cl::desc("Display contents of faultmap section"));
static StringRef ToolName;
-static int ReturnValue = EXIT_SUCCESS;
namespace {
typedef std::function<bool(llvm::object::SectionRef const &)> FilterPredicate;
: Predicate(P), Iterator(I), End(E) {
ScanPredicate();
}
- llvm::object::SectionRef operator*() const { return *Iterator; }
+ const llvm::object::SectionRef &operator*() const { return *Iterator; }
SectionFilterIterator &operator++() {
++Iterator;
ScanPredicate();
private:
void ScanPredicate() {
- while (Iterator != End && Predicate(*Iterator)) {
+ while (Iterator != End && !Predicate(*Iterator)) {
++Iterator;
}
}
SectionFilter ToolSectionFilter(llvm::object::ObjectFile const &O) {
return SectionFilter([](llvm::object::SectionRef const &S) {
if(FilterSections.empty())
- return false;
+ return true;
llvm::StringRef String;
std::error_code error = S.getName(String);
if (error)
- return true;
+ return false;
return std::find(FilterSections.begin(),
FilterSections.end(),
- String) == FilterSections.end();
+ String) != FilterSections.end();
},
O);
}
}
-bool llvm::error(std::error_code EC) {
+void llvm::error(std::error_code EC) {
if (!EC)
- return false;
+ return;
outs() << ToolName << ": error reading file: " << EC.message() << ".\n";
outs().flush();
- ReturnValue = EXIT_FAILURE;
- return true;
+ exit(1);
}
-static void report_error(StringRef File, std::error_code EC) {
+void llvm::report_error(StringRef File, std::error_code EC) {
assert(EC);
errs() << ToolName << ": '" << File << "': " << EC.message() << ".\n";
- ReturnValue = EXIT_FAILURE;
+ exit(1);
}
static const Target *getTarget(const ObjectFile *Obj = nullptr) {
std::string Error;
const Target *TheTarget = TargetRegistry::lookupTarget(ArchName, TheTriple,
Error);
- if (!TheTarget) {
- errs() << ToolName << ": " << Error;
- return nullptr;
- }
+ if (!TheTarget)
+ report_fatal_error("can't find target: " + Error);
// Update the triple name and return the found target.
TripleName = TheTriple.getTriple();
template <class ELFT>
static std::error_code getRelocationValueString(const ELFObjectFile<ELFT> *Obj,
- DataRefImpl Rel,
+ const RelocationRef &RelRef,
SmallVectorImpl<char> &Result) {
+ DataRefImpl Rel = RelRef.getRawDataRefImpl();
+
typedef typename ELFObjectFile<ELFT>::Elf_Sym Elf_Sym;
typedef typename ELFObjectFile<ELFT>::Elf_Shdr Elf_Shdr;
- typedef typename ELFObjectFile<ELFT>::Elf_Rel Elf_Rel;
typedef typename ELFObjectFile<ELFT>::Elf_Rela Elf_Rela;
const ELFFile<ELFT> &EF = *Obj->getELFFile();
if (std::error_code EC = StrTabOrErr.getError())
return EC;
StringRef StrTab = *StrTabOrErr;
- uint8_t type;
+ uint8_t type = RelRef.getType();
StringRef res;
int64_t addend = 0;
- uint16_t symbol_index = 0;
switch (Sec->sh_type) {
default:
return object_error::parse_failed;
case ELF::SHT_REL: {
- const Elf_Rel *ERel = Obj->getRel(Rel);
- type = ERel->getType(EF.isMips64EL());
- symbol_index = ERel->getSymbol(EF.isMips64EL());
// TODO: Read implicit addend from section data.
