Add support for the .symver directive. This is really ugly, but most of it is

contained in the ELF object writer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117448 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/ELFObjectWriter.cpp

@@ -134,6 +134,7 @@ namespace {
     };
 
     SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
+    DenseMap<const MCSymbol *, const MCSymbol *> Renames;
 
     llvm::DenseMap<const MCSectionData*,
                    std::vector<ELFRelocationEntry> > Relocations;
@@ -292,8 +293,7 @@ namespace {
 
     void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout);
 
-    void ExecutePostLayoutBinding(MCAssembler &Asm) {
+    void ExecutePostLayoutBinding(MCAssembler &Asm);
-    }
 
     void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
                           uint64_t Address, uint64_t Offset,
@@ -449,6 +449,30 @@ static const MCSymbol &AliasedSymbol(const MCSymbol &Symbol) {
   return *S;
 }
 
+void ELFObjectWriterImpl::ExecutePostLayoutBinding(MCAssembler &Asm) {
+  // The presence of symbol versions causes undefined symbols and
+  // versions declared with @@@ to be renamed.
+
+  for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
+         ie = Asm.symbol_end(); it != ie; ++it) {
+    const MCSymbol &Alias = it->getSymbol();
+    if (!Alias.isVariable())
+      continue;
+    const MCSymbol &Symbol = AliasedSymbol(Alias);
+    const StringRef &AliasName = Alias.getName();
+    size_t Pos = AliasName.find('@');
+    if (Pos == StringRef::npos)
+      continue;
+
+    StringRef Rest(AliasName.begin() + Pos);
+    if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
+      continue;
+
+    std::pair<const MCSymbol *, const MCSymbol *> t(&Symbol, &Alias);
+    Renames.insert(t);
+  }
+}
+
 void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
                                       const MCAsmLayout &Layout) {
   MCSymbolData &OrigData = *MSD.SymbolData;
@@ -593,6 +617,9 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm,
   bool IsPCRel = isFixupKindX86PCRel(Fixup.getKind());
   if (!Target.isAbsolute()) {
     Symbol = &AliasedSymbol(Target.getSymA()->getSymbol());
+    const MCSymbol *Renamed = Renames.lookup(Symbol);
+    if (Renamed)
+      Symbol = Renamed;
     MCSymbolData &SD = Asm.getSymbolData(*Symbol);
     MCFragment *F = SD.getFragment();
 
@@ -765,10 +792,13 @@ ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
 }
 
 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
-                       bool Used) {
+                       bool Used, bool Renamed) {
   if (Used)
     return true;
 
+  if (Renamed)
+    return false;
+
   const MCSymbol &Symbol = Data.getSymbol();
 
   const MCSymbol &A = AliasedSymbol(Symbol);
@@ -821,40 +851,52 @@ void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) {
          ie = Asm.symbol_end(); it != ie; ++it) {
     const MCSymbol &Symbol = it->getSymbol();
 
-    if (!isInSymtab(Asm, *it, UsedInReloc.count(&Symbol)))
+    if (!isInSymtab(Asm, *it, UsedInReloc.count(&Symbol),
+                    Renames.count(&Symbol)))
       continue;
 
     ELFSymbolData MSD;
     MSD.SymbolData = it;
     bool Local = isLocal(*it);
+    const MCSymbol &RefSymbol = AliasedSymbol(Symbol);
 
     if (it->isCommon()) {
       assert(!Local);
       MSD.SectionIndex = ELF::SHN_COMMON;
     } else if (Symbol.isAbsolute()) {
       MSD.SectionIndex = ELF::SHN_ABS;
-    } else if (Symbol.isVariable()) {
+    } else if (RefSymbol.isUndefined()) {
-      const MCSymbol &RefSymbol = AliasedSymbol(Symbol);
-      if (RefSymbol.isDefined()) {
-        MSD.SectionIndex = SectionIndexMap.lookup(&RefSymbol.getSection());
-        assert(MSD.SectionIndex && "Invalid section index!");
-      }
-    } else if (Symbol.isUndefined()) {
-      assert(!Local);
       MSD.SectionIndex = ELF::SHN_UNDEF;
       // FIXME: Undefined symbols are global, but this is the first place we
       // are able to set it.
       if (GetBinding(*it) == ELF::STB_LOCAL)
         SetBinding(*it, ELF::STB_GLOBAL);
+    } else if (Symbol.isVariable()) {
+      MSD.SectionIndex = SectionIndexMap.lookup(&RefSymbol.getSection());
+      assert(MSD.SectionIndex && "Invalid section index!");
     } else {
       MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
       assert(MSD.SectionIndex && "Invalid section index!");
     }
 
