[lld] r297008 - [ELF] - Make Bss and BssRelRo sections to be synthetic (#2).
George Rimar via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 6 06:37:46 PST 2017
Author: grimar
Date: Mon Mar 6 08:37:45 2017
New Revision: 297008
URL: http://llvm.org/viewvc/llvm-project?rev=297008&view=rev
Log:
[ELF] - Make Bss and BssRelRo sections to be synthetic (#2).
In compare with D30458, this makes Bss/BssRelRo to be pure
synthetic sections.
That removes CopyRelSection class completely, making
Bss/BssRelRo to be just regular synthetics.
SharedSymbols involved in creating copy relocations are
converted to DefinedRegular, what also simplifies things.
Differential revision: https://reviews.llvm.org/D30541
Modified:
lld/trunk/ELF/OutputSections.cpp
lld/trunk/ELF/OutputSections.h
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=297008&r1=297007&r2=297008&view=diff
==============================================================================
--- lld/trunk/ELF/OutputSections.cpp (original)
+++ lld/trunk/ELF/OutputSections.cpp Mon Mar 6 08:37:45 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/OutputSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.h?rev=297008&r1=297007&r2=297008&view=diff
==============================================================================
--- lld/trunk/ELF/OutputSections.h (original)
+++ lld/trunk/ELF/OutputSections.h Mon Mar 6 08:37:45 2017
@@ -98,8 +98,6 @@ public:
// until Writer is initialized.
struct Out {
static uint8_t First;
- static OutputSection *Bss;
- static OutputSection *BssRelRo;
static OutputSection *Opd;
static uint8_t *OpdBuf;
static PhdrEntry *TlsPhdr;
Modified: lld/trunk/ELF/Relocations.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Relocations.cpp?rev=297008&r1=297007&r2=297008&view=diff
==============================================================================
--- lld/trunk/ELF/Relocations.cpp (original)
+++ lld/trunk/ELF/Relocations.cpp Mon Mar 6 08:37:45 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);
+ BssRelSection<ELFT> *RelSec = IsReadOnly ? In<ELFT>::BssRelRo : In<ELFT>::Bss;
+ size_t Off = RelSec->addCopyRelocation(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->symbol()->IsUsedInRegularObj = true;
+ replaceBody<DefinedRegular>(Sym->symbol(), Sym->getName(),
+ /*IsLocal=*/false, Sym->StOther, Sym->Type, Off,
+ Sym->getSize<ELFT>(), RelSec, nullptr);
}
- In<ELFT>::RelaDyn->addReloc({Target->CopyRel, ISec, 0, false, SS, 0});
+ In<ELFT>::RelaDyn->addReloc({Target->CopyRel, RelSec, Off, false, SS, 0});
}
template <class ELFT>
@@ -535,14 +532,12 @@ static RelExpr adjustExpr(const elf::Obj
if (Body.isObject()) {
// Produce a copy relocation.
auto *B = cast<SharedSymbol>(&Body);
- if (!B->NeedsCopy) {
- if (Config->ZNocopyreloc)
- error(S.getLocation<ELFT>(RelOff) + ": unresolvable relocation " +
- toString(Type) + " against symbol '" + toString(*B) +
- "'; recompile with -fPIC or remove '-z nocopyreloc'");
+ if (Config->ZNocopyreloc)
+ error(S.getLocation<ELFT>(RelOff) + ": unresolvable relocation " +
+ toString(Type) + " against symbol '" + toString(*B) +
+ "'; recompile with -fPIC or remove '-z nocopyreloc'");
- addCopyRelSymbol<ELFT>(B);
- }
+ addCopyRelSymbol<ELFT>(B);
return Expr;
}
if (Body.isFunc()) {
Modified: lld/trunk/ELF/Symbols.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Symbols.cpp?rev=297008&r1=297007&r2=297008&view=diff
==============================================================================
--- lld/trunk/ELF/Symbols.cpp (original)
+++ lld/trunk/ELF/Symbols.cpp Mon Mar 6 08:37:45 2017
@@ -114,14 +114,10 @@ static typename ELFT::uint getSymVA(cons
return 0;
return In<ELFT>::Common->OutSec->Addr + In<ELFT>::Common->OutSecOff +
cast<DefinedCommon>(Body).Offset;
- case SymbolBody::SharedKind: {
- auto &SS = cast<SharedSymbol>(Body);
- if (SS.NeedsCopy)
- return SS.Section->OutSec->Addr + SS.Section->OutSecOff;
- if (SS.NeedsPltAddr)
+ case SymbolBody::SharedKind:
+ if (cast<SharedSymbol>(Body).NeedsPltAddr)
return Body.getPltVA<ELFT>();
return 0;
- }
case SymbolBody::UndefinedKind:
return 0;
case SymbolBody::LazyArchiveKind:
@@ -134,7 +130,7 @@ static typename ELFT::uint getSymVA(cons
SymbolBody::SymbolBody(Kind K, StringRefZ Name, bool IsLocal, uint8_t StOther,
uint8_t Type)
- : SymbolKind(K), NeedsCopy(false), NeedsPltAddr(false), IsLocal(IsLocal),
+ : SymbolKind(K), NeedsPltAddr(false), IsLocal(IsLocal),
IsInGlobalMipsGot(false), Is32BitMipsGot(false), IsInIplt(false),
IsInIgot(false), Type(Type), StOther(StOther), Name(Name) {}
@@ -145,10 +141,9 @@ bool SymbolBody::isPreemptible() const {
return false;
// Shared symbols resolve to the definition in the DSO. The exceptions are
- // symbols with copy relocations (which resolve to .bss) or preempt plt
- // entries (which resolve to that plt entry).
