[ELF] - Implemented --compress-debug-sections option.
Patch implements --compress-debug-sections=zlib.
In compare with D20211 (a year old patch, abandoned), it implementation
uses streaming and fully reimplemented, does not support zlib-gnu for
simplification.
This is PR32308.
Differential revision: https://reviews.llvm.org/D31941
llvm-svn: 300444
diff --git a/lld/ELF/Config.h b/lld/ELF/Config.h
index c8eecec..d25c63c 100644
--- a/lld/ELF/Config.h
+++ b/lld/ELF/Config.h
@@ -104,6 +104,7 @@
bool Bsymbolic;
bool BsymbolicFunctions;
bool ColorDiagnostics = false;
+ bool CompressDebugSections;
bool DefineCommon;
bool Demangle = true;
bool DisableVerify;
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 47ecd60..649c096 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -45,6 +45,7 @@
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Object/Decompressor.h"
#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compression.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/TarWriter.h"
#include "llvm/Support/TargetSelect.h"
@@ -564,12 +565,25 @@
return Ret;
}
+static bool getCompressDebugSections(opt::InputArgList &Args) {
+ if (auto *Arg = Args.getLastArg(OPT_compress_debug_sections)) {
+ StringRef S = Arg->getValue();
+ if (S == "none")
+ return false;
+ if (S == "zlib")
+ return zlib::isAvailable();
+ error("unknown --compress-debug-sections value: " + S);
+ }
+ return false;
+}
+
// Initializes Config members by the command line options.
void LinkerDriver::readConfigs(opt::InputArgList &Args) {
Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);
Config->AuxiliaryList = getArgs(Args, OPT_auxiliary);
Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
+ Config->CompressDebugSections = getCompressDebugSections(Args);
Config->DefineCommon = getArg(Args, OPT_define_common, OPT_no_define_common,
!Args.hasArg(OPT_relocatable));
Config->Demangle = getArg(Args, OPT_demangle, OPT_no_demangle, true);
diff --git a/lld/ELF/Options.td b/lld/ELF/Options.td
index 7ed8dfb..4cf14c9 100644
--- a/lld/ELF/Options.td
+++ b/lld/ELF/Options.td
@@ -22,6 +22,9 @@
def build_id_eq: J<"build-id=">, HelpText<"Generate build ID note">;
+def compress_debug_sections : J<"compress-debug-sections=">,
+ HelpText<"Compress DWARF debug sections">;
+
def L: JoinedOrSeparate<["-"], "L">, MetaVarName<"<dir>">,
HelpText<"Add a directory to the library search path">;
diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index 93f8310..9fc6969 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -16,6 +16,7 @@
#include "SyntheticSections.h"
#include "Target.h"
#include "Threads.h"
+#include "llvm/Support/Compression.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/MD5.h"
#include "llvm/Support/MathExtras.h"
@@ -83,6 +84,55 @@
return LA->OutSecOff < LB->OutSecOff;
}
+// Compressed sections has header which we create in this function.
+// Format is explaned here:
+// https://docs.oracle.com/cd/E53394_01/html/E54813/section_compression.html
+template <class ELFT>
+static std::vector<uint8_t> createHeader(size_t Size, uint32_t Alignment) {
+ const endianness E = ELFT::TargetEndianness;
+
+ std::vector<uint8_t> Ret(sizeof(typename ELFT::Chdr));
+ uint8_t *Buf = &Ret[0];
+ write32<E>(Buf, ELFCOMPRESS_ZLIB);
+ Buf += 4;
+
+ if (Config->Is64) {
+ Buf += sizeof(Elf64_Word); // Skip ch_reserved field.
+ write64<E>(Buf, Size);
+ Buf += sizeof(ELFT::Chdr::ch_size);
+ write64<E>(Buf, Alignment);
+ Buf += sizeof(ELFT::Chdr::ch_addralign);
+ } else {
+ write32<E>(Buf, Size);
+ Buf += sizeof(ELFT::Chdr::ch_size);
+ write32<E>(Buf, Alignment);
+ Buf += sizeof(ELFT::Chdr::ch_addralign);
+ }
+
+ return Ret;
+}
+
+template <class ELFT> void OutputSection::maybeCompress() {
+ // If -compress-debug-sections is specified, we compress output debug
+ // sections.
+ if (!Config->CompressDebugSections || !Name.startswith(".debug_") ||
+ (Flags & SHF_ALLOC))
+ return;
+
+ this->Flags |= SHF_COMPRESSED;
+ CompressedHeader = createHeader<ELFT>(this->Size, this->Alignment);
+
+ // Here we write relocated content of sections and compress it.
+ std::vector<uint8_t> Data(this->Size);
+ this->writeTo<ELFT>(&Data[0]);
+
+ if (Error E = zlib::compress(StringRef((char *)Data.data(), Data.size()),
+ CompressedData))
+ fatal("compress failed: " + llvm::toString(std::move(E)));
+
+ this->Size = this->CompressedHeader.size() + this->CompressedData.size();
+}
+
template <class ELFT> void OutputSection::finalize() {
if ((this->Flags & SHF_LINK_ORDER) && !this->Sections.empty()) {
std::sort(Sections.begin(), Sections.end(), compareByFilePosition);
@@ -245,6 +295,15 @@
template <class ELFT> void OutputSection::writeTo(uint8_t *Buf) {
Loc = Buf;
+ // We may have already rendered compressed content when using
+ // -compress-debug-sections option. Write it together with header.