-    uint64_t &Entry = StringIndexMap[Symbol.getName()];
+    // The @@@ in symbol version is replaced with @ in undefined symbols and
+    // @@ in defined ones.
+    StringRef Name = Symbol.getName();
+    size_t Pos = Name.find("@@@");
+    std::string FinalName;
+    if (Pos != StringRef::npos) {
+      StringRef Prefix(Name.begin(), Pos);
+      unsigned n = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
+      StringRef Suffix(Name.begin() + Pos + n);
+      FinalName = Prefix.str() + Suffix.str();
+    } else {
+      FinalName = Name.str();
+    }
+
+    uint64_t &Entry = StringIndexMap[FinalName];
     if (!Entry) {
       Entry = StringTable.size();
-      StringTable += Symbol.getName();
+      StringTable += FinalName;
       StringTable += '\x00';
     }
     MSD.StringIndex = Entry;

lib/MC/MCParser/ELFAsmParser.cpp

@@ -12,6 +12,7 @@
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCStreamer.h"
@@ -51,6 +52,7 @@ public:
     AddDirectiveHandler<&ELFAsmParser::ParseDirectivePrevious>(".previous");
     AddDirectiveHandler<&ELFAsmParser::ParseDirectiveType>(".type");
     AddDirectiveHandler<&ELFAsmParser::ParseDirectiveIdent>(".ident");
+    AddDirectiveHandler<&ELFAsmParser::ParseDirectiveSymver>(".symver");
   }
 
   // FIXME: Part of this logic is duplicated in the MCELFStreamer. What is
@@ -116,6 +118,7 @@ public:
   bool ParseDirectivePrevious(StringRef, SMLoc);
   bool ParseDirectiveType(StringRef, SMLoc);
   bool ParseDirectiveIdent(StringRef, SMLoc);
+  bool ParseDirectiveSymver(StringRef, SMLoc);
 
 private:
   bool ParseSectionName(StringRef &SectionName);
@@ -377,6 +380,33 @@ bool ELFAsmParser::ParseDirectiveIdent(StringRef, SMLoc) {
   return false;
 }
 
+/// ParseDirectiveSymver
+///  ::= .symver foo, bar2@zed
+bool ELFAsmParser::ParseDirectiveSymver(StringRef, SMLoc) {
+  StringRef Name;
+  if (getParser().ParseIdentifier(Name))
+    return TokError("expected identifier in directive");
+
+  if (getLexer().isNot(AsmToken::Comma))
+    return TokError("expected a comma");
+
+  Lex();
+
+  StringRef AliasName;
+  if (getParser().ParseIdentifier(AliasName))
+    return TokError("expected identifier in directive");
+
+  if (AliasName.find('@') == StringRef::npos)
+    return TokError("expected a '@' in the name");
+
+  MCSymbol *Alias = getContext().GetOrCreateSymbol(AliasName);
+  MCSymbol *Sym = getContext().GetOrCreateSymbol(Name);
+  const MCExpr *Value = MCSymbolRefExpr::Create(Sym, getContext());
+
+  getStreamer().EmitAssignment(Alias, Value);
+  return false;
+}
+
 namespace llvm {
 
