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Bug 725284 - Preserve PT_LOAD alignment, except when it's the default on x86-64. r=tglek

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This commit is contained in:
Mike Hommey
2012-02-21 08:08:41 +01:00
parent 528539b755
commit 21a0f2d6a4
4 changed files with 27 additions and 10 deletions
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22
build/unix/elfhack/elf.cpp
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@@ -265,6 +265,15 @@ Elf::Elf(std::ifstream &file)
file.seekg(ehdr->e_phoff);
for (int i = 0; i < ehdr->e_phnum; i++) {
Elf_Phdr phdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]);
if (phdr.p_type == PT_LOAD) {
// Default alignment for PT_LOAD on x86-64 prevents elfhack from
// doing anything useful. However, the system doesn't actually
// require such a big alignment, so in order for elfhack to work
// efficiently, reduce alignment when it's originally the default
// one.
if ((ehdr->e_machine == EM_X86_64) && (phdr.p_align == 0x200000))
phdr.p_align = 0x1000;
}
ElfSegment *segment = new ElfSegment(&phdr);
// Some segments aren't entirely filled (if at all) by sections
// For those, we use fake sections
@@ -503,12 +512,17 @@ unsigned int ElfSection::getOffset()
if (previous->getType() != SHT_NOBITS)
offset += previous->getSize();
Elf32_Word align = 0x1000;
for (std::vector<ElfSegment *>::iterator seg = segments.begin(); seg != segments.end(); seg++)
align = std::max(align, (*seg)->getAlign());
Elf32_Word mask = align - 1;
// SHF_TLS is used for .tbss which is some kind of special case.
if (((getType() != SHT_NOBITS) || (getFlags() & SHF_TLS)) && (getFlags() & SHF_ALLOC)) {
if ((getAddr() & 4095) < (offset & 4095))
offset = (offset | 4095) + (getAddr() & 4095) + 1;
if ((getAddr() & mask) < (offset & mask))
offset = (offset | mask) + (getAddr() & mask) + 1;
else
offset = (offset & ~4095) + (getAddr() & 4095);
offset = (offset & ~mask) + (getAddr() & mask);
}
if ((getType() != SHT_NOBITS) && (offset & (getAddrAlign() - 1)))
offset = (offset | (getAddrAlign() - 1)) + 1;
@@ -632,7 +646,7 @@ ElfSegment *ElfSegment::splitBefore(ElfSection *section)
phdr.p_vaddr = 0;
phdr.p_paddr = phdr.p_vaddr + v_p_diff;
phdr.p_flags = flags;
phdr.p_align = 0x1000;
phdr.p_align = getAlign();
phdr.p_filesz = (unsigned int)-1;
phdr.p_memsz = (unsigned int)-1;
ElfSegment *segment = new ElfSegment(&phdr);