break;
}
case ELF::SHT_RELA: {
const Elf_Rela *ERela = Obj->getRela(Rel);
- type = ERela->getType(EF.isMips64EL());
- symbol_index = ERela->getSymbol(EF.isMips64EL());
addend = ERela->r_addend;
break;
}
}
- const Elf_Sym *symb =
- EF.template getEntry<Elf_Sym>(Sec->sh_link, symbol_index);
+ symbol_iterator SI = RelRef.getSymbol();
+ const Elf_Sym *symb = Obj->getSymbol(SI->getRawDataRefImpl());
StringRef Target;
- ErrorOr<const Elf_Shdr *> SymSec = EF.getSection(symb);
- if (std::error_code EC = SymSec.getError())
- return EC;
if (symb->getType() == ELF::STT_SECTION) {
- ErrorOr<StringRef> SecName = EF.getSectionName(*SymSec);
+ ErrorOr<section_iterator> SymSI = SI->getSection();
+ if (std::error_code EC = SymSI.getError())
+ return EC;
+ const Elf_Shdr *SymSec = Obj->getSection((*SymSI)->getRawDataRefImpl());
+ ErrorOr<StringRef> SecName = EF.getSectionName(SymSec);
if (std::error_code EC = SecName.getError())
return EC;
Target = *SecName;
break;
}
case ELF::EM_386:
+ case ELF::EM_IAMCU:
case ELF::EM_ARM:
case ELF::EM_HEXAGON:
case ELF::EM_MIPS:
}
static std::error_code getRelocationValueString(const ELFObjectFileBase *Obj,
- const RelocationRef &RelRef,
+ const RelocationRef &Rel,
SmallVectorImpl<char> &Result) {
- DataRefImpl Rel = RelRef.getRawDataRefImpl();
if (auto *ELF32LE = dyn_cast<ELF32LEObjectFile>(Obj))
return getRelocationValueString(ELF32LE, Rel, Result);
if (auto *ELF64LE = dyn_cast<ELF64LEObjectFile>(Obj))
symbol_iterator SI = O->symbol_begin();
advance(SI, Val);
ErrorOr<StringRef> SOrErr = SI->getName();
- if (!error(SOrErr.getError()))
- S = *SOrErr;
+ error(SOrErr.getError());
+ S = *SOrErr;
} else {
section_iterator SI = O->section_begin();
// Adjust for the fact that sections are 1-indexed.
static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
const Target *TheTarget = getTarget(Obj);
- // getTarget() will have already issued a diagnostic if necessary, so
- // just bail here if it failed.
- if (!TheTarget)
- return;
// Package up features to be passed to target/subtarget
std::string FeaturesStr;
}
// Create a mapping from virtual address to symbol name. This is used to
- // pretty print the target of a call.
- std::vector<std::pair<uint64_t, StringRef>> AllSymbols;
- if (MIA) {
- for (const SymbolRef &Symbol : Obj->symbols()) {
- if (Symbol.getType() != SymbolRef::ST_Function)
- continue;
+ // pretty print the symbols while disassembling.
+ typedef std::vector<std::pair<uint64_t, StringRef>> SectionSymbolsTy;
+ std::map<SectionRef, SectionSymbolsTy> AllSymbols;
+ for (const SymbolRef &Symbol : Obj->symbols()) {
+ ErrorOr<uint64_t> AddressOrErr = Symbol.getAddress();
+ error(AddressOrErr.getError());
+ uint64_t Address = *AddressOrErr;
+
+ ErrorOr<StringRef> Name = Symbol.getName();
+ error(Name.getError());
+ if (Name->empty())
+ continue;
- ErrorOr<uint64_t> AddressOrErr = Symbol.getAddress();
- if (error(AddressOrErr.getError()))
- break;
- uint64_t Address = *AddressOrErr;
+ ErrorOr<section_iterator> SectionOrErr = Symbol.getSection();
+ error(SectionOrErr.getError());
+ section_iterator SecI = *SectionOrErr;
+ if (SecI == Obj->section_end())
+ continue;
- ErrorOr<StringRef> Name = Symbol.getName();
- if (error(Name.getError()))
- break;
- if (Name->empty())
+ AllSymbols[*SecI].emplace_back(Address, *Name);
+ }
+
+ // Create a mapping from virtual address to section.
+ std::vector<std::pair<uint64_t, SectionRef>> SectionAddresses;
+ for (SectionRef Sec : Obj->sections())
+ SectionAddresses.emplace_back(Sec.getAddress(), Sec);
+ array_pod_sort(SectionAddresses.begin(), SectionAddresses.end());
+
+ // Linked executables (.exe and .dll files) typically don't include a real
+ // symbol table but they might contain an export table.