 MCAsmParserExtension *createELFAsmParser() {

test/MC/ELF/symref.s

@@ -0,0 +1,142 @@
+// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | elf-dump  | FileCheck %s
+
+defined1:
+defined2:
+defined3:
+        .symver defined1, bar1@zed
+        .symver undefined1, bar2@zed
+
+        .symver defined2, bar3@@zed
+
+        .symver defined3, bar5@@@zed
+        .symver undefined3, bar6@@@zed
+
+        .long defined1
+        .long undefined1
+        .long defined2
+        .long defined3
+        .long undefined3
+
+// CHECK:      # Symbol 0x00000001
+// CHECK-NEXT: (('st_name', 0x00000013) # 'bar1@zed'
+// CHECK-NEXT:  ('st_bind', 0x00000000)
+// CHECK-NEXT:  ('st_type', 0x00000000)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000001)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Symbol 0x00000002
+// CHECK-NEXT: (('st_name', 0x00000025) # 'bar3@@zed'
+// CHECK-NEXT:  ('st_bind', 0x00000000)
+// CHECK-NEXT:  ('st_type', 0x00000000)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000001)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Symbol 0x00000003
+// CHECK-NEXT: (('st_name', 0x0000002f) # 'bar5@@zed'
+// CHECK-NEXT:  ('st_bind', 0x00000000)
+// CHECK-NEXT:  ('st_type', 0x00000000)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000001)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Symbol 0x00000004
+// CHECK-NEXT: (('st_name', 0x00000001) # 'defined1'
+// CHECK-NEXT:  ('st_bind', 0x00000000)
+// CHECK-NEXT:  ('st_type', 0x00000000)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000001)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Symbol 0x00000005
+// CHECK-NEXT: (('st_name', 0x0000000a) # 'defined2'
+// CHECK-NEXT:  ('st_bind', 0x00000000)
+// CHECK-NEXT:  ('st_type', 0x00000000)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000001)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Symbol 0x00000006
+// CHECK-NEXT: (('st_name', 0x00000000) # ''
+// CHECK-NEXT:  ('st_bind', 0x00000000)
+// CHECK-NEXT:  ('st_type', 0x00000003)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000001)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Symbol 0x00000007
+// CHECK-NEXT: (('st_name', 0x00000000) # ''
+// CHECK-NEXT:  ('st_bind', 0x00000000)
+// CHECK-NEXT:  ('st_type', 0x00000003)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000002)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Symbol 0x00000008
+// CHECK-NEXT: (('st_name', 0x00000000) # ''
+// CHECK-NEXT:  ('st_bind', 0x00000000)
+// CHECK-NEXT:  ('st_type', 0x00000003)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000003)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Symbol 0x00000009
+// CHECK-NEXT: (('st_name', 0x0000001c) # 'bar2@zed'
+// CHECK-NEXT:  ('st_bind', 0x00000001)
+// CHECK-NEXT:  ('st_type', 0x00000000)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000000)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Symbol 0x0000000a
+// CHECK-NEXT: (('st_name', 0x00000039) # 'bar6@zed'
+// CHECK-NEXT:  ('st_bind', 0x00000001)
+// CHECK-NEXT:  ('st_type', 0x00000000)
+// CHECK-NEXT:  ('st_other', 0x00000000)
+// CHECK-NEXT:  ('st_shndx', 0x00000000)
+// CHECK-NEXT:  ('st_value', 0x00000000)
+// CHECK-NEXT:  ('st_size', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT:])
+
+// CHECK:      # Relocation 0x00000000
+// CHECK-NEXT: (('r_offset', 0x00000000)
+// CHECK-NEXT:  ('r_sym', 0x00000006)
+// CHECK-NEXT:  ('r_type', 0x0000000a)
+// CHECK-NEXT:  ('r_addend', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Relocation 0x00000001
+// CHECK-NEXT: (('r_offset', 0x00000004)
+// CHECK-NEXT:  ('r_sym', 0x00000009)
+// CHECK-NEXT:  ('r_type', 0x0000000a)
+// CHECK-NEXT:  ('r_addend', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Relocation 0x00000002
+// CHECK-NEXT: (('r_offset', 0x00000008)
+// CHECK-NEXT:  ('r_sym', 0x00000006)
+// CHECK-NEXT:  ('r_type', 0x0000000a)
+// CHECK-NEXT:  ('r_addend', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Relocation 0x00000003
+// CHECK-NEXT: (('r_offset', 0x0000000c)
+// CHECK-NEXT:  ('r_sym', 0x00000006)
+// CHECK-NEXT:  ('r_type', 0x0000000a)
+// CHECK-NEXT:  ('r_addend', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT: # Relocation 0x00000004
+// CHECK-NEXT: (('r_offset', 0x00000010)
+// CHECK-NEXT:  ('r_sym', 0x0000000a)
+// CHECK-NEXT:  ('r_type', 0x0000000a)
+// CHECK-NEXT:  ('r_addend', 0x00000000)
+// CHECK-NEXT: ),
+// CHECK-NEXT:])