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[BOLT] Fix RELR addend updates for non-zero image bases (#213000)

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This patch fixes an AArch64 BOLT failure exposed by LLVM commit
`fbba327208d7f6994f9a28a51dca3e913e3b444a`, which enabled packed
relative relocations (RELR) globally. BOLT incorrectly used a virtual
relocation address as a file offset when updating RELR addends,
corrupting instrumented executables when their image base was non-zero.
The observed CMake compiler-check failure was only a consequence of the
corrupted BOLT-instrumented Clang executable crashing; the defect itself
is in BOLT, not CMake.

The regression test links an AArch64 PIE with a non-zero image base and
verifies that BOLT updates the RELR addend at the correct file offset.

Assisted-by: Codex
This commit is contained in:
Adam Bzowski 2026-07-30 23:03:38 +01:00 committed by GitHub
parent 56a48d7120
commit 30611cae03
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GPG key ID: B5690EEEBB952194
2 changed files with 16 additions and 1 deletions
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2
bolt/lib/Rewrite/RewriteInstance.cpp
View file

@ -5990,7 +5990,7 @@ void RewriteInstance::patchELFAllocatableRelrSection(
RelOffset = RelOffset == 0 ? SectionAddress + Rel.Offset : RelOffset;
assert((RelOffset & 1) == 0 && "Wrong relocation offset");
RelOffsets.emplace(RelOffset);
FixAddend(Section, Rel, RelOffset);
FixAddend(Section, Rel, getFileOffsetForAddress(RelOffset));
}
}

15
bolt/test/AArch64/constant_island_pie_update.s
View file

@ -21,8 +21,23 @@
# RUN: llvm-readelf -rsW %t.relr.bolt | FileCheck --check-prefix=RELRELFCHECK %s
# RUN: llvm-readelf -SW %t.relr.bolt | FileCheck --check-prefix=RELRSZCHECK %s
// Check that RELR addends are patched at file offsets rather than virtual
// addresses when the two differ.
# RUN: %clang %cflags -fPIC -pie %t.o -o %t.relr.bias.exe -nostdlib \
# RUN: -Wl,-q -Wl,-z,notext -Wl,--pack-dyn-relocs=relr \
# RUN: -Wl,--image-base=0x20000
# RUN: llvm-objcopy --remove-section .rela.mytext %t.relr.bias.exe
# RUN: llvm-readelf -lW %t.relr.bias.exe | FileCheck --check-prefix=BIAS %s
# RUN: llvm-bolt %t.relr.bias.exe -o %t.relr.bias.bolt --use-old-text=0 \
# RUN: --lite=0
# RUN: llvm-objdump -j .text -d -z %t.relr.bias.bolt | \
# RUN: FileCheck %s --check-prefix=ADDENDCHECK
// Check that the CI value was updated
# CHECK: [[#%x,ADDR:]] <exitLocal>:
# BIAS: LOAD {{.*}} 0x0000000000020000
# CHECK: {{.*}} <$d>:
# CHECK-NEXT: {{.*}} .word 0x{{[0]+}}[[#ADDR]]
# CHECK-NEXT: {{.*}} .word 0x00000000