+ if (!CompressedData.empty()) {
+ memcpy(Buf, CompressedHeader.data(), CompressedHeader.size());
+ Buf += CompressedHeader.size();
+ memcpy(Buf, CompressedData.data(), CompressedData.size());
+ return;
+ }
+
// Write leading padding.
uint32_t Filler = getFiller();
if (Filler)
@@ -422,6 +481,11 @@
template void OutputSection::finalize<ELF64LE>();
template void OutputSection::finalize<ELF64BE>();
+template void OutputSection::maybeCompress<ELF32LE>();
+template void OutputSection::maybeCompress<ELF32BE>();
+template void OutputSection::maybeCompress<ELF64LE>();
+template void OutputSection::maybeCompress<ELF64BE>();
+
template void OutputSection::writeTo<ELF32LE>(uint8_t *Buf);
template void OutputSection::writeTo<ELF32BE>(uint8_t *Buf);
template void OutputSection::writeTo<ELF64LE>(uint8_t *Buf);
diff --git a/lld/ELF/OutputSections.h b/lld/ELF/OutputSections.h
index 0ae3df5..9534df5 100644
--- a/lld/ELF/OutputSections.h
+++ b/lld/ELF/OutputSections.h
@@ -84,9 +84,14 @@
uint32_t getFiller();
template <class ELFT> void writeTo(uint8_t *Buf);
template <class ELFT> void finalize();
+ template <class ELFT> void maybeCompress();
void assignOffsets();
std::vector<InputSection *> Sections;
+ // Used for implementation of --compress-debug-sections option.
+ llvm::SmallVector<char, 1> CompressedData;
+ std::vector<uint8_t> CompressedHeader;
+
// Location in the output buffer.
uint8_t *Loc = nullptr;
};
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 3ded0c6..b4a25e6 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -19,6 +19,7 @@
#include "SymbolTable.h"
#include "SyntheticSections.h"
#include "Target.h"
+#include "Threads.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/FileOutputBuffer.h"
@@ -1216,6 +1217,11 @@
for (OutputSection *Sec : OutputSections)
Sec->finalize<ELFT>();
+ // Some sections may require compression. That happens for
+ // debug sections when --compress-debug-sections option used.
+ parallelForEach(OutputSections.begin(), OutputSections.end(),
+ [](OutputSection *S) { S->maybeCompress<ELFT>(); });
+
// createThunks may have added local symbols to the static symbol table
applySynthetic({In<ELFT>::SymTab, In<ELFT>::ShStrTab, In<ELFT>::StrTab},
[](SyntheticSection *SS) { SS->postThunkContents(); });
diff --git a/lld/test/ELF/compress-debug-output.s b/lld/test/ELF/compress-debug-output.s
new file mode 100644
index 0000000..40958c4
--- /dev/null
+++ b/lld/test/ELF/compress-debug-output.s
@@ -0,0 +1,33 @@
+# REQUIRES: x86
+# REQUIRES: zlib
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: ld.lld %t.o -o %t1 --compress-debug-sections=zlib
+
+# RUN: llvm-objdump -s %t1 | FileCheck %s --check-prefix=ZLIBCONTENT
+# ZLIBCONTENT: Contents of section .debug_str:
+# ZLIBCONTENT-NOT: AAAAAAAAA
+
+# RUN: llvm-readobj -s %t1 | FileCheck %s --check-prefix=ZLIBFLAGS
+# ZLIBFLAGS: Section {
+# ZLIBFLAGS: Index:
+# ZLIBFLAGS: Name: .debug_str
+# ZLIBFLAGS-NEXT: Type: SHT_PROGBITS
+# ZLIBFLAGS-NEXT: Flags [
+# ZLIBFLAGS-NEXT: SHF_COMPRESSED
+
+# RUN: llvm-dwarfdump %t1 -debug-dump=str | \
+# RUN: FileCheck %s --check-prefix=DEBUGSTR
+# DEBUGSTR: .debug_str contents:
+# DEBUGSTR-NEXT: AAAAAAAAAAAAAAAAAAAAAAAAAAA
+# DEBUGSTR-NEXT: BBBBBBBBBBBBBBBBBBBBBBBBBBB
+
+# RUN: not ld.lld %t.o -o %t1 --compress-debug-sections=zlib-gabi 2>&1 | \
+# RUN: FileCheck -check-prefix=ERR %s
+# ERR: unknown --compress-debug-sections value: zlib-gabi
+
+.section .debug_str,"MS",@progbits,1
+.Linfo_string0:
+ .asciz "AAAAAAAAAAAAAAAAAAAAAAAAAAA"
+.Linfo_string1:
+ .asciz "BBBBBBBBBBBBBBBBBBBBBBBBBBB"