[llvm] r332915 - [llvm-objcopy] Add --strip-unneeded option
Paul Semel via llvm-commits
llvm-commits at lists.llvm.org
Mon May 21 15:50:32 PDT 2018
Author: paulsemel
Date: Mon May 21 15:50:32 2018
New Revision: 332915
URL: http://llvm.org/viewvc/llvm-project?rev=332915&view=rev
Log:
[llvm-objcopy] Add --strip-unneeded option
This option removes symbols that are not needed by relocations.
Differential Revision: https://reviews.llvm.org/D46896
Added:
llvm/trunk/test/tools/llvm-objcopy/strip-unneeded.test
Modified:
llvm/trunk/tools/llvm-objcopy/ObjcopyOpts.td
llvm/trunk/tools/llvm-objcopy/Object.cpp
llvm/trunk/tools/llvm-objcopy/Object.h
llvm/trunk/tools/llvm-objcopy/llvm-objcopy.cpp
Added: llvm/trunk/test/tools/llvm-objcopy/strip-unneeded.test
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/tools/llvm-objcopy/strip-unneeded.test?rev=332915&view=auto
==============================================================================
--- llvm/trunk/test/tools/llvm-objcopy/strip-unneeded.test (added)
+++ llvm/trunk/test/tools/llvm-objcopy/strip-unneeded.test Mon May 21 15:50:32 2018
@@ -0,0 +1,136 @@
+# RUN: yaml2obj %s > %t
+# RUN: llvm-objcopy --strip-unneeded %t %t2
+# RUN: llvm-readobj -symbols %t2 | FileCheck %s
+
+!ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_REL
+ Machine: EM_X86_64
+Sections:
+ - Name: .text
+ Type: SHT_PROGBITS
+ Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
+ Address: 0x1000
+ AddressAlign: 0x0000000000000010
+ Size: 64
+ - Name: .group
+ Type: SHT_GROUP
+ Link: .symtab
+ AddressAlign: 0x0000000000000004
+ Info: barfoo
+ Members:
+ - SectionOrType: GRP_COMDAT
+ - SectionOrType: .text
+ - Name: .rel.text
+ Type: SHT_REL
+ Link: .symtab
+ Info: .text
+ Relocations:
+ - Offset: 0x1000
+ Symbol: foo
+ Type: R_X86_64_PC32
+Symbols:
+ Local:
+ - Name: foo
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x1000
+ Size: 8
+ - Name: bar
+ Type: STT_FUNC
+ Size: 8
+ Section: .text
+ Value: 0x1008
+ - Name: barfoo
+ Type: STT_FUNC
+ Size: 8
+ Section: .text
+ Value: 0x1010
+ - Name: fileSymbol
+ Type: STT_FILE
+ - Name: sectionSymbol
+ Type: STT_SECTION
+ Weak:
+ - Name: baz
+ Type: STT_FUNC
+ Size: 8
+ Section: .text
+ Value: 0x1018
+ - Name: foobaz
+ Type: STT_FUNC
+ Global:
+ - Name: foobar
+ Type: STT_FUNC
+ - Name: barbaz
+ Type: STT_FUNC
+ Size: 8
+ Section: .text
+ Value: 0x1020
+
+#CHECK: Symbols [
+#CHECK-NEXT: Symbol {
+#CHECK-NEXT: Name:
+#CHECK-NEXT: Value: 0x0
+#CHECK-NEXT: Size: 0
+#CHECK-NEXT: Binding: Local
+#CHECK-NEXT: Type: None
+#CHECK-NEXT: Other: 0
+#CHECK-NEXT: Section: Undefined
+#CHECK-NEXT: }
+#CHECK-NEXT: Symbol {
+#CHECK-NEXT: Name: foo
+#CHECK-NEXT: Value: 0x1000
+#CHECK-NEXT: Size: 8
+#CHECK-NEXT: Binding: Local
+#CHECK-NEXT: Type: Function
+#CHECK-NEXT: Other: 0
+#CHECK-NEXT: Section: .text
+#CHECK-NEXT: }
+#CHECK-NEXT: Symbol {
+#CHECK-NEXT: Name: barfoo
+#CHECK-NEXT: Value: 0x1010
+#CHECK-NEXT: Size: 8
+#CHECK-NEXT: Binding: Local
+#CHECK-NEXT: Type: Function
+#CHECK-NEXT: Other: 0
+#CHECK-NEXT: Section: .text
+#CHECK-NEXT: }
+#CHECK-NEXT: Symbol {
+#CHECK-NEXT: Name: fileSymbol
+#CHECK-NEXT: Value: 0x0
+#CHECK-NEXT: Size: 0
+#CHECK-NEXT: Binding: Local
+#CHECK-NEXT: Type: File
+#CHECK-NEXT: Other: 0
+#CHECK-NEXT: Section: Undefined
+#CHECK-NEXT: }
+#CHECK-NEXT: Symbol {
+#CHECK-NEXT: Name: sectionSymbol
+#CHECK-NEXT: Value: 0x0
