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authorGeorge Rimar <grimar@accesssoftek.com>2016-05-19 15:08:31 +0000
committerGeorge Rimar <grimar@accesssoftek.com>2016-05-19 15:08:31 +0000
commitc9c693751fdc2c884b8f2f514d4a4ce5863b96b9 (patch)
tree6d585078336d9d3f47d26360b1ef31bd01712754 /lib/MC
parentae7c8ddf9452411908800fa6f1c3892340e026c0 (diff)
downloadllvm-c9c693751fdc2c884b8f2f514d4a4ce5863b96b9.tar.gz
[llvm-mc] - Teach llvm-mc to generate compressed debug sections in zlib style.
Before this patch llvm-mc generated zlib-gnu styled sections. That means no SHF_COMPRESSED flag was set, magic 'zlib' signature was used in combination with full size field. Sections were renamed to "*.z*". This patch reimplements the compression style to zlib one as zlib-gnu looks to be depricated everywhere. Differential revision: http://reviews.llvm.org/D20331 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270070 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/MC')
-rw-r--r--lib/MC/ELFObjectWriter.cpp44
-rw-r--r--lib/MC/MCContext.cpp16
2 files changed, 21 insertions, 39 deletions
diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index 900dcf51a26b..7250806167ff 100644
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -979,26 +979,6 @@ ELFObjectWriter::createRelocationSection(MCContext &Ctx,
return RelaSection;
}
-// Include the debug info compression header:
-// "ZLIB" followed by 8 bytes representing the uncompressed size of the section,
-// useful for consumers to preallocate a buffer to decompress into.
-static bool
-prependCompressionHeader(uint64_t Size,
- SmallVectorImpl<char> &CompressedContents) {
- const StringRef Magic = "ZLIB";
- if (Size <= Magic.size() + sizeof(Size) + CompressedContents.size())
- return false;
- if (sys::IsLittleEndianHost)
- sys::swapByteOrder(Size);
- CompressedContents.insert(CompressedContents.begin(),
- Magic.size() + sizeof(Size), 0);
- std::copy(Magic.begin(), Magic.end(), CompressedContents.begin());
- std::copy(reinterpret_cast<char *>(&Size),
- reinterpret_cast<char *>(&Size + 1),
- CompressedContents.begin() + Magic.size());
- return true;
-}
-
void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
const MCAsmLayout &Layout) {
MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
@@ -1029,12 +1009,30 @@ void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
return;
}
- if (!prependCompressionHeader(UncompressedData.size(), CompressedContents)) {
+ uint64_t HdrSize =
+ is64Bit() ? sizeof(ELF::Elf32_Chdr) : sizeof(ELF::Elf64_Chdr);
+ if (UncompressedData.size() <= HdrSize + CompressedContents.size()) {
getStream() << UncompressedData;
return;
}
- Asm.getContext().renameELFSection(&Section,
- (".z" + SectionName.drop_front(1)).str());
+
+ // Set the compressed flag. That is zlib style.
+ Section.setFlags(Section.getFlags() | ELF::SHF_COMPRESSED);
+
+ // Platform specific header is followed by compressed data.
+ if (is64Bit()) {
+ // Write Elf64_Chdr header.
+ write(static_cast<ELF::Elf64_Word>(ELF::ELFCOMPRESS_ZLIB));
+ write(static_cast<ELF::Elf64_Word>(0)); // ch_reserved field.
+ write(static_cast<ELF::Elf64_Xword>(UncompressedData.size()));
+ write(static_cast<ELF::Elf64_Xword>(Sec.getAlignment()));
+ } else {
+ // Write Elf32_Chdr header otherwise.
+ write(static_cast<ELF::Elf32_Word>(ELF::ELFCOMPRESS_ZLIB));
+ write(static_cast<ELF::Elf32_Word>(UncompressedData.size()));
+ write(static_cast<ELF::Elf32_Word>(Sec.getAlignment()));
+ }
+
getStream() << CompressedContents;
}
diff --git a/lib/MC/MCContext.cpp b/lib/MC/MCContext.cpp
index 67463e583d73..aa15ff69904c 100644
--- a/lib/MC/MCContext.cpp
+++ b/lib/MC/MCContext.cpp
@@ -285,22 +285,6 @@ MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
Segment, Section, TypeAndAttributes, Reserved2, Kind, Begin);
}
-void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
- StringRef GroupName;
- if (const MCSymbol *Group = Section->getGroup())
- GroupName = Group->getName();
-
- unsigned UniqueID = Section->getUniqueID();
- ELFUniquingMap.erase(
- ELFSectionKey{Section->getSectionName(), GroupName, UniqueID});
- auto I = ELFUniquingMap.insert(std::make_pair(
- ELFSectionKey{Name, GroupName, UniqueID},
- Section))
- .first;
- StringRef CachedName = I->first.SectionName;
- const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
-}
-
MCSectionELF *MCContext::createELFRelSection(StringRef Name, unsigned Type,
unsigned Flags, unsigned EntrySize,
const MCSymbolELF *Group,