+ if (const auto *COFFObj = dyn_cast<COFFObjectFile>(Obj)) {
+ for (const auto &ExportEntry : COFFObj->export_directories()) {
+ StringRef Name;
+ error(ExportEntry.getSymbolName(Name));
+ if (Name.empty())
continue;
- AllSymbols.push_back(std::make_pair(Address, *Name));
- }
+ uint32_t RVA;
+ error(ExportEntry.getExportRVA(RVA));
+
+ uint64_t VA = COFFObj->getImageBase() + RVA;
+ auto Sec = std::upper_bound(
+ SectionAddresses.begin(), SectionAddresses.end(), VA,
+ [](uint64_t LHS, const std::pair<uint64_t, SectionRef> &RHS) {
+ return LHS < RHS.first;
+ });
+ if (Sec != SectionAddresses.begin())
+ --Sec;
+ else
+ Sec = SectionAddresses.end();
- array_pod_sort(AllSymbols.begin(), AllSymbols.end());
+ if (Sec != SectionAddresses.end())
+ AllSymbols[Sec->second].emplace_back(VA, Name);
+ }
}
+ // Sort all the symbols, this allows us to use a simple binary search to find
+ // a symbol near an address.
+ for (std::pair<const SectionRef, SectionSymbolsTy> &SecSyms : AllSymbols)
+ array_pod_sort(SecSyms.second.begin(), SecSyms.second.end());
+
for (const SectionRef &Section : ToolSectionFilter(*Obj)) {
if (!DisassembleAll && (!Section.isText() || Section.isVirtual()))
continue;
if (!SectSize)
continue;
- // Make a list of all the symbols in this section.
- std::vector<std::pair<uint64_t, StringRef>> Symbols;
- for (const SymbolRef &Symbol : Obj->symbols()) {
- if (Section.containsSymbol(Symbol)) {
- ErrorOr<uint64_t> AddressOrErr = Symbol.getAddress();
- if (error(AddressOrErr.getError()))
- break;
- uint64_t Address = *AddressOrErr;
- Address -= SectionAddr;
- if (Address >= SectSize)
- continue;
-
- ErrorOr<StringRef> Name = Symbol.getName();
- if (error(Name.getError()))
- break;
- Symbols.push_back(std::make_pair(Address, *Name));
+ // Get the list of all the symbols in this section.
+ SectionSymbolsTy &Symbols = AllSymbols[Section];
+ std::vector<uint64_t> DataMappingSymsAddr;
+ std::vector<uint64_t> TextMappingSymsAddr;
+ if (Obj->isELF() && Obj->getArch() == Triple::aarch64) {
+ for (const auto &Symb : Symbols) {
+ uint64_t Address = Symb.first;
+ StringRef Name = Symb.second;
+ if (Name.startswith("$d"))
+ DataMappingSymsAddr.push_back(Address - SectionAddr);
+ if (Name.startswith("$x"))
+ TextMappingSymsAddr.push_back(Address - SectionAddr);
}
}
- // Sort the symbols by address, just in case they didn't come in that way.
- array_pod_sort(Symbols.begin(), Symbols.end());
+ std::sort(DataMappingSymsAddr.begin(), DataMappingSymsAddr.end());
+ std::sort(TextMappingSymsAddr.begin(), TextMappingSymsAddr.end());
// Make a list of all the relocations for this section.
std::vector<RelocationRef> Rels;
SegmentName = MachO->getSectionFinalSegmentName(DR);
}
StringRef name;
- if (error(Section.getName(name)))
- break;
+ error(Section.getName(name));
outs() << "Disassembly of section ";
if (!SegmentName.empty())
outs() << SegmentName << ",";
// If the section has no symbol at the start, just insert a dummy one.
if (Symbols.empty() || Symbols[0].first != 0)
- Symbols.insert(Symbols.begin(), std::make_pair(0, name));
+ Symbols.insert(Symbols.begin(), std::make_pair(SectionAddr, name));
SmallString<40> Comments;
raw_svector_ostream CommentStream(Comments);
StringRef BytesStr;
- if (error(Section.getContents(BytesStr)))
- break;
+ error(Section.getContents(BytesStr));
ArrayRef<uint8_t> Bytes(reinterpret_cast<const uint8_t *>(BytesStr.data()),
BytesStr.size());
// Disassemble symbol by symbol.
for (unsigned si = 0, se = Symbols.size(); si != se; ++si) {
- uint64_t Start = Symbols[si].first;
- // The end is either the section end or the beginning of the next symbol.