+#CHECK-NEXT: Size: 0
+#CHECK-NEXT: Binding: Local
+#CHECK-NEXT: Type: Section
+#CHECK-NEXT: Other: 0
+#CHECK-NEXT: Section: Undefined
+#CHECK-NEXT: }
+#CHECK-NEXT: Symbol {
+#CHECK-NEXT: Name: barbaz
+#CHECK-NEXT: Value: 0x1020
+#CHECK-NEXT: Size: 8
+#CHECK-NEXT: Binding: Global
+#CHECK-NEXT: Type: Function
+#CHECK-NEXT: Other: 0
+#CHECK-NEXT: Section: .text
+#CHECK-NEXT: }
+#CHECK-NEXT: Symbol {
+#CHECK-NEXT: Name: baz
+#CHECK-NEXT: Value: 0x1018
+#CHECK-NEXT: Size: 8
+#CHECK-NEXT: Binding: Weak
+#CHECK-NEXT: Type: Function
+#CHECK-NEXT: Other: 0
+#CHECK-NEXT: Section: .text
+#CHECK-NEXT: }
+#CHECK-NEXT:]
Modified: llvm/trunk/tools/llvm-objcopy/ObjcopyOpts.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-objcopy/ObjcopyOpts.td?rev=332915&r1=332914&r2=332915&view=diff
==============================================================================
--- llvm/trunk/tools/llvm-objcopy/ObjcopyOpts.td (original)
+++ llvm/trunk/tools/llvm-objcopy/ObjcopyOpts.td Mon May 21 15:50:32 2018
@@ -90,3 +90,5 @@ def K : JoinedOrSeparate<["-"], "K">,
Alias<keep_symbol>;
def only_keep_debug : Flag<["-", "--"], "only-keep-debug">,
HelpText<"Currently ignored. Only for compaitability with GNU objcopy.">;
+def strip_unneeded : Flag<["-", "--"], "strip-unneeded">,
+ HelpText<"Remove all symbols not needed by relocations">;
Modified: llvm/trunk/tools/llvm-objcopy/Object.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-objcopy/Object.cpp?rev=332915&r1=332914&r2=332915&view=diff
==============================================================================
--- llvm/trunk/tools/llvm-objcopy/Object.cpp (original)
+++ llvm/trunk/tools/llvm-objcopy/Object.cpp Mon May 21 15:50:32 2018
@@ -185,6 +185,7 @@ void SymbolTableSection::addSymbol(Strin
Sym.Visibility = Visibility;
Sym.Size = Sz;
Sym.Index = Symbols.size();
+ Sym.ReferenceCount = 0;
Symbols.emplace_back(llvm::make_unique<Symbol>(Sym));
Size += this->EntrySize;
}
@@ -255,6 +256,11 @@ const Symbol *SymbolTableSection::getSym
return Symbols[Index].get();
}
+Symbol *SymbolTableSection::getSymbolByIndex(uint32_t Index) {
+ return const_cast<Symbol *>(
+ static_cast<const SymbolTableSection *>(this)->getSymbolByIndex(Index));
+}
+
template <class ELFT>
void ELFSectionWriter<ELFT>::visit(const SymbolTableSection &Sec) {
uint8_t *Buf = Out.getBufferStart();
@@ -344,6 +350,12 @@ void RelocationSection::accept(SectionVi
Visitor.visit(*this);
}
+RelocationSection::~RelocationSection() {
+ for (auto &Rel : Relocations) {
+ --Rel.RelocSymbol->ReferenceCount;
+ }
+}
+
void RelocationSection::removeSymbols(
function_ref<bool(const Symbol &)> ToRemove) {
for (const Relocation &Reloc : Relocations)
@@ -647,7 +659,9 @@ void initRelocations(RelocationSection *
ToAdd.Offset = Rel.r_offset;
getAddend(ToAdd.Addend, Rel);
ToAdd.Type = Rel.getType(false);
- ToAdd.RelocSymbol = SymbolTable->getSymbolByIndex(Rel.getSymbol(false));
+ Symbol *Sym = SymbolTable->getSymbolByIndex(Rel.getSymbol(false));
+ ++Sym->ReferenceCount;
+ ToAdd.RelocSymbol = Sym;
Relocs->addRelocation(ToAdd);
}
}
Modified: llvm/trunk/tools/llvm-objcopy/Object.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-objcopy/Object.h?rev=332915&r1=332914&r2=332915&view=diff
==============================================================================
--- llvm/trunk/tools/llvm-objcopy/Object.h (original)
