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[ELF] - Give automatically generated __start_* and __stop_* symbols d…
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…efault visibility.

This patch is opposite to D19024, which made this symbols to be hidden by default.

Unfortunately FreeBSD loader wants to see
start_set_modmetadata_set/stop_set_modmetadata_set in the dynamic symbol table. 
They were not placed there because had hidden visibility.

Patch makes them to have default visibility again.

Differential revision: https://reviews.llvm.org/D23552

llvm-svn: 279262
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George Rimar committed Aug 19, 2016
1 parent 9989f80 commit e1937bb
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Showing 6 changed files with 45 additions and 25 deletions.
4 changes: 2 additions & 2 deletions lld/ELF/LinkerScript.cpp
View file
Expand Up @@ -51,8 +51,8 @@ static void addRegular(SymbolAssignment *Cmd) {
}

template <class ELFT> static void addSynthetic(SymbolAssignment *Cmd) {
Symbol *Sym = Symtab<ELFT>::X->addSynthetic(Cmd->Name, nullptr, 0);
Sym->Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
Symbol *Sym = Symtab<ELFT>::X->addSynthetic(
Cmd->Name, nullptr, 0, Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT);
Cmd->Sym = Sym->body();
}

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8 changes: 4 additions & 4 deletions lld/ELF/SymbolTable.cpp
View file
Expand Up @@ -418,12 +418,12 @@ Symbol *SymbolTable<ELFT>::addRegular(StringRef Name, uint8_t Binding,
template <typename ELFT>
Symbol *SymbolTable<ELFT>::addSynthetic(StringRef N,
OutputSectionBase<ELFT> *Section,
uintX_t Value) {
uintX_t Value, uint8_t StOther) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) =
insert(N, STT_NOTYPE, STV_HIDDEN, /*CanOmitFromDynSym*/ false,
/*IsUsedInRegularObj*/ true, nullptr);
std::tie(S, WasInserted) = insert(N, STT_NOTYPE, /*Visibility*/ StOther & 0x3,
/*CanOmitFromDynSym*/ false,
/*IsUsedInRegularObj*/ true, nullptr);
int Cmp = compareDefinedNonCommon<ELFT>(S, WasInserted, STB_GLOBAL);
if (Cmp > 0)
replaceBody<DefinedSynthetic<ELFT>>(S, N, Value, Section);
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2 changes: 1 addition & 1 deletion lld/ELF/SymbolTable.h
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Expand Up @@ -65,7 +65,7 @@ template <class ELFT> class SymbolTable {
InputSectionBase<ELFT> *Section);
Symbol *addRegular(StringRef Name, uint8_t Binding, uint8_t StOther);
Symbol *addSynthetic(StringRef N, OutputSectionBase<ELFT> *Section,
uintX_t Value);
uintX_t Value, uint8_t StOther);
void addShared(SharedFile<ELFT> *F, StringRef Name, const Elf_Sym &Sym,
const typename ELFT::Verdef *Verdef);

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16 changes: 9 additions & 7 deletions lld/ELF/Writer.cpp
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Expand Up @@ -519,15 +519,15 @@ static Symbol *addOptionalSynthetic(StringRef Name,
return nullptr;
if (!S->isUndefined() && !S->isShared())
return S->symbol();
return Symtab<ELFT>::X->addSynthetic(Name, Sec, Val);
return Symtab<ELFT>::X->addSynthetic(Name, Sec, Val, STV_HIDDEN);
}

template <class ELFT>
static void addSynthetic(StringRef Name, OutputSectionBase<ELFT> *Sec,
typename ELFT::uint Val) {
SymbolBody *S = Symtab<ELFT>::X->find(Name);
if (!S || S->isUndefined() || S->isShared())
Symtab<ELFT>::X->addSynthetic(Name, Sec, Val);
Symtab<ELFT>::X->addSynthetic(Name, Sec, Val, STV_HIDDEN);
}
// The beginning and the ending of .rel[a].plt section are marked
// with __rel[a]_iplt_{start,end} symbols if it is a statically linked
Expand All @@ -554,7 +554,8 @@ template <class ELFT> void Writer<ELFT>::addReservedSymbols() {
// so that it points to an absolute address which is relative to GOT.
// See "Global Data Symbols" in Chapter 6 in the following document:
// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
Symtab<ELFT>::X->addSynthetic("_gp", Out<ELFT>::Got, MipsGPOffset);
Symtab<ELFT>::X->addSynthetic("_gp", Out<ELFT>::Got, MipsGPOffset,
STV_HIDDEN);

// On MIPS O32 ABI, _gp_disp is a magic symbol designates offset between
// start of function and 'gp' pointer into GOT.
Expand Down Expand Up @@ -701,7 +702,8 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
// Even the author of gold doesn't remember why gold behaves that way.
// https://sourceware.org/ml/binutils/2002-03/msg00360.html
if (Out<ELFT>::DynSymTab)
Symtab<ELFT>::X->addSynthetic("_DYNAMIC", Out<ELFT>::Dynamic, 0);
Symtab<ELFT>::X->addSynthetic("_DYNAMIC", Out<ELFT>::Dynamic, 0,
STV_HIDDEN);