- uint64_t End = (si == se - 1) ? SectSize : Symbols[si + 1].first;
+ uint64_t Start = Symbols[si].first - SectionAddr;
+ // The end is either the section end or the beginning of the next
+ // symbol.
+ uint64_t End =
+ (si == se - 1) ? SectSize : Symbols[si + 1].first - SectionAddr;
+ // Don't try to disassemble beyond the end of section contents.
+ if (End > SectSize)
+ End = SectSize;
// If this symbol has the same address as the next symbol, then skip it.
- if (Start == End)
+ if (Start >= End)
continue;
outs() << '\n' << Symbols[si].second << ":\n";
for (Index = Start; Index < End; Index += Size) {
MCInst Inst;
+ // AArch64 ELF binaries can interleave data and text in the
+ // same section. We rely on the markers introduced to
+ // understand what we need to dump.
+ if (Obj->isELF() && Obj->getArch() == Triple::aarch64) {
+ uint64_t Stride = 0;
+
+ auto DAI = std::lower_bound(DataMappingSymsAddr.begin(),
+ DataMappingSymsAddr.end(), Index);
+ if (DAI != DataMappingSymsAddr.end() && *DAI == Index) {
+ // Switch to data.
+ while (Index < End) {
+ outs() << format("%8" PRIx64 ":", SectionAddr + Index);
+ outs() << "\t";
+ if (Index + 4 <= End) {
+ Stride = 4;
+ dumpBytes(Bytes.slice(Index, 4), outs());
+ outs() << "\t.word";
+ } else if (Index + 2 <= End) {
+ Stride = 2;
+ dumpBytes(Bytes.slice(Index, 2), outs());
+ outs() << "\t.short";
+ } else {
+ Stride = 1;
+ dumpBytes(Bytes.slice(Index, 1), outs());
+ outs() << "\t.byte";
+ }
+ Index += Stride;
+ outs() << "\n";
+ auto TAI = std::lower_bound(TextMappingSymsAddr.begin(),
+ TextMappingSymsAddr.end(), Index);
+ if (TAI != TextMappingSymsAddr.end() && *TAI == Index)
+ break;
+ }
+ }
+ }
+
+ if (Index >= End)
+ break;
+
if (DisAsm->getInstruction(Inst, Size, Bytes.slice(Index),
SectionAddr + Index, DebugOut,
CommentStream)) {
SectionAddr + Index, outs(), "", *STI);
outs() << CommentStream.str();
Comments.clear();
+
+ // Try to resolve the target of a call, tail call, etc. to a specific
+ // symbol.
if (MIA && (MIA->isCall(Inst) || MIA->isUnconditionalBranch(Inst) ||
MIA->isConditionalBranch(Inst))) {
uint64_t Target;
if (MIA->evaluateBranch(Inst, SectionAddr + Index, Size, Target)) {
- auto TargetSym = std::upper_bound(
- AllSymbols.begin(), AllSymbols.end(), Target,
- [](uint64_t LHS, const std::pair<uint64_t, StringRef> &RHS) {
- return LHS < RHS.first;
- });
- if (TargetSym != AllSymbols.begin())
- --TargetSym;
- else
- TargetSym = AllSymbols.end();
-
- if (TargetSym != AllSymbols.end()) {
- outs() << " <" << TargetSym->second;
- uint64_t Disp = Target - TargetSym->first;
- if (Disp)
- outs() << '+' << utohexstr(Disp);
- outs() << '>';
+ // In a relocatable object, the target's section must reside in
+ // the same section as the call instruction or it is accessed
+ // through a relocation.
+ //
+ // In a non-relocatable object, the target may be in any section.
+ //
+ // N.B. We don't walk the relocations in the relocatable case yet.
+ auto *TargetSectionSymbols = &Symbols;
+ if (!Obj->isRelocatableObject()) {
+ auto SectionAddress = std::upper_bound(
+ SectionAddresses.begin(), SectionAddresses.end(), Target,
+ [](uint64_t LHS,
+ const std::pair<uint64_t, SectionRef> &RHS) {
+ return LHS < RHS.first;
+ });
+ if (SectionAddress != SectionAddresses.begin()) {
+ --SectionAddress;
+ TargetSectionSymbols = &AllSymbols[SectionAddress->second];
+ } else {
+ TargetSectionSymbols = nullptr;
+ }
+ }
+
+ // Find the first symbol in the section whose offset is less than
+ // or equal to the target.
