[llvm-objcopy] Dwarf .debug section compression support (zlib, zlib-gnu).
Third Attempt:
- Alignment issues resolved.
- zlib::isAvailable() detected.
- ArrayRef misuse fixed.
Usage:
llvm-objcopy --compress-debug-sections=zlib foo.o
llvm-objcopy --compress-debug-sections=zlib-gnu foo.o
In both cases the debug section contents is compressed with zlib. In the GNU
style case the header is the "ZLIB" magic string followed by the uint64 big-
endian decompressed size. In the non-GNU mode the header is the
Elf(32|64)_Chdr.
Decompression support is coming soon.
Differential Revision: https://reviews.llvm.org/D49678
llvm-svn: 341635
diff --git a/llvm/tools/llvm-objcopy/Object.cpp b/llvm/tools/llvm-objcopy/Object.cpp
index 2ff24ce..aaefcf9 100644
--- a/llvm/tools/llvm-objcopy/Object.cpp
+++ b/llvm/tools/llvm-objcopy/Object.cpp
@@ -15,7 +15,9 @@
#include "llvm/ADT/Twine.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/MC/MCTargetOptions.h"
#include "llvm/Object/ELFObjectFile.h"
+#include "llvm/Support/Compression.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/Path.h"
@@ -138,6 +140,76 @@
Visitor.visit(*this);
}
+void BinarySectionWriter::visit(const CompressedSection &Sec) {
+ error("Cannot write compressed section '" + Sec.Name + "' ");
+}
+
+template <class ELFT>
+void ELFSectionWriter<ELFT>::visit(const CompressedSection &Sec) {
+ uint8_t *Buf = Out.getBufferStart();
+ Buf += Sec.Offset;
+
+ if (Sec.CompressionType == DebugCompressionType::None) {
+ std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(), Buf);
+ return;
+ }
+
+ if (Sec.CompressionType == DebugCompressionType::GNU) {
+ const char *Magic = "ZLIB";
+ memcpy(Buf, Magic, strlen(Magic));
+ Buf += strlen(Magic);
+ const uint64_t DecompressedSize =
+ support::endian::read64be(&Sec.DecompressedSize);
+ memcpy(Buf, &DecompressedSize, sizeof(DecompressedSize));
+ Buf += sizeof(DecompressedSize);
+ } else {
+ Elf_Chdr_Impl<ELFT> Chdr;
+ Chdr.ch_type = ELF::ELFCOMPRESS_ZLIB;
+ Chdr.ch_size = Sec.DecompressedSize;
+ Chdr.ch_addralign = Sec.DecompressedAlign;
+ memcpy(Buf, &Chdr, sizeof(Chdr));
+ Buf += sizeof(Chdr);
+ }
+
+ std::copy(Sec.CompressedData.begin(), Sec.CompressedData.end(), Buf);
+}
+
+CompressedSection::CompressedSection(const SectionBase &Sec,
+ DebugCompressionType CompressionType)
+ : SectionBase(Sec), CompressionType(CompressionType),
+ DecompressedSize(Sec.OriginalData.size()), DecompressedAlign(Sec.Align) {
+
+ if (!zlib::isAvailable()) {
+ CompressionType = DebugCompressionType::None;
+ return;
+ }
+
+ if (Error E = zlib::compress(
+ StringRef(reinterpret_cast<const char *>(OriginalData.data()),
+ OriginalData.size()),
+ CompressedData))
+ reportError(Name, std::move(E));
+
+ size_t ChdrSize;
+ if (CompressionType == DebugCompressionType::GNU) {
+ Name = ".z" + Sec.Name.substr(1);
+ ChdrSize = sizeof("ZLIB") - 1 + sizeof(uint64_t);
+ } else {
+ Flags |= ELF::SHF_COMPRESSED;
+ ChdrSize =
+ std::max(std::max(sizeof(object::Elf_Chdr_Impl<object::ELF64LE>),
+ sizeof(object::Elf_Chdr_Impl<object::ELF64BE>)),
+ std::max(sizeof(object::Elf_Chdr_Impl<object::ELF32LE>),
+ sizeof(object::Elf_Chdr_Impl<object::ELF32BE>)));
+ }
+ Size = ChdrSize + CompressedData.size();
+ Align = 8;
+}
+
+void CompressedSection::accept(SectionVisitor &Visitor) const {
+ Visitor.visit(*this);
+}
+
void StringTableSection::addString(StringRef Name) {
StrTabBuilder.add(Name);
Size = StrTabBuilder.getSize();