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llvm-mirror/lib/Object/ELF.cpp
Peter Collingbourne 69450b777d llvm-readobj: Fix addend in relocations for android packed format 
If a relocation group doesn't have the RELOCATION_GROUP_HAS_ADDEND_FLAG set, then this implies the group's addend equals zero.
In this case android packed format won't encode an explicit addend delta, instead we need to set Addend, the "previous addend" variable, to zero by ourself.

Patch by Yi-Yo Chiang!

Differential Revision: https://reviews.llvm.org/D50601

llvm-svn: 339799
2018-08-15 17:58:22 +00:00

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//===- ELF.cpp - ELF object file implementation ---------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/Object/ELF.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/Support/LEB128.h"
using namespace llvm;
using namespace object;
#define STRINGIFY_ENUM_CASE(ns, name) \
case ns::name: \
return #name;
#define ELF_RELOC(name, value) STRINGIFY_ENUM_CASE(ELF, name)
StringRef llvm::object::getELFRelocationTypeName(uint32_t Machine,
uint32_t Type) {
switch (Machine) {
case ELF::EM_X86_64:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/x86_64.def"
default:
break;
}
break;
case ELF::EM_386:
case ELF::EM_IAMCU:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/i386.def"
default:
break;
}
break;
case ELF::EM_MIPS:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/Mips.def"
default:
break;
}
break;
case ELF::EM_AARCH64:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/AArch64.def"
default:
break;
}
break;
case ELF::EM_ARM:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/ARM.def"
default:
break;
}
break;
case ELF::EM_ARC_COMPACT:
case ELF::EM_ARC_COMPACT2:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/ARC.def"
default:
break;
}
break;
case ELF::EM_AVR:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/AVR.def"
default:
break;
}
break;
case ELF::EM_HEXAGON:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/Hexagon.def"
default:
break;
}
break;
case ELF::EM_LANAI:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/Lanai.def"
default:
break;
}
break;
case ELF::EM_PPC:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/PowerPC.def"
default:
break;
}
break;
case ELF::EM_PPC64:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/PowerPC64.def"
default:
break;
}
break;
case ELF::EM_RISCV:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/RISCV.def"
default:
break;
}
break;
case ELF::EM_S390:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/SystemZ.def"
default:
break;
}
break;
case ELF::EM_SPARC:
case ELF::EM_SPARC32PLUS:
case ELF::EM_SPARCV9:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/Sparc.def"
default:
break;
}
break;
case ELF::EM_AMDGPU:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/AMDGPU.def"
default:
break;
}
break;
case ELF::EM_BPF:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/BPF.def"
default:
break;
}
break;
default:
break;
}
return "Unknown";
}
#undef ELF_RELOC
uint32_t llvm::object::getELFRelrRelocationType(uint32_t Machine) {
switch (Machine) {
case ELF::EM_X86_64:
return ELF::R_X86_64_RELATIVE;
case ELF::EM_386:
case ELF::EM_IAMCU:
return ELF::R_386_RELATIVE;
case ELF::EM_MIPS:
break;
case ELF::EM_AARCH64:
return ELF::R_AARCH64_RELATIVE;
case ELF::EM_ARM:
return ELF::R_ARM_RELATIVE;
case ELF::EM_ARC_COMPACT:
case ELF::EM_ARC_COMPACT2:
return ELF::R_ARC_RELATIVE;
case ELF::EM_AVR:
break;
case ELF::EM_HEXAGON:
return ELF::R_HEX_RELATIVE;
case ELF::EM_LANAI:
break;
case ELF::EM_PPC:
break;
case ELF::EM_PPC64:
return ELF::R_PPC64_RELATIVE;
case ELF::EM_RISCV:
return ELF::R_RISCV_RELATIVE;
case ELF::EM_S390:
return ELF::R_390_RELATIVE;
case ELF::EM_SPARC:
case ELF::EM_SPARC32PLUS:
case ELF::EM_SPARCV9:
return ELF::R_SPARC_RELATIVE;
case ELF::EM_AMDGPU:
break;
case ELF::EM_BPF:
break;
default:
break;
}
return 0;
}
StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {
switch (Machine) {
case ELF::EM_ARM:
switch (Type) {
STRINGIFY_ENUM_CASE(ELF, SHT_ARM_EXIDX);
STRINGIFY_ENUM_CASE(ELF, SHT_ARM_PREEMPTMAP);
