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Split a function and add comments. 

This is slightly inefficient than the previous code, but that is really
negligible as this function is usually called at most only a few times.

llvm-svn: 295282
This commit is contained in:
Rui Ueyama 2017-02-16 04:39:45 +00:00
parent f0393bf0a5
commit 750c11c099
1 changed files with 23 additions and 8 deletions
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31
lld/ELF/Relocations.cpp
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@ -413,10 +413,30 @@ template <class ELFT> static bool isReadOnly(SharedSymbol<ELFT> *SS) {
return false;
}
// Returns symbols at the same offset as a given symbol.
//
// If two or more symbols are at the same offset, and at least one of
// them are copied by a copy relocation, all of them need to be copied.
// Otherwise, they would refer different places at runtime.
template <class ELFT>
static std::vector<SharedSymbol<ELFT> *> getAliases(SharedSymbol<ELFT> *SS) {
typedef typename ELFT::Sym Elf_Sym;
std::vector<SharedSymbol<ELFT> *> Ret;
for (const Elf_Sym &S : SS->file()->getGlobalSymbols()) {
if (S.st_shndx != SS->Sym.st_shndx || S.st_value != SS->Sym.st_value)
continue;
StringRef Name = check(S.getName(SS->file()->getStringTable()));
SymbolBody *Sym = Symtab<ELFT>::X->find(Name);
if (auto *Alias = dyn_cast_or_null<SharedSymbol<ELFT>>(Sym))
Ret.push_back(Alias);
}
return Ret;
}
// Reserve space in .bss or .bss.rel.ro for copy relocation.
template <class ELFT> static void addCopyRelSymbol(SharedSymbol<ELFT> *SS) {
typedef typename ELFT::uint uintX_t;
typedef typename ELFT::Sym Elf_Sym;
// Copy relocation against zero-sized symbol doesn't make sense.
uintX_t SymSize = SS->template getSize<ELFT>();
@ -436,17 +456,12 @@ template <class ELFT> static void addCopyRelSymbol(SharedSymbol<ELFT> *SS) {
// Look through the DSO's dynamic symbol table for aliases and create a
// dynamic symbol for each one. This causes the copy relocation to correctly
// interpose any aliases.
for (const Elf_Sym &S : SS->file()->getGlobalSymbols()) {
if (S.st_shndx != SS->Sym.st_shndx || S.st_value != SS->Sym.st_value)
continue;
auto *Alias = dyn_cast_or_null<SharedSymbol<ELFT>>(
Symtab<ELFT>::X->find(check(S.getName(SS->file()->getStringTable()))));
if (!Alias)
continue;
for (SharedSymbol<ELFT> *Alias : getAliases(SS)) {
Alias->CopySection = ISec;
Alias->NeedsCopyOrPltAddr = true;
Alias->symbol()->IsUsedInRegularObj = true;
}
In<ELFT>::RelaDyn->addReloc({Target->CopyRel, ISec, 0, false, SS, 0});
}