[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/llvm-objcopy.cpp b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
index 8ffab54..36ed77a 100644
--- a/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
+++ b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
@@ -17,6 +17,7 @@
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/MC/MCTargetOptions.h"
#include "llvm/Object/Archive.h"
#include "llvm/Object/ArchiveWriter.h"
#include "llvm/Object/Binary.h"
@@ -29,6 +30,7 @@
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Compression.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ErrorOr.h"
@@ -176,6 +178,7 @@
bool StripSections = false;
bool StripUnneeded = false;
bool Weaken = false;
+ DebugCompressionType CompressionType = DebugCompressionType::None;
};
// Configuration for the overall invocation of this tool. When invoked as
@@ -298,12 +301,12 @@
}
static bool isDebugSection(const SectionBase &Sec) {
- return Sec.Name.startswith(".debug") || Sec.Name.startswith(".zdebug") ||
- Sec.Name == ".gdb_index";
+ return StringRef(Sec.Name).startswith(".debug") ||
+ StringRef(Sec.Name).startswith(".zdebug") || Sec.Name == ".gdb_index";
}
static bool isDWOSection(const SectionBase &Sec) {
- return Sec.Name.endswith(".dwo");
+ return StringRef(Sec.Name).endswith(".dwo");
}
static bool onlyKeepDWOPred(const Object &Obj, const SectionBase &Sec) {
@@ -413,6 +416,50 @@
object_error::parse_failed);
}
+static bool isCompressed(const SectionBase &Section) {
+ const char *Magic = "ZLIB";
+ return StringRef(Section.Name).startswith(".zdebug") ||
+ (Section.OriginalData.size() > strlen(Magic) &&
+ !strncmp(reinterpret_cast<const char *>(Section.OriginalData.data()),
+ Magic, strlen(Magic))) ||
+ (Section.Flags & ELF::SHF_COMPRESSED);
+}
+
+static bool isCompressable(const SectionBase &Section) {
+ return !isCompressed(Section) && isDebugSection(Section) &&
+ Section.Name != ".gdb_index";
+}
+
+static void compressSections(const CopyConfig &Config, Object &Obj,
+ SectionPred &RemovePred) {
+ SmallVector<SectionBase *, 13> ToCompress;
+ SmallVector<RelocationSection *, 13> RelocationSections;
+ for (auto &Sec : Obj.sections()) {
+ if (RelocationSection *R = dyn_cast<RelocationSection>(&Sec)) {
+ if (isCompressable(*R->getSection()))
+ RelocationSections.push_back(R);
+ continue;
+ }
+
+ if (isCompressable(Sec))
+ ToCompress.push_back(&Sec);
+ }
+
+ for (SectionBase *S : ToCompress) {
+ CompressedSection &CS =
+ Obj.addSection<CompressedSection>(*S, Config.CompressionType);
+
+ for (RelocationSection *RS : RelocationSections) {
+ if (RS->getSection() == S)
+ RS->setSection(&CS);
+ }
+ }
+
+ RemovePred = [RemovePred](const SectionBase &Sec) {
+ return isCompressable(Sec) || RemovePred(Sec);
+ };
+}
+
// This function handles the high level operations of GNU objcopy including
// handling command line options. It's important to outline certain properties
// we expect to hold of the command line operations. Any operation that "keeps"
@@ -572,7 +619,7 @@
return true;
if (&Sec == Obj.SectionNames)
return false;
- if (Sec.Name.startswith(".gnu.warning"))
+ if (StringRef(Sec.Name).startswith(".gnu.warning"))
return false;
return (Sec.Flags & SHF_ALLOC) == 0;
};
@@ -624,6 +671,9 @@
};
}
+ if (Config.CompressionType != DebugCompressionType::None)
+ compressSections(Config, Obj, RemovePred);
+
Obj.removeSections(RemovePred);
if (!Config.SectionsToRename.empty()) {
@@ -868,6 +918,25 @@
Config.BinaryArch = getMachineInfo(BinaryArch);
}
+ if (auto Arg = InputArgs.getLastArg(OBJCOPY_compress_debug_sections,
+ OBJCOPY_compress_debug_sections_eq)) {
+ Config.CompressionType = DebugCompressionType::Z;
+
+ if (Arg->getOption().getID() == OBJCOPY_compress_debug_sections_eq) {
+ Config.CompressionType =
+ StringSwitch<DebugCompressionType>(
+ InputArgs.getLastArgValue(OBJCOPY_compress_debug_sections_eq))
+ .Case("zlib-gnu", DebugCompressionType::GNU)
+ .Case("zlib", DebugCompressionType::Z)
+ .Default(DebugCompressionType::None);
+ if (Config.CompressionType == DebugCompressionType::None)
+ error("Invalid or unsupported --compress-debug-sections format: " +
+ InputArgs.getLastArgValue(OBJCOPY_compress_debug_sections_eq));
+ if (!zlib::isAvailable())
+ error("LLVM was not compiled with LLVM_ENABLE_ZLIB: can not compress.");
+ }
+ }
+
Config.SplitDWO = InputArgs.getLastArgValue(OBJCOPY_split_dwo);
Config.AddGnuDebugLink = InputArgs.getLastArgValue(OBJCOPY_add_gnu_debuglink);
Config.SymbolsPrefix = InputArgs.getLastArgValue(OBJCOPY_prefix_symbols);