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Align startOffset with p_align instead of pagesize for compatibility #510

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Align startOffset with p_align instead of pagesize for compatibility #510

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dba325e
align startOffset with p_align instead of pagesize for compatibility
yuta-hayama Jul 28, 2023
9188cb8
make LOAD segment extensions based on p_align instead of pagesize
yuta-hayama Jul 31, 2023
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10 changes: 8 additions & 2 deletions src/patchelf.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -843,7 +843,13 @@ void ElfFile<ElfFileParamNames>::rewriteSectionsLibrary()
neededSpace += headerTableSpace;
debug("needed space is %d\n", neededSpace);

Elf_Off startOffset = roundUp(fileContents->size(), getPageSize());
/* glibc earlier than 2.35 requires that the LOAD segment satisfies
(p_vaddr mod p_align) == (p_offset mod p_align).
The ELF specification requires that loadable process segments satisfy
(p_vaddr mod pagesize) == (p_offset mod pagesize), so glibc is probably
wrong, but here startOffset is calculated according to p_align for
compatibility. */
Elf_Off startOffset = roundUp(fileContents->size(), alignStartPage);

// In older version of binutils (2.30), readelf would check if the dynamic
// section segment is strictly smaller than the file (and not same size).
Expand Down Expand Up @@ -879,7 +885,7 @@ void ElfFile<ElfFileParamNames>::rewriteSectionsLibrary()
rdi(lastSeg.p_type) == PT_LOAD &&
rdi(lastSeg.p_flags) == (PF_R | PF_W) &&
rdi(lastSeg.p_align) == alignStartPage) {
auto segEnd = roundUp(rdi(lastSeg.p_offset) + rdi(lastSeg.p_memsz), getPageSize());
auto segEnd = roundUp(rdi(lastSeg.p_offset) + rdi(lastSeg.p_memsz), alignStartPage);
if (segEnd == startOffset) {
auto newSz = startOffset + neededSpace - rdi(lastSeg.p_offset);
wri(lastSeg.p_filesz, wri(lastSeg.p_memsz, newSz));
Expand Down