[ELF] - Give automatically generated __start_* and __stop_* symbols default 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

6 files changed, 45 insertions, 25 deletions

diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 6b037a021fb..9cfbb48a2ca 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -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();
 }
 
diff --git a/lld/ELF/SymbolTable.cpp b/lld/ELF/SymbolTable.cpp
index b4f9411ac49..c657a3a0608 100644
--- a/lld/ELF/SymbolTable.cpp
+++ b/lld/ELF/SymbolTable.cpp
@@ -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);
diff --git a/lld/ELF/SymbolTable.h b/lld/ELF/SymbolTable.h
index 416e9434296..7a2121c870f 100644
--- a/lld/ELF/SymbolTable.h
+++ b/lld/ELF/SymbolTable.h
@@ -65,7 +65,7 @@ public:
                      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);
 
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index ecbbc0a3352..b39897f8200 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -519,7 +519,7 @@ 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>
@@ -527,7 +527,7 @@ 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
@@ -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.
@@ -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();
@@ -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>
diff --git a/lld/test/ELF/startstop-shared.s b/lld/test/ELF/startstop-shared.s
index 77411f3f25c..80ccf3df0aa 100644
--- a/lld/test/ELF/startstop-shared.s
+++ b/lld/test/ELF/startstop-shared.s
@@ -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
diff --git a/lld/test/ELF/startstop.s b/lld/test/ELF/startstop.s
index a7b2e43e6a5..326196dafa6 100644
--- a/lld/test/ELF/startstop.s
+++ b/lld/test/ELF/startstop.s
@@ -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