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Add CopyRelSection instances to BSS in the regular way. 

Previously, space in a BSS section for copy relocations are reserved
in a special way. We directly manipulated size of the BSS section.
r294577 changed the way of doing it. Now, we create an instance of
CopyRelSection (which is a synthetic input section) for each copy
relocation.

This patch removes the remains of the old way and add CopyRelSections
to BSS sections using `addSections` function, which is the usual
way to add an input section to an output section.

llvm-svn: 295278
This commit is contained in:
Rui Ueyama 2017-02-16 04:12:19 +00:00
parent 86a1b135f0
commit da5cc84661
3 changed files with 19 additions and 23 deletions
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25
lld/ELF/Relocations.cpp
View File

@ -426,37 +426,28 @@ template <class ELFT> static void addCopyRelSymbol(SharedSymbol<ELFT> *SS) {
// See if this symbol is in a read-only segment. If so, preserve the symbol's
// memory protection by reserving space in the .bss.rel.ro section.
bool IsReadOnly = isReadOnly(SS);
OutputSection<ELFT> *CopySec =
IsReadOnly ? Out<ELFT>::BssRelRo : Out<ELFT>::Bss;
OutputSection<ELFT> *OSec = IsReadOnly ? Out<ELFT>::BssRelRo : Out<ELFT>::Bss;
uintX_t Alignment = getAlignment(SS);
uintX_t Off = alignTo(CopySec->Size, Alignment);
CopySec->Size = Off + SymSize;
CopySec->updateAlignment(Alignment);
uintX_t Shndx = SS->Sym.st_shndx;
uintX_t Value = SS->Sym.st_value;
// Create a SyntheticSection in CopySec to hold the .bss and the Copy Reloc
auto *CopyISec = make<CopyRelSection<ELFT>>(IsReadOnly, Alignment, SymSize);
CopyISec->OutSecOff = Off;
CopyISec->OutSec = CopySec;
CopySec->Sections.push_back(CopyISec);
// Create a SyntheticSection in Out to hold the .bss and the Copy Reloc.
auto *ISec =
make<CopyRelSection<ELFT>>(IsReadOnly, getAlignment(SS), SymSize);
OSec->addSection(ISec);
// 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 != Shndx || S.st_value != Value)
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;
Alias->CopySection = CopyISec;
Alias->CopySection = ISec;
Alias->NeedsCopyOrPltAddr = true;
Alias->symbol()->IsUsedInRegularObj = true;
}
In<ELFT>::RelaDyn->addReloc({Target->CopyRel, CopyISec, 0, false, SS, 0});
In<ELFT>::RelaDyn->addReloc({Target->CopyRel, ISec, 0, false, SS, 0});
}
template <class ELFT>

3
lld/ELF/SyntheticSections.h
View File

@ -107,7 +107,8 @@ private:
uint8_t *HashBuf;
};
// SHT_NOBITS section created for a copyReloc
// For each copy relocation, we create an instance of this class to
// reserve space in .bss or .bss.rel.ro.
template <class ELFT>
class CopyRelSection final : public SyntheticSection<ELFT> {
typedef typename ELFT::uint uintX_t;

14
lld/ELF/Writer.cpp
View File

@ -1184,12 +1184,16 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
}
template <class ELFT> void Writer<ELFT>::addPredefinedSections() {
if (Out<ELFT>::Bss->Size > 0)
OutputSections.push_back(Out<ELFT>::Bss);
if (Out<ELFT>::BssRelRo->Size > 0)
OutputSections.push_back(Out<ELFT>::BssRelRo);
auto Add = [=](OutputSection<ELFT> *Sec) {
if (!Sec->Sections.empty()) {
Sec->assignOffsets();
OutputSections.push_back(Sec);
}
};
Add(Out<ELFT>::Bss);
Add(Out<ELFT>::BssRelRo);
auto OS = dyn_cast_or_null<OutputSection<ELFT>>(findSection(".ARM.exidx"));
auto *OS = dyn_cast_or_null<OutputSection<ELFT>>(findSection(".ARM.exidx"));
if (OS && !OS->Sections.empty() && !Config->Relocatable)
OS->addSection(make<ARMExidxSentinelSection<ELFT>>());
}