[llvm-objcopy] [COFF] Add support for removing symbols

Differential Revision: https://reviews.llvm.org/D55881 llvm-svn: 350893

Author: mstorsjo

llvm/test/tools/llvm-objcopy/COFF/Inputs/strip-symbols.yaml

@@ -0,0 +1,53 @@
+--- !COFF
+header: 
+ Machine: IMAGE_FILE_MACHINE_AMD64
+ Characteristics: [ ]
+sections: 
+ - Name: .text
+ Characteristics: [ ]
+ Alignment: 4
+ SectionData: 488B0500000000488B0500000000488B0500000000
+ Relocations: 
+ - VirtualAddress: 3
+ SymbolTableIndex: 0
+ Type: IMAGE_REL_AMD64_REL32
+ - VirtualAddress: 10
+ SymbolTableIndex: 1
+ Type: IMAGE_REL_AMD64_REL32
+ - VirtualAddress: 17
+ SymbolName: foo
+ Type: IMAGE_REL_AMD64_REL32
+ - Name: .rdata
+ Characteristics: [ ]
+ Alignment: 1
+ SectionData: '00'
+ - Name: .rdata
+ Characteristics: [ ]
+ Alignment: 1
+ SectionData: '01'
+symbols: 
+ - Name: .rdata
+ Value: 0
+ SectionNumber: 2
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_STATIC
+ - Name: .rdata
+ Value: 0
+ SectionNumber: 3
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_STATIC
+ - Name: mainfunc
+ Value: 0
+ SectionNumber: 1
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_EXTERNAL
+ - Name: foo
+ Value: 0
+ SectionNumber: 3
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_EXTERNAL
+...

llvm/test/tools/llvm-objcopy/COFF/strip-reloc-symbol.test

@@ -0,0 +1,5 @@
+# RUN: yaml2obj %p/Inputs/strip-symbols.yaml > %t.o
+# RUN: not llvm-objcopy -N foo %t.o 2>&1 | FileCheck %s --check-prefix=ERROR
+# RUN: not llvm-objcopy --strip-symbol foo %t.o 2>&1 | FileCheck %s --check-prefix=ERROR
+
+# ERROR: error: '{{.*}}/strip-reloc-symbol.test.tmp.o': not stripping symbol 'foo' because it is named in a relocation.

llvm/test/tools/llvm-objcopy/COFF/strip-symbol.test

@@ -0,0 +1,32 @@
+# RUN: yaml2obj %p/Inputs/strip-symbols.yaml > %t.in.o
+
+# RUN: llvm-readobj -relocations %t.in.o | FileCheck %s --check-prefixes=RELOCS,RELOCS-PRE
+# RUN: llvm-objdump -t %t.in.o | FileCheck %s --check-prefixes=SYMBOLS,SYMBOLS-PRE
+
+# RUN: llvm-objcopy -N mainfunc %t.in.o %t.out.o
+# RUN: llvm-readobj -relocations %t.out.o | FileCheck %s --check-prefixes=RELOCS,RELOCS-POST
+# RUN: llvm-objdump -t %t.out.o | FileCheck %s --check-prefix=SYMBOLS
+
+# RUN: llvm-objcopy --strip-symbol mainfunc %t.in.o %t.out.o
+# RUN: llvm-readobj -relocations %t.out.o | FileCheck %s --check-prefixes=RELOCS,RELOCS-POST
+# RUN: llvm-objdump -t %t.out.o | FileCheck %s --check-prefix=SYMBOLS
+
+# Explicitly listing the relocations for the input as well, to show
+# that the symbol index of the symbol foo is updated in the relocations,
+# while keeping relocations to two distinct .rdata symbols separate.
+
+# RELOCS: Relocations [
+# RELOCS-NEXT: Section (1) .text {
+# RELOCS-NEXT: 0x3 IMAGE_REL_AMD64_REL32 .rdata (0)
+# RELOCS-NEXT: 0xA IMAGE_REL_AMD64_REL32 .rdata (1)
+# RELOCS-PRE-NEXT: 0x11 IMAGE_REL_AMD64_REL32 foo (3)
+# RELOCS-POST-NEXT: 0x11 IMAGE_REL_AMD64_REL32 foo (2)
+# RELOCS-NEXT: }
+# RELOCS-NEXT: ]
+
+# SYMBOLS: SYMBOL TABLE:
+# SYMBOLS-NEXT: .rdata
+# SYMBOLS-NEXT: .rdata
+# SYMBOLS-PRE-NEXT: mainfunc
+# SYMBOLS-NEXT: foo
+# SYMBOLS-EMPTY:

llvm/tools/llvm-objcopy/CMakeLists.txt

@@ -18,6 +18,7 @@ add_llvm_tool(llvm-objcopy
  CopyConfig.cpp
  llvm-objcopy.cpp
  COFF/COFFObjcopy.cpp
+ COFF/Object.cpp
  COFF/Reader.cpp
  COFF/Writer.cpp
  ELF/ELFObjcopy.cpp

llvm/tools/llvm-objcopy/COFF/COFFObjcopy.cpp

@@ -17,6 +17,7 @@
 
 #include "llvm/Object/Binary.h"
 #include "llvm/Object/COFF.h"
+#include "llvm/Support/Errc.h"
 #include <cassert>
 
 namespace llvm {
@@ -26,6 +27,30 @@ namespace coff {
 using namespace object;
 using namespace COFF;
 
