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Cleanup .gnu.version_r after removing symbol version

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If --clear-symbol-version is used to remove all occurrances of a symbol
version, it nevertheless remains in the .gnu.version_r section as being
required by a particular dependency.

Instead, after removing symbol versions, loop over the .gnu.version and
gnu.version_r tables to find any unused version, and unlink them from
the linked-lists in the .gnu.version_r section.
This commit is contained in:
David Gow
2022-04-11 14:06:31 +08:00
parent c2b419dc2a
commit 85b83d010d
2 changed files with 77 additions and 4 deletions
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75
src/patchelf.cc
View File

@@ -1709,6 +1709,73 @@ void ElfFile<ElfFileParamNames>::addDebugTag()
changed = true;
}
/* Remove any unused dependency symbol versions from .gnu.version_r */
template<ElfFileParams>
void ElfFile<ElfFileParamNames>::cleanDependencySymbolVersions()
{
auto shdrVersym = findSectionHeader(".gnu.version");
auto shdrVersymR = findSectionHeader(".gnu.version_r");
auto versyms = (Elf_Versym *)(fileContents->data() + rdi(shdrVersym.sh_offset));
size_t count = rdi(shdrVersym.sh_size) / sizeof(Elf_Versym);
/* Set of versions actually used. */
std::set<Elf_Versym> allVersions;
for (size_t i = 0; i < count; i++) {
allVersions.insert(versyms[i]);
}
/* Strings associated with .gnu_version_r section: used for debug only. */
Elf_Shdr & shdrVersionRStrings = shdrs.at(rdi(shdrVersymR.sh_link));
char * verStrTab = (char *) fileContents->data() + rdi(shdrVersionRStrings.sh_offset);
auto ver_r = (Elf_Verneed *)(fileContents->data() + rdi(shdrVersymR.sh_offset));
while (true) {
auto prev = (Elf_Vernaux *)nullptr;
auto vern_aux = (Elf_Vernaux *)((char *)ver_r + rdi(ver_r->vn_aux));
char * file = verStrTab + rdi(ver_r->vn_file);
for (size_t j = 0; j < ver_r->vn_cnt ; j++) {
char * ver_name = verStrTab + rdi(vern_aux->vna_name);
auto next = (Elf_Vernaux *)((char *)vern_aux + rdi(vern_aux->vna_next));
if (!allVersions.count(rdi(vern_aux->vna_other) & ~0x8000)) {
debug("Removing version identifier %d %s@%s\n", rdi(vern_aux->vna_other), file, ver_name);
/* Symbol version is no longer used, unlink it. */
if (!prev) {
auto next_off = (intptr_t)(vern_aux) + rdi(vern_aux->vna_next) - (intptr_t)(ver_r);
wri(ver_r->vn_aux, next_off);
} else {
auto next_off = (intptr_t)(vern_aux) + rdi(vern_aux->vna_next) - (intptr_t)(prev);
wri(prev->vna_next, next_off);
}
wri(ver_r->vn_cnt, rdi(ver_r->vn_cnt) - 1);
} else {
prev = vern_aux;
}
if (vern_aux == next) {
if (j != rdi(ver_r->vn_cnt)) {
debug("Section missing elements! Ended on element %d, expected %d\n", j, rdi(ver_r->vn_cnt));
}
break;
}
vern_aux = next;
}
/* If this was the last entry, we're done. */
if (!rdi(ver_r->vn_next)) {
break;
}
ver_r = (Elf_Verneed *) (((char *) ver_r) + rdi(ver_r->vn_next));
}
changed = true;
this->rewriteSections();
}
template<ElfFileParams>
void ElfFile<ElfFileParamNames>::clearSymbolVersions(const std::set<std::string> & syms)
{
@@ -1734,6 +1801,10 @@ void ElfFile<ElfFileParamNames>::clearSymbolVersions(const std::set<std::string>
wri(versyms[i], 1);
}
}
/* Remove entries in the .gnu.versions_r table which are no;-longer required. */
cleanDependencySymbolVersions();
changed = true;
this->rewriteSections();
}
@@ -1817,9 +1888,9 @@ static void patchElf()
const std::string & outputFileName2 = outputFileName.empty() ? fileName : outputFileName;
if (getElfType(fileContents).is32Bit)
patchElf2(ElfFile<Elf32_Ehdr, Elf32_Phdr, Elf32_Shdr, Elf32_Addr, Elf32_Off, Elf32_Dyn, Elf32_Sym, Elf32_Verneed, Elf32_Versym>(fileContents), fileContents, outputFileName2);
patchElf2(ElfFile<Elf32_Ehdr, Elf32_Phdr, Elf32_Shdr, Elf32_Addr, Elf32_Off, Elf32_Dyn, Elf32_Sym, Elf32_Verneed, Elf32_Vernaux, Elf32_Versym>(fileContents), fileContents, outputFileName2);
else
patchElf2(ElfFile<Elf64_Ehdr, Elf64_Phdr, Elf64_Shdr, Elf64_Addr, Elf64_Off, Elf64_Dyn, Elf64_Sym, Elf64_Verneed, Elf64_Versym>(fileContents), fileContents, outputFileName2);
patchElf2(ElfFile<Elf64_Ehdr, Elf64_Phdr, Elf64_Shdr, Elf64_Addr, Elf64_Off, Elf64_Dyn, Elf64_Sym, Elf64_Verneed, Elf64_Vernaux, Elf64_Versym>(fileContents), fileContents, outputFileName2);
}
}

6
src/patchelf.h
View File

@@ -1,7 +1,7 @@
using FileContents = std::shared_ptr<std::vector<unsigned char>>;
#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, class Elf_Versym
#define ElfFileParamNames Elf_Ehdr, Elf_Phdr, Elf_Shdr, Elf_Addr, Elf_Off, Elf_Dyn, Elf_Sym, Elf_Verneed, Elf_Versym
#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, class Elf_Vernaux, class Elf_Versym
#define ElfFileParamNames Elf_Ehdr, Elf_Phdr, Elf_Shdr, Elf_Addr, Elf_Off, Elf_Dyn, Elf_Sym, Elf_Verneed, Elf_Vernaux, Elf_Versym
template<ElfFileParams>
class ElfFile
@@ -133,6 +133,8 @@ public:
void addDebugTag();
void cleanDependencySymbolVersions();
void clearSymbolVersions(const std::set<std::string> & syms);
private: