[lld] r219353 - [ELF] Only mark as DT_NEEDED libs that are strictly necessary
Rafael Auler
rafaelauler at gmail.com
Wed Oct 8 15:53:49 PDT 2014
Author: rafauler
Date: Wed Oct 8 17:53:49 2014
New Revision: 219353
URL: http://llvm.org/viewvc/llvm-project?rev=219353&view=rev
Log:
[ELF] Only mark as DT_NEEDED libs that are strictly necessary
Enhances the creation of an ELF dynamic executable by avoiding recording
unnecessary shared libraries as NEEDED to load a program.
To do this, we must keep track of not only symbols that were referenced but
also of COPY relocations, which steal the symbol from a shared library but does
not store from which lib this symbol came from. To fix this, this commit changes
ObjectSymbol to store the original library from which this symbol came. With
this information, we are able to build a list of the exact shared libraries that
must be marked as DT_NEEDED, instead of blindly marking all shared libraries as
needed.
This logic originally came from the MIPS backend with some adaptation.
Reviewers: atanasyan, shankar.easwaran
http://reviews.llvm.org/D5574
Modified:
lld/trunk/include/lld/ReaderWriter/ELFLinkingContext.h
lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64LinkingContext.h
lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64RelocationPass.cpp
lld/trunk/lib/ReaderWriter/ELF/Atoms.h
lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h
lld/trunk/lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h
lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h
lld/trunk/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h
lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp
lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h
lld/trunk/lib/ReaderWriter/ELF/Mips/MipsRelocationPass.cpp
lld/trunk/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h
lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h
lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64LinkingContext.h
lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp
Modified: lld/trunk/include/lld/ReaderWriter/ELFLinkingContext.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/include/lld/ReaderWriter/ELFLinkingContext.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/include/lld/ReaderWriter/ELFLinkingContext.h (original)
+++ lld/trunk/include/lld/ReaderWriter/ELFLinkingContext.h Wed Oct 8 17:53:49 2014
@@ -90,6 +90,15 @@ public:
const Reference &) const {
return false;
}
+
+ /// \brief Is this a copy relocation?
+ ///
+ /// If this is a copy relocation, its target must be an ObjectAtom. We must
+ /// include in DT_NEEDED the name of the library where this object came from.
+ virtual bool isCopyRelocation(const Reference &) const {
+ return false;
+ }
+
bool validateImpl(raw_ostream &diagnostics) override;
/// \brief Does the linker allow dynamic libraries to be linked with?
Modified: lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64LinkingContext.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64LinkingContext.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64LinkingContext.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64LinkingContext.h Wed Oct 8 17:53:49 2014
@@ -59,6 +59,15 @@ public:
}
}
+ bool isCopyRelocation(const Reference &r) const override {
+ if (r.kindNamespace() != Reference::KindNamespace::ELF)
+ return false;
+ assert(r.kindArch() == Reference::KindArch::AArch64);
+ if (r.kindValue() == llvm::ELF::R_AARCH64_COPY)
+ return true;
+ return false;
+ }
+
bool isPLTRelocation(const DefinedAtom &,
const Reference &r) const override {
if (r.kindNamespace() != Reference::KindNamespace::ELF)
Modified: lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64RelocationPass.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64RelocationPass.cpp?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64RelocationPass.cpp (original)
+++ lld/trunk/lib/ReaderWriter/ELF/AArch64/AArch64RelocationPass.cpp Wed Oct 8 17:53:49 2014
@@ -452,7 +452,7 @@ public:
if (obj != _objectMap.end())
return obj->second;
- auto oa = new (_file._alloc) ObjectAtom(_file);
+ auto oa = new (_file._alloc) ObjectAtom(_file, a);
// This needs to point to the atom that we just created.
oa->addReferenceELF_AArch64(R_AARCH64_COPY, 0, oa, 0);
Modified: lld/trunk/lib/ReaderWriter/ELF/Atoms.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/Atoms.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/Atoms.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/Atoms.h Wed Oct 8 17:53:49 2014
@@ -689,8 +689,11 @@ public:
/// \brief Atom which represents an object for which a COPY relocation will be
/// generated.
