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llvm-mirror/lib/Object/ELF.cpp
Rahman Lavaee a688c9d8f1 Use DataExtractor to decode SLEB128 in android_relas. 
A simple refactoring patch which let us use `DataExtractor::getSLEB128` rather than using a lambda function.

Differential Revision: https://reviews.llvm.org/D95158
2021-01-28 01:35:18 -08:00

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//===- ELF.cpp - ELF object file implementation ---------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/Object/ELF.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/Support/DataExtractor.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;
case ELF::EM_MSP430:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/MSP430.def"
default:
break;
}
break;
case ELF::EM_VE:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/VE.def"
default:
break;
}
break;
case ELF::EM_CSKY:
switch (Type) {
#include "llvm/BinaryFormat/ELFRelocs/CSKY.def"
default:
break;
}
break;
default:
break;
}
return "Unknown";
}
#undef ELF_RELOC
uint32_t llvm::object::getELFRelativeRelocationType(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_CSKY:
return ELF::R_CKCORE_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_DWARF);
STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_ABIFLAGS);
}
break;
case ELF::EM_RISCV:
switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_RISCV_ATTRIBUTES); }
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_LLVM_DEPENDENT_LIBRARIES);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_SYMPART);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_PART_EHDR);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_PART_PHDR);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_BB_ADDR_MAP);
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>
std::vector<typename ELFT::Rel>
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_Rel Rel;
Rel.r_info = 0;
Rel.setType(getRelativeRelocationType(), false);
std::vector<Elf_Rel> 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.
Rel.r_offset = Entry;
Relocs.push_back(Rel);
// 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) {
Rel.r_offset = Offset;
Relocs.push_back(Rel);
}
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();
ArrayRef<uint8_t> Content = *ContentsOrErr;
if (Content.size() < 4 || Content[0] != 'A' || Content[1] != 'P' ||
Content[2] != 'S' || Content[3] != '2')
return createError("invalid packed relocation header");
DataExtractor Data(Content, isLE(), ELFT::Is64Bits ? 8 : 4);
DataExtractor::Cursor Cur(/*Offset=*/4);
uint64_t NumRelocs = Data.getSLEB128(Cur);
uint64_t Offset = Data.getSLEB128(Cur);
uint64_t Addend = 0;
if (!Cur)
return std::move(Cur.takeError());
std::vector<Elf_Rela> Relocs;
Relocs.reserve(NumRelocs);
while (NumRelocs) {
uint64_t NumRelocsInGroup = Data.getSLEB128(Cur);
if (!Cur)
return std::move(Cur.takeError());
if (NumRelocsInGroup > NumRelocs)
return createError("relocation group unexpectedly large");
NumRelocs -= NumRelocsInGroup;
uint64_t GroupFlags = Data.getSLEB128(Cur);
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 = Data.getSLEB128(Cur);
uint64_t GroupRInfo;
if (GroupedByInfo)
GroupRInfo = Data.getSLEB128(Cur);
if (GroupedByAddend && GroupHasAddend)
Addend += Data.getSLEB128(Cur);
if (!GroupHasAddend)
Addend = 0;
for (uint64_t I = 0; Cur && I != NumRelocsInGroup; ++I) {
Elf_Rela R;
Offset += GroupedByOffsetDelta ? GroupOffsetDelta : Data.getSLEB128(Cur);
R.r_offset = Offset;
R.r_info = GroupedByInfo ? GroupRInfo : Data.getSLEB128(Cur);
if (GroupHasAddend && !GroupedByAddend)
Addend += Data.getSLEB128(Cur);
R.r_addend = Addend;
Relocs.push_back(R);
}
if (!Cur)
return std::move(Cur.takeError());
}
return Relocs;
}
template <class ELFT>
std::string 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_AARCH64:
switch (Type) {
#define AARCH64_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
#include "llvm/BinaryFormat/DynamicTags.def"
#undef AARCH64_DYNAMIC_TAG
}
break;
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
}
break;
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
}
break;
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
}
break;
}
#undef DYNAMIC_TAG
switch (Type) {
// Now handle all dynamic tags except the architecture specific ones
#define AARCH64_DYNAMIC_TAG(name, value)
#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) case value: return #name;
#include "llvm/BinaryFormat/DynamicTags.def"
#undef DYNAMIC_TAG
#undef AARCH64_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:>0x" + utohexstr(Type, true);
}
}
template <class ELFT>
std::string 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;
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));
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;
break;
}
}
if (!Dyn.data())
return ArrayRef<Elf_Dyn>();
}
if (Dyn.empty())
// TODO: this error is untested.
return createError("invalid empty dynamic section");
if (Dyn.back().d_tag != ELF::DT_NULL)
// TODO: this error is untested.
return createError("dynamic sections must be DT_NULL terminated");
return Dyn;
}
template <class ELFT>
Expected<const uint8_t *>
ELFFile<ELFT>::toMappedAddr(uint64_t VAddr, WarningHandler WarnHandler) 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));
auto SortPred = [](const Elf_Phdr_Impl<ELFT> *A,
const Elf_Phdr_Impl<ELFT> *B) {
return A->p_vaddr < B->p_vaddr;
};
if (!llvm::is_sorted(LoadSegments, SortPred)) {
if (Error E =
WarnHandler("loadable segments are unsorted by virtual address"))
return std::move(E);
llvm::stable_sort(LoadSegments, SortPred);
}
const Elf_Phdr *const *I = llvm::upper_bound(
LoadSegments, 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: 0x" +
Twine::utohexstr(VAddr));
--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: 0x" +
Twine::utohexstr(VAddr));
uint64_t Offset = Phdr.p_offset + Delta;
if (Offset >= getBufSize())
return createError("can't map virtual address 0x" +
Twine::utohexstr(VAddr) + " to the segment with index " +
Twine(&Phdr - (*ProgramHeadersOrError).data() + 1) +
": the segment ends at 0x" +
Twine::utohexstr(Phdr.p_offset + Phdr.p_filesz) +
", which is greater than the file size (0x" +
Twine::utohexstr(getBufSize()) + ")");
return base() + Offset;
}
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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