// Define __rel[a]_iplt_{start,end} symbols if needed.
addRelIpltSymbols();
Expand Down Expand Up @@ -893,11 +895,11 @@ void Writer<ELFT>::addStartStopSymbols(OutputSectionBase<ELFT> *Sec) {
StringRef Stop = Saver.save("__stop_" + S);
if (SymbolBody *B = Symtab<ELFT>::X->find(Start))
if (B->isUndefined())
Symtab<ELFT>::X->addSynthetic(Start, Sec, 0);
Symtab<ELFT>::X->addSynthetic(Start, Sec, 0, B->getVisibility());
if (SymbolBody *B = Symtab<ELFT>::X->find(Stop))
if (B->isUndefined())
Symtab<ELFT>::X->addSynthetic(Stop, Sec,
DefinedSynthetic<ELFT>::SectionEnd);
Symtab<ELFT>::X->addSynthetic(
Stop, Sec, DefinedSynthetic<ELFT>::SectionEnd, B->getVisibility());
}

template <class ELFT>
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16 changes: 9 additions & 7 deletions lld/test/ELF/startstop-shared.s
View file
Expand Up @@ -6,21 +6,23 @@
.data
.quad __start_foo
.section foo,"aw"
// By default the symbol is hidden.
// CHECK: R_X86_64_RELATIVE - 0x[[ADDR1:.*]]

.hidden __start_bar
.quad __start_bar
.section bar,"a"
// References do not affect the visibility.
// CHECK: R_X86_64_RELATIVE - 0x[[ADDR2:.*]]

// Test that we are able to hide the symbol.
// CHECK: R_X86_64_RELATIVE - 0x[[ADDR:.*]]

// By default the symbol is visible and we need a dynamic reloc.
// CHECK: R_X86_64_64 __start_foo 0x0

// CHECK: Name: __start_bar
// CHECK-NEXT: Value: 0x[[ADDR2]]
// CHECK-NEXT: Value: 0x[[ADDR]]
// CHECK-NEXT: Size:
// CHECK-NEXT: Binding: Local

// CHECK: Name: __start_foo
// CHECK-NEXT: Value: 0x[[ADDR1]]
// CHECK-NEXT: Value:
// CHECK-NEXT: Size:
// CHECK-NEXT: Binding: Local
// CHECK-NEXT: Binding: Global
24 changes: 20 additions & 4 deletions lld/test/ELF/startstop.s
View file
Expand Up @@ -22,30 +22,46 @@

// SYMBOL: Relocations [
// SYMBOL-NEXT: Section ({{.*}}) .rela.dyn {
// SYMBOL-NEXT: 0x3000 R_X86_64_RELATIVE - 0x3020
// SYMBOL-NEXT: 0x3008 R_X86_64_RELATIVE - 0x3021
// SYMBOL-NEXT: 0x3010 R_X86_64_RELATIVE - 0x3010
// SYMBOL-NEXT: 0x3018 R_X86_64_RELATIVE - 0x3011
// SYMBOL-NEXT: 0x3010 R_X86_64_64 __stop_zed1 0x0
// SYMBOL-NEXT: 0x3018 R_X86_64_64 __stop_zed1 0x1
// SYMBOL-NEXT: 0x3000 R_X86_64_64 __stop_zed2 0x0
// SYMBOL-NEXT: 0x3008 R_X86_64_64 __stop_zed2 0x1
// SYMBOL-NEXT: }
// SYMBOL-NEXT: ]

// SYMBOL: Symbol {
// SYMBOL: Name: __start_bar
// SYMBOL: Value: 0x1012
// SYMBOL: STV_HIDDEN
// SYMBOL: Section: bar
// SYMBOL: }
// SYMBOL-NOT: Section: __stop_bar
// SYMBOL: Symbol {
// SYMBOL: Name: __start_foo
// SYMBOL: Value: 0x100F
// SYMBOL: STV_HIDDEN
// SYMBOL: Section: foo
// SYMBOL: }
// SYMBOL: Symbol {
// SYMBOL: Name: __stop_foo
// SYMBOL: Value: 0x1012
// STMBOL: STV_HIDDEN
// SYMBOL: Section: foo
// SYMBOL: }

// SYMBOL: Symbol {
// SYMBOL: Name: __stop_zed1
// SYMBOL: Value: 0x3010
// STMBOL: Other: 0
// SYMBOL: Section: zed1
// SYMBOL: }
// SYMBOL: Symbol {
// SYMBOL: Name: __stop_zed2
// SYMBOL: Value: 0x3020
// STMBOL: Other: 0
// SYMBOL: Section: zed2
// SYMBOL: }

.hidden __start_foo
.hidden __stop_foo
.hidden __start_bar
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