fix: symbol mismatch in object file (#4171)
* fix: symbol kind in obj * actually patch TLS * update docs and cleanup size impl for tls * remove debug logs --------- Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>
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Daniel GallupsandJonathan Kelley authored and GitHub committed
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@@ -15,7 +15,7 @@ use std::{
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sync::{Arc, RwLock},
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};
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use subsecond_types::{AddressMap, JumpTable};
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use target_lexicon::{Architecture, OperatingSystem, Triple};
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use target_lexicon::{Architecture, OperatingSystem, PointerWidth, Triple};
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use thiserror::Error;
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use walrus::{
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ConstExpr, DataKind, ElementItems, ElementKind, FunctionBuilder, FunctionId, FunctionKind,
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@@ -83,6 +83,7 @@ pub struct CachedSymbol {
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pub kind: SymbolKind,
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pub is_undefined: bool,
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pub is_weak: bool,
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pub size: u64,
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}
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impl PartialEq for HotpatchModuleCache {
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@@ -137,6 +138,7 @@ impl HotpatchModuleCache {
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},
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is_undefined,
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is_weak: false,
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size: 0,
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},
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);
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}
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@@ -155,6 +157,7 @@ impl HotpatchModuleCache {
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kind: SymbolKind::Data,
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is_undefined,
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is_weak: false,
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size: 0,
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},
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);
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}
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@@ -256,6 +259,7 @@ impl HotpatchModuleCache {
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is_undefined: s.is_undefined(),
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is_weak: s.is_weak(),
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kind: s.kind(),
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size: s.size(),
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},
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))
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})
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@@ -905,32 +909,7 @@ pub fn create_undefined_symbol_stub(
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// Unfortunately this isn't simply cross-platform, so we need to handle Unix and Windows
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// calling conventions separately. It also depends on the architecture, making it even more
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// complicated.
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//
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// Rust code typically generates Tls symbols as functions (text), so we handle them as jumps too.
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// Figured this out by checking the disassembly of the symbols causing the violation.
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// ```
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// __ZN17crossbeam_channel5waker17current_thread_id9THREAD_ID29_$u7b$$u7b$constant$u7d$$u7d$28_$u7b$$u7b$closure$u7d$$u7d$17h33618d877d86bb77E:
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// stp x20, x19, [sp, #-0x20]!
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// stp x29, x30, [sp, #0x10]
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// add x29, sp, #0x10
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// adrp x19, 21603 ; 0x1054bd000
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// add x19, x19, #0x998
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// ldr x20, [x19]
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// mov x0, x19
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// blr x20
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// ldr x8, [x0]
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// cbz x8, 0x10005acc0
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// mov x0, x19
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// blr x20
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// ldp x29, x30, [sp, #0x10]
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// ldp x20, x19, [sp], #0x20
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// ret
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// mov x0, x19
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// blr x20
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// bl __ZN3std3sys12thread_local6native4lazy20Storage$LT$T$C$D$GT$10initialize17h818476638edff4e6E
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// b 0x10005acac
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// ```
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SymbolKind::Text | SymbolKind::Tls => {
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SymbolKind::Text => {
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let jump_asm = match triple.operating_system {
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// The windows ABI and calling convention is different than the SystemV ABI.
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OperatingSystem::Windows => match triple.architecture {
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@@ -1053,6 +1032,75 @@ pub fn create_undefined_symbol_stub(
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});
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}
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// Rust code typically generates Tls accessors as functions (text), but they are referenced
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// indirectly as data symbols. We end up handling this by adding the TLS symbol as a data
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// symbol with the initializer as the address of the original tls initializer. That way
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// if new TLS are added at runtime, they get initialized properly, but otherwise, the
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// tls initialization check (cbz) properly skips re-initialization on patches.
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//
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// ```
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// __ZN17crossbeam_channel5waker17current_thread_id9THREAD_ID29_$u7b$$u7b$constant$u7d$$u7d$28_$u7b$$u7b$closure$u7d$$u7d$17h33618d877d86bb77E:
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// stp x20, x19, [sp, #-0x20]!
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// stp x29, x30, [sp, #0x10]
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// add x29, sp, #0x10
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// adrp x19, 21603 ; 0x1054bd000
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// add x19, x19, #0x998
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// ldr x20, [x19]
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// mov x0, x19
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// blr x20
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// ldr x8, [x0]
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// cbz x8, 0x10005acc0
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// mov x0, x19
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// blr x20
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// ldp x29, x30, [sp, #0x10]
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// ldp x20, x19, [sp], #0x20
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// ret
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// mov x0, x19
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// blr x20
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// bl __ZN3std3sys12thread_local6native4lazy20Storage$LT$T$C$D$GT$10initialize17h818476638edff4e6E
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// b 0x10005acac
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// ```
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SymbolKind::Tls => {
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let tls_section = obj.section_id(StandardSection::Tls);
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let pointer_width = match triple.pointer_width().unwrap() {
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PointerWidth::U16 => 2,
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PointerWidth::U32 => 4,
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PointerWidth::U64 => 8,
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};
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let size = if sym.size == 0 {
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pointer_width
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} else {
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sym.size
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};
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let align = size.min(pointer_width).next_power_of_two();
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let mut init = vec![0u8; size as usize];
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// write the contents of the symbol to the init vec
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init.iter_mut()
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.zip(match triple.endianness() {
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Ok(target_lexicon::Endianness::Little) => abs_addr.to_le_bytes(),
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Ok(target_lexicon::Endianness::Big) => abs_addr.to_be_bytes(),
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_ => return Err(PatchError::UnsupportedPlatform(triple.to_string())),
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})
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.for_each(|(b, v)| *b = v);
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let offset = obj.append_section_data(tls_section, &init, align);
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obj.add_symbol(Symbol {
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name: name.as_bytes()[name_offset..].to_vec(),
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value: offset, // offset inside .tdata
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size,
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scope: SymbolScope::Linkage,
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kind: SymbolKind::Tls,
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weak: false,
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section: SymbolSection::Section(tls_section),
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flags: object::SymbolFlags::None,
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});
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}
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// We just assume all non-text symbols are data (globals, statics, etc)
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_ => {
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// darwin statics show up as "unknown" symbols even though they are data symbols.
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