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 @@ -16,6 +16,7 @@ #include "llvm/InterfaceStub/ELFStub.h" #include "llvm/Object/ELFObjectFile.h" #include "llvm/Object/ELFTypes.h" +#include "llvm/Support/FileSystem.h" namespace llvm { @@ -35,8 +36,10 @@ /// @param FilePath File path for writing the ELF binary. /// @param Stub Source ELFStub to generate a binary ELF stub from. /// @param OutputFormat Target ELFType to write binary as. +/// @param WriteIfChanged Whether or not to preserve timestamp if +/// the output stays the same. Error writeBinaryStub(StringRef FilePath, const ELFStub &Stub, - ELFTarget OutputFormat); + ELFTarget OutputFormat, bool WriteIfChanged = 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 @@ -17,6 +17,7 @@ #include "llvm/Support/FileOutputBuffer.h" #include "llvm/Support/MathExtras.h" #include "llvm/Support/MemoryBuffer.h" +#include "llvm/Support/Process.h" using llvm::MemoryBufferRef; using llvm::object::ELFObjectFile; @@ -663,8 +664,25 @@ /// @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 WriteIfChanged) { ELFStubBuilder Builder{Stub}; + // Write Stub to memory first. + std::vector Buf(Builder.getSize()); + Builder.write(Buf.data()); + + if (WriteIfChanged) { + if (ErrorOr> BufOrError = + MemoryBuffer::getFile(FilePath)) { + // Compare Stub output with existing Stub file. + // If Stub file unchanged, abort updating. + if ((*BufOrError)->getBufferSize() == Builder.getSize() && + !memcmp((*BufOrError)->getBufferStart(), Buf.data(), + Builder.getSize())) + return Error::success(); + } + } + Expected> BufOrError = FileOutputBuffer::create(FilePath, Builder.getSize()); if (!BufOrError) @@ -674,13 +692,10 @@ "` 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.data(), Buf.size()); - if (Error E = Buf->commit()) - return E; - - return Error::success(); + return FileBuf->commit(); } Expected> readELFFile(MemoryBufferRef Buf) { @@ -705,15 +720,15 @@ // 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 WriteIfChanged) { if (OutputFormat == ELFTarget::ELF32LE) - return writeELFBinaryToFile(FilePath, Stub); + return writeELFBinaryToFile(FilePath, Stub, WriteIfChanged); if (OutputFormat == ELFTarget::ELF32BE) - return writeELFBinaryToFile(FilePath, Stub); + return writeELFBinaryToFile(FilePath, Stub, WriteIfChanged); if (OutputFormat == ELFTarget::ELF64LE) - return writeELFBinaryToFile(FilePath, Stub); + return writeELFBinaryToFile(FilePath, Stub, WriteIfChanged); if (OutputFormat == ELFTarget::ELF64BE) - return writeELFBinaryToFile(FilePath, Stub); + return writeELFBinaryToFile(FilePath, Stub, WriteIfChanged); 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 --write-if-changed flag. + +# RUN: llvm-elfabi %s --output-target=elf64-little %t +# RUN: touch -m -t 197001010000 %t +# RUN: llvm-elfabi %s --output-target=elf64-little %t --write-if-changed +# 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 --write-if-changed flag. + +# RUN: llvm-elfabi --elf %p/Inputs/gnu_hash.so --emit-tbe=%t +# RUN: touch -m -t 197001010000 %t +# RUN: llvm-elfabi --elf %p/Inputs/gnu_hash.so --emit-tbe=%t --write-if-changed +# 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 +57,37 @@ clEnumValN(ELFTarget::ELF64BE, "elf64-big", "64-bit big-endian ELF stub"))); cl::opt BinaryOutputFilePath(cl::Positional, cl::desc("output")); +cl::opt WriteIfChanged( + "write-if-changed", + cl::desc("Write the output file only if it is new or has changed.")); /// 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.flush(); + + if (WriteIfChanged) { + if (ErrorOr> BufOrError = + MemoryBuffer::getFile(FilePath)) { + // Compare TBE output with existing TBE file. + // If TBE file unchanged, abort updating. + if ((*BufOrError)->getBuffer() == 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(); } @@ -153,8 +168,8 @@ if (BinaryOutputTarget.getNumOccurrences() == 0) fatalError(createStringError(errc::not_supported, "no binary output target specified.")); - Error BinaryWriteError = - writeBinaryStub(BinaryOutputFilePath, *TargetStub, BinaryOutputTarget); + Error BinaryWriteError = writeBinaryStub( + BinaryOutputFilePath, *TargetStub, BinaryOutputTarget, WriteIfChanged); if (BinaryWriteError) fatalError(std::move(BinaryWriteError)); }