
+        let done = val == 0;
+        if !done {
+            byte |= 0x80;
+        }
+
+        buf.push(byte);
+        len += 1;
+
+        if done {
+            return len;
+        }
+    }
+}
+
+/// Write a signed number using the LEB128 encoding to a buffer.
+///
+/// Returns the number of bytes written.
+#[allow(dead_code)]
+pub(crate) fn write_sleb128(buf: &mut Vec<u8>, mut val: i64) -> usize {
+    let mut len = 0;
+    loop {
+        let mut byte = val as u8;
+        // Keep the sign bit for testing
+        val >>= 6;
+        let done = val == 0 || val == -1;
+        if done {
+            byte &= !0x80;
+        } else {
+            // Remove the sign bit
+            val >>= 1;
+            byte |= 0x80;
+        }
+
+        buf.push(byte);
+        len += 1;
+
+        if done {
+            return len;
+        }
+    }
+}
+
+pub(crate) fn align(offset: usize, size: usize) -> usize {
+    (offset + (size - 1)) & !(size - 1)
+}
+
+#[allow(dead_code)]
+pub(crate) fn align_u32(offset: u32, size: u32) -> u32 {
+    (offset + (size - 1)) & !(size - 1)
+}
+
+#[allow(dead_code)]
+pub(crate) fn align_u64(offset: u64, size: u64) -> u64 {
+    (offset + (size - 1)) & !(size - 1)
+}
+
+pub(crate) fn write_align(buffer: &mut dyn WritableBuffer, size: usize) {
+    let new_len = align(buffer.len(), size);
+    buffer.resize(new_len);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn bytes_mut() {
+        let data = vec![0x01, 0x23, 0x45, 0x67];
+
+        let mut bytes = data.clone();
+        bytes.extend_from_slice(bytes_of(&u16::to_be(0x89ab)));
+        assert_eq!(bytes, [0x01, 0x23, 0x45, 0x67, 0x89, 0xab]);
+
+        let mut bytes = data.clone();
+        assert_eq!(bytes.write_at(0, &u16::to_be(0x89ab)), Ok(()));
+        assert_eq!(bytes, [0x89, 0xab, 0x45, 0x67]);
+
+        let mut bytes = data.clone();
+        assert_eq!(bytes.write_at(2, &u16::to_be(0x89ab)), Ok(()));
+        assert_eq!(bytes, [0x01, 0x23, 0x89, 0xab]);
+
+        assert_eq!(bytes.write_at(3, &u16::to_be(0x89ab)), Err(()));
+        assert_eq!(bytes.write_at(4, &u16::to_be(0x89ab)), Err(()));
+        assert_eq!([].write_at(0, &u32::to_be(0x89ab)), Err(()));
+    }
+}

vendor/object/src/write/xcoff.rs

@@ -0,0 +1,588 @@
+use core::mem;
+
+use crate::endian::{BigEndian as BE, I16, U16, U32};
+use crate::write::string::*;
+use crate::write::util::*;
+use crate::write::*;
+
+use crate::xcoff;
+
+#[derive(Default, Clone, Copy)]
+struct SectionOffsets {
+    address: u64,
+    data_offset: usize,
+    reloc_offset: usize,
+}
+
+#[derive(Default, Clone, Copy)]
+struct SymbolOffsets {
+    index: usize,
+    str_id: Option<StringId>,
+    aux_count: u8,
+    storage_class: u8,
+}
+
+impl<'a> Object<'a> {
+    pub(crate) fn xcoff_section_info(
+        &self,
+        section: StandardSection,
+    ) -> (&'static [u8], &'static [u8], SectionKind, SectionFlags) {
+        match section {
+            StandardSection::Text => (&[], &b".text"[..], SectionKind::Text, SectionFlags::None),
+            StandardSection::Data => (&[], &b".data"[..], SectionKind::Data, SectionFlags::None),
+            StandardSection::ReadOnlyData
+            | StandardSection::ReadOnlyDataWithRel
+            | StandardSection::ReadOnlyString => (
+                &[],
+                &b".rdata"[..],
+                SectionKind::ReadOnlyData,
+                SectionFlags::None,
+            ),
+            StandardSection::UninitializedData => (
+                &[],
+                &b".bss"[..],
+                SectionKind::UninitializedData,
+                SectionFlags::None,
+            ),
+            StandardSection::Tls => (&[], &b".tdata"[..], SectionKind::Tls, SectionFlags::None),
+            StandardSection::UninitializedTls => (
+                &[],
+                &b".tbss"[..],
+                SectionKind::UninitializedTls,
+                SectionFlags::None,
+            ),
+            StandardSection::TlsVariables => {
+                // Unsupported section.
