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llvm-readobj: Add support for reading relocations in the Android packed format. 

This is in preparation for testing lld's upcoming relocation packing
feature (D39152). I have verified that this implementation correctly
unpacks the relocations from a Chromium DSO built with gold and the
Android relocation packer for ARM32 and ARM64.

Differential Revision: https://reviews.llvm.org/D39272

llvm-svn: 316543
This commit is contained in:
Peter Collingbourne 2017-10-25 03:37:12 +00:00
parent 9f46ece85a
commit 689e6c052e
14 changed files with 338 additions and 5 deletions
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19
llvm/include/llvm/BinaryFormat/ELF.h
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@ -730,6 +730,10 @@ enum : unsigned {
SHT_GROUP = 17, // Section group.
SHT_SYMTAB_SHNDX = 18, // Indices for SHN_XINDEX entries.
SHT_LOOS = 0x60000000, // Lowest operating system-specific type.
// Android packed relocation section types.
// https://android.googlesource.com/platform/bionic/+/6f12bfece5dcc01325e0abba56a46b1bcf991c69/tools/relocation_packer/src/elf_file.cc#37
SHT_ANDROID_REL = 0x60000001,
SHT_ANDROID_RELA = 0x60000002,
SHT_LLVM_ODRTAB = 0x6fff4c00, // LLVM ODR table.
SHT_GNU_ATTRIBUTES = 0x6ffffff5, // Object attributes.
SHT_GNU_HASH = 0x6ffffff6, // GNU-style hash table.
@ -1166,6 +1170,13 @@ enum {
DT_LOPROC = 0x70000000, // Start of processor specific tags.
DT_HIPROC = 0x7FFFFFFF, // End of processor specific tags.
// Android packed relocation section tags.
// https://android.googlesource.com/platform/bionic/+/6f12bfece5dcc01325e0abba56a46b1bcf991c69/tools/relocation_packer/src/elf_file.cc#31
DT_ANDROID_REL = 0x6000000F,
DT_ANDROID_RELSZ = 0x60000010,
DT_ANDROID_RELA = 0x60000011,
DT_ANDROID_RELASZ = 0x60000012,
DT_GNU_HASH = 0x6FFFFEF5, // Reference to the GNU hash table.
DT_TLSDESC_PLT =
0x6FFFFEF6, // Location of PLT entry for TLS descriptor resolver calls.
@ -1387,6 +1398,14 @@ enum {
GNU_ABI_TAG_NACL = 6,
};
// Android packed relocation group flags.
enum {
RELOCATION_GROUPED_BY_INFO_FLAG = 1,
RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG = 2,
RELOCATION_GROUPED_BY_ADDEND_FLAG = 4,
RELOCATION_GROUP_HAS_ADDEND_FLAG = 8,
};
// Compressed section header for ELF32.
struct Elf32_Chdr {
Elf32_Word ch_type;

2
llvm/include/llvm/Object/ELF.h
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@ -142,6 +142,8 @@ public:
return getSectionContentsAsArray<Elf_Rel>(Sec);
}
Expected<std::vector<Elf_Rela>> android_relas(const Elf_Shdr *Sec) const;
/// \brief Iterate over program header table.
Expected<Elf_Phdr_Range> program_headers() const {
if (getHeader()->e_phnum && getHeader()->e_phentsize != sizeof(Elf_Phdr))

90
llvm/lib/Object/ELF.cpp
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@ -9,6 +9,7 @@
#include "llvm/Object/ELF.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/Support/LEB128.h"
using namespace llvm;
using namespace object;
@ -210,3 +211,92 @@ StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {
return "Unknown";
}
}
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();
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) {
if (!GroupedByAddend)
Addend += ReadSLEB();
R.r_addend = Addend;
} else {
R.r_addend = 0;
}
Relocs.push_back(R);
if (ErrStr)
return createError(ErrStr);
}
if (ErrStr)
return createError(ErrStr);
}
return Relocs;
}
template class llvm::object::ELFFile<ELF32LE>;
template class llvm::object::ELFFile<ELF32BE>;
template class llvm::object::ELFFile<ELF64LE>;
template class llvm::object::ELFFile<ELF64BE>;

2
llvm/lib/ObjectYAML/ELFYAML.cpp
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@ -405,6 +405,8 @@ void ScalarEnumerationTraits<ELFYAML::ELF_SHT>::enumeration(
ECase(SHT_GROUP);
ECase(SHT_SYMTAB_SHNDX);
ECase(SHT_LOOS);
ECase(SHT_ANDROID_REL);
ECase(SHT_ANDROID_RELA);
ECase(SHT_LLVM_ODRTAB);
ECase(SHT_GNU_ATTRIBUTES);
ECase(SHT_GNU_HASH);