+++ llvm/trunk/tools/llvm-objcopy/Object.h Mon May 21 15:50:32 2018
@@ -344,6 +344,7 @@ struct Symbol {
uint8_t Type;
uint64_t Value;
uint8_t Visibility;
+ uint32_t ReferenceCount;
uint16_t getShndx() const;
};
@@ -367,6 +368,7 @@ public:
void addSymbolNames();
const SectionBase *getStrTab() const { return SymbolNames; }
const Symbol *getSymbolByIndex(uint32_t Index) const;
+ Symbol *getSymbolByIndex(uint32_t Index);
void updateSymbols(function_ref<void(Symbol &)> Callable);
void removeSectionReferences(const SectionBase *Sec) override;
@@ -381,7 +383,7 @@ public:
};
struct Relocation {
- const Symbol *RelocSymbol = nullptr;
+ Symbol *RelocSymbol = nullptr;
uint64_t Offset;
uint64_t Addend;
uint32_t Type;
@@ -432,6 +434,7 @@ class RelocationSection
std::vector<Relocation> Relocations;
public:
+ ~RelocationSection();
void addRelocation(Relocation Rel) { Relocations.push_back(Rel); }
void accept(SectionVisitor &Visitor) const override;
void removeSymbols(function_ref<bool(const Symbol &)> ToRemove) override;
@@ -449,7 +452,7 @@ public:
class GroupSection : public SectionBase {
MAKE_SEC_WRITER_FRIEND
const SymbolTableSection *SymTab = nullptr;
- const Symbol *Sym = nullptr;
+ Symbol *Sym = nullptr;
ELF::Elf32_Word FlagWord;
SmallVector<SectionBase *, 3> GroupMembers;
@@ -459,9 +462,16 @@ public:
ArrayRef<uint8_t> Contents;
explicit GroupSection(ArrayRef<uint8_t> Data) : Contents(Data) {}
+ ~GroupSection() {
+ if (Sym)
+ --Sym->ReferenceCount;
+ }
void setSymTab(const SymbolTableSection *SymTabSec) { SymTab = SymTabSec; }
- void setSymbol(const Symbol *S) { Sym = S; }
+ void setSymbol(Symbol *S) {
+ Sym = S;
+ ++Sym->ReferenceCount;
+ }
void setFlagWord(ELF::Elf32_Word W) { FlagWord = W; }
void addMember(SectionBase *Sec) { GroupMembers.push_back(Sec); }
Modified: llvm/trunk/tools/llvm-objcopy/llvm-objcopy.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-objcopy/llvm-objcopy.cpp?rev=332915&r1=332914&r2=332915&view=diff
==============================================================================
--- llvm/trunk/tools/llvm-objcopy/llvm-objcopy.cpp (original)
+++ llvm/trunk/tools/llvm-objcopy/llvm-objcopy.cpp Mon May 21 15:50:32 2018
@@ -156,6 +156,7 @@ struct CopyConfig {
bool StripSections = false;
bool StripNonAlloc = false;
bool StripDWO = false;
+ bool StripUnneeded = false;
bool ExtractDWO = false;
bool LocalizeHidden = false;
bool Weaken = false;
@@ -389,6 +390,13 @@ void HandleArgs(const CopyConfig &Config
return true;
}
+ // TODO: We might handle the 'null symbol' in a different way
+ // by probably handling it the same way as we handle 'null section' ?
+ if (Config.StripUnneeded && !Sym.ReferenceCount && Sym.Index != 0 &&
+ (Sym.Binding == STB_LOCAL || Sym.getShndx() == SHN_UNDEF) &&
+ Sym.Type != STT_FILE && Sym.Type != STT_SECTION)
+ return true;
+
return false;
});
}
@@ -479,6 +487,7 @@ CopyConfig ParseObjcopyOptions(ArrayRef<
Config.StripDWO = InputArgs.hasArg(OBJCOPY_strip_dwo);
Config.StripSections = InputArgs.hasArg(OBJCOPY_strip_sections);
Config.StripNonAlloc = InputArgs.hasArg(OBJCOPY_strip_non_alloc);
+ Config.StripUnneeded = InputArgs.hasArg(OBJCOPY_strip_unneeded);
Config.ExtractDWO = InputArgs.hasArg(OBJCOPY_extract_dwo);
Config.LocalizeHidden = InputArgs.hasArg(OBJCOPY_localize_hidden);
Config.Weaken = InputArgs.hasArg(OBJCOPY_weaken);
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