+                (&[], &[], SectionKind::TlsVariables, SectionFlags::None)
+            }
+            StandardSection::Common => {
+                // Unsupported section.
+                (&[], &[], SectionKind::Common, SectionFlags::None)
+            }
+            StandardSection::GnuProperty => {
+                // Unsupported section.
+                (&[], &[], SectionKind::Note, SectionFlags::None)
+            }
+        }
+    }
+
+    pub(crate) fn xcoff_translate_relocation(&mut self, reloc: &mut Relocation) -> Result<()> {
+        let (kind, _encoding, size) = if let RelocationFlags::Generic {
+            kind,
+            encoding,
+            size,
+        } = reloc.flags
+        {
+            (kind, encoding, size)
+        } else {
+            return Ok(());
+        };
+
+        let r_rtype = match kind {
+            RelocationKind::Absolute => xcoff::R_POS,
+            RelocationKind::Relative => xcoff::R_REL,
+            RelocationKind::Got => xcoff::R_TOC,
+            _ => {
+                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+            }
+        };
+        let r_rsize = size - 1;
+        reloc.flags = RelocationFlags::Xcoff { r_rtype, r_rsize };
+        Ok(())
+    }
+
+    pub(crate) fn xcoff_adjust_addend(&mut self, relocation: &mut Relocation) -> Result<bool> {
+        let r_rtype = if let RelocationFlags::Xcoff { r_rtype, .. } = relocation.flags {
+            r_rtype
+        } else {
+            return Err(Error(format!("invalid relocation flags {:?}", relocation)));
+        };
+        if r_rtype == xcoff::R_REL {
+            relocation.addend += 4;
+        }
+        Ok(true)
+    }
+
+    pub(crate) fn xcoff_relocation_size(&self, reloc: &Relocation) -> Result<u8> {
+        let r_rsize = if let RelocationFlags::Xcoff { r_rsize, .. } = reloc.flags {
+            r_rsize
+        } else {
+            return Err(Error(format!("unexpected relocation {:?}", reloc)));
+        };
+        Ok(r_rsize + 1)
+    }
+
+    pub(crate) fn xcoff_write(&self, buffer: &mut dyn WritableBuffer) -> Result<()> {
+        let is_64 = match self.architecture.address_size().unwrap() {
+            AddressSize::U8 | AddressSize::U16 | AddressSize::U32 => false,
+            AddressSize::U64 => true,
+        };
+
+        let (hdr_size, sechdr_size, rel_size, sym_size) = if is_64 {
+            (
+                mem::size_of::<xcoff::FileHeader64>(),
+                mem::size_of::<xcoff::SectionHeader64>(),
+                mem::size_of::<xcoff::Rel64>(),
+                mem::size_of::<xcoff::Symbol64>(),
+            )
+        } else {
+            (
+                mem::size_of::<xcoff::FileHeader32>(),
+                mem::size_of::<xcoff::SectionHeader32>(),
+                mem::size_of::<xcoff::Rel32>(),
+                mem::size_of::<xcoff::Symbol32>(),
+            )
+        };
+
+        // Calculate offsets and build strtab.
+        let mut offset = 0;
+        let mut strtab = StringTable::default();
+        // We place the shared address 0 immediately after the section header table.
+        let mut address = 0;
+
+        // XCOFF file header.
+        offset += hdr_size;
+        // Section headers.
+        offset += self.sections.len() * sechdr_size;
+
+        // Calculate size of section data.
+        let mut section_offsets = vec![SectionOffsets::default(); self.sections.len()];
+        for (index, section) in self.sections.iter().enumerate() {
+            let len = section.data.len();
+            let sectype = section.kind;
+            // Section address should be 0 for all sections except the .text, .data, and .bss sections.
+            if sectype == SectionKind::Data
+                || sectype == SectionKind::Text
+                || sectype == SectionKind::UninitializedData
+            {
+                section_offsets[index].address = address as u64;
+                address += len;
+                address = align(address, 4);
+            } else {
+                section_offsets[index].address = 0;
+            }
+            if len != 0 {
+                // Set the default section alignment as 4.
