[llvm] r270569 - Recommit r270070 ([llvm-mc] - Teach llvm-mc to generate compressed debug sections in zlib style.)
Richard Smith via llvm-commits
llvm-commits at lists.llvm.org
Tue May 24 17:21:18 PDT 2016
This breaks linking on Linux with -Wa,--compress-debug-sections (it causes
errors with GNU ld and crashes Gold). Reverted in r270638. Sorry :( Maybe
this could be brought back behind a flag?
Testcase (using attached x.c):
$ clang -Wa,--compress-debug-sections x.c -c -o x.o -g
$ ld x.o -o x
ld: x.o(.debug_info+0x85): reloc against `.debug_str': error 2
$ gold x.o -o x
gold: warning: x.o: last entry in mergeable string section
'.debug_gdb_scripts' not null terminated
gold: internal error in read_header_prolog, at
../../gold/dwarf_reader.cc:1618
$ ld --version
GNU ld (GNU Binutils for Ubuntu) 2.24
[...]
$ gold --version
GNU gold (GNU Binutils for Ubuntu 2.24) 1.11
[...]
On Tue, May 24, 2016 at 8:19 AM, George Rimar via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: grimar
> Date: Tue May 24 10:19:35 2016
> New Revision: 270569
>
> URL: http://llvm.org/viewvc/llvm-project?rev=270569&view=rev
> Log:
> Recommit r270070 ([llvm-mc] - Teach llvm-mc to generate compressed debug
> sections in zlib style.)
>
> Now, after landing r270560, r270557, r270320 it is a proper time.
>
> Original commit message:
> [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
>
> Modified:
> llvm/trunk/include/llvm/MC/MCContext.h
> llvm/trunk/include/llvm/MC/MCSectionELF.h
> llvm/trunk/lib/MC/ELFObjectWriter.cpp
> llvm/trunk/lib/MC/MCContext.cpp
> llvm/trunk/test/MC/ELF/compression.s
>
> Modified: llvm/trunk/include/llvm/MC/MCContext.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCContext.h?rev=270569&r1=270568&r2=270569&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCContext.h (original)
> +++ llvm/trunk/include/llvm/MC/MCContext.h Tue May 24 10:19:35 2016
> @@ -385,8 +385,6 @@ namespace llvm {
> const MCSymbolELF *Group,
> const MCSectionELF *Associated);
>
> - void renameELFSection(MCSectionELF *Section, StringRef Name);
> -
> MCSectionELF *createELFGroupSection(const MCSymbolELF *Group);
>
> MCSectionCOFF *getCOFFSection(StringRef Section, unsigned
> Characteristics,
>
> Modified: llvm/trunk/include/llvm/MC/MCSectionELF.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCSectionELF.h?rev=270569&r1=270568&r2=270569&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCSectionELF.h (original)
> +++ llvm/trunk/include/llvm/MC/MCSectionELF.h Tue May 24 10:19:35 2016
> @@ -62,8 +62,6 @@ private:
> Group->setIsSignature();
> }
>
> - void setSectionName(StringRef Name) { SectionName = Name; }
> -
> public:
> ~MCSectionELF();
>
> @@ -75,6 +73,7 @@ public:
> unsigned getType() const { return Type; }
> unsigned getFlags() const { return Flags; }
> unsigned getEntrySize() const { return EntrySize; }
> + void setFlags(unsigned F) { Flags = F; }
> const MCSymbolELF *getGroup() const { return Group; }
>
> void PrintSwitchToSection(const MCAsmInfo &MAI, raw_ostream &OS,
>
> Modified: llvm/trunk/lib/MC/ELFObjectWriter.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/ELFObjectWriter.cpp?rev=270569&r1=270568&r2=270569&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/MC/ELFObjectWriter.cpp (original)
> +++ llvm/trunk/lib/MC/ELFObjectWriter.cpp Tue May 24 10:19:35 2016
> @@ -979,26 +979,6 @@ ELFObjectWriter::createRelocationSection
> 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(c
> 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;
> }
>
>
> Modified: llvm/trunk/lib/MC/MCContext.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCContext.cpp?rev=270569&r1=270568&r2=270569&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/MC/MCContext.cpp (original)
> +++ llvm/trunk/lib/MC/MCContext.cpp Tue May 24 10:19:35 2016
> @@ -285,22 +285,6 @@ MCSectionMachO *MCContext::getMachOSecti
> 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,
>
> Modified: llvm/trunk/test/MC/ELF/compression.s
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/compression.s?rev=270569&r1=270568&r2=270569&view=diff
>
> ==============================================================================
> --- llvm/trunk/test/MC/ELF/compression.s (original)
> +++ llvm/trunk/test/MC/ELF/compression.s Tue May 24 10:19:35 2016
> @@ -3,6 +3,7 @@
> // RUN: llvm-dwarfdump -debug-dump=str %t | FileCheck --check-prefix=STR
> %s
> // RUN: llvm-mc -filetype=obj -compress-debug-sections -triple
> i386-pc-linux-gnu < %s \
> // RUN: | llvm-readobj -symbols - | FileCheck
> --check-prefix=386-SYMBOLS %s
> +// RUN: llvm-readobj -sections %t | FileCheck --check-prefix=ZLIB %s
>
> // REQUIRES: zlib
>
> @@ -13,10 +14,14 @@
>
> // CHECK: Contents of section .debug_info:
>
> -// CHECK: Contents of section .zdebug_str:
> -// Check for the 'ZLIB' file magic at the start of the section only
> -// CHECK-NEXT: ZLIB
> -// CHECK-NOT: ZLIB
> +// Check that debug_line section was not renamed, so it is
> +// zlib-style, not zlib-gnu one. Check that SHF_COMPRESSED was set.
> +// ZLIB: Section {
> +// ZLIB: Index:
> +// ZLIB: Name: .debug_str
> +// ZLIB-NEXT: Type: SHT_PROGBITS
> +// ZLIB-NEXT: Flags [
> +// ZLIB-NEXT: SHF_COMPRESSED
>
> // FIXME: Handle compressing alignment fragments to support compressing
> debug_frame
> // CHECK: Contents of section .debug_frame:
> @@ -31,7 +36,7 @@
> // sections, so make sure we handle symbols inside compressed sections
> // 386-SYMBOLS: Name: .Linfo_string0
> // 386-SYMBOLS-NOT: }
> -// 386-SYMBOLS: Section: .zdebug_str
> +// 386-SYMBOLS: Section: .debug_str
>
> .section .debug_line,"", at progbits
>
>
>
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> llvm-commits at lists.llvm.org
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