STRINGIFY_ENUM_CASE(ELF, SHT_ARM_ATTRIBUTES);
STRINGIFY_ENUM_CASE(ELF, SHT_ARM_DEBUGOVERLAY);
STRINGIFY_ENUM_CASE(ELF, SHT_ARM_OVERLAYSECTION);
}
break;
case ELF::EM_HEXAGON:
switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_HEX_ORDERED); }
break;
case ELF::EM_X86_64:
switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_X86_64_UNWIND); }
break;
case ELF::EM_MIPS:
case ELF::EM_MIPS_RS3_LE:
switch (Type) {
STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_REGINFO);
STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_OPTIONS);
STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_ABIFLAGS);
STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_DWARF);
}
break;
default:
break;
}
switch (Type) {
STRINGIFY_ENUM_CASE(ELF, SHT_NULL);
STRINGIFY_ENUM_CASE(ELF, SHT_PROGBITS);
STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB);
STRINGIFY_ENUM_CASE(ELF, SHT_STRTAB);
STRINGIFY_ENUM_CASE(ELF, SHT_RELA);
STRINGIFY_ENUM_CASE(ELF, SHT_HASH);
STRINGIFY_ENUM_CASE(ELF, SHT_DYNAMIC);
STRINGIFY_ENUM_CASE(ELF, SHT_NOTE);
STRINGIFY_ENUM_CASE(ELF, SHT_NOBITS);
STRINGIFY_ENUM_CASE(ELF, SHT_REL);
STRINGIFY_ENUM_CASE(ELF, SHT_SHLIB);
STRINGIFY_ENUM_CASE(ELF, SHT_DYNSYM);
STRINGIFY_ENUM_CASE(ELF, SHT_INIT_ARRAY);
STRINGIFY_ENUM_CASE(ELF, SHT_FINI_ARRAY);
STRINGIFY_ENUM_CASE(ELF, SHT_PREINIT_ARRAY);
STRINGIFY_ENUM_CASE(ELF, SHT_GROUP);
STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB_SHNDX);
STRINGIFY_ENUM_CASE(ELF, SHT_RELR);
STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_REL);
STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_RELA);
STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_RELR);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ODRTAB);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_LINKER_OPTIONS);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CALL_GRAPH_PROFILE);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ADDRSIG);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verneed);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_versym);
default:
return "Unknown";
}
}
template <class ELFT>
Expected<std::vector<typename ELFT::Rela>>
ELFFile<ELFT>::decode_relrs(Elf_Relr_Range relrs) const {
// This function decodes the contents of an SHT_RELR packed relocation
// section.
//
// Proposal for adding SHT_RELR sections to generic-abi is here:
// https://groups.google.com/forum/#!topic/generic-abi/bX460iggiKg
//
// The encoded sequence of Elf64_Relr entries in a SHT_RELR section looks
// like [ AAAAAAAA BBBBBBB1 BBBBBBB1 ... AAAAAAAA BBBBBB1 ... ]
//
// i.e. start with an address, followed by any number of bitmaps. The address
// entry encodes 1 relocation. The subsequent bitmap entries encode up to 63
// relocations each, at subsequent offsets following the last address entry.
//
// The bitmap entries must have 1 in the least significant bit. The assumption
// here is that an address cannot have 1 in lsb. Odd addresses are not
// supported.
//
// Excluding the least significant bit in the bitmap, each non-zero bit in
// the bitmap represents a relocation to be applied to a corresponding machine
// word that follows the base address word. The second least significant bit
// represents the machine word immediately following the initial address, and
// each bit that follows represents the next word, in linear order. As such,
// a single bitmap can encode up to 31 relocations in a 32-bit object, and
// 63 relocations in a 64-bit object.
//
// This encoding has a couple of interesting properties:
// 1. Looking at any entry, it is clear whether it's an address or a bitmap:
// even means address, odd means bitmap.
// 2. Just a simple list of addresses is a valid encoding.
Elf_Rela Rela;
Rela.r_info = 0;
Rela.r_addend = 0;
Rela.setType(getRelrRelocationType(), false);
std::vector<Elf_Rela> Relocs;
// Word type: uint32_t for Elf32, and uint64_t for Elf64.
typedef typename ELFT::uint Word;
// Word size in number of bytes.
const size_t WordSize = sizeof(Word);
// Number of bits used for the relocation offsets bitmap.