+                offset = align(offset, 4);
+                section_offsets[index].data_offset = offset;
+                offset += len;
+            } else {
+                section_offsets[index].data_offset = 0;
+            }
+        }
+
+        // Calculate size of relocations.
+        for (index, section) in self.sections.iter().enumerate() {
+            let count = section.relocations.len();
+            if count != 0 {
+                section_offsets[index].reloc_offset = offset;
+                offset += count * rel_size;
+            } else {
+                section_offsets[index].reloc_offset = 0;
+            }
+        }
+
+        // Calculate size of symbols.
+        let mut file_str_id = None;
+        let mut symbol_offsets = vec![SymbolOffsets::default(); self.symbols.len()];
+        let mut symtab_count = 0;
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            symbol_offsets[index].index = symtab_count;
+            symtab_count += 1;
+
+            let storage_class = if let SymbolFlags::Xcoff { n_sclass, .. } = symbol.flags {
+                n_sclass
+            } else {
+                match symbol.kind {
+                    SymbolKind::File => xcoff::C_FILE,
+                    SymbolKind::Text | SymbolKind::Data | SymbolKind::Tls => {
+                        if symbol.is_local() {
+                            xcoff::C_STAT
+                        } else if symbol.weak {
+                            xcoff::C_WEAKEXT
+                        } else {
+                            xcoff::C_EXT
+                        }
+                    }
+                    SymbolKind::Section | SymbolKind::Label | SymbolKind::Unknown => {
+                        return Err(Error(format!(
+                            "unimplemented symbol `{}` kind {:?}",
+                            symbol.name().unwrap_or(""),
+                            symbol.kind
+                        )));
+                    }
+                }
+            };
+            symbol_offsets[index].storage_class = storage_class;
+
+            if storage_class == xcoff::C_FILE {
+                if is_64 && file_str_id.is_none() {
+                    file_str_id = Some(strtab.add(b".file"));
+                }
+                if symbol.name.len() > 8 {
+                    symbol_offsets[index].str_id = Some(strtab.add(&symbol.name));
+                }
+            } else if is_64 || symbol.name.len() > 8 {
+                symbol_offsets[index].str_id = Some(strtab.add(&symbol.name));
+            }
+
+            symbol_offsets[index].aux_count = 0;
+            match storage_class {
+                xcoff::C_FILE => {
+                    symbol_offsets[index].aux_count = 1;
+                    symtab_count += 1;
+                }
+                xcoff::C_EXT | xcoff::C_WEAKEXT | xcoff::C_HIDEXT => {
+                    symbol_offsets[index].aux_count = 1;
+                    symtab_count += 1;
+                }
+                // TODO: support auxiliary entry for other types of symbol.
+                _ => {}
+            }
+        }
+        let symtab_offset = offset;
+        let symtab_len = symtab_count * sym_size;
+        offset += symtab_len;
+
+        // Calculate size of strtab.
+        let strtab_offset = offset;
+        let mut strtab_data = Vec::new();
+        // First 4 bytes of strtab are the length.
+        strtab.write(4, &mut strtab_data);
+        let strtab_len = strtab_data.len() + 4;
+        offset += strtab_len;
+
+        // Start writing.
+        buffer
+            .reserve(offset)
+            .map_err(|_| Error(String::from("Cannot allocate buffer")))?;
+
+        // Write file header.
+        if is_64 {
+            let header = xcoff::FileHeader64 {
+                f_magic: U16::new(BE, xcoff::MAGIC_64),
+                f_nscns: U16::new(BE, self.sections.len() as u16),
+                f_timdat: U32::new(BE, 0),
+                f_symptr: U64::new(BE, symtab_offset as u64),
+                f_nsyms: U32::new(BE, symtab_count as u32),
+                f_opthdr: U16::new(BE, 0),
+                f_flags: match self.flags {
+                    FileFlags::Xcoff { f_flags } => U16::new(BE, f_flags),
+                    _ => U16::default(),
+                },
+            };
+            buffer.write(&header);
+        } else {
+            let header = xcoff::FileHeader32 {
+                f_magic: U16::new(BE, xcoff::MAGIC_32),
+                f_nscns: U16::new(BE, self.sections.len() as u16),
+                f_timdat: U32::new(BE, 0),
+                f_symptr: U32::new(BE, symtab_offset as u32),
+                f_nsyms: U32::new(BE, symtab_count as u32),
+                f_opthdr: U16::new(BE, 0),
+                f_flags: match self.flags {
+                    FileFlags::Xcoff { f_flags } => U16::new(BE, f_flags),
+                    _ => U16::default(),
+                },
+            };
+            buffer.write(&header);
+        }
+
+        // Write section headers.
