[llvm-objcopy] Add --localize-hidden option

This change adds support in llvm-objcopy for GNU objcopy's --localize-hidden
option. This option changes every hidden or internal symbol into a local symbol.

llvm-svn: 321884

test/tools/llvm-objcopy/localize-hidden.test

@@ -0,0 +1,164 @@
+# RUN: yaml2obj %s > %t
+# RUN: llvm-objcopy -localize-hidden %t %t2
+# RUN: llvm-readobj -relocations -symbols %t2 | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Size:            64
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    Address:         0x2000
+    AddressAlign:    0x0000000000000010
+    Content:         "0000000000000000"
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Info:            .text
+    Relocations:
+      - Offset: 0x1000
+        Symbol: undefGlobal
+        Type:   R_X86_64_PC32
+Symbols:
+  Local:
+    - Name:     hiddenLocal
+      Type:     STT_FUNC
+      Section:  .text
+      Value:    0x1008
+      Size:     8
+      Visibility: STV_HIDDEN
+  Weak:
+    - Name:     hiddenWeak
+      Type:     STT_FUNC
+      Section:  .text
+      Value:    0x1010
+      Size:     8
+      Visibility: STV_HIDDEN
+  Global:
+    - Name:     defaultGlobal
+      Type:     STT_FUNC
+      Size:     8
+      Section:  .text
+      Value:    0x1000
+    - Name:     hiddenGlobal
+      Type:     STT_OBJECT
+      Section:  .data
+      Value:    0x2006
+      Size:     2
+      Visibility: STV_HIDDEN
+    - Name:     undefGlobal
+      Type:     STT_FUNC
+      Size:     8
+    - Name:     internalGlobal
+      Type:     STT_OBJECT
+      Section:  .data
+      Value:    0x2002
+      Size:     2
+      Visibility: STV_INTERNAL
+    - Name:     protectedGlobal
+      Type:     STT_OBJECT
+      Section:  .data
+      Value:    0x2000
+      Size:     4
+      Visibility: STV_PROTECTED
+
+#CHECK:     Relocations [
+#CHECK-NEXT:  Section (3) .rel.text {
+#CHECK-NEXT:    0x1000 R_X86_64_PC32 undefGlobal 0x0
+#CHECK-NEXT:  }
+#CHECK-NEXT:]
+
+
+#CHECK: Symbols [
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name:
+#CHECK-NEXT:    Value: 0x0
+#CHECK-NEXT:    Size: 0
+#CHECK-NEXT:    Binding: Local
+#CHECK-NEXT:    Type: None
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: Undefined
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: hiddenLocal
+#CHECK-NEXT:    Value: 0x1008
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Local
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other [
+#CHECK-NEXT:      STV_HIDDEN
+#CHECK-NEXT:    ]
+#CHECK-NEXT:    Section: .text
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: hiddenGlobal
+#CHECK-NEXT:    Value: 0x2006
+#CHECK-NEXT:    Size: 2
+#CHECK-NEXT:    Binding: Local
+#CHECK-NEXT:    Type: Object
+#CHECK-NEXT:    Other [
+#CHECK-NEXT:      STV_HIDDEN
+#CHECK-NEXT:    ]
+#CHECK-NEXT:    Section: .data
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: internalGlobal
+#CHECK-NEXT:    Value: 0x2002
+#CHECK-NEXT:    Size: 2
+#CHECK-NEXT:    Binding: Local
+#CHECK-NEXT:    Type: Object
+#CHECK-NEXT:    Other [
+#CHECK-NEXT:      STV_INTERNAL
+#CHECK-NEXT:    ]
+#CHECK-NEXT:    Section: .data
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: hiddenWeak
+#CHECK-NEXT:    Value: 0x1010
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Local
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other [
+#CHECK-NEXT:      STV_HIDDEN
+#CHECK-NEXT:    ]
+#CHECK-NEXT:    Section: .text
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: defaultGlobal
+#CHECK-NEXT:    Value: 0x1000
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Global
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: .text
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: undefGlobal
+#CHECK-NEXT:    Value: 0x0
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Global
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section:
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: protectedGlobal
+#CHECK-NEXT:    Value: 0x2000
+#CHECK-NEXT:    Size: 4
+#CHECK-NEXT:    Binding: Global
+#CHECK-NEXT:    Type: Object
+#CHECK-NEXT:    Other [
+#CHECK-NEXT:      STV_PROTECTED
+#CHECK-NEXT:    ]
+#CHECK-NEXT:    Section: .data
+#CHECK-NEXT:  }
+#CHECK-NEXT:]

