[lld] r297814 - [ELF] - Make Bss and BssRelRo sections to be synthetic (#3).
George Rimar via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 15 02:21:29 PDT 2017
Author: grimar
Date: Wed Mar 15 04:21:29 2017
New Revision: 297814
URL: http://llvm.org/viewvc/llvm-project?rev=297814&view=rev
Log:
[ELF] - Make Bss and BssRelRo sections to be synthetic (#3).
That removes CopyRelSection class completely, making
Bss/BssRelRo to be just regular synthetics.
This is splitted from D30541 and polished.
Difference from D30541 that all logic of SharedSymbol
converting to DefinedRegular was removed for now and
probably will be posted as separate patch.
Differential revision: https://reviews.llvm.org/D30892
Modified:
lld/trunk/ELF/OutputSections.cpp
lld/trunk/ELF/Relocations.cpp
lld/trunk/ELF/Symbols.cpp
lld/trunk/ELF/Symbols.h
lld/trunk/ELF/SyntheticSections.cpp
lld/trunk/ELF/SyntheticSections.h
lld/trunk/ELF/Writer.cpp
Modified: lld/trunk/ELF/OutputSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=297814&r1=297813&r2=297814&view=diff
==============================================================================
--- lld/trunk/ELF/OutputSections.cpp (original)
+++ lld/trunk/ELF/OutputSections.cpp Wed Mar 15 04:21:29 2017
@@ -31,8 +31,6 @@ using namespace lld;
using namespace lld::elf;
uint8_t Out::First;
-OutputSection *Out::Bss;
-OutputSection *Out::BssRelRo;
OutputSection *Out::Opd;
uint8_t *Out::OpdBuf;
PhdrEntry *Out::TlsPhdr;
Modified: lld/trunk/ELF/Relocations.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Relocations.cpp?rev=297814&r1=297813&r2=297814&view=diff
==============================================================================
--- lld/trunk/ELF/Relocations.cpp (original)
+++ lld/trunk/ELF/Relocations.cpp Wed Mar 15 04:21:29 2017
@@ -479,23 +479,20 @@ template <class ELFT> static void addCop
// 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<ELFT>(SS);
- OutputSection *OSec = IsReadOnly ? Out::BssRelRo : Out::Bss;
-
- // Create a SyntheticSection in Out to hold the .bss and the Copy Reloc.
- auto *ISec =
- make<CopyRelSection<ELFT>>(IsReadOnly, SS->getAlignment<ELFT>(), SymSize);
- OSec->addSection(ISec);
+ BssSection *Sec = IsReadOnly ? In<ELFT>::BssRelRo : In<ELFT>::Bss;
+ uintX_t Off = Sec->reserveSpace(SS->getAlignment<ELFT>(), SymSize);
// 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 (SharedSymbol *Sym : getSymbolsAt<ELFT>(SS)) {
Sym->NeedsCopy = true;
- Sym->Section = ISec;
+ Sym->CopyRelSec = Sec;
+ Sym->CopyRelSecOff = Off;
Sym->symbol()->IsUsedInRegularObj = true;
}
- In<ELFT>::RelaDyn->addReloc({Target->CopyRel, ISec, 0, false, SS, 0});
+ In<ELFT>::RelaDyn->addReloc({Target->CopyRel, Sec, Off, false, SS, 0});
}
template <class ELFT>
Modified: lld/trunk/ELF/Symbols.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Symbols.cpp?rev=297814&r1=297813&r2=297814&view=diff
==============================================================================
--- lld/trunk/ELF/Symbols.cpp (original)
+++ lld/trunk/ELF/Symbols.cpp Wed Mar 15 04:21:29 2017
@@ -106,7 +106,8 @@ static typename ELFT::uint getSymVA(cons
case SymbolBody::SharedKind: {
auto &SS = cast<SharedSymbol>(Body);
if (SS.NeedsCopy)
- return SS.Section->OutSec->Addr + SS.Section->OutSecOff;
+ return SS.CopyRelSec->OutSec->Addr + SS.CopyRelSec->OutSecOff +
+ SS.CopyRelSecOff;
if (SS.NeedsPltAddr)
return Body.getPltVA<ELFT>();
return 0;
@@ -207,7 +208,7 @@ template <class ELFT> OutputSection *Sym
if (auto *S = dyn_cast<SharedSymbol>(this)) {
if (S->NeedsCopy)
- return S->Section->OutSec;
+ return S->CopyRelSec->OutSec;
return nullptr;
}
Modified: lld/trunk/ELF/Symbols.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Symbols.h?rev=297814&r1=297813&r2=297814&view=diff
==============================================================================
--- lld/trunk/ELF/Symbols.h (original)
+++ lld/trunk/ELF/Symbols.h Wed Mar 15 04:21:29 2017
@@ -238,8 +238,9 @@ public:
// This field is a pointer to the symbol's version definition.
const void *Verdef;
- // Section is significant only when NeedsCopy is true.