37
llvm/test/tools/llvm-readobj/Inputs/elf-packed-relocs1.s Normal file
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@ -0,0 +1,37 @@
.ascii "APS2"
.sleb128 8 // Number of relocations
.sleb128 4096 // Initial offset
.sleb128 2 // Number of relocations in group
.sleb128 1 // RELOCATION_GROUPED_BY_INFO_FLAG
.sleb128 8 // R_X86_RELATIVE
.sleb128 256 // Reloc 1: r_offset delta
.sleb128 128 // Reloc 2: r_offset delta
.sleb128 2 // Number of relocations in group
.sleb128 2 // RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG
.sleb128 8 // offset delta
.sleb128 (1 << 32) | 1 // R_X86_64_64 (sym index 1)
.sleb128 (2 << 32) | 1 // R_X86_64_64 (sym index 2)
.sleb128 2 // Number of relocations in group
.sleb128 8 // RELOCATION_GROUP_HAS_ADDEND_FLAG
.sleb128 1 // offset delta
.sleb128 (1 << 32) | 1 // R_X86_64_64 (sym index 1)
.sleb128 8 // addend delta
.sleb128 2 // offset delta
.sleb128 (2 << 32) | 1 // R_X86_64_64 (sym index 2)
.sleb128 4 // addend delta
.sleb128 2 // Number of relocations in group
.sleb128 12 // RELOCATION_GROUP_HAS_ADDEND_FLAG | RELOCATION_GROUPED_BY_ADDEND_FLAG
.sleb128 -2 // addend delta
.sleb128 4 // offset delta
.sleb128 (1 << 32) | 1 // R_X86_64_64 (sym index 1)
.sleb128 8 // offset delta
.sleb128 (2 << 32) | 1 // R_X86_64_64 (sym index 2)

15
llvm/test/tools/llvm-readobj/Inputs/elf-packed-relocs2.s Normal file
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@ -0,0 +1,15 @@
.ascii "APS2"
.sleb128 10 // Number of relocations
.sleb128 4096 // Initial offset
.sleb128 2 // Number of relocations in group
.sleb128 2 // RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG
.sleb128 8 // offset delta
.sleb128 (1 << 8) | 1 // R_386_32 (sym index 1)
.sleb128 (2 << 8) | 3 // R_386_GOT32 (sym index 2)
.sleb128 8 // Number of relocations in group
.sleb128 3 // RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG | RELOCATION_GROUPED_BY_INFO_FLAG
.sleb128 -4 // offset delta
.sleb128 8 // R_386_RELATIVE

11
llvm/test/tools/llvm-readobj/elf-packed-relocs-empty.s Normal file
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@ -0,0 +1,11 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -relocations - | FileCheck %s
// CHECK: Relocations [
// CHECK-NEXT: Section (3) .rela.dyn {
// CHECK-NEXT: }
// CHECK-NEXT: ]
.section .rela.dyn, "a", @0x60000001
.ascii "APS2"
.sleb128 0
.sleb128 0

6
llvm/test/tools/llvm-readobj/elf-packed-relocs-error1.s Normal file
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@ -0,0 +1,6 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | not llvm-readobj -relocations - 2>&1 | FileCheck %s
// CHECK: Error reading file: invalid packed relocation header
.section .rela.dyn, "a", @0x60000001
.ascii "APS9"

6
llvm/test/tools/llvm-readobj/elf-packed-relocs-error2.s Normal file
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@ -0,0 +1,6 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | not llvm-readobj -relocations - 2>&1 | FileCheck %s
// CHECK: Error reading file: malformed sleb128, extends past end
.section .rela.dyn, "a", @0x60000001
.ascii "APS2"

8
llvm/test/tools/llvm-readobj/elf-packed-relocs-error3.s Normal file
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@ -0,0 +1,8 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | not llvm-readobj -relocations - 2>&1 | FileCheck %s
// CHECK: Error reading file: malformed sleb128, extends past end
.section .rela.dyn, "a", @0x60000001
.ascii "APS2"
.sleb128 4 // Number of relocations
.sleb128 0 // Initial offset

12
llvm/test/tools/llvm-readobj/elf-packed-relocs-error4.s Normal file
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@ -0,0 +1,12 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | not llvm-readobj -relocations - 2>&1 | FileCheck %s
// CHECK: Error reading file: malformed sleb128, extends past end
.section .rela.dyn, "a", @0x60000001
.ascii "APS2"
.sleb128 4 // Number of relocations
.sleb128 0 // Initial offset
.sleb128 2 // Number of relocations in group
.sleb128 2 // RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG
.sleb128 8 // offset delta

12
llvm/test/tools/llvm-readobj/elf-packed-relocs-error5.s Normal file
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@ -0,0 +1,12 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | not llvm-readobj -relocations - 2>&1 | FileCheck %s
// CHECK: Error reading file: relocation group unexpectedly large
.section .rela.dyn, "a", @0x60000001
.ascii "APS2"
.sleb128 4 // Number of relocations
.sleb128 0 // Initial offset
.sleb128 5 // Number of relocations in group
.sleb128 2 // RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG
.sleb128 8 // offset delta

