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[ELF] Implemented -Bsymbolic-functions command line option
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-Bsymbolic-functions: 
When creating a shared library, bind references to global 
function symbols to the definition within the shared library, if any.

This patch also fixed behavior of already existent -Bsymbolic:
previously PLT entries were created even if -Bsymbolic was specified.

Differential revision: http://reviews.llvm.org/D16411

llvm-svn: 259481
George Rimar committed Feb 2, 2016
1 parent ffe19f5 commit 5c36e59
Showing 7 changed files with 58 additions and 11 deletions.
1 change: 1 addition & 0 deletions lld/ELF/Config.h
Original file line number Diff line number Diff line change
@@ -53,6 +53,7 @@ struct Configuration {
bool AllowMultipleDefinition;
bool AsNeeded = false;
bool Bsymbolic;
bool BsymbolicFunctions;
bool Demangle = true;
bool DiscardAll;
bool DiscardLocals;
1 change: 1 addition & 0 deletions lld/ELF/Driver.cpp
Original file line number Diff line number Diff line change
@@ -188,6 +188,7 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {

Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);
Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
Config->Demangle = !Args.hasArg(OPT_no_demangle);
Config->DiscardAll = Args.hasArg(OPT_discard_all);
Config->DiscardLocals = Args.hasArg(OPT_discard_locals);
3 changes: 3 additions & 0 deletions lld/ELF/Options.td
Original file line number Diff line number Diff line change
@@ -3,6 +3,9 @@ include "llvm/Option/OptParser.td"
def Bsymbolic: Flag<["-"], "Bsymbolic">,
HelpText<"Bind defined symbols locally">;

def Bsymbolic_functions: Flag<["-"], "Bsymbolic-functions">,
HelpText<"Bind defined function symbols locally">;

def Bdynamic: Flag<["-"], "Bdynamic">,
HelpText<"Link against shared libraries">;

6 changes: 5 additions & 1 deletion lld/ELF/OutputSections.cpp
Original file line number Diff line number Diff line change
@@ -895,7 +895,11 @@ bool elf2::canBePreempted(const SymbolBody *Body, bool NeedsGot) {
}
if (!Config->Shared)
return false;
return Body->getVisibility() == STV_DEFAULT;
if (Body->getVisibility() != STV_DEFAULT)
return false;
if (Config->Bsymbolic || (Config->BsymbolicFunctions && Body->isFunc()))
return false;
return true;
}

template <class ELFT> void OutputSection<ELFT>::writeTo(uint8_t *Buf) {
13 changes: 8 additions & 5 deletions lld/ELF/Symbols.cpp
Original file line number Diff line number Diff line change
@@ -146,12 +146,13 @@ template <class ELFT> int SymbolBody::compare(SymbolBody *Other) {
}

Defined::Defined(Kind K, StringRef Name, bool IsWeak, uint8_t Visibility,
bool IsTls)
: SymbolBody(K, Name, IsWeak, Visibility, IsTls) {}
bool IsTls, bool IsFunction)
: SymbolBody(K, Name, IsWeak, Visibility, IsTls, IsFunction) {}

Undefined::Undefined(SymbolBody::Kind K, StringRef N, bool IsWeak,
uint8_t Visibility, bool IsTls)
: SymbolBody(K, N, IsWeak, Visibility, IsTls), CanKeepUndefined(false) {}
: SymbolBody(K, N, IsWeak, Visibility, IsTls, /*IsFunction*/ false),
CanKeepUndefined(false) {}

Undefined::Undefined(StringRef N, bool IsWeak, uint8_t Visibility,
bool CanKeepUndefined)
@@ -170,12 +171,14 @@ UndefinedElf<ELFT>::UndefinedElf(StringRef N, const Elf_Sym &Sym)
template <typename ELFT>
DefinedSynthetic<ELFT>::DefinedSynthetic(StringRef N, uintX_t Value,
OutputSectionBase<ELFT> &Section)
: Defined(SymbolBody::DefinedSyntheticKind, N, false, STV_DEFAULT, false),
: Defined(SymbolBody::DefinedSyntheticKind, N, false, STV_DEFAULT,
/*IsTls*/ false, /*IsFunction*/ false),
Value(Value), Section(Section) {}