class ObjectAtom : public SimpleELFDefinedAtom {
+ const SharedLibraryAtom *_sla;
+
public:
- ObjectAtom(const File &f) : SimpleELFDefinedAtom(f) {}
+ ObjectAtom(const File &f, const SharedLibraryAtom *sla)
+ : SimpleELFDefinedAtom(f), _sla(sla) {}
Scope scope() const override { return scopeGlobal; }
@@ -713,6 +716,8 @@ public:
StringRef name() const override { return _name; }
+ const SharedLibraryAtom *getOriginalOwner() const { return _sla; }
+
std::string _name;
uint64_t _size;
};
Modified: lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h Wed Oct 8 17:53:49 2014
@@ -10,6 +10,7 @@
#ifndef LLD_READER_WRITER_ELF_DEFAULT_LAYOUT_H
#define LLD_READER_WRITER_ELF_DEFAULT_LAYOUT_H
+#include "Atoms.h"
#include "Chunk.h"
#include "HeaderChunks.h"
#include "Layout.h"
@@ -171,6 +172,7 @@ public:
typedef typename std::vector<lld::AtomLayout *>::iterator AbsoluteAtomIterT;
typedef llvm::DenseSet<const Atom *> AtomSetT;
+ typedef llvm::DenseSet<const SharedLibraryAtom *> SharedLibraryAtomSetT;
DefaultLayout(const ELFLinkingContext &context) : _context(context) {}
@@ -303,6 +305,10 @@ public:
return _referencedDynAtoms.count(a);
}
+ const SharedLibraryAtomSetT &getCopiedDynAtoms() const {
+ return _copiedDynAtoms;
+ }
+
protected:
/// \brief Allocate a new section.
virtual AtomSection<ELFT> *createSection(
@@ -325,6 +331,7 @@ protected:
LLD_UNIQUE_BUMP_PTR(RelocationTable<ELFT>) _pltRelocationTable;
std::vector<lld::AtomLayout *> _absoluteAtoms;
AtomSetT _referencedDynAtoms;
+ SharedLibraryAtomSetT _copiedDynAtoms;
const ELFLinkingContext &_context;
};
@@ -582,7 +589,14 @@ ErrorOr<const lld::AtomLayout &> Default
if (isa<UndefinedAtom>(reloc->target()) && isLocalReloc)
continue;
- _referencedDynAtoms.insert(reloc->target());
+ if (!_context.isCopyRelocation(*reloc)) {
+ _referencedDynAtoms.insert(reloc->target());
+ continue;
+ }
+
+ const ObjectAtom *oa = dyn_cast<ObjectAtom>(reloc->target());
+ assert (oa != nullptr && "Targets of copy relocs must be ObjectAtoms");
+ _copiedDynAtoms.insert(oa->getOriginalOwner());
}
return section->appendAtom(atom);
Modified: lld/trunk/lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h Wed Oct 8 17:53:49 2014
@@ -37,10 +37,6 @@ protected:
return std::error_code();
}
- bool isNeededTagRequired(const SharedLibraryAtom *sla) const override {
- return _writeHelper.isNeededTagRequired(sla);
- }
-
LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) createDynamicTable();
LLD_UNIQUE_BUMP_PTR(DynamicSymbolTable<ELFT>) createDynamicSymbolTable();
Modified: lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h Wed Oct 8 17:53:49 2014
@@ -69,11 +69,6 @@ public:
return file;
}
- bool isNeededTagRequired(const SharedLibraryAtom *sla) const {
- return _targetLayout.isReferencedByDefinedAtom(sla) ||
- _targetLayout.isCopied(sla);
- }
-
private:
MipsLinkingContext &_ctx;
MipsTargetLayout<ELFT> &_targetLayout;
Modified: lld/trunk/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h Wed Oct 8 17:53:49 2014
@@ -38,10 +38,6 @@ protected:
return std::error_code();
}
- bool isNeededTagRequired(const SharedLibraryAtom *sla) const override {
- return _writeHelper.isNeededTagRequired(sla);
- }
-
LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) createDynamicTable();
LLD_UNIQUE_BUMP_PTR(DynamicSymbolTable<ELFT>) createDynamicSymbolTable();
Modified: lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp (original)
+++ lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp Wed Oct 8 17:53:49 2014
@@ -65,6 +65,15 @@ bool MipsLinkingContext::isDynamicReloca
}
}
+bool MipsLinkingContext::isCopyRelocation(const Reference &r) const {
+ if (r.kindNamespace() != Reference::KindNamespace::ELF)
+ return false;
+ assert(r.kindArch() == Reference::KindArch::Mips);
+ if (r.kindValue() == llvm::ELF::R_MIPS_COPY)
+ return true;
+ return false;
+}
+
bool MipsLinkingContext::isPLTRelocation(const DefinedAtom &,
const Reference &r) const {
if (r.kindNamespace() != Reference::KindNamespace::ELF)
Modified: lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h Wed Oct 8 17:53:49 2014
@@ -47,6 +47,7 @@ public:
bool isRelaOutputFormat() const override { return false; }
bool isDynamicRelocation(const DefinedAtom &,
const Reference &r) const override;
+ bool isCopyRelocation(const Reference &r) const override;
bool isPLTRelocation(const DefinedAtom &, const Reference &r) const override;
};
Modified: lld/trunk/lib/ReaderWriter/ELF/Mips/MipsRelocationPass.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/Mips/MipsRelocationPass.cpp?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/Mips/MipsRelocationPass.cpp (original)
+++ lld/trunk/lib/ReaderWriter/ELF/Mips/MipsRelocationPass.cpp Wed Oct 8 17:53:49 2014
@@ -781,7 +781,7 @@ RelocationPass<ELFT>::getObjectEntry(con
if (obj != _objectMap.end())
return obj->second;
- auto oa = new (_file._alloc) ObjectAtom(_file);
+ auto oa = new (_file._alloc) ObjectAtom(_file, a);
oa->addReferenceELF_Mips(R_MIPS_COPY, 0, oa, 0);
oa->_name = a->name();
oa->_size = a->size();
Modified: lld/trunk/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h Wed Oct 8 17:53:49 2014
@@ -62,26 +62,6 @@ public:
}
}
- ErrorOr<const lld::AtomLayout &> addAtom(const Atom *atom) override {
- // Maintain:
- // 1. Set of shared library atoms referenced by regular defined atoms.