tools/llvm-objcopy/Object.cpp

@@ -175,6 +175,25 @@ void SymbolTableSection::removeSectionReferences(const SectionBase *Sec) {
   Symbols.erase(Iter, std::end(Symbols));
 }
 
+void SymbolTableSection::localize(
+    std::function<bool(const Symbol &)> ToLocalize) {
+  for (const auto &Sym : Symbols) {
+    if (ToLocalize(*Sym))
+      Sym->Binding = STB_LOCAL;
+  }
+
+  // Now that the local symbols aren't grouped at the start we have to reorder
+  // the symbols to respect this property.
+  std::stable_partition(
+      std::begin(Symbols), std::end(Symbols),
+      [](const SymPtr &Sym) { return Sym->Binding == STB_LOCAL; });
+
+  // Lastly we fix the symbol indexes.
+  uint32_t Index = 0;
+  for (auto &Sym : Symbols)
+    Sym->Index = Index++;
+}
+
 void SymbolTableSection::initialize(SectionTableRef SecTable) {
   Size = 0;
   setStrTab(SecTable.getSectionOfType<StringTableSection>(

tools/llvm-objcopy/Object.h

@@ -214,6 +214,7 @@ public:
   const SectionBase *getStrTab() const { return SymbolNames; }
   const Symbol *getSymbolByIndex(uint32_t Index) const;
   void removeSectionReferences(const SectionBase *Sec) override;
+  void localize(std::function<bool(const Symbol &)> ToLocalize);
   void initialize(SectionTableRef SecTable) override;
   void finalize() override;
 
@@ -384,7 +385,7 @@ public:
   Object(const object::ELFObjectFile<ELFT> &Obj);
   virtual ~Object() = default;
 
-  const SymbolTableSection *getSymTab() const { return SymbolTable; }
+  SymbolTableSection *getSymTab() const { return SymbolTable; }
   const SectionBase *getSectionHeaderStrTab() const { return SectionNames; }
   void removeSections(std::function<bool(const SectionBase &)> ToRemove);
   void addSection(StringRef SecName, ArrayRef<uint8_t> Data);

tools/llvm-objcopy/llvm-objcopy.cpp

@@ -117,6 +117,10 @@ static cl::list<std::string> AddSection(
     "add-section",
     cl::desc("Make a section named <section> with the contents of <file>."),
     cl::value_desc("section=file"));
+static cl::opt<bool> LocalizeHidden(
+    "localize-hidden",
+    cl::desc(
+        "Mark all symbols that have hidden or internal visibility as local"));
 
 using SectionPred = std::function<bool(const SectionBase &Sec)>;
 
@@ -180,6 +184,14 @@ template <class ELFT> void CopyBinary(const ELFObjectFile<ELFT> &ObjFile) {
   if (!SplitDWO.empty())
     SplitDWOToFile<ELFT>(ObjFile, SplitDWO.getValue());
 
+  // Localize:
+
+  if (LocalizeHidden) {
+    Obj->getSymTab()->localize([](const Symbol &Sym) {
+      return Sym.Visibility == STV_HIDDEN || Sym.Visibility == STV_INTERNAL;
+    });
+  }
+
   SectionPred RemovePred = [](const SectionBase &) { return false; };
 
   // Removes: