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Revert "[llvm-objcopy] Add support for --strip-sections to remove all section headers leaving only program headers and loadable segment data" 

This reverts commit rL315412

llvm-svn: 315417
This commit is contained in:
Jake Ehrlich 2017-10-11 02:42:29 +00:00
parent 183aa2731e
commit d9a283463a
4 changed files with 20 additions and 114 deletions
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66
llvm/test/tools/llvm-objcopy/strip-sections.test
View File

@ -1,66 +0,0 @@
# RUN: yaml2obj %s > %t
# RUN: llvm-objcopy --strip-sections %t %t2
# RUN: llvm-readobj -file-headers -program-headers %t2 | FileCheck %s
# RUN: od -t x1 -j 4096 %t2 | FileCheck %s --check-prefix=DATA
!ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_EXEC
Machine: EM_X86_64
Sections:
- Name: .text
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
AddressAlign: 0x0000000000001000
Content: "DEADBEEF"
ProgramHeaders:
- Type: PT_LOAD
Flags: [ PF_X, PF_R ]
Sections:
- Section: .text
#DATA: 0010000 de ad be ef
#CHECK: ElfHeader {
#CHECK-NEXT: Ident {
#CHECK-NEXT: Magic: (7F 45 4C 46)
#CHECK-NEXT: Class: 64-bit (0x2)
#CHECK-NEXT: DataEncoding: LittleEndian (0x1)
#CHECK-NEXT: FileVersion: 1
#CHECK-NEXT: OS/ABI: SystemV (0x0)
#CHECK-NEXT: ABIVersion: 0
#CHECK-NEXT: Unused: (00 00 00 00 00 00 00)
#CHECK-NEXT: }
#CHECK-NEXT: Type: Executable (0x2)
#CHECK-NEXT: Machine: EM_X86_64 (0x3E)
#CHECK-NEXT: Version: 1
#CHECK-NEXT: Entry: 0x0
#CHECK-NEXT: ProgramHeaderOffset: 0x40
#CHECK-NEXT: SectionHeaderOffset: 0x0
#CHECK-NEXT: Flags [ (0x0)
#CHECK-NEXT: ]
#CHECK-NEXT: HeaderSize: 64
#CHECK-NEXT: ProgramHeaderEntrySize: 56
#CHECK-NEXT: ProgramHeaderCount: 1
#CHECK-NEXT: SectionHeaderEntrySize: 64
#CHECK-NEXT: SectionHeaderCount: 0
#CHECK-NEXT: StringTableSectionIndex: 0
#CHECK-NEXT: }
#CHECK: ProgramHeaders [
#CHECK-NEXT: ProgramHeader {
#CHECK-NEXT: Type: PT_LOAD (0x1)
#CHECK-NEXT: Offset: 0x1000
#CHECK-NEXT: VirtualAddress: 0x0
#CHECK-NEXT: PhysicalAddress: 0x0
#CHECK-NEXT: FileSize: 4
#CHECK-NEXT: MemSize: 4
#CHECK-NEXT: Flags [ (0x5)
#CHECK-NEXT: PF_R (0x4)
#CHECK-NEXT: PF_X (0x1)
#CHECK-NEXT: ]
#CHECK-NEXT: Alignment: 4096
#CHECK-NEXT: }
#CHECK-NEXT:]

