diff --git a/llvm/include/llvm/InterfaceStub/ELFObjHandler.h b/llvm/include/llvm/InterfaceStub/ELFObjHandler.h --- a/llvm/include/llvm/InterfaceStub/ELFObjHandler.h +++ b/llvm/include/llvm/InterfaceStub/ELFObjHandler.h @@ -36,7 +36,7 @@ /// @param Stub Source ELFStub to generate a binary ELF stub from. /// @param OutputFormat Target ELFType to write binary as. Error writeBinaryStub(StringRef FilePath, const ELFStub &Stub, - ELFTarget OutputFormat); + ELFTarget OutputFormat, bool PreserveDates = false); } // end namespace elfabi } // end namespace llvm diff --git a/llvm/lib/InterfaceStub/ELFObjHandler.cpp b/llvm/lib/InterfaceStub/ELFObjHandler.cpp --- a/llvm/lib/InterfaceStub/ELFObjHandler.cpp +++ b/llvm/lib/InterfaceStub/ELFObjHandler.cpp @@ -663,8 +663,27 @@ /// @param FilePath File path for writing the ELF binary. /// @param Stub Source ELFStub to generate a binary ELF stub from. template -static Error writeELFBinaryToFile(StringRef FilePath, const ELFStub &Stub) { +static Error writeELFBinaryToFile(StringRef FilePath, const ELFStub &Stub, + bool PreserveDates) { ELFStubBuilder Builder{Stub}; + // Write Stub to memory first. + std::unique_ptr Buf(new uint8_t[Builder.getSize()]); + memset(Buf.get(), 0, Builder.getSize()); + Builder.write(Buf.get()); + + if (PreserveDates) { + ErrorOr> BufOrError = + MemoryBuffer::getFile(FilePath); + if (BufOrError) { + // Compare Stub output with existing Stub file. + std::unique_ptr FileReadBuffer = std::move(*BufOrError); + // If Stub file unchanged, abort updating. + if (FileReadBuffer->getBufferSize() == Builder.getSize() && + !memcmp(FileReadBuffer->getBufferStart(), Buf.get(), + Builder.getSize())) + return Error::success(); + } + } Expected> BufOrError = FileOutputBuffer::create(FilePath, Builder.getSize()); if (!BufOrError) @@ -672,12 +691,11 @@ toString(BufOrError.takeError()) + " when trying to open `" + FilePath + "` for writing"); - // Write binary to file. - std::unique_ptr Buf = std::move(*BufOrError); - Builder.write(Buf->getBufferStart()); + std::unique_ptr FileBuf = std::move(*BufOrError); + memcpy(FileBuf->getBufferStart(), Buf.get(), Builder.getSize()); - if (Error E = Buf->commit()) + if (Error E = FileBuf->commit()) return E; return Error::success(); @@ -705,15 +723,15 @@ // This function wraps the ELFT writeELFBinaryToFile() so writeBinaryStub() // can be called without having to use ELFType templates directly. Error writeBinaryStub(StringRef FilePath, const ELFStub &Stub, - ELFTarget OutputFormat) { + ELFTarget OutputFormat, bool PreserveDates) { if (OutputFormat == ELFTarget::ELF32LE) - return writeELFBinaryToFile(FilePath, Stub); + return writeELFBinaryToFile(FilePath, Stub, PreserveDates); if (OutputFormat == ELFTarget::ELF32BE) - return writeELFBinaryToFile(FilePath, Stub); + return writeELFBinaryToFile(FilePath, Stub, PreserveDates); if (OutputFormat == ELFTarget::ELF64LE) - return writeELFBinaryToFile(FilePath, Stub); + return writeELFBinaryToFile(FilePath, Stub, PreserveDates); if (OutputFormat == ELFTarget::ELF64BE) - return writeELFBinaryToFile(FilePath, Stub); + return writeELFBinaryToFile(FilePath, Stub, PreserveDates); llvm_unreachable("invalid binary output target"); } diff --git a/llvm/test/tools/llvm-elfabi/preserve-dates-stub.test