+static Error handleArgs(const CopyConfig &Config, Object &Obj) {
+ // If we need to do per-symbol removals, initialize the Referenced field.
+ if (!Config.SymbolsToRemove.empty())
+ if (Error E = Obj.markSymbols())
+ return E;
+
+ // Actually do removals of symbols.
+ Obj.removeSymbols([&](const Symbol &Sym) {
+ if (is_contained(Config.SymbolsToRemove, Sym.Name)) {
+ // Explicitly removing a referenced symbol is an error.
+ if (Sym.Referenced)
+ reportError(Config.OutputFilename,
+ make_error<StringError>(
+ "not stripping symbol '" + Sym.Name +
+ "' because it is named in a relocation.",
+ llvm::errc::invalid_argument));
+ return true;
+ }
+
+ return false;
+ });
+ return Error::success();
+}
+
 void executeObjcopyOnBinary(const CopyConfig &Config,
  object::COFFObjectFile &In, Buffer &Out) {
  COFFReader Reader(In);
@@ -34,6 +59,8 @@ void executeObjcopyOnBinary(const CopyConfig &Config,
  reportError(Config.InputFilename, ObjOrErr.takeError());
  Object *Obj = ObjOrErr->get();
  assert(Obj && "Unable to deserialize COFF object");
+ if (Error E = handleArgs(Config, *Obj))
+ reportError(Config.InputFilename, std::move(E));
  COFFWriter Writer(*Obj, Out);
  if (Error E = Writer.write())
  reportError(Config.OutputFilename, std::move(E));

llvm/tools/llvm-objcopy/COFF/Object.cpp

@@ -0,0 +1,70 @@
+//===- Object.cpp ---------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Object.h"
+#include <algorithm>
+
+namespace llvm {
+namespace objcopy {
+namespace coff {
+
+using namespace object;
+
+void Object::addSymbols(ArrayRef<Symbol> NewSymbols) {
+ for (Symbol S : NewSymbols) {
+ S.UniqueId = NextSymbolUniqueId++;
+ Symbols.emplace_back(S);
+ }
+ updateSymbols();
+}
+
+void Object::updateSymbols() {
+ SymbolMap = DenseMap<size_t, Symbol *>(Symbols.size());
+ size_t RawSymIndex = 0;
+ for (Symbol &Sym : Symbols) {
+ SymbolMap[Sym.UniqueId] = &Sym;
+ Sym.RawIndex = RawSymIndex;
+ RawSymIndex += 1 + Sym.Sym.NumberOfAuxSymbols;
+ }
+}
+
+const Symbol *Object::findSymbol(size_t UniqueId) const {
+ auto It = SymbolMap.find(UniqueId);
+ if (It == SymbolMap.end())
+ return nullptr;
+ return It->second;
+}
+
+void Object::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
+ Symbols.erase(
+ std::remove_if(std::begin(Symbols), std::end(Symbols),
+ [ToRemove](const Symbol &Sym) { return ToRemove(Sym); }),
+ std::end(Symbols));
+ updateSymbols();
+}
+
+Error Object::markSymbols() {
+ for (Symbol &Sym : Symbols)
+ Sym.Referenced = false;
+ for (const Section &Sec : Sections) {
+ for (const Relocation &R : Sec.Relocs) {
+ auto It = SymbolMap.find(R.Target);
+ if (It == SymbolMap.end())
+ return make_error<StringError>("Relocation target " + Twine(R.Target) +
+ " not found",
+ object_error::invalid_symbol_index);
+ It->second->Referenced = true;
+ }
+ }
+ return Error::success();
+}
+
+} // end namespace coff
+} // end namespace objcopy
+} // end namespace llvm

llvm/tools/llvm-objcopy/COFF/Object.h

@@ -11,7 +11,9 @@
 #define LLVM_TOOLS_OBJCOPY_COFF_OBJECT_H
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/iterator_range.h"
 #include "llvm/BinaryFormat/COFF.h"
 #include "llvm/Object/COFF.h"
 #include <cstddef>
@@ -22,17 +24,26 @@ namespace llvm {
 namespace objcopy {
 namespace coff {
 