DefinedCommon::DefinedCommon(StringRef N, uint64_t Size, uint64_t Alignment,
bool IsWeak, uint8_t Visibility)
: Defined(SymbolBody::DefinedCommonKind, N, IsWeak, Visibility, false) {
: Defined(SymbolBody::DefinedCommonKind, N, IsWeak, Visibility,
/*IsTls*/ false, /*IsFunction*/ false) {
MaxAlignment = Alignment;
this->Size = Size;
}
15 changes: 10 additions & 5 deletions lld/ELF/Symbols.h
Original file line number Diff line number Diff line change
@@ -86,6 +86,7 @@ class SymbolBody {
bool isUsedInDynamicReloc() const { return IsUsedInDynamicReloc; }
void setUsedInDynamicReloc() { IsUsedInDynamicReloc = true; }
bool isTls() const { return IsTls; }
bool isFunc() const { return IsFunc; }

// Returns the symbol name.
StringRef getName() const { return Name; }
@@ -127,9 +128,9 @@ class SymbolBody {

protected:
SymbolBody(Kind K, StringRef Name, bool IsWeak, uint8_t Visibility,
bool IsTls)
bool IsTls, bool IsFunc)
: SymbolKind(K), IsWeak(IsWeak), Visibility(Visibility), IsTls(IsTls),
Name(Name) {
IsFunc(IsFunc), Name(Name) {
IsUsedInRegularObj = K != SharedKind && K != LazyKind;
IsUsedInDynamicReloc = 0;
}
@@ -148,14 +149,16 @@ class SymbolBody {
unsigned IsUsedInDynamicReloc : 1;

unsigned IsTls : 1;
unsigned IsFunc : 1;
StringRef Name;
Symbol *Backref = nullptr;
};

// The base class for any defined symbols.
class Defined : public SymbolBody {
public:
Defined(Kind K, StringRef Name, bool IsWeak, uint8_t Visibility, bool IsTls);
Defined(Kind K, StringRef Name, bool IsWeak, uint8_t Visibility, bool IsTls,
bool IsFunction);
static bool classof(const SymbolBody *S) { return S->isDefined(); }
};

@@ -167,7 +170,8 @@ template <class ELFT> class DefinedElf : public Defined {
public:
DefinedElf(Kind K, StringRef N, const Elf_Sym &Sym)
: Defined(K, N, Sym.getBinding() == llvm::ELF::STB_WEAK,
Sym.getVisibility(), Sym.getType() == llvm::ELF::STT_TLS),
Sym.getVisibility(), Sym.getType() == llvm::ELF::STT_TLS,
Sym.getType() == llvm::ELF::STT_FUNC),
Sym(Sym) {}

const Elf_Sym &Sym;
@@ -289,7 +293,8 @@ template <class ELFT> class SharedSymbol : public DefinedElf<ELFT> {
class Lazy : public SymbolBody {
public:
Lazy(ArchiveFile *F, const llvm::object::Archive::Symbol S)
: SymbolBody(LazyKind, S.getName(), false, llvm::ELF::STV_DEFAULT, false),
: SymbolBody(LazyKind, S.getName(), false, llvm::ELF::STV_DEFAULT,
/*IsTls*/ false, /*IsFunction*/ false),
File(F), Sym(S) {}

static bool classof(const SymbolBody *S) { return S->kind() == LazyKind; }
30 changes: 30 additions & 0 deletions lld/test/ELF/bsymbolic.s
Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
// RUN: ld.lld -shared %t.o -o %t0.so
// RUN: ld.lld -shared -Bsymbolic %t.o -o %t1.so
// RUN: ld.lld -shared -Bsymbolic-functions %t.o -o %t2.so
// RUN: llvm-readobj -s %t0.so | FileCheck -check-prefix=NOOPTION %s
// RUN: llvm-readobj -s %t1.so | FileCheck -check-prefix=SYMBOLIC %s
// RUN: llvm-readobj -s %t2.so | FileCheck -check-prefix=SYMBOLIC %s

// NOOPTION: Section {
// NOOPTION: Name: .plt

// SYMBOLIC: Section {
// SYMBOLIC-NOT: Name: .plt

.text
.globl foo
.type foo,@function
foo:
nop

.globl bar
.type bar,@function
bar:
nop

.globl do
.type do,@function
do:
callq foo@PLT
callq bar@PLT

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