45
llvm/tools/llvm-objcopy/Object.cpp
View File

@ -575,20 +575,14 @@ void Object<ELFT>::writeHeader(FileOutputBuffer &Out) const {
Ehdr.e_version = Version;
Ehdr.e_entry = Entry;
Ehdr.e_phoff = sizeof(Elf_Ehdr);
Ehdr.e_shoff = SHOffset;
Ehdr.e_flags = Flags;
Ehdr.e_ehsize = sizeof(Elf_Ehdr);
Ehdr.e_phentsize = sizeof(Elf_Phdr);
Ehdr.e_phnum = Segments.size();
Ehdr.e_shentsize = sizeof(Elf_Shdr);
if (WriteSectionHeaders) {
Ehdr.e_shoff = SHOffset;
Ehdr.e_shnum = Sections.size() + 1;
Ehdr.e_shstrndx = SectionNames->Index;
} else {
Ehdr.e_shoff = 0;
Ehdr.e_shnum = 0;
Ehdr.e_shstrndx = 0;
}
Ehdr.e_shnum = Sections.size() + 1;
Ehdr.e_shstrndx = SectionNames->Index;
}
template <class ELFT>
@ -639,10 +633,12 @@ void Object<ELFT>::removeSections(
if (SymbolTable != nullptr && ToRemove(*SymbolTable))
SymbolTable = nullptr;
if (ToRemove(*SectionNames)) {
if (WriteSectionHeaders)
error("Cannot remove " + SectionNames->Name +
" because it is the section header string table.");
SectionNames = nullptr;
// Right now llvm-objcopy always outputs section headers. This will not
// always be the case. Eventully the section header table will become
// optional and if no section header is output then there dosn't need to be
// a section header string table.
error("Cannot remove " + SectionNames->Name +
" because it is the section header string table.");
}
// Now make sure there are no remaining references to the sections that will
// be removed. Sometimes it is impossible to remove a reference so we emit
@ -736,34 +732,29 @@ template <class ELFT> void ELFObject<ELFT>::assignOffsets() {
}
}
if (this->WriteSectionHeaders) {
Offset = alignTo(Offset, sizeof(typename ELFT::Addr));
}
Offset = alignTo(Offset, sizeof(typename ELFT::Addr));
this->SHOffset = Offset;
}
template <class ELFT> size_t ELFObject<ELFT>::totalSize() const {
// We already have the section header offset so we can calculate the total
// size by just adding up the size of each section header.
auto NullSectionSize = this->WriteSectionHeaders ? sizeof(Elf_Shdr) : 0;
return this->SHOffset + this->Sections.size() * sizeof(Elf_Shdr) +
NullSectionSize;
sizeof(Elf_Shdr);
}
template <class ELFT> void ELFObject<ELFT>::write(FileOutputBuffer &Out) const {
this->writeHeader(Out);
this->writeProgramHeaders(Out);
this->writeSectionData(Out);
if (this->WriteSectionHeaders)
this->writeSectionHeaders(Out);
this->writeSectionHeaders(Out);
}
template <class ELFT> void ELFObject<ELFT>::finalize() {
// Make sure we add the names of all the sections.
if (this->SectionNames != nullptr)
for (const auto &Section : this->Sections) {
this->SectionNames->addString(Section->Name);
}
for (const auto &Section : this->Sections) {
this->SectionNames->addString(Section->Name);
}
// Make sure we add the names of all the symbols.
if (this->SymbolTable != nullptr)
this->SymbolTable->addSymbolNames();
@ -772,16 +763,14 @@ template <class ELFT> void ELFObject<ELFT>::finalize() {
assignOffsets();
// Finalize SectionNames first so that we can assign name indexes.
if (this->SectionNames != nullptr)
this->SectionNames->finalize();
this->SectionNames->finalize();
// Finally now that all offsets and indexes have been set we can finalize any
// remaining issues.
uint64_t Offset = this->SHOffset + sizeof(Elf_Shdr);
for (auto &Section : this->Sections) {
Section->HeaderOffset = Offset;
Offset += sizeof(Elf_Shdr);
if (this->WriteSectionHeaders)
Section->NameIndex = this->SectionNames->findIndex(Section->Name);
Section->NameIndex = this->SectionNames->findIndex(Section->Name);
Section->finalize();
}
}

1
llvm/tools/llvm-objcopy/Object.h
View File

@ -346,7 +346,6 @@ public:
uint32_t Machine;
uint32_t Version;
uint32_t Flags;
bool WriteSectionHeaders = true;
Object(const llvm::object::ELFObjectFile<ELFT> &Obj);
void removeSections(std::function<bool(const SectionBase &)> ToRemove);

22
llvm/tools/llvm-objcopy/llvm-objcopy.cpp
View File

@ -56,14 +56,11 @@ cl::opt<std::string> OutputFilename(cl::Positional, cl::desc("<output>"),
cl::opt<std::string>
OutputFormat("O", cl::desc("set output format to one of the following:"
"\n\tbinary"));
cl::list<std::string> ToRemove("remove-section",
cl::desc("Remove a specific section"));
cl::alias ToRemoveA("R", cl::desc("Alias for remove-section"),
cl::aliasopt(ToRemove));
cl::opt<bool> StripSections("strip-sections",
cl::desc("Remove all section headers"));
typedef std::function<bool(const SectionBase &Sec)> SectionPred;
void CopyBinary(const ELFObjectFile<ELF64LE> &ObjFile) {
std::unique_ptr<FileOutputBuffer> Buffer;
@ -74,25 +71,12 @@ void CopyBinary(const ELFObjectFile<ELF64LE> &ObjFile) {
Obj = llvm::make_unique<BinaryObject<ELF64LE>>(ObjFile);
else
Obj = llvm::make_unique<ELFObject<ELF64LE>>(ObjFile);
SectionPred RemovePred = [](const SectionBase &) { return false; };
if (!ToRemove.empty()) {
RemovePred = [&](const SectionBase &Sec) {
Obj->removeSections([&](const SectionBase &Sec) {
return std::find(std::begin(ToRemove), std::end(ToRemove), Sec.Name) !=
std::end(ToRemove);
};
});
}
if (StripSections) {
RemovePred = [RemovePred](const SectionBase &Sec) {
return RemovePred(Sec) || (Sec.Flags & SHF_ALLOC) == 0;
};
Obj->WriteSectionHeaders = false;
}
Obj->removeSections(RemovePred);
Obj->finalize();
ErrorOr<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
FileOutputBuffer::create(OutputFilename, Obj->totalSize(),