94
llvm/test/tools/llvm-readobj/elf-packed-relocs.test Normal file
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@ -0,0 +1,94 @@
# The binary blobs in this file were created like this:
# llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu Inputs/elf-packed-relocs1.s -o - | obj2yaml | grep Content:
# RUN: yaml2obj -docnum 1 %s | llvm-readobj -elf-output-style=LLVM -relocations - | FileCheck --check-prefix=LLVM1 %s
# LLVM1: Section (1) .rela.dyn {
# LLVM1-NEXT: 0x1100 R_X86_64_RELATIVE - 0x0
# LLVM1-NEXT: 0x1180 R_X86_64_RELATIVE - 0x0
# LLVM1-NEXT: 0x1188 R_X86_64_64 sym1 0x0
# LLVM1-NEXT: 0x1190 R_X86_64_64 sym2 0x0
# LLVM1-NEXT: 0x1191 R_X86_64_64 sym1 0x8
# LLVM1-NEXT: 0x1193 R_X86_64_64 sym2 0xC
# LLVM1-NEXT: 0x1197 R_X86_64_64 sym1 0xA
# LLVM1-NEXT: 0x119F R_X86_64_64 sym2 0xA
# LLVM1-NEXT: }
# RUN: yaml2obj -docnum 1 %s | llvm-readobj -elf-output-style=GNU -relocations - | FileCheck --check-prefix=GNU1 %s
# GNU1: 0000000000001100 0000000000000008 R_X86_64_RELATIVE 0
# GNU1-NEXT: 0000000000001180 0000000000000008 R_X86_64_RELATIVE 0
# GNU1-NEXT: 0000000000001188 0000000100000001 R_X86_64_64 0000000000000000 sym1 + 0
# GNU1-NEXT: 0000000000001190 0000000200000001 R_X86_64_64 0000000000000000 sym2 + 0
# GNU1-NEXT: 0000000000001191 0000000100000001 R_X86_64_64 0000000000000000 sym1 + 8
# GNU1-NEXT: 0000000000001193 0000000200000001 R_X86_64_64 0000000000000000 sym2 + c
# GNU1-NEXT: 0000000000001197 0000000100000001 R_X86_64_64 0000000000000000 sym1 + a
# GNU1-NEXT: 000000000000119f 0000000200000001 R_X86_64_64 0000000000000000 sym2 + a
# elf-packed-relocs1.s
--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_DYN
Machine: EM_X86_64
Entry: 0x0000000000001000
Sections:
- Name: .rela.dyn
Type: SHT_ANDROID_RELA
Flags: [ SHF_ALLOC ]
Address: 0x00000000000001C8
Link: .symtab
AddressAlign: 0x0000000000000001
Content: 41505332088020020108800280010202088180808010818080802002080181808080100802818080802004020C7E048180808010088180808020
Symbols:
Global:
- Name: sym1
- Name: sym2
...
# RUN: yaml2obj -docnum 2 %s | llvm-readobj -elf-output-style=LLVM -relocations - | FileCheck --check-prefix=LLVM2 %s
# LLVM2: Section (1) .rel.dyn {
# LLVM2-NEXT: 0x1008 R_386_32 sym1 0x0
# LLVM2-NEXT: 0x1010 R_386_GOT32 sym2 0x0
# LLVM2-NEXT: 0x100C R_386_RELATIVE - 0x0
# LLVM2-NEXT: 0x1008 R_386_RELATIVE - 0x0
# LLVM2-NEXT: 0x1004 R_386_RELATIVE - 0x0
# LLVM2-NEXT: 0x1000 R_386_RELATIVE - 0x0
# LLVM2-NEXT: 0xFFC R_386_RELATIVE - 0x0
# LLVM2-NEXT: 0xFF8 R_386_RELATIVE - 0x0
# LLVM2-NEXT: 0xFF4 R_386_RELATIVE - 0x0
# LLVM2-NEXT: 0xFF0 R_386_RELATIVE - 0x0
# LLVM2-NEXT: }
# RUN: yaml2obj -docnum 2 %s | llvm-readobj -elf-output-style=GNU -relocations - | FileCheck --check-prefix=GNU2 %s
# GNU2: 00001008 00000101 R_386_32 00000000 sym1
# GNU2-NEXT: 00001010 00000203 R_386_GOT32 00000000 sym2
# GNU2-NEXT: 0000100c 00000008 R_386_RELATIVE
# GNU2-NEXT: 00001008 00000008 R_386_RELATIVE
# GNU2-NEXT: 00001004 00000008 R_386_RELATIVE
# GNU2-NEXT: 00001000 00000008 R_386_RELATIVE
# GNU2-NEXT: 00000ffc 00000008 R_386_RELATIVE
# GNU2-NEXT: 00000ff8 00000008 R_386_RELATIVE
# GNU2-NEXT: 00000ff4 00000008 R_386_RELATIVE
# GNU2-NEXT: 00000ff0 00000008 R_386_RELATIVE
# elf-packed-relocs2.s
--- !ELF
FileHeader:
Class: ELFCLASS32
Data: ELFDATA2LSB
Type: ET_DYN
Machine: EM_386
Entry: 0x0000000000001000
Sections:
- Name: .rel.dyn
Type: SHT_ANDROID_REL
Flags: [ SHF_ALLOC ]
Address: 0x00000000000001C8
Link: .symtab
AddressAlign: 0x0000000000000001
Content: 415053320A80200202088102830408037C08
Symbols:
Global:
- Name: sym1
- Name: sym2
...