+        for (index, section) in self.sections.iter().enumerate() {
+            let mut sectname = [0; 8];
+            sectname
+                .get_mut(..section.name.len())
+                .ok_or_else(|| {
+                    Error(format!(
+                        "section name `{}` is too long",
+                        section.name().unwrap_or(""),
+                    ))
+                })?
+                .copy_from_slice(&section.name);
+            let flags = if let SectionFlags::Xcoff { s_flags } = section.flags {
+                s_flags
+            } else {
+                match section.kind {
+                    SectionKind::Text
+                    | SectionKind::ReadOnlyData
+                    | SectionKind::ReadOnlyString
+                    | SectionKind::ReadOnlyDataWithRel => xcoff::STYP_TEXT,
+                    SectionKind::Data => xcoff::STYP_DATA,
+                    SectionKind::UninitializedData => xcoff::STYP_BSS,
+                    SectionKind::Tls => xcoff::STYP_TDATA,
+                    SectionKind::UninitializedTls => xcoff::STYP_TBSS,
+                    SectionKind::OtherString => xcoff::STYP_INFO,
+                    SectionKind::Debug | SectionKind::DebugString => xcoff::STYP_DEBUG,
+                    SectionKind::Other | SectionKind::Metadata => 0,
+                    SectionKind::Note
+                    | SectionKind::Linker
+                    | SectionKind::Common
+                    | SectionKind::Unknown
+                    | SectionKind::TlsVariables
+                    | SectionKind::Elf(_) => {
+                        return Err(Error(format!(
+                            "unimplemented section `{}` kind {:?}",
+                            section.name().unwrap_or(""),
+                            section.kind
+                        )));
+                    }
+                }
+                .into()
+            };
+            if is_64 {
+                let section_header = xcoff::SectionHeader64 {
+                    s_name: sectname,
+                    s_paddr: U64::new(BE, section_offsets[index].address),
+                    // This field has the same value as the s_paddr field.
+                    s_vaddr: U64::new(BE, section_offsets[index].address),
+                    s_size: U64::new(BE, section.data.len() as u64),
+                    s_scnptr: U64::new(BE, section_offsets[index].data_offset as u64),
+                    s_relptr: U64::new(BE, section_offsets[index].reloc_offset as u64),
+                    s_lnnoptr: U64::new(BE, 0),
+                    s_nreloc: U32::new(BE, section.relocations.len() as u32),
+                    s_nlnno: U32::new(BE, 0),
+                    s_flags: U32::new(BE, flags),
+                    s_reserve: U32::new(BE, 0),
+                };
+                buffer.write(&section_header);
+            } else {
+                let section_header = xcoff::SectionHeader32 {
+                    s_name: sectname,
+                    s_paddr: U32::new(BE, section_offsets[index].address as u32),
+                    // This field has the same value as the s_paddr field.
+                    s_vaddr: U32::new(BE, section_offsets[index].address as u32),
+                    s_size: U32::new(BE, section.data.len() as u32),
+                    s_scnptr: U32::new(BE, section_offsets[index].data_offset as u32),
+                    s_relptr: U32::new(BE, section_offsets[index].reloc_offset as u32),
+                    s_lnnoptr: U32::new(BE, 0),
+                    // TODO: If more than 65,534 relocation entries are required, the field
+                    // value will be 65535, and an STYP_OVRFLO section header will contain
+                    // the actual count of relocation entries in the s_paddr field.
+                    s_nreloc: U16::new(BE, section.relocations.len() as u16),
+                    s_nlnno: U16::new(BE, 0),
+                    s_flags: U32::new(BE, flags),
+                };
+                buffer.write(&section_header);
+            }
+        }
+
+        // Write section data.
+        for (index, section) in self.sections.iter().enumerate() {
+            let len = section.data.len();
+            if len != 0 {
+                write_align(buffer, 4);
+                debug_assert_eq!(section_offsets[index].data_offset, buffer.len());
+                buffer.write_bytes(&section.data);
+            }
+        }
+
+        // Write relocations.