+struct Relocation {
+ object::coff_relocation Reloc;
+ size_t Target;
+ StringRef TargetName; // Used for diagnostics only
+};
+
 struct Section {
  object::coff_section Header;
  ArrayRef<uint8_t> Contents;
- std::vector<object::coff_relocation> Relocs;
+ std::vector<Relocation> Relocs;
  StringRef Name;
 };
 
 struct Symbol {
  object::coff_symbol32 Sym;
  StringRef Name;
  ArrayRef<uint8_t> AuxData;
+ size_t UniqueId;
+ size_t RawIndex;
+ bool Referenced;
 };
 
 struct Object {
@@ -49,7 +60,31 @@ struct Object {
 
  std::vector<object::data_directory> DataDirectories;
  std::vector<Section> Sections;
+
+ ArrayRef<Symbol> getSymbols() const { return Symbols; }
+ // This allows mutating individual Symbols, but not mutating the list
+ // of symbols itself.
+ iterator_range<std::vector<Symbol>::iterator> getMutableSymbols() {
+ return make_range(Symbols.begin(), Symbols.end());
+ }
+
+ const Symbol *findSymbol(size_t UniqueId) const;
+
+ void addSymbols(ArrayRef<Symbol> NewSymbols);
+ void removeSymbols(function_ref<bool(const Symbol &)> ToRemove);
+
+ // Set the Referenced field on all Symbols, based on relocations in
+ // all sections.
+ Error markSymbols();
+
+private:
  std::vector<Symbol> Symbols;
+ DenseMap<size_t, Symbol *> SymbolMap;
+
+ size_t NextSymbolUniqueId = 0;
+
+ // Update SymbolMap and RawIndex in each Symbol.
+ void updateSymbols();
 };
 
 // Copy between coff_symbol16 and coff_symbol32.

llvm/tools/llvm-objcopy/COFF/Reader.cpp

@@ -73,7 +73,7 @@ Error COFFReader::readSections(Object &Obj) const {
  return errorCodeToError(EC);
  ArrayRef<coff_relocation> Relocs = COFFObj.getRelocations(Sec);
  for (const coff_relocation &R : Relocs)
- S.Relocs.push_back(R);
+ S.Relocs.push_back(Relocation{R});
  if (auto EC = COFFObj.getSectionName(Sec, S.Name))
  return errorCodeToError(EC);
  if (Sec->hasExtendedRelocations())
@@ -84,14 +84,16 @@ Error COFFReader::readSections(Object &Obj) const {
 }
 
 Error COFFReader::readSymbols(Object &Obj, bool IsBigObj) const {
+ std::vector<Symbol> Symbols;
+ Symbols.reserve(COFFObj.getRawNumberOfSymbols());
  for (uint32_t I = 0, E = COFFObj.getRawNumberOfSymbols(); I < E;) {
  Expected<COFFSymbolRef> SymOrErr = COFFObj.getSymbol(I);
  if (!SymOrErr)
  return SymOrErr.takeError();
  COFFSymbolRef SymRef = *SymOrErr;
 
- Obj.Symbols.push_back(Symbol());
- Symbol &Sym = Obj.Symbols.back();
+ Symbols.push_back(Symbol());
+ Symbol &Sym = Symbols.back();
  // Copy symbols from the original form into an intermediate coff_symbol32.
  if (IsBigObj)
  copySymbol(Sym.Sym,
@@ -106,6 +108,30 @@ Error COFFReader::readSymbols(Object &Obj, bool IsBigObj) const {
  (IsBigObj ? sizeof(coff_symbol32) : sizeof(coff_symbol16))) == 0);
  I += 1 + SymRef.getNumberOfAuxSymbols();
  }
+ Obj.addSymbols(Symbols);
+ return Error::success();
+}
+
+Error COFFReader::setRelocTargets(Object &Obj) const {
+ std::vector<const Symbol *> RawSymbolTable;
+ for (const Symbol &Sym : Obj.getSymbols()) {
+ RawSymbolTable.push_back(&Sym);
+ for (size_t I = 0; I < Sym.Sym.NumberOfAuxSymbols; I++)
+ RawSymbolTable.push_back(nullptr);
+ }
+ for (Section &Sec : Obj.Sections) {
+ for (Relocation &R : Sec.Relocs) {
+ if (R.Reloc.SymbolTableIndex >= RawSymbolTable.size())
+ return make_error<StringError>("SymbolTableIndex out of range",
+ object_error::parse_failed);
+ const Symbol *Sym = RawSymbolTable[R.Reloc.SymbolTableIndex];
+ if (Sym == nullptr)
+ return make_error<StringError>("Invalid SymbolTableIndex",
+ object_error::parse_failed);
+ R.Target = Sym->UniqueId;
+ R.TargetName = Sym->Name;
+ }
+ }
  return Error::success();
 }
 
@@ -136,6 +162,8 @@ Expected<std::unique_ptr<Object>> COFFReader::create() const {
  return std::move(E);
  if (Error E = readSymbols(*Obj, IsBigObj))
  return std::move(E);
+ if (Error E = setRelocTargets(*Obj))
+ return std::move(E);
 
  return std::move(Obj);
 }

llvm/tools/llvm-objcopy/COFF/Reader.h

@@ -35,6 +35,7 @@ class COFFReader : public Reader {
  Error readExecutableHeaders(Object &Obj) const;
  Error readSections(Object &Obj) const;
  Error readSymbols(Object &Obj, bool IsBigObj) const;
+ Error setRelocTargets(Object &Obj) const;
 
 public:
  explicit COFFReader(const COFFObjectFile &O) : COFFObj(O) {}