29
llvm/tools/llvm-readobj/ELFDumper.cpp
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@ -2591,7 +2591,9 @@ static inline void printRelocHeader(raw_ostream &OS, bool Is64, bool IsRela) {
template <class ELFT> void GNUStyle<ELFT>::printRelocations(const ELFO *Obj) {
bool HasRelocSections = false;
for (const Elf_Shdr &Sec : unwrapOrError(Obj->sections())) {
if (Sec.sh_type != ELF::SHT_REL && Sec.sh_type != ELF::SHT_RELA)
if (Sec.sh_type != ELF::SHT_REL && Sec.sh_type != ELF::SHT_RELA &&
Sec.sh_type != ELF::SHT_ANDROID_REL &&
Sec.sh_type != ELF::SHT_ANDROID_RELA)
continue;
HasRelocSections = true;
StringRef Name = unwrapOrError(Obj->getSectionName(&Sec));
@ -2600,9 +2602,12 @@ template <class ELFT> void GNUStyle<ELFT>::printRelocations(const ELFO *Obj) {
OS << "\nRelocation section '" << Name << "' at offset 0x"
<< to_hexString(Offset, false) << " contains " << Entries
<< " entries:\n";
printRelocHeader(OS, ELFT::Is64Bits, (Sec.sh_type == ELF::SHT_RELA));
printRelocHeader(OS, ELFT::Is64Bits,
Sec.sh_type == ELF::SHT_RELA ||
Sec.sh_type == ELF::SHT_ANDROID_RELA);
const Elf_Shdr *SymTab = unwrapOrError(Obj->getSection(Sec.sh_link));
if (Sec.sh_type == ELF::SHT_REL) {
switch (Sec.sh_type) {
case ELF::SHT_REL:
for (const auto &R : unwrapOrError(Obj->rels(&Sec))) {
Elf_Rela Rela;
Rela.r_offset = R.r_offset;
@ -2610,9 +2615,16 @@ template <class ELFT> void GNUStyle<ELFT>::printRelocations(const ELFO *Obj) {
Rela.r_addend = 0;
printRelocation(Obj, SymTab, Rela, false);
}
} else {
break;
case ELF::SHT_RELA:
for (const auto &R : unwrapOrError(Obj->relas(&Sec)))
printRelocation(Obj, SymTab, R, true);
break;
case ELF::SHT_ANDROID_REL:
case ELF::SHT_ANDROID_RELA:
for (const auto &R : unwrapOrError(Obj->android_relas(&Sec)))
printRelocation(Obj, SymTab, R, Sec.sh_type == ELF::SHT_ANDROID_RELA);
break;
}
}
if (!HasRelocSections)
@ -3650,7 +3662,9 @@ template <class ELFT> void LLVMStyle<ELFT>::printRelocations(const ELFO *Obj) {
for (const Elf_Shdr &Sec : unwrapOrError(Obj->sections())) {
++SectionNumber;
if (Sec.sh_type != ELF::SHT_REL && Sec.sh_type != ELF::SHT_RELA)
if (Sec.sh_type != ELF::SHT_REL && Sec.sh_type != ELF::SHT_RELA &&
Sec.sh_type != ELF::SHT_ANDROID_REL &&
Sec.sh_type != ELF::SHT_ANDROID_RELA)
continue;
StringRef Name = unwrapOrError(Obj->getSectionName(&Sec));
@ -3683,6 +3697,11 @@ void LLVMStyle<ELFT>::printRelocations(const Elf_Shdr *Sec, const ELFO *Obj) {
for (const Elf_Rela &R : unwrapOrError(Obj->relas(Sec)))
printRelocation(Obj, R, SymTab);
break;
case ELF::SHT_ANDROID_REL:
case ELF::SHT_ANDROID_RELA:
for (const Elf_Rela &R : unwrapOrError(Obj->android_relas(Sec)))
printRelocation(Obj, R, SymTab);
break;
}
}