// These many relative relocations can be encoded in a single entry.
const size_t NBits = 8*WordSize - 1;
Word Base = 0;
for (const Elf_Relr &R : relrs) {
Word Entry = R;
if ((Entry&1) == 0) {
// Even entry: encodes the offset for next relocation.
Rela.r_offset = Entry;
Relocs.push_back(Rela);
// Set base offset for subsequent bitmap entries.
Base = Entry + WordSize;
continue;
}
// Odd entry: encodes bitmap for relocations starting at base.
Word Offset = Base;
while (Entry != 0) {
Entry >>= 1;
if ((Entry&1) != 0) {
Rela.r_offset = Offset;
Relocs.push_back(Rela);
}
Offset += WordSize;
}
// Advance base offset by NBits words.
Base += NBits * WordSize;
}
return Relocs;
}
template <class ELFT>
Expected<std::vector<typename ELFT::Rela>>
ELFFile<ELFT>::android_relas(const Elf_Shdr *Sec) const {
// This function reads relocations in Android's packed relocation format,
// which is based on SLEB128 and delta encoding.
Expected<ArrayRef<uint8_t>> ContentsOrErr = getSectionContents(Sec);
if (!ContentsOrErr)
return ContentsOrErr.takeError();
const uint8_t *Cur = ContentsOrErr->begin();
const uint8_t *End = ContentsOrErr->end();
if (ContentsOrErr->size() < 4 || Cur[0] != 'A' || Cur[1] != 'P' ||
Cur[2] != 'S' || Cur[3] != '2')
return createError("invalid packed relocation header");
Cur += 4;
const char *ErrStr = nullptr;
auto ReadSLEB = [&]() -> int64_t {
if (ErrStr)
return 0;
unsigned Len;
int64_t Result = decodeSLEB128(Cur, &Len, End, &ErrStr);
Cur += Len;
return Result;
};
uint64_t NumRelocs = ReadSLEB();
uint64_t Offset = ReadSLEB();
uint64_t Addend = 0;
if (ErrStr)
return createError(ErrStr);
std::vector<Elf_Rela> Relocs;
Relocs.reserve(NumRelocs);
while (NumRelocs) {
uint64_t NumRelocsInGroup = ReadSLEB();
if (NumRelocsInGroup > NumRelocs)
return createError("relocation group unexpectedly large");
NumRelocs -= NumRelocsInGroup;
uint64_t GroupFlags = ReadSLEB();
bool GroupedByInfo = GroupFlags & ELF::RELOCATION_GROUPED_BY_INFO_FLAG;
bool GroupedByOffsetDelta = GroupFlags & ELF::RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG;
bool GroupedByAddend = GroupFlags & ELF::RELOCATION_GROUPED_BY_ADDEND_FLAG;
bool GroupHasAddend = GroupFlags & ELF::RELOCATION_GROUP_HAS_ADDEND_FLAG;
uint64_t GroupOffsetDelta;
if (GroupedByOffsetDelta)
GroupOffsetDelta = ReadSLEB();
uint64_t GroupRInfo;
if (GroupedByInfo)
GroupRInfo = ReadSLEB();
if (GroupedByAddend && GroupHasAddend)
Addend += ReadSLEB();
if (!GroupHasAddend)
Addend = 0;
for (uint64_t I = 0; I != NumRelocsInGroup; ++I) {
Elf_Rela R;
Offset += GroupedByOffsetDelta ? GroupOffsetDelta : ReadSLEB();
R.r_offset = Offset;
R.r_info = GroupedByInfo ? GroupRInfo : ReadSLEB();
if (GroupHasAddend && !GroupedByAddend)
Addend += ReadSLEB();
R.r_addend = Addend;
Relocs.push_back(R);
if (ErrStr)
return createError(ErrStr);
}
if (ErrStr)
return createError(ErrStr);
}
return Relocs;
}
template <class ELFT>
const char *ELFFile<ELFT>::getDynamicTagAsString(unsigned Arch,
uint64_t Type) const {
#define DYNAMIC_STRINGIFY_ENUM(tag, value) \
case value: \
return #tag;
#define DYNAMIC_TAG(n, v)
switch (Arch) {
case ELF::EM_HEXAGON:
switch (Type) {
#define HEXAGON_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
#include "llvm/BinaryFormat/DynamicTags.def"
#undef HEXAGON_DYNAMIC_TAG
}
case ELF::EM_MIPS:
switch (Type) {
#define MIPS_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
#include "llvm/BinaryFormat/DynamicTags.def"
#undef MIPS_DYNAMIC_TAG
}
case ELF::EM_PPC64:
switch (Type) {
#define PPC64_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
#include "llvm/BinaryFormat/DynamicTags.def"
#undef PPC64_DYNAMIC_TAG
}
}
#undef DYNAMIC_TAG
switch (Type) {
// Now handle all dynamic tags except the architecture specific ones
#define MIPS_DYNAMIC_TAG(name, value)
#define HEXAGON_DYNAMIC_TAG(name, value)
#define PPC64_DYNAMIC_TAG(name, value)
// Also ignore marker tags such as DT_HIOS (maps to DT_VERNEEDNUM), etc.
