[llvm-objcopy] Add support for --rename-section flags from gnu objcopy
Summary:
Add support for --rename-section flags from gnu objcopy.
Not all flags appear to have an effect for ELF objects, but allowing them would allow easier drop-in replacement. Other unrecognized flags are rejected.
This was only tested by comparing flags printed by "readelf -e <.o>" against the output of gnu vs llvm objcopy, it hasn't been tested to be valid beyond that.
Reviewers: jakehehrlich, alexshap
Subscribers: llvm-commits, paulsemel, alexshap
Differential Revision: https://reviews.llvm.org/D49870
llvm-svn: 338582
diff --git a/llvm/tools/llvm-objcopy/llvm-objcopy.cpp b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
index 21a1622..ad31e6d 100644
--- a/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
+++ b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
@@ -9,7 +9,10 @@
#include "llvm-objcopy.h"
#include "Object.h"
+#include "llvm/ADT/BitmaskEnum.h"
+#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/ELF.h"
@@ -115,6 +118,12 @@
StripOptTable() : OptTable(StripInfoTable, true) {}
};
+struct SectionRename {
+ StringRef OriginalName;
+ StringRef NewName;
+ Optional<uint64_t> NewFlags;
+};
+
struct CopyConfig {
StringRef OutputFilename;
StringRef InputFilename;
@@ -133,7 +142,7 @@
std::vector<StringRef> SymbolsToWeaken;
std::vector<StringRef> SymbolsToRemove;
std::vector<StringRef> SymbolsToKeep;
- StringMap<StringRef> SectionsToRename;
+ StringMap<SectionRename> SectionsToRename;
StringMap<StringRef> SymbolsToRename;
bool StripAll = false;
bool StripAllGNU = false;
@@ -152,6 +161,23 @@
using SectionPred = std::function<bool(const SectionBase &Sec)>;
+enum SectionFlag {
+ SecNone = 0,
+ SecAlloc = 1 << 0,
+ SecLoad = 1 << 1,
+ SecNoload = 1 << 2,
+ SecReadonly = 1 << 3,
+ SecDebug = 1 << 4,
+ SecCode = 1 << 5,
+ SecData = 1 << 6,
+ SecRom = 1 << 7,
+ SecMerge = 1 << 8,
+ SecStrings = 1 << 9,
+ SecContents = 1 << 10,
+ SecShare = 1 << 11,
+ LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ SecShare)
+};
+
} // namespace
namespace llvm {
@@ -185,6 +211,65 @@
} // end namespace objcopy
} // end namespace llvm
+static SectionFlag ParseSectionRenameFlag(StringRef SectionName) {
+ return llvm::StringSwitch<SectionFlag>(SectionName)
+ .Case("alloc", SectionFlag::SecAlloc)
+ .Case("load", SectionFlag::SecLoad)
+ .Case("noload", SectionFlag::SecNoload)
+ .Case("readonly", SectionFlag::SecReadonly)
+ .Case("debug", SectionFlag::SecDebug)
+ .Case("code", SectionFlag::SecCode)
+ .Case("data", SectionFlag::SecData)
+ .Case("rom", SectionFlag::SecRom)
+ .Case("merge", SectionFlag::SecMerge)
+ .Case("strings", SectionFlag::SecStrings)
+ .Case("contents", SectionFlag::SecContents)
+ .Case("share", SectionFlag::SecShare)
+ .Default(SectionFlag::SecNone);
+}
+
+static SectionRename ParseRenameSectionValue(StringRef FlagValue) {
+ if (!FlagValue.contains('='))
+ error("Bad format for --rename-section: missing '='");
+
+ // Initial split: ".foo" = ".bar,f1,f2,..."
+ auto Old2New = FlagValue.split('=');
+ SectionRename SR;
+ SR.OriginalName = Old2New.first;
+
+ // Flags split: ".bar" "f1" "f2" ...
+ SmallVector<StringRef, 6> NameAndFlags;
+ Old2New.second.split(NameAndFlags, ',');
+ SR.NewName = NameAndFlags[0];
+
+ if (NameAndFlags.size() > 1) {
+ SectionFlag Flags = SectionFlag::SecNone;
+ for (size_t I = 1, Size = NameAndFlags.size(); I < Size; ++I) {
+ SectionFlag Flag = ParseSectionRenameFlag(NameAndFlags[I]);
+ if (Flag == SectionFlag::SecNone)
+ error("Unrecognized section flag '" + NameAndFlags[I] +
+ "'. Flags supported for GNU compatibility: alloc, load, noload, "
+ "readonly, debug, code, data, rom, share, contents, merge, "
+ "strings.");
+ Flags |= Flag;
+ }
+
+ SR.NewFlags = 0;
+ if (Flags & SectionFlag::SecAlloc)
+ *SR.NewFlags |= ELF::SHF_ALLOC;
+ if (!(Flags & SectionFlag::SecReadonly))
+ *SR.NewFlags |= ELF::SHF_WRITE;
+ if (Flags & SectionFlag::SecCode)
+ *SR.NewFlags |= ELF::SHF_EXECINSTR;
+ if (Flags & SectionFlag::SecMerge)
+ *SR.NewFlags |= ELF::SHF_MERGE;
+ if (Flags & SectionFlag::SecStrings)
+ *SR.NewFlags |= ELF::SHF_STRINGS;
+ }
+
+ return SR;
+}
+
static bool IsDebugSection(const SectionBase &Sec) {
return Sec.Name.startswith(".debug") || Sec.Name.startswith(".zdebug") ||
Sec.Name == ".gdb_index";
@@ -437,8 +522,20 @@
if (!Config.SectionsToRename.empty()) {
for (auto &Sec : Obj.sections()) {
const auto Iter = Config.SectionsToRename.find(Sec.Name);
- if (Iter != Config.SectionsToRename.end())
- Sec.Name = Iter->second;
+ if (Iter != Config.SectionsToRename.end()) {
+ const SectionRename &SR = Iter->second;
+ Sec.Name = SR.NewName;
+ if (SR.NewFlags.hasValue()) {
+ // Preserve some flags which should not be dropped when setting flags.
+ // Also, preserve anything OS/processor dependant.
+ const uint64_t PreserveMask = ELF::SHF_COMPRESSED | ELF::SHF_EXCLUDE |
+ ELF::SHF_GROUP | ELF::SHF_LINK_ORDER |
+ ELF::SHF_MASKOS | ELF::SHF_MASKPROC |
+ ELF::SHF_TLS | ELF::SHF_INFO_LINK;
+ Sec.Flags = (Sec.Flags & PreserveMask) |
+ (SR.NewFlags.getValue() & ~PreserveMask);
+ }
+ }
}
}
@@ -600,11 +697,9 @@
}
for (auto Arg : InputArgs.filtered(OBJCOPY_rename_section)) {
- if (!StringRef(Arg->getValue()).contains('='))
- error("Bad format for --rename-section");
- auto Old2New = StringRef(Arg->getValue()).split('=');
- if (!Config.SectionsToRename.insert(Old2New).second)
- error("Already have a section rename for " + Old2New.first);
+ SectionRename SR = ParseRenameSectionValue(StringRef(Arg->getValue()));
+ if (!Config.SectionsToRename.try_emplace(SR.OriginalName, SR).second)
+ error("Multiple renames of section " + SR.OriginalName);
}
for (auto Arg : InputArgs.filtered(OBJCOPY_remove_section))