- // 2. Set of shared library atoms have corresponding R_MIPS_COPY copies.
- if (const auto *da = dyn_cast<DefinedAtom>(atom))
- for (const Reference *ref : *da) {
- if (ref->kindNamespace() == lld::Reference::KindNamespace::ELF) {
- assert(ref->kindArch() == Reference::KindArch::Mips);
- if (ref->kindValue() == llvm::ELF::R_MIPS_COPY)
- _copiedDynSymNames.insert(atom->name());
- }
- }
-
- return TargetLayout<ELFType>::addAtom(atom);
- }
-
- bool isCopied(const SharedLibraryAtom *sla) const {
- return _copiedDynSymNames.count(sla->name());
- }
-
/// \brief GP offset relative to .got section.
uint64_t getGPOffset() const { return 0x7FF0; }
@@ -109,7 +89,6 @@ private:
MipsPLTSection<ELFType> *_pltSection;
llvm::Optional<AtomLayout *> _gpAtom;
llvm::Optional<AtomLayout *> _gpDispAtom;
- llvm::StringSet<> _copiedDynSymNames;
};
/// \brief Mips Runtime file.
Modified: lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/OutputELFWriter.h Wed Oct 8 17:53:49 2014
@@ -180,11 +180,14 @@ template <class ELFT>
void OutputELFWriter<ELFT>::buildDynamicSymbolTable(const File &file) {
ScopedTask task(getDefaultDomain(), "buildDynamicSymbolTable");
for (const auto &sla : file.sharedLibrary()) {
- if (isDynSymEntryRequired(sla))
- _dynamicSymbolTable->addSymbol(sla, ELF::SHN_UNDEF);
+ if (!isDynSymEntryRequired(sla))
+ continue;
+ _dynamicSymbolTable->addSymbol(sla, ELF::SHN_UNDEF);
if (isNeededTagRequired(sla))
_soNeeded.insert(sla->loadName());
}
+ for (const auto &sla : _layout.getCopiedDynAtoms())
+ _soNeeded.insert(sla->loadName());
// Never mark the dynamic linker as DT_NEEDED
_soNeeded.erase(sys::path::filename(_context.getInterpreter()));
for (const auto &loadName : _soNeeded) {
Modified: lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64LinkingContext.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64LinkingContext.h?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64LinkingContext.h (original)
+++ lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64LinkingContext.h Wed Oct 8 17:53:49 2014
@@ -58,6 +58,15 @@ public:
}
}
+ bool isCopyRelocation(const Reference &r) const override {
+ if (r.kindNamespace() != Reference::KindNamespace::ELF)
+ return false;
+ assert(r.kindArch() == Reference::KindArch::x86_64);
+ if (r.kindValue() == llvm::ELF::R_X86_64_COPY)
+ return true;
+ return false;
+ }
+
virtual bool isPLTRelocation(const DefinedAtom &,
const Reference &r) const override {
if (r.kindNamespace() != Reference::KindNamespace::ELF)
Modified: lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp?rev=219353&r1=219352&r2=219353&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp (original)
+++ lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp Wed Oct 8 17:53:49 2014
@@ -430,7 +430,7 @@ public:
if (obj != _objectMap.end())
return obj->second;
- auto oa = new (_file._alloc) ObjectAtom(_file);
+ auto oa = new (_file._alloc) ObjectAtom(_file, a);
// This needs to point to the atom that we just created.
oa->addReferenceELF_x86_64(R_X86_64_COPY, 0, oa, 0);
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