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Fix getting section info in large mach-o files. #165940

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Fix getting section info in large mach-o files. #165940

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159cfd7
Fix getting section info in large mach-o files.
clayborg Oct 31, 2025
350328a
Address user feedback to check for increasing sections sizes.
clayborg Nov 3, 2025
1391dd7
Fix comment to reflect new code.
clayborg Nov 3, 2025
ade2ccc
Run clang format.
clayborg Nov 3, 2025
eac2e6a
Improve error message when section data exceeds 4GB.
clayborg Nov 3, 2025
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2 changes: 1 addition & 1 deletion llvm/include/llvm/Object/MachO.h
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Original file line number Diff line number Diff line change
Expand Up @@ -447,7 +447,7 @@ class LLVM_ABI MachOObjectFile : public ObjectFile {
uint64_t getSectionAddress(DataRefImpl Sec) const override;
uint64_t getSectionIndex(DataRefImpl Sec) const override;
uint64_t getSectionSize(DataRefImpl Sec) const override;
ArrayRef<uint8_t> getSectionContents(uint32_t Offset, uint64_t Size) const;
ArrayRef<uint8_t> getSectionContents(uint64_t Offset, uint64_t Size) const;
Expected<ArrayRef<uint8_t>>
getSectionContents(DataRefImpl Sec) const override;
uint64_t getSectionAlignment(DataRefImpl Sec) const override;
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18 changes: 16 additions & 2 deletions llvm/lib/Object/MachOObjectFile.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1978,20 +1978,34 @@ uint64_t MachOObjectFile::getSectionSize(DataRefImpl Sec) const {
return SectSize;
}

ArrayRef<uint8_t> MachOObjectFile::getSectionContents(uint32_t Offset,
ArrayRef<uint8_t> MachOObjectFile::getSectionContents(uint64_t Offset,
uint64_t Size) const {
return arrayRefFromStringRef(getData().substr(Offset, Size));
}

Expected<ArrayRef<uint8_t>>
MachOObjectFile::getSectionContents(DataRefImpl Sec) const {
uint32_t Offset;
uint64_t Offset;
uint64_t Size;

if (is64Bit()) {
MachO::section_64 Sect = getSection64(Sec);
Offset = Sect.offset;
Size = Sect.size;
// Check for large mach-o files where the section contents might exceed
// 4GB. MachO::section_64 objects only have 32 bit file offsets to the
// section contents and can overflow in dSYM files. We can track this and
// adjust the section offset to be 64 bit safe.
uint64_t SectOffsetAdjust = 0;
for (uint32_t SectIdx=0; SectIdx<Sec.d.a; ++SectIdx) {
MachO::section_64 CurrSect =
getStruct<MachO::section_64>(*this, Sections[SectIdx]);
const uint64_t EndSectFileOffset =
(uint64_t)CurrSect.offset + CurrSect.size;
if (EndSectFileOffset >= UINT32_MAX)
SectOffsetAdjust += EndSectFileOffset & 0xFFFFFFFF00000000ull;
}
Offset += SectOffsetAdjust;
} else {
MachO::section Sect = getSection(Sec);
Offset = Sect.offset;
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