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Move section headers if they would be overwritten

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When rewriting the sections of an executable, it can happen that the
section headers occur too early in the file and would be overwritten by
the replaced sections. If this would happen, we move the section headers
to the end of the file.
This commit is contained in:
Thomas Tuegel
2014-09-11 16:04:26 -05:00
parent bf4b579d63
commit 4e8c47fa84
1 changed files with 16 additions and 5 deletions
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21
src/patchelf.cc
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@@ -711,11 +711,22 @@ void ElfFile<ElfFileParamNames>::rewriteSectionsExecutable()
Elf_Addr firstPage = startAddr - startOffset;
debug("first page is 0x%llx\n", (unsigned long long) firstPage);
/* Right now we assume that the section headers are somewhere near
the end, which appears to be the case most of the time.
Therefore they're not accidentally overwritten by the replaced
sections. !!! Fix this. */
assert((off_t) rdi(hdr->e_shoff) >= startOffset);
if ((off_t) rdi(hdr->e_shoff) < startOffset) {
/* The section headers occur too early in the file and would be
overwritten by the replaced sections. Move them to the end of the file
before proceeding. */
off_t shoffNew = fileSize;
off_t shSize = rdi(hdr->e_shoff) + rdi(hdr->e_shnum) * rdi(hdr->e_shentsize);
growFile (fileSize + shSize);
wri(hdr->e_shoff, shoffNew);
/* Rewrite the section header table. For neatness, keep the
sections sorted. */
assert(rdi(hdr->e_shnum) == shdrs.size());
sortShdrs();
for (unsigned int i = 1; i < rdi(hdr->e_shnum); ++i)
* ((Elf_Shdr *) (contents + rdi(hdr->e_shoff)) + i) = shdrs[i];
}
/* Compute the total space needed for the replaced sections, the