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Simplify __rel[a]_iplt_{start,end} handling a bit. 

Also updated a comment.

llvm-svn: 256444
This commit is contained in:
Rui Ueyama 2015-12-26 09:47:57 +00:00
parent d71999ef1b
commit 0168722e39
1 changed files with 19 additions and 17 deletions
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36
lld/ELF/Writer.cpp
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@ -79,6 +79,7 @@ private:
std::vector<std::unique_ptr<OutputSectionBase<ELFT>>> OwningSections;
unsigned getNumSections() const { return OutputSections.size() + 1; }
void addRelIpltSymbols();
void addStartStopSymbols(OutputSectionBase<ELFT> *Sec);
void setPhdr(Elf_Phdr *PH, uint32_t Type, uint32_t Flags, uintX_t FileOff,
uintX_t VA, uintX_t Size, uintX_t Align);
@ -574,25 +575,25 @@ static bool compareSections(OutputSectionBase<ELFT> *A,
return std::distance(ItA, ItB) > 0;
}
// A statically linked executable will have rel[a].plt section
// to hold R_[*]_IRELATIVE relocations.
// The multi-arch libc will use these symbols to locate
// these relocations at program startup time.
// If RelaPlt is empty then there is no reason to create this symbols.
// The beginning and the ending of .rel[a].plt section are marked
// with __rel[a]_iplt_{start,end} symbols if it is a statically linked
// executable. The runtime needs these symbols in order to resolve
// all IRELATIVE relocs on startup. For dynamic executables, we don't
// need these symbols, since IRELATIVE relocs are resolved through GOT
// and PLT. For details, see http://www.airs.com/blog/archives/403.
template <class ELFT>
static void addIRelocMarkers(SymbolTable<ELFT> &Symtab, bool IsDynamic) {
if (IsDynamic || !Out<ELFT>::RelaPlt || !Out<ELFT>::RelaPlt->hasRelocs())
void Writer<ELFT>::addRelIpltSymbols() {
if (isOutputDynamic() || !Out<ELFT>::RelaPlt)
return;
bool IsRela = shouldUseRela<ELFT>();
auto AddMarker = [&](StringRef Name, typename Writer<ELFT>::Elf_Sym &Sym) {
if (SymbolBody *B = Symtab.find(Name))
if (B->isUndefined())
Symtab.addAbsolute(Name, Sym);
};
AddMarker(IsRela ? "__rela_iplt_start" : "__rel_iplt_start",
ElfSym<ELFT>::RelaIpltStart);
AddMarker(IsRela ? "__rela_iplt_end" : "__rel_iplt_end",
ElfSym<ELFT>::RelaIpltEnd);
StringRef S = IsRela ? "__rela_iplt_start" : "__rel_iplt_start";
if (Symtab.find(S))
Symtab.addAbsolute(S, ElfSym<ELFT>::RelaIpltStart);
S = IsRela ? "__rela_iplt_end" : "__rel_iplt_end";
if (Symtab.find(S))
Symtab.addAbsolute(S, ElfSym<ELFT>::RelaIpltEnd);
}
template <class ELFT> static bool includeInSymtab(const SymbolBody &B) {
@ -806,7 +807,8 @@ template <class ELFT> void Writer<ELFT>::createSections() {
}
}
addIRelocMarkers<ELFT>(Symtab, isOutputDynamic());
// Define __rel[a]_iplt_{start,end} symbols if needed.
addRelIpltSymbols();
std::vector<DefinedCommon *> CommonSymbols;
std::vector<SharedSymbol<ELFT> *> SharedCopySymbols;