+ if (TargetSectionSymbols) {
+ auto TargetSym = std::upper_bound(
+ TargetSectionSymbols->begin(), TargetSectionSymbols->end(),
+ Target, [](uint64_t LHS,
+ const std::pair<uint64_t, StringRef> &RHS) {
+ return LHS < RHS.first;
+ });
+ if (TargetSym != TargetSectionSymbols->begin()) {
+ --TargetSym;
+ uint64_t TargetAddress = std::get<0>(*TargetSym);
+ StringRef TargetName = std::get<1>(*TargetSym);
+ outs() << " <" << TargetName;
+ uint64_t Disp = Target - TargetAddress;
+ if (Disp)
+ outs() << '+' << utohexstr(Disp);
+ outs() << '>';
+ }
}
}
}
// Stop when rel_cur's address is past the current instruction.
if (addr >= Index + Size) break;
rel_cur->getTypeName(name);
- if (error(getRelocationValueString(*rel_cur, val)))
- goto skip_print_rel;
+ error(getRelocationValueString(*rel_cur, val));
outs() << format(Fmt.data(), SectionAddr + addr) << name
<< "\t" << val << "\n";
if (Section.relocation_begin() == Section.relocation_end())
continue;
StringRef secname;
- if (error(Section.getName(secname)))
- continue;
+ error(Section.getName(secname));
outs() << "RELOCATION RECORDS FOR [" << secname << "]:\n";
for (const RelocationRef &Reloc : Section.relocations()) {
bool hidden = getHidden(Reloc);
if (hidden)
continue;
Reloc.getTypeName(relocname);
- if (error(getRelocationValueString(Reloc, valuestr)))
- continue;
+ error(getRelocationValueString(Reloc, valuestr));
outs() << format(Fmt.data(), address) << " " << relocname << " "
<< valuestr << "\n";
}
unsigned i = 0;
for (const SectionRef &Section : ToolSectionFilter(*Obj)) {
StringRef Name;
- if (error(Section.getName(Name)))
- return;
+ error(Section.getName(Name));
uint64_t Address = Section.getAddress();
uint64_t Size = Section.getSize();
bool Text = Section.isText();
for (const SectionRef &Section : ToolSectionFilter(*Obj)) {
StringRef Name;
StringRef Contents;
- if (error(Section.getName(Name)))
- continue;
+ error(Section.getName(Name));
uint64_t BaseAddr = Section.getAddress();
uint64_t Size = Section.getSize();
if (!Size)
continue;
}
- if (error(Section.getContents(Contents)))
- continue;
+ error(Section.getContents(Contents));
// Dump out the content as hex and printable ascii characters.
for (std::size_t addr = 0, end = Contents.size(); addr < end; addr += 16) {
for (unsigned SI = 0, SE = coff->getNumberOfSymbols(); SI != SE; ++SI) {
ErrorOr<COFFSymbolRef> Symbol = coff->getSymbol(SI);
StringRef Name;
- if (error(Symbol.getError()))
- return;
-
- if (error(coff->getSymbolName(*Symbol, Name)))
- return;
+ error(Symbol.getError());
+ error(coff->getSymbolName(*Symbol, Name));
outs() << "[" << format("%2d", SI) << "]"
<< "(sec " << format("%2d", int(Symbol->getSectionNumber())) << ")"
for (unsigned AI = 0, AE = Symbol->getNumberOfAuxSymbols(); AI < AE; ++AI, ++SI) {
if (Symbol->isSectionDefinition()) {
const coff_aux_section_definition *asd;
- if (error(coff->getAuxSymbol<coff_aux_section_definition>(SI + 1, asd)))
- return;
+ error(coff->getAuxSymbol<coff_aux_section_definition>(SI + 1, asd));
int32_t AuxNumber = asd->getNumber(Symbol->isBigObj());
, unsigned(asd->Selection));
} else if (Symbol->isFileRecord()) {
const char *FileName;
- if (error(coff->getAuxSymbol<char>(SI + 1, FileName)))
- return;
+ error(coff->getAuxSymbol<char>(SI + 1, FileName));
StringRef Name(FileName, Symbol->getNumberOfAuxSymbols() *
coff->getSymbolTableEntrySize());
}
for (const SymbolRef &Symbol : o->symbols()) {
ErrorOr<uint64_t> AddressOrError = Symbol.getAddress();