+        for (index, section) in self.sections.iter().enumerate() {
+            if !section.relocations.is_empty() {
+                debug_assert_eq!(section_offsets[index].reloc_offset, buffer.len());
+                for reloc in &section.relocations {
+                    let (r_rtype, r_rsize) =
+                        if let RelocationFlags::Xcoff { r_rtype, r_rsize } = reloc.flags {
+                            (r_rtype, r_rsize)
+                        } else {
+                            return Err(Error("invalid relocation flags".into()));
+                        };
+                    if is_64 {
+                        let xcoff_rel = xcoff::Rel64 {
+                            r_vaddr: U64::new(BE, reloc.offset),
+                            r_symndx: U32::new(BE, symbol_offsets[reloc.symbol.0].index as u32),
+                            r_rsize,
+                            r_rtype,
+                        };
+                        buffer.write(&xcoff_rel);
+                    } else {
+                        let xcoff_rel = xcoff::Rel32 {
+                            r_vaddr: U32::new(BE, reloc.offset as u32),
+                            r_symndx: U32::new(BE, symbol_offsets[reloc.symbol.0].index as u32),
+                            r_rsize,
+                            r_rtype,
+                        };
+                        buffer.write(&xcoff_rel);
+                    }
+                }
+            }
+        }
+
+        // Write symbols.
+        debug_assert_eq!(symtab_offset, buffer.len());
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            let (n_value, section_kind) = if let SymbolSection::Section(id) = symbol.section {
+                (
+                    section_offsets[id.0].address + symbol.value,
+                    self.sections[id.0].kind,
+                )
+            } else {
+                (symbol.value, SectionKind::Unknown)
+            };
+            let n_scnum = match symbol.section {
+                SymbolSection::None => {
+                    debug_assert_eq!(symbol.kind, SymbolKind::File);
+                    xcoff::N_DEBUG
+                }
+                SymbolSection::Undefined | SymbolSection::Common => xcoff::N_UNDEF,
+                SymbolSection::Absolute => xcoff::N_ABS,
+                SymbolSection::Section(id) => id.0 as i16 + 1,
+            };
+            let n_sclass = symbol_offsets[index].storage_class;
+            let n_type = if (symbol.scope == SymbolScope::Linkage)
+                && (n_sclass == xcoff::C_EXT
+                    || n_sclass == xcoff::C_WEAKEXT
+                    || n_sclass == xcoff::C_HIDEXT)
+            {
+                xcoff::SYM_V_HIDDEN
+            } else {
+                0
+            };
+            let n_numaux = symbol_offsets[index].aux_count;
+            if is_64 {
+                let str_id = if n_sclass == xcoff::C_FILE {
+                    file_str_id.unwrap()
+                } else {
+                    symbol_offsets[index].str_id.unwrap()
+                };
+                let xcoff_sym = xcoff::Symbol64 {
+                    n_value: U64::new(BE, n_value),
+                    n_offset: U32::new(BE, strtab.get_offset(str_id) as u32),
+                    n_scnum: I16::new(BE, n_scnum),
+                    n_type: U16::new(BE, n_type),
+                    n_sclass,
+                    n_numaux,
+                };
+                buffer.write(&xcoff_sym);
+            } else {
+                let mut sym_name = [0; 8];
+                if n_sclass == xcoff::C_FILE {
+                    sym_name[..5].copy_from_slice(b".file");
+                } else if symbol.name.len() <= 8 {
+                    sym_name[..symbol.name.len()].copy_from_slice(&symbol.name[..]);
+                } else {
+                    let str_offset = strtab.get_offset(symbol_offsets[index].str_id.unwrap());
+                    sym_name[4..8].copy_from_slice(&u32::to_be_bytes(str_offset as u32));
+                }
+                let xcoff_sym = xcoff::Symbol32 {
+                    n_name: sym_name,
+                    n_value: U32::new(BE, n_value as u32),
+                    n_scnum: I16::new(BE, n_scnum),
+                    n_type: U16::new(BE, n_type),
+                    n_sclass,
+                    n_numaux,
+                };
+                buffer.write(&xcoff_sym);
+            }
+            // Generate auxiliary entries.