+ // symbols that needs plt entries (which resolve to that plt entry).
if (isShared())
- return !NeedsCopy && !NeedsPltAddr;
+ return !NeedsPltAddr;
// That's all that can be preempted in a non-DSO.
if (!Config->Shared)
@@ -217,11 +212,8 @@ const OutputSection *SymbolBody::getOutp
return nullptr;
}
- if (auto *S = dyn_cast<SharedSymbol>(this)) {
- if (S->NeedsCopy)
- return S->Section->OutSec;
+ if (auto *S = dyn_cast<SharedSymbol>(this))
return nullptr;
- }
if (isa<DefinedCommon>(this)) {
if (Config->DefineCommon)
Modified: lld/trunk/ELF/Symbols.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Symbols.h?rev=297008&r1=297007&r2=297008&view=diff
==============================================================================
--- lld/trunk/ELF/Symbols.h (original)
+++ lld/trunk/ELF/Symbols.h Mon Mar 6 08:37:45 2017
@@ -102,10 +102,6 @@ protected:
const unsigned SymbolKind : 8;
public:
- // True if the linker has to generate a copy relocation.
- // For SharedSymbol only.
- unsigned NeedsCopy : 1;
-
// True the symbol should point to its PLT entry.
// For SharedSymbol only.
unsigned NeedsPltAddr : 1;
@@ -270,9 +266,6 @@ 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;
-
private:
template <class ELFT> const typename ELFT::Sym &getSym() const {
return *(const typename ELFT::Sym *)ElfSym;
Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=297008&r1=297007&r2=297008&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Mon Mar 6 08:37:45 2017
@@ -376,10 +376,17 @@ void BuildIdSection<ELFT>::computeHash(
}
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) {}
+BssRelSection<ELFT>::BssRelSection(bool RelRo)
+ : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_NOBITS, 0,
+ RelRo ? ".bss.rel.ro" : ".bss"),
+ Size(0) {}
+
+template <class ELFT>
+size_t BssRelSection<ELFT>::addCopyRelocation(uintX_t AddrAlign, size_t Size) {
+ OutSec->updateAlignment(AddrAlign);
+ this->Size = alignTo(this->Size, AddrAlign) + Size;
+ return this->Size - Size;
+}
template <class ELFT>
void BuildIdSection<ELFT>::writeBuildId(ArrayRef<uint8_t> Buf) {
@@ -2303,10 +2310,10 @@ 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::BssRelSection<ELF32LE>;
+template class elf::BssRelSection<ELF32BE>;
+template class elf::BssRelSection<ELF64LE>;
+template class elf::BssRelSection<ELF64BE>;
template class elf::GotSection<ELF32LE>;
template class elf::GotSection<ELF32BE>;
Modified: lld/trunk/ELF/SyntheticSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.h?rev=297008&r1=297007&r2=297008&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.h (original)
+++ lld/trunk/ELF/SyntheticSections.h Mon Mar 6 08:37:45 2017
@@ -147,14 +147,16 @@ 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 {
+// Section used for storing copy relocations. We create two sections now,
+// .bss.rel.ro for RelRo case and .bss for regular case.
+template <class ELFT> class BssRelSection final : public SyntheticSection {
typedef typename ELFT::uint uintX_t;
public:
- CopyRelSection(bool ReadOnly, uintX_t AddrAlign, size_t Size);
+ BssRelSection(bool RelRo);
void writeTo(uint8_t *) override {}
+ bool empty() const override { return getSize() == 0; }
+ size_t addCopyRelocation(uintX_t AddrAlign, size_t Size);
size_t getSize() const override { return Size; }
size_t Size;
};
@@ -760,6 +762,8 @@ SymbolBody *addSyntheticLocal(StringRef
template <class ELFT> struct In {
static InputSection *ARMAttributes;
static BuildIdSection<ELFT> *BuildId;
+ static BssRelSection<ELFT> *Bss;
+ static BssRelSection<ELFT> *BssRelRo;
static InputSection *Common;
static DynamicSection<ELFT> *Dynamic;
static StringTableSection<ELFT> *DynStrTab;
@@ -789,6 +793,8 @@ template <class ELFT> struct In {
};
template <class ELFT> InputSection *In<ELFT>::ARMAttributes;
+template <class ELFT> BssRelSection<ELFT> *In<ELFT>::Bss;
+template <class ELFT> BssRelSection<ELFT> *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=297008&r1=297007&r2=297008&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Mon Mar 6 08:37:45 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)
@@ -309,10 +309,6 @@ 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>>(
@@ -350,6 +346,11 @@ template <class ELFT> void Writer<ELFT>:
Add(Common);
}
+ In<ELFT>::Bss = make<BssRelSection<ELFT>>(false /*RelRo*/);
+ Add(In<ELFT>::Bss);
+ In<ELFT>::BssRelRo = make<BssRelSection<ELFT>>(true /*RelRo*/);
+ Add(In<ELFT>::BssRelRo);
+
// Add MIPS-specific sections.
bool HasDynSymTab =
!Symtab<ELFT>::X->getSharedFiles().empty() || Config->pic() ||
@@ -595,7 +596,7 @@ 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;
@@ -1159,27 +1160,18 @@ 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.
finalizeSynthetic<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});
}
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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