[lld] r198728 - [mach-o] properly extract atom content from subrange of section content

[Joey Gouly]

Thanks Nick, this is nicer than my local solution!
On 8 Jan 2014 02:59, "Nick Kledzik" <kledzik at apple.com> wrote:

> Author: kledzik
> Date: Tue Jan  7 20:52:58 2014
> New Revision: 198728
>
> URL: http://llvm.org/viewvc/llvm-project?rev=198728&view=rev
> Log:
> [mach-o] properly extract atom content from subrange of section content
>
> Modified:
>     lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
>     lld/trunk/unittests/MachOTests/MachONormalizedFileToAtomsTests.cpp
>
> Modified: lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp?rev=198728&r1=198727&r2=198728&view=diff
>
> ==============================================================================
> --- lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
> (original)
> +++ lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp Tue
> Jan  7 20:52:58 2014
> @@ -34,13 +34,38 @@ namespace lld {
>  namespace mach_o {
>  namespace normalized {
>
> +static uint64_t nextSymbolAddress(const NormalizedFile &normalizedFile,
> +                                const Symbol &symbol) {
> +  uint64_t symbolAddr = symbol.value;
> +  uint8_t symbolSectionIndex = symbol.sect;
> +  const Section &section = normalizedFile.sections[symbolSectionIndex -
> 1];
> +  // If no symbol after this address, use end of section address.
> +  uint64_t closestAddr = section.address + section.content.size();
> +  for (const Symbol &s : normalizedFile.globalSymbols) {
> +    if (s.sect != symbolSectionIndex)
> +      continue;
> +    uint64_t sValue = s.value;
> +    if (sValue <= symbolAddr)
> +      continue;
> +    if (sValue < closestAddr)
> +      closestAddr = s.value;
> +  }
> +  return closestAddr;
> +}
> +
>  static ErrorOr<std::unique_ptr<lld::File>>
>  normalizedObjectToAtoms(const NormalizedFile &normalizedFile, StringRef
> path) {
>    std::unique_ptr<MachOFile> file(new MachOFile(path));
>
> -  for (auto &sym : normalizedFile.globalSymbols) {
> -    file->addDefinedAtom(sym.name,
> -                         normalizedFile.sections[sym.sect - 1].content);
> + for (const Symbol &sym : normalizedFile.globalSymbols) {
> +    // Mach-O symbol table does have size in it, so need to scan ahead
> +    // to find symbol with next highest address.
> +    const Section &section = normalizedFile.sections[sym.sect - 1];
> +    uint64_t offset = sym.value - section.address;
> +    uint64_t size = nextSymbolAddress(normalizedFile, sym) - sym.value;
> +    ArrayRef<uint8_t> atomContent =
> llvm::makeArrayRef(&section.content[offset],
> +                                                      size);
> +    file->addDefinedAtom(sym.name, atomContent);
>    }
>
>    assert(normalizedFile.localSymbols.empty() &&
>
> Modified:
> lld/trunk/unittests/MachOTests/MachONormalizedFileToAtomsTests.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/unittests/MachOTests/MachONormalizedFileToAtomsTests.cpp?rev=198728&r1=198727&r2=198728&view=diff
>
> ==============================================================================
> --- lld/trunk/unittests/MachOTests/MachONormalizedFileToAtomsTests.cpp
> (original)
> +++ lld/trunk/unittests/MachOTests/MachONormalizedFileToAtomsTests.cpp Tue
> Jan  7 20:52:58 2014
> @@ -20,42 +20,50 @@ using llvm::ErrorOr;
>  using namespace lld::mach_o::normalized;
>  using namespace llvm::MachO;
>
> -unsigned countDefinedAtoms(const lld::File &file) {
> -  unsigned count = 0;
> -  for (const auto &d : file.defined()) {
> -    (void)d;
> -    ++count;
> -  }
> -  return count;
> -}
> -
>  TEST(ToAtomsTest, empty_obj_x86_64) {
>    NormalizedFile f;
>    f.arch = lld::MachOLinkingContext::arch_x86_64;
>    ErrorOr<std::unique_ptr<const lld::File>> atom_f = normalizedToAtoms(f,
> "");
>    EXPECT_FALSE(!atom_f);
> -  EXPECT_EQ(0U, countDefinedAtoms(**atom_f));
> +  EXPECT_EQ(0U, (*atom_f)->defined().size());
>  }
>
>  TEST(ToAtomsTest, basic_obj_x86_64) {
>    NormalizedFile f;
>    f.arch = lld::MachOLinkingContext::arch_x86_64;
>    Section textSection;
> -  static const uint8_t contentBytes[] = { 0x55, 0x48, 0x89, 0xE5,
> -                                          0x31, 0xC0, 0x5D, 0xC3 };
> +  static const uint8_t contentBytes[] = { 0x90, 0xC3, 0xC3 };
>    const unsigned contentSize = sizeof(contentBytes) /
> sizeof(contentBytes[0]);
>    textSection.content.insert(textSection.content.begin(), contentBytes,
>                               &contentBytes[contentSize]);
>    f.sections.push_back(textSection);
> -  Symbol mainSymbol;
> -  mainSymbol.name = "_main";
> -  mainSymbol.type = N_SECT;
> -  mainSymbol.sect = 1;
> -  f.globalSymbols.push_back(mainSymbol);
> +  Symbol fooSymbol;
> +  fooSymbol.name = "_foo";
> +  fooSymbol.type = N_SECT;
> +  fooSymbol.sect = 1;
> +  fooSymbol.value = 0;
> +  f.globalSymbols.push_back(fooSymbol);
> +  Symbol barSymbol;
> +  barSymbol.name = "_bar";
> +  barSymbol.type = N_SECT;
> +  barSymbol.sect = 1;
> +  barSymbol.value = 2;
> +  f.globalSymbols.push_back(barSymbol);
> +
>    ErrorOr<std::unique_ptr<const lld::File>> atom_f = normalizedToAtoms(f,
> "");
>    EXPECT_FALSE(!atom_f);
> -  EXPECT_EQ(1U, countDefinedAtoms(**atom_f));
> -  const lld::DefinedAtom *singleAtom = *(*atom_f)->defined().begin();
> -  llvm::ArrayRef<uint8_t> atomContent(singleAtom->rawContent());
> -  EXPECT_EQ(0, memcmp(atomContent.data(), contentBytes, contentSize));
> +  const lld::File &file = **atom_f;
> +  EXPECT_EQ(2U, file.defined().size());
> +  lld::File::defined_iterator it = file.defined().begin();
> +  const lld::DefinedAtom *atom1 = *it;
> +  ++it;
> +  const lld::DefinedAtom *atom2 = *it;
> +  EXPECT_TRUE(atom1->name().equals("_foo"));
> +  EXPECT_EQ(2U, atom1->rawContent().size());
> +  EXPECT_EQ(0x90, atom1->rawContent()[0]);
> +  EXPECT_EQ(0xC3, atom1->rawContent()[1]);
> +
> +  EXPECT_TRUE(atom2->name().equals("_bar"));
> +  EXPECT_EQ(1U, atom2->rawContent().size());
> +  EXPECT_EQ(0xC3, atom2->rawContent()[0]);
>  }
>
>
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