#define DYNAMIC_TAG_MARKER(name, value)
#define DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
#include "llvm/BinaryFormat/DynamicTags.def"
#undef DYNAMIC_TAG
#undef MIPS_DYNAMIC_TAG
#undef HEXAGON_DYNAMIC_TAG
#undef PPC64_DYNAMIC_TAG
#undef DYNAMIC_TAG_MARKER
#undef DYNAMIC_STRINGIFY_ENUM
default:
return "unknown";
}
}
template <class ELFT>
const char *ELFFile<ELFT>::getDynamicTagAsString(uint64_t Type) const {
return getDynamicTagAsString(getHeader()->e_machine, Type);
}
template <class ELFT>
Expected<typename ELFT::DynRange> ELFFile<ELFT>::dynamicEntries() const {
ArrayRef<Elf_Dyn> Dyn;
size_t DynSecSize = 0;
auto ProgramHeadersOrError = program_headers();
if (!ProgramHeadersOrError)
return ProgramHeadersOrError.takeError();
for (const Elf_Phdr &Phdr : *ProgramHeadersOrError) {
if (Phdr.p_type == ELF::PT_DYNAMIC) {
Dyn = makeArrayRef(
reinterpret_cast<const Elf_Dyn *>(base() + Phdr.p_offset),
Phdr.p_filesz / sizeof(Elf_Dyn));
DynSecSize = Phdr.p_filesz;
break;
}
}
// If we can't find the dynamic section in the program headers, we just fall
// back on the sections.
if (Dyn.empty()) {
auto SectionsOrError = sections();
if (!SectionsOrError)
return SectionsOrError.takeError();
for (const Elf_Shdr &Sec : *SectionsOrError) {
if (Sec.sh_type == ELF::SHT_DYNAMIC) {
Expected<ArrayRef<Elf_Dyn>> DynOrError =
getSectionContentsAsArray<Elf_Dyn>(&Sec);
if (!DynOrError)
return DynOrError.takeError();
Dyn = *DynOrError;
DynSecSize = Sec.sh_size;
break;
}
}
if (!Dyn.data())
return ArrayRef<Elf_Dyn>();
}
if (Dyn.empty())
return createError("invalid empty dynamic section");
if (DynSecSize % sizeof(Elf_Dyn) != 0)
return createError("malformed dynamic section");
if (Dyn.back().d_tag != ELF::DT_NULL)
return createError("dynamic sections must be DT_NULL terminated");
return Dyn;
}
template <class ELFT>
Expected<const uint8_t *> ELFFile<ELFT>::toMappedAddr(uint64_t VAddr) const {
auto ProgramHeadersOrError = program_headers();
if (!ProgramHeadersOrError)
return ProgramHeadersOrError.takeError();
llvm::SmallVector<Elf_Phdr *, 4> LoadSegments;
for (const Elf_Phdr &Phdr : *ProgramHeadersOrError)
if (Phdr.p_type == ELF::PT_LOAD)
LoadSegments.push_back(const_cast<Elf_Phdr *>(&Phdr));
const Elf_Phdr *const *I =
std::upper_bound(LoadSegments.begin(), LoadSegments.end(), VAddr,
[](uint64_t VAddr, const Elf_Phdr_Impl<ELFT> *Phdr) {
return VAddr < Phdr->p_vaddr;
});
if (I == LoadSegments.begin())
return createError("Virtual address is not in any segment");
--I;
const Elf_Phdr &Phdr = **I;
uint64_t Delta = VAddr - Phdr.p_vaddr;
if (Delta >= Phdr.p_filesz)
return createError("Virtual address is not in any segment");
return base() + Phdr.p_offset + Delta;
}
template class llvm::object::ELFFile<ELF32LE>;
template class llvm::object::ELFFile<ELF32BE>;
template class llvm::object::ELFFile<ELF64LE>;
template class llvm::object::ELFFile<ELF64BE>;
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