[llvm] fddb417 - [llvm-elfabi] Add flag to preserve timestamp when output is the same
Haowei Wu via llvm-commits
llvm-commits at lists.llvm.org
Tue Dec 29 15:05:56 PST 2020
Author: Haowei Wu
Date: 2020-12-29T14:43:47-08:00
New Revision: fddb41744958d21635a60622cfb4067122810bcc
URL: https://github.com/llvm/llvm-project/commit/fddb41744958d21635a60622cfb4067122810bcc
DIFF: https://github.com/llvm/llvm-project/commit/fddb41744958d21635a60622cfb4067122810bcc.diff
LOG: [llvm-elfabi] Add flag to preserve timestamp when output is the same
This change adds '--write-if-changed' flag to llvm-elfabi tool. When
enabled, llvm-elfabi will not overwrite the existing file if the
content of the file will not be changed, which preserves the
timestamp.
Differential Revision: https://reviews.llvm.org/D92902
Added:
llvm/test/tools/llvm-elfabi/preserve-dates-stub.test
llvm/test/tools/llvm-elfabi/preserve-dates-tbe.test
Modified:
llvm/include/llvm/InterfaceStub/ELFObjHandler.h
llvm/lib/InterfaceStub/ELFObjHandler.cpp
llvm/tools/llvm-elfabi/llvm-elfabi.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/InterfaceStub/ELFObjHandler.h b/llvm/include/llvm/InterfaceStub/ELFObjHandler.h
index cbb9420cb666..4ec158c1405f 100644
--- 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 @@ Expected<std::unique_ptr<ELFStub>> readELFFile(MemoryBufferRef Buf);
/// @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
index e50ebd7b8ba1..40d8afa88ad2 100644
--- 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 @@ buildStub(const ELFObjectFile<ELFT> &ElfObj) {
/// @param FilePath File path for writing the ELF binary.
/// @param Stub Source ELFStub to generate a binary ELF stub from.
template <class ELFT>
-static Error writeELFBinaryToFile(StringRef FilePath, const ELFStub &Stub) {
+static Error writeELFBinaryToFile(StringRef FilePath, const ELFStub &Stub,
+ bool WriteIfChanged) {
ELFStubBuilder<ELFT> Builder{Stub};
+ // Write Stub to memory first.
+ std::vector<uint8_t> Buf(Builder.getSize());
+ Builder.write(Buf.data());
+
+ if (WriteIfChanged) {
+ if (ErrorOr<std::unique_ptr<MemoryBuffer>> 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<std::unique_ptr<FileOutputBuffer>> BufOrError =
FileOutputBuffer::create(FilePath, Builder.getSize());
if (!BufOrError)
@@ -674,13 +692,10 @@ static Error writeELFBinaryToFile(StringRef FilePath, const ELFStub &Stub) {
"` for writing");
// Write binary to file.
- std::unique_ptr<FileOutputBuffer> Buf = std::move(*BufOrError);
- Builder.write(Buf->getBufferStart());
+ std::unique_ptr<FileOutputBuffer> 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<std::unique_ptr<ELFStub>> readELFFile(MemoryBufferRef Buf) {
@@ -705,15 +720,15 @@ Expected<std::unique_ptr<ELFStub>> readELFFile(MemoryBufferRef Buf) {
// 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<ELF32LE>(FilePath, Stub);
+ return writeELFBinaryToFile<ELF32LE>(FilePath, Stub, WriteIfChanged);
if (OutputFormat == ELFTarget::ELF32BE)
- return writeELFBinaryToFile<ELF32BE>(FilePath, Stub);
+ return writeELFBinaryToFile<ELF32BE>(FilePath, Stub, WriteIfChanged);
if (OutputFormat == ELFTarget::ELF64LE)
- return writeELFBinaryToFile<ELF64LE>(FilePath, Stub);
+ return writeELFBinaryToFile<ELF64LE>(FilePath, Stub, WriteIfChanged);
if (OutputFormat == ELFTarget::ELF64BE)
- return writeELFBinaryToFile<ELF64BE>(FilePath, Stub);
+ return writeELFBinaryToFile<ELF64BE>(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
index 000000000000..f612fe57aa4d
--- /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 -d "1970-01-01 00:00:00" %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
index 000000000000..ec9cf7e1e3d6
--- /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 -d "1970-01-01 00:00:00" %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
index 6fff54fd9355..761c6a80b345 100644
--- a/llvm/tools/llvm-elfabi/llvm-elfabi.cpp
+++ b/llvm/tools/llvm-elfabi/llvm-elfabi.cpp
@@ -57,22 +57,37 @@ cl::opt<ELFTarget> BinaryOutputTarget(
clEnumValN(ELFTarget::ELF64BE, "elf64-big",
"64-bit big-endian ELF stub")));
cl::opt<std::string> BinaryOutputFilePath(cl::Positional, cl::desc("output"));
+cl::opt<bool> 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<std::unique_ptr<MemoryBuffer>> 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 @@ int main(int argc, char *argv[]) {
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));
}
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