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[BOLT][AArch64] Detect veneers with missing data markers (#142069)

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The linker may omit data markers for long absolute veneers causing BOLT
to treat data as code. Detect such veneers and introduce data markers
artificially before BOLT's disassembler kicks in.
This commit is contained in:
Maksim Panchenko 2025-05-29 19:24:34 -07:00 committed by GitHub
parent 587d6fcbb6
commit c9022a29b4
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2 changed files with 25 additions and 1 deletions
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13
bolt/lib/Rewrite/RewriteInstance.cpp
View File

@ -1341,6 +1341,19 @@ void RewriteInstance::discoverFileObjects() {
}
}
}
// The linker may omit data markers for absolute long veneers. Introduce
// those markers artificially to assist the disassembler.
for (BinaryFunction &BF :
llvm::make_second_range(BC->getBinaryFunctions())) {
if (BF.getOneName().starts_with("__AArch64AbsLongThunk_") &&
BF.getSize() == 16 && !BF.getSizeOfDataInCodeAt(8)) {
BC->errs() << "BOLT-WARNING: missing data marker detected in veneer "
<< BF << '\n';
BF.markDataAtOffset(8);
BC->AddressToConstantIslandMap[BF.getAddress() + 8] = &BF;
}
}
}
if (!BC->IsLinuxKernel) {

13
bolt/test/AArch64/veneer-lld-abs.s
View File

@ -6,10 +6,21 @@
# RUN: -fuse-ld=lld -Wl,-q
# RUN: llvm-objdump -d %t.exe | FileCheck --check-prefix=CHECK-INPUT %s
# RUN: llvm-objcopy --remove-section .rela.mytext %t.exe
# RUN: llvm-bolt %t.exe -o %t.bolt --elim-link-veneers=true --lite=0
# RUN: llvm-bolt %t.exe -o %t.bolt
# RUN: llvm-objdump -d -j .text %t.bolt | \
# RUN: FileCheck --check-prefix=CHECK-OUTPUT %s
## Occasionally, we see the linker not generating $d symbols for long veneers
## causing BOLT to fail veneer elimination.
# RUN: llvm-objcopy --remove-symbol-prefix=\$d %t.exe %t.no-marker.exe
# RUN: llvm-bolt %t.no-marker.exe -o %t.no-marker.bolt \
# RUN: 2>&1 | FileCheck %s --check-prefix=CHECK-BOLT
# RUN: llvm-objdump -d -j .text %t.no-marker.bolt | \
# RUN: FileCheck --check-prefix=CHECK-OUTPUT %s
# CHECK-BOLT-NOT: BOLT-WARNING: unable to disassemble instruction
# CHECK-BOLT: BOLT-WARNING: missing data marker detected in veneer __AArch64AbsLongThunk_far_function
.text
.balign 4
.global far_function