- InputSection *Section = nullptr;
+ // CopyRelSec and CopyRelSecOff are significant only when NeedsCopy is true.
+ InputSection *CopyRelSec;
+ size_t CopyRelSecOff;
private:
template <class ELFT> const typename ELFT::Sym &getSym() const {
Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=297814&r1=297813&r2=297814&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Wed Mar 15 04:21:29 2017
@@ -376,11 +376,14 @@ void BuildIdSection<ELFT>::computeHash(
HashFn(HashBuf, Hashes);
}
-template <class ELFT>
-CopyRelSection<ELFT>::CopyRelSection(bool ReadOnly, uintX_t AddrAlign, size_t S)
- : SyntheticSection(SHF_ALLOC, SHT_NOBITS, AddrAlign,
- ReadOnly ? ".bss.rel.ro" : ".bss"),
- Size(S) {}
+BssSection::BssSection(StringRef Name)
+ : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_NOBITS, 0, Name) {}
+
+size_t BssSection::reserveSpace(uint32_t Alignment, size_t Size) {
+ OutSec->updateAlignment(Alignment);
+ this->Size = alignTo(this->Size, Alignment) + Size;
+ return this->Size - Size;
+}
template <class ELFT>
void BuildIdSection<ELFT>::writeBuildId(ArrayRef<uint8_t> Buf) {
@@ -2307,11 +2310,6 @@ template class elf::BuildIdSection<ELF32
template class elf::BuildIdSection<ELF64LE>;
template class elf::BuildIdSection<ELF64BE>;
-template class elf::CopyRelSection<ELF32LE>;
-template class elf::CopyRelSection<ELF32BE>;
-template class elf::CopyRelSection<ELF64LE>;
-template class elf::CopyRelSection<ELF64BE>;
-
template class elf::GotSection<ELF32LE>;
template class elf::GotSection<ELF32BE>;
template class elf::GotSection<ELF64LE>;
Modified: lld/trunk/ELF/SyntheticSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.h?rev=297814&r1=297813&r2=297814&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.h (original)
+++ lld/trunk/ELF/SyntheticSections.h Wed Mar 15 04:21:29 2017
@@ -153,16 +153,19 @@ private:
uint8_t *HashBuf;
};
-// 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 {
- typedef typename ELFT::uint uintX_t;
-
+// BssSection is used to reserve space for copy relocations. We create two
+// instances of this class for .bss and .bss.rel.ro. .bss is used for writable
+// symbols, and .bss.rel.ro is used for read-only symbols.
+class BssSection final : public SyntheticSection {
public:
- CopyRelSection(bool ReadOnly, uintX_t AddrAlign, size_t Size);
+ BssSection(StringRef Name);
void writeTo(uint8_t *) override {}
+ bool empty() const override { return getSize() == 0; }
+ size_t reserveSpace(uint32_t Alignment, size_t Size);
size_t getSize() const override { return Size; }
- size_t Size;
+
+private:
+ size_t Size = 0;
};
template <class ELFT> class MipsGotSection final : public SyntheticSection {
@@ -759,6 +762,8 @@ SymbolBody *addSyntheticLocal(StringRef
template <class ELFT> struct In {
static InputSection *ARMAttributes;
static BuildIdSection<ELFT> *BuildId;
+ static BssSection *Bss;
+ static BssSection *BssRelRo;
static InputSection *Common;
static DynamicSection<ELFT> *Dynamic;
static StringTableSection<ELFT> *DynStrTab;
@@ -788,6 +793,8 @@ template <class ELFT> struct In {
};
template <class ELFT> InputSection *In<ELFT>::ARMAttributes;
+template <class ELFT> BssSection *In<ELFT>::Bss;
+template <class ELFT> BssSection *In<ELFT>::BssRelRo;
template <class ELFT> BuildIdSection<ELFT> *In<ELFT>::BuildId;
template <class ELFT> InputSection *In<ELFT>::Common;
template <class ELFT> DynamicSection<ELFT> *In<ELFT>::Dynamic;
Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=297814&r1=297813&r2=297814&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Wed Mar 15 04:21:29 2017
@@ -111,8 +111,8 @@ StringRef elf::getOutputSectionName(Stri
}
for (StringRef V :
- {".text.", ".rodata.", ".data.rel.ro.", ".data.", ".bss.",
- ".init_array.", ".fini_array.", ".ctors.", ".dtors.", ".tbss.",
+ {".text.", ".rodata.", ".data.rel.ro.", ".data.", ".bss.rel.ro.",
+ ".bss.", ".init_array.", ".fini_array.", ".ctors.", ".dtors.", ".tbss.",
".gcc_except_table.", ".tdata.", ".ARM.exidx."}) {
StringRef Prefix = V.drop_back();
if (Name.startswith(V) || Name == Prefix)
@@ -330,10 +330,6 @@ template <class ELFT> void Writer<ELFT>:
auto Add = [](InputSectionBase *Sec) { InputSections.push_back(Sec); };
- // Create singleton output sections.
