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Teach --replace-needed to update .gnu.version_r table

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If the ELF binary that we're patching is linked to a DSO that uses
symbol versioning, then the DSO's SONAME appears in two different
places: once as a DT_NEEDED entry, and once in the .gnu.version_r
version requirements section. Previously, patchelf --replace-needed
would update DT_NEEDED entry, but fail to update the .gnu.version_r
table. This resulted in completely broken binaries -- trying to load
them would trigger an assertion failure inside the dynamic loader, as it
tries to check the version of a library that was never loaded:

  Inconsistency detected by ld.so: dl-version.c: 224: _dl_check_map_versions: Assertion `needed != ((void *)0)' failed!

This commit teaches --replace-needed to update the .gnu.version_r
table.

Fixes: gh-84
This commit is contained in:
Nathaniel J. Smith
2016-03-31 18:06:47 -07:00
parent 44b7f9583f
commit 25cb97cc4f
1 changed files with 34 additions and 4 deletions
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38
src/patchelf.cc
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@@ -53,8 +53,8 @@ off_t fileSize, maxSize;
unsigned char * contents = 0;
#define ElfFileParams class Elf_Ehdr, class Elf_Phdr, class Elf_Shdr, class Elf_Addr, class Elf_Off, class Elf_Dyn, class Elf_Sym
#define ElfFileParamNames Elf_Ehdr, Elf_Phdr, Elf_Shdr, Elf_Addr, Elf_Off, Elf_Dyn, Elf_Sym
#define ElfFileParams class Elf_Ehdr, class Elf_Phdr, class Elf_Shdr, class Elf_Addr, class Elf_Off, class Elf_Dyn, class Elf_Sym, class Elf_Verneed
#define ElfFileParamNames Elf_Ehdr, Elf_Phdr, Elf_Shdr, Elf_Addr, Elf_Off, Elf_Dyn, Elf_Sym, Elf_Verneed
static unsigned int getPageSize(){
@@ -1260,6 +1260,8 @@ void ElfFile<ElfFileParamNames>::replaceNeeded(map<string, string>& libs)
Elf_Dyn * dyn = (Elf_Dyn *) (contents + rdi(shdrDynamic.sh_offset));
unsigned int verNeedNum = 0;
unsigned int dynStrAddedBytes = 0;
for ( ; rdi(dyn->d_tag) != DT_NULL; dyn++) {
@@ -1287,6 +1289,34 @@ void ElfFile<ElfFileParamNames>::replaceNeeded(map<string, string>& libs)
debug("keeping DT_NEEDED entry `%s'\n", name);
}
}
if (rdi(dyn->d_tag) == DT_VERNEEDNUM) {
verNeedNum = rdi(dyn->d_un.d_val);
}
}
// If a replaced library uses symbol versions, then there will also be
// references to it in the "version needed" table, and these also need to
// be replaced.
if (verNeedNum) {
Elf_Shdr & shdrVersionR = findSection3(".gnu.version_r");
// The filename strings in the .gnu.version_r aren't necessarily in
// .dynstr -- we have to look at ->sh_link to find the section with
// the strings in it.
Elf_Shdr & shdrVersionRStrings = *shdrs[rdi(shdrVersionR->sh_link)];
Elf_Verneed * need = (Elf_Verneed *) (contents + rdi(shdrVersionR.sh_offset));
while (verNeedNum > 0) {
// XX check need->vn_file, which is an offset into the
// shdrVersionRStrings section
// if if matches one of the entries in `libs`, then use
// replaceSection logic like that above to add the new string to
// this section and change vn_file
need = (Elf_Verneed *) (contents + rdi(need->vn_next));
verNeedNum--;
}
}
}
@@ -1474,13 +1504,13 @@ static void patchElf()
if (contents[EI_CLASS] == ELFCLASS32 &&
contents[EI_VERSION] == EV_CURRENT)
{
ElfFile<Elf32_Ehdr, Elf32_Phdr, Elf32_Shdr, Elf32_Addr, Elf32_Off, Elf32_Dyn, Elf32_Sym> elfFile;
ElfFile<Elf32_Ehdr, Elf32_Phdr, Elf32_Shdr, Elf32_Addr, Elf32_Off, Elf32_Dyn, Elf32_Sym, Elf32_Verneed> elfFile;
patchElf2(elfFile);
}
else if (contents[EI_CLASS] == ELFCLASS64 &&
contents[EI_VERSION] == EV_CURRENT)
{
ElfFile<Elf64_Ehdr, Elf64_Phdr, Elf64_Shdr, Elf64_Addr, Elf64_Off, Elf64_Dyn, Elf64_Sym> elfFile;
ElfFile<Elf64_Ehdr, Elf64_Phdr, Elf64_Shdr, Elf64_Addr, Elf64_Off, Elf64_Dyn, Elf64_Sym, Elf64_Verneed> elfFile;
patchElf2(elfFile);
}
else {