+            if n_sclass == xcoff::C_FILE {
+                debug_assert_eq!(n_numaux, 1);
+                let mut x_fname = [0; 8];
+                if symbol.name.len() <= 8 {
+                    x_fname[..symbol.name.len()].copy_from_slice(&symbol.name[..]);
+                } else {
+                    let str_offset = strtab.get_offset(symbol_offsets[index].str_id.unwrap());
+                    x_fname[4..8].copy_from_slice(&u32::to_be_bytes(str_offset as u32));
+                }
+                if is_64 {
+                    let file_aux = xcoff::FileAux64 {
+                        x_fname,
+                        x_fpad: Default::default(),
+                        x_ftype: xcoff::XFT_FN,
+                        x_freserve: Default::default(),
+                        x_auxtype: xcoff::AUX_FILE,
+                    };
+                    buffer.write(&file_aux);
+                } else {
+                    let file_aux = xcoff::FileAux32 {
+                        x_fname,
+                        x_fpad: Default::default(),
+                        x_ftype: xcoff::XFT_FN,
+                        x_freserve: Default::default(),
+                    };
+                    buffer.write(&file_aux);
+                }
+            } else if n_sclass == xcoff::C_EXT
+                || n_sclass == xcoff::C_WEAKEXT
+                || n_sclass == xcoff::C_HIDEXT
+            {
+                debug_assert_eq!(n_numaux, 1);
+                let (x_smtyp, x_smclas) = if let SymbolFlags::Xcoff {
+                    x_smtyp, x_smclas, ..
+                } = symbol.flags
+                {
+                    (x_smtyp, x_smclas)
+                } else {
+                    match symbol.kind {
+                        SymbolKind::Text => (xcoff::XTY_SD, xcoff::XMC_PR),
+                        SymbolKind::Data => {
+                            if section_kind == SectionKind::UninitializedData {
+                                (xcoff::XTY_CM, xcoff::XMC_BS)
+                            } else if section_kind == SectionKind::ReadOnlyData {
+                                (xcoff::XTY_SD, xcoff::XMC_RO)
+                            } else {
+                                (xcoff::XTY_SD, xcoff::XMC_RW)
+                            }
+                        }
+                        SymbolKind::Tls => {
+                            if section_kind == SectionKind::UninitializedTls {
+                                (xcoff::XTY_CM, xcoff::XMC_UL)
+                            } else {
+                                (xcoff::XTY_SD, xcoff::XMC_TL)
+                            }
+                        }
+                        _ => {
+                            return Err(Error(format!(
+                                "unimplemented symbol `{}` kind {:?}",
+                                symbol.name().unwrap_or(""),
+                                symbol.kind
+                            )));
+                        }
+                    }
+                };
+                let scnlen = if let SymbolFlags::Xcoff {
+                    containing_csect: Some(containing_csect),
+                    ..
+                } = symbol.flags
+                {
+                    symbol_offsets[containing_csect.0].index as u64
+                } else {
+                    symbol.size
+                };
+                if is_64 {
+                    let csect_aux = xcoff::CsectAux64 {
+                        x_scnlen_lo: U32::new(BE, (scnlen & 0xFFFFFFFF) as u32),
+                        x_scnlen_hi: U32::new(BE, ((scnlen >> 32) & 0xFFFFFFFF) as u32),
+                        x_parmhash: U32::new(BE, 0),
+                        x_snhash: U16::new(BE, 0),
+                        x_smtyp,
+                        x_smclas,
+                        pad: 0,
+                        x_auxtype: xcoff::AUX_CSECT,
+                    };
+                    buffer.write(&csect_aux);
+                } else {
+                    let csect_aux = xcoff::CsectAux32 {
+                        x_scnlen: U32::new(BE, scnlen as u32),
+                        x_parmhash: U32::new(BE, 0),
+                        x_snhash: U16::new(BE, 0),
+                        x_smtyp,
+                        x_smclas,
+                        x_stab: U32::new(BE, 0),
+                        x_snstab: U16::new(BE, 0),
+                    };
+                    buffer.write(&csect_aux);
+                }
+            }
+        }
+
+        // Write string table.
+        debug_assert_eq!(strtab_offset, buffer.len());
+        buffer.write_bytes(&u32::to_be_bytes(strtab_len as u32));
+        buffer.write_bytes(&strtab_data);
+
+        debug_assert_eq!(offset, buffer.len());
+        Ok(())
+    }
+}