- Out::Bss = make<OutputSection>(".bss", SHT_NOBITS, SHF_ALLOC | SHF_WRITE);
- Out::BssRelRo =
- make<OutputSection>(".bss.rel.ro", SHT_NOBITS, SHF_ALLOC | SHF_WRITE);
In<ELFT>::DynStrTab = make<StringTableSection<ELFT>>(".dynstr", true);
In<ELFT>::Dynamic = make<DynamicSection<ELFT>>();
In<ELFT>::RelaDyn = make<RelocationSection<ELFT>>(
@@ -371,6 +367,11 @@ template <class ELFT> void Writer<ELFT>:
Add(Common);
}
+ In<ELFT>::Bss = make<BssSection>(".bss");
+ Add(In<ELFT>::Bss);
+ In<ELFT>::BssRelRo = make<BssSection>(".bss.rel.ro");
+ Add(In<ELFT>::BssRelRo);
+
// Add MIPS-specific sections.
bool HasDynSymTab =
!Symtab<ELFT>::X->getSharedFiles().empty() || Config->pic() ||
@@ -620,7 +621,7 @@ template <class ELFT> bool elf::isRelroS
return true;
if (In<ELFT>::Got && Sec == In<ELFT>::Got->OutSec)
return true;
- if (Sec == Out::BssRelRo)
+ if (Sec == In<ELFT>::BssRelRo->OutSec)
return true;
StringRef S = Sec->Name;
@@ -1170,14 +1171,15 @@ template <class ELFT> void Writer<ELFT>:
// Dynamic section must be the last one in this list and dynamic
// symbol table section (DynSymTab) must be the first one.
applySynthetic<ELFT>(
- {In<ELFT>::DynSymTab, In<ELFT>::GnuHashTab, In<ELFT>::HashTab,
- In<ELFT>::SymTab, In<ELFT>::ShStrTab, In<ELFT>::StrTab,
- In<ELFT>::VerDef, In<ELFT>::DynStrTab, In<ELFT>::GdbIndex,
- In<ELFT>::Got, In<ELFT>::MipsGot, In<ELFT>::IgotPlt,
- In<ELFT>::GotPlt, In<ELFT>::RelaDyn, In<ELFT>::RelaIplt,
- In<ELFT>::RelaPlt, In<ELFT>::Plt, In<ELFT>::Iplt,
- In<ELFT>::Plt, In<ELFT>::EhFrameHdr, In<ELFT>::VerSym,
- In<ELFT>::VerNeed, In<ELFT>::Dynamic},
+ {In<ELFT>::DynSymTab, In<ELFT>::Bss, In<ELFT>::BssRelRo,
+ In<ELFT>::GnuHashTab, In<ELFT>::HashTab, In<ELFT>::SymTab,
+ In<ELFT>::ShStrTab, In<ELFT>::StrTab, In<ELFT>::VerDef,
+ In<ELFT>::DynStrTab, In<ELFT>::GdbIndex, In<ELFT>::Got,
+ In<ELFT>::MipsGot, In<ELFT>::IgotPlt, In<ELFT>::GotPlt,
+ In<ELFT>::RelaDyn, In<ELFT>::RelaIplt, In<ELFT>::RelaPlt,
+ In<ELFT>::Plt, In<ELFT>::Iplt, In<ELFT>::Plt,
+ In<ELFT>::EhFrameHdr, In<ELFT>::VerSym, In<ELFT>::VerNeed,
+ In<ELFT>::Dynamic},
[](SyntheticSection *SS) { SS->finalizeContents(); });
// Some architectures use small displacements for jump instructions.
@@ -1206,16 +1208,6 @@ template <class ELFT> void Writer<ELFT>:
}
template <class ELFT> void Writer<ELFT>::addPredefinedSections() {
- // Add BSS sections.
- auto Add = [=](OutputSection *Sec) {
- if (!Sec->Sections.empty()) {
- Sec->assignOffsets<ELFT>();
- OutputSections.push_back(Sec);
- }
- };
- Add(Out::Bss);
- Add(Out::BssRelRo);
-
// ARM ABI requires .ARM.exidx to be terminated by some piece of data.
// We have the terminater synthetic section class. Add that at the end.
auto *OS = dyn_cast_or_null<OutputSection>(findSection(".ARM.exidx"));
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