- if (error(AddressOrError.getError()))
- continue;
+ error(AddressOrError.getError());
uint64_t Address = *AddressOrError;
SymbolRef::Type Type = Symbol.getType();
uint32_t Flags = Symbol.getFlags();
- section_iterator Section = o->section_end();
- if (error(Symbol.getSection(Section)))
- continue;
+ ErrorOr<section_iterator> SectionOrErr = Symbol.getSection();
+ error(SectionOrErr.getError());
+ section_iterator Section = *SectionOrErr;
StringRef Name;
if (Type == SymbolRef::ST_Debug && Section != o->section_end()) {
Section->getName(Name);
} else {
ErrorOr<StringRef> NameOrErr = Symbol.getName();
- if (error(NameOrErr.getError()))
- continue;
+ error(NameOrErr.getError());
Name = *NameOrErr;
}
outs() << SegmentName << ",";
}
StringRef SectionName;
- if (error(Section->getName(SectionName)))
- SectionName = "";
+ error(Section->getName(SectionName));
outs() << SectionName;
}
return;
StringRef ClangASTContents;
- if (error(ClangASTSection.getValue().getContents(ClangASTContents))) {
- errs() << "Could not read the " << ClangASTSectionName << " section!\n";
- return;
- }
-
+ error(ClangASTSection.getValue().getContents(ClangASTContents));
outs().write(ClangASTContents.data(), ClangASTContents.size());
}
}
StringRef FaultMapContents;
- if (error(FaultMapSection.getValue().getContents(FaultMapContents))) {
- errs() << "Could not read the " << FaultMapContents << " section!\n";
- return;
- }
+ error(FaultMapSection.getValue().getContents(FaultMapContents));
FaultMapParser FMP(FaultMapContents.bytes_begin(),
FaultMapContents.bytes_end());
/// @brief Dump each object file in \a a;
static void DumpArchive(const Archive *a) {
- for (Archive::child_iterator i = a->child_begin(), e = a->child_end(); i != e;
- ++i) {
- ErrorOr<std::unique_ptr<Binary>> ChildOrErr = i->getAsBinary();
- if (std::error_code EC = ChildOrErr.getError()) {
- // Ignore non-object files.
+ for (auto &ErrorOrChild : a->children()) {
+ if (std::error_code EC = ErrorOrChild.getError())
+ report_error(a->getFileName(), EC);
+ const Archive::Child &C = *ErrorOrChild;
+ ErrorOr<std::unique_ptr<Binary>> ChildOrErr = C.getAsBinary();
+ if (std::error_code EC = ChildOrErr.getError())
if (EC != object_error::invalid_file_type)
report_error(a->getFileName(), EC);
- continue;
- }
if (ObjectFile *o = dyn_cast<ObjectFile>(&*ChildOrErr.get()))
DumpObject(o);
else
/// @brief Open file and figure out how to dump it.
static void DumpInput(StringRef file) {
- // If file isn't stdin, check that it exists.
- if (file != "-" && !sys::fs::exists(file)) {
- report_error(file, errc::no_such_file_or_directory);
- return;
- }
// If we are using the Mach-O specific object file parser, then let it parse
// the file and process the command line options. So the -arch flags can
// Attempt to open the binary.
ErrorOr<OwningBinary<Binary>> BinaryOrErr = createBinary(file);
- if (std::error_code EC = BinaryOrErr.getError()) {
+ if (std::error_code EC = BinaryOrErr.getError())
report_error(file, EC);
- return;
- }
Binary &Binary = *BinaryOrErr.get().getBinary();
if (Archive *a = dyn_cast<Archive>(&Binary))
// Initialize targets and assembly printers/parsers.
llvm::InitializeAllTargetInfos();
llvm::InitializeAllTargetMCs();
- llvm::InitializeAllAsmParsers();
llvm::InitializeAllDisassemblers();
// Register the target printer for --version.
std::for_each(InputFilenames.begin(), InputFilenames.end(),
DumpInput);
- return ReturnValue;
+ return EXIT_SUCCESS;
}
projects / oota-llvm.git / blobdiff