b/llvm/test/tools/llvm-elfabi/preserve-dates-stub.test new file mode 100644 --- /dev/null +++ b/llvm/test/tools/llvm-elfabi/preserve-dates-stub.test @@ -0,0 +1,19 @@ +## Test writing unchanged content to ELF Stub file with --preserve-dates flag. + +# RUN: llvm-elfabi %s --output-target=elf64-little %t +# RUN: touch -m -d "1970-01-01 00:00:00" %t +# RUN: llvm-elfabi %s --output-target=elf64-little %t -p +# RUN: ls -l %t | FileCheck %s + +--- !tapi-tbe +TbeVersion: 1.0 +Arch: x86_64 +NeededLibs: + - libc.so.6 +Symbols: + bar: { Type: Object, Size: 42 } + baz: { Type: TLS, Size: 3 } + plus: { Type: Func } +... + +# CHECK: {{[[:space:]]1970}} diff --git a/llvm/test/tools/llvm-elfabi/preserve-dates-tbe.test b/llvm/test/tools/llvm-elfabi/preserve-dates-tbe.test new file mode 100644 --- /dev/null +++ b/llvm/test/tools/llvm-elfabi/preserve-dates-tbe.test @@ -0,0 +1,8 @@ +## Test writing unchanged content to TBE file with --preserve-dates flag. + +# RUN: llvm-elfabi --elf %p/Inputs/gnu_hash.so --emit-tbe=%t +# RUN: touch -m -d "1970-01-01 00:00:00" %t +# RUN: llvm-elfabi --elf %p/Inputs/gnu_hash.so --emit-tbe=%t --preserve-dates +# RUN: ls -l %t | FileCheck %s + +# CHECK: {{[[:space:]]1970}} diff --git a/llvm/tools/llvm-elfabi/llvm-elfabi.cpp b/llvm/tools/llvm-elfabi/llvm-elfabi.cpp --- a/llvm/tools/llvm-elfabi/llvm-elfabi.cpp +++ b/llvm/tools/llvm-elfabi/llvm-elfabi.cpp @@ -57,22 +57,42 @@ clEnumValN(ELFTarget::ELF64BE, "elf64-big", "64-bit big-endian ELF stub"))); cl::opt BinaryOutputFilePath(cl::Positional, cl::desc("output")); +cl::opt + PreserveDates("preserve-dates", + cl::desc("preserve the timestamp of the output file " + "if the content is not changed")); +cl::alias PreserveDatesA("p", cl::desc("Alias for --preserve-dates"), + cl::aliasopt(PreserveDates)); /// writeTBE() writes a Text-Based ELF stub to a file using the latest version /// of the YAML parser. static Error writeTBE(StringRef FilePath, ELFStub &Stub) { + // Write TBE to memory first. + std::string TBEStr; + raw_string_ostream OutStr(TBEStr); + Error YAMLErr = writeTBEToOutputStream(OutStr, Stub); + if (YAMLErr) + return YAMLErr; + OutStr.str(); + + if (PreserveDates) { + ErrorOr> BufOrError = + MemoryBuffer::getFile(FilePath); + if (BufOrError) { + // Compare TBE output with existing TBE file. + std::unique_ptr FileReadBuffer = std::move(*BufOrError); + // If TBE file unchanged, abort updating. + if (FileReadBuffer->getBuffer().equals(TBEStr)) + return Error::success(); + } + } + // Open TBE file for writing. std::error_code SysErr; - - // Open file for writing. raw_fd_ostream Out(FilePath, SysErr); if (SysErr) return createStringError(SysErr, "Couldn't open `%s` for writing", FilePath.data()); - // Write file. - Error YAMLErr = writeTBEToOutputStream(Out, Stub); - if (YAMLErr) - return YAMLErr; - + Out << TBEStr; return Error::success(); } @@ -154,7 +174,7 @@ fatalError(createStringError(errc::not_supported, "no binary output target specified.")); Error BinaryWriteError = - writeBinaryStub(BinaryOutputFilePath, *TargetStub, BinaryOutputTarget); + writeBinaryStub(BinaryOutputFilePath, *TargetStub, BinaryOutputTarget, PreserveDates); if (BinaryWriteError) fatalError(std::move(BinaryWriteError)); }