forked from OSchip/llvm-project
172 lines
5.0 KiB
C++
172 lines
5.0 KiB
C++
//===- EhFrame.cpp -------------------------------------------------------===//
|
|
//
|
|
// The LLVM Linker
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// .eh_frame section contains information on how to unwind the stack when
|
|
// an exception is thrown. The section consists of sequence of CIE and FDE
|
|
// records. The linker needs to merge CIEs and associate FDEs to CIEs.
|
|
// That means the linker has to understand the format of the section.
|
|
//
|
|
// This file contains a few utility functions to read .eh_frame contents.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "EhFrame.h"
|
|
#include "Error.h"
|
|
#include "Strings.h"
|
|
|
|
#include "llvm/Object/ELF.h"
|
|
#include "llvm/Support/Dwarf.h"
|
|
#include "llvm/Support/Endian.h"
|
|
|
|
using namespace llvm;
|
|
using namespace llvm::ELF;
|
|
using namespace llvm::dwarf;
|
|
using namespace llvm::object;
|
|
using namespace llvm::support::endian;
|
|
|
|
namespace lld {
|
|
namespace elf {
|
|
|
|
// .eh_frame section is a sequence of records. Each record starts with
|
|
// a 4 byte length field. This function reads the length.
|
|
template <class ELFT> size_t readEhRecordSize(ArrayRef<uint8_t> D) {
|
|
const endianness E = ELFT::TargetEndianness;
|
|
if (D.size() < 4)
|
|
fatal("CIE/FDE too small");
|
|
|
|
// First 4 bytes of CIE/FDE is the size of the record.
|
|
// If it is 0xFFFFFFFF, the next 8 bytes contain the size instead,
|
|
// but we do not support that format yet.
|
|
uint64_t V = read32<E>(D.data());
|
|
if (V == UINT32_MAX)
|
|
fatal("CIE/FDE too large");
|
|
uint64_t Size = V + 4;
|
|
if (Size > D.size())
|
|
fatal("CIE/FDE ends past the end of the section");
|
|
return Size;
|
|
}
|
|
|
|
// Read a byte and advance D by one byte.
|
|
static uint8_t readByte(ArrayRef<uint8_t> &D) {
|
|
if (D.empty())
|
|
fatal("corrupted or unsupported CIE information");
|
|
uint8_t B = D.front();
|
|
D = D.slice(1);
|
|
return B;
|
|
}
|
|
|
|
// Read a null-terminated string.
|
|
static StringRef readString(ArrayRef<uint8_t> &D) {
|
|
const uint8_t *End = std::find(D.begin(), D.end(), '\0');
|
|
if (End == D.end())
|
|
fatal("corrupted CIE");
|
|
StringRef S = toStringRef(D.slice(0, End - D.begin()));
|
|
D = D.slice(S.size() + 1);
|
|
return S;
|
|
}
|
|
|
|
// Skip an integer encoded in the LEB128 format.
|
|
// Actual number is not of interest because only the runtime needs it.
|
|
// But we need to be at least able to skip it so that we can read
|
|
// the field that follows a LEB128 number.
|
|
static void skipLeb128(ArrayRef<uint8_t> &D) {
|
|
while (!D.empty()) {
|
|
uint8_t Val = D.front();
|
|
D = D.slice(1);
|
|
if ((Val & 0x80) == 0)
|
|
return;
|
|
}
|
|
fatal("corrupted or unsupported CIE information");
|
|
}
|
|
|
|
template <class ELFT> static size_t getAugPSize(unsigned Enc) {
|
|
switch (Enc & 0x0f) {
|
|
case DW_EH_PE_absptr:
|
|
case DW_EH_PE_signed:
|
|
return ELFT::Is64Bits ? 8 : 4;
|
|
case DW_EH_PE_udata2:
|
|
case DW_EH_PE_sdata2:
|
|
return 2;
|
|
case DW_EH_PE_udata4:
|
|
case DW_EH_PE_sdata4:
|
|
return 4;
|
|
case DW_EH_PE_udata8:
|
|
case DW_EH_PE_sdata8:
|
|
return 8;
|
|
}
|
|
fatal("unknown FDE encoding");
|
|
}
|
|
|
|
template <class ELFT> static void skipAugP(ArrayRef<uint8_t> &D) {
|
|
uint8_t Enc = readByte(D);
|
|
if ((Enc & 0xf0) == DW_EH_PE_aligned)
|
|
fatal("DW_EH_PE_aligned encoding is not supported");
|
|
size_t Size = getAugPSize<ELFT>(Enc);
|
|
if (Size >= D.size())
|
|
fatal("corrupted CIE");
|
|
D = D.slice(Size);
|
|
}
|
|
|
|
template <class ELFT> uint8_t getFdeEncoding(ArrayRef<uint8_t> D) {
|
|
if (D.size() < 8)
|
|
fatal("CIE too small");
|
|
D = D.slice(8);
|
|
|
|
int Version = readByte(D);
|
|
if (Version != 1 && Version != 3)
|
|
fatal("FDE version 1 or 3 expected, but got " + Twine(Version));
|
|
|
|
StringRef Aug = readString(D);
|
|
|
|
// Skip code and data alignment factors.
|
|
skipLeb128(D);
|
|
skipLeb128(D);
|
|
|
|
// Skip the return address register. In CIE version 1 this is a single
|
|
// byte. In CIE version 3 this is an unsigned LEB128.
|
|
if (Version == 1)
|
|
readByte(D);
|
|
else
|
|
skipLeb128(D);
|
|
|
|
// We only care about an 'R' value, but other records may precede an 'R'
|
|
// record. Unfortunately records are not in TLV (type-length-value) format,
|
|
// so we need to teach the linker how to skip records for each type.
|
|
for (char C : Aug) {
|
|
if (C == 'R')
|
|
return readByte(D);
|
|
if (C == 'z') {
|
|
skipLeb128(D);
|
|
continue;
|
|
}
|
|
if (C == 'P') {
|
|
skipAugP<ELFT>(D);
|
|
continue;
|
|
}
|
|
if (C == 'L') {
|
|
readByte(D);
|
|
continue;
|
|
}
|
|
fatal("unknown .eh_frame augmentation string: " + Aug);
|
|
}
|
|
return DW_EH_PE_absptr;
|
|
}
|
|
|
|
template size_t readEhRecordSize<ELF32LE>(ArrayRef<uint8_t>);
|
|
template size_t readEhRecordSize<ELF32BE>(ArrayRef<uint8_t>);
|
|
template size_t readEhRecordSize<ELF64LE>(ArrayRef<uint8_t>);
|
|
template size_t readEhRecordSize<ELF64BE>(ArrayRef<uint8_t>);
|
|
|
|
template uint8_t getFdeEncoding<ELF32LE>(ArrayRef<uint8_t>);
|
|
template uint8_t getFdeEncoding<ELF32BE>(ArrayRef<uint8_t>);
|
|
template uint8_t getFdeEncoding<ELF64LE>(ArrayRef<uint8_t>);
|
|
template uint8_t getFdeEncoding<ELF64BE>(ArrayRef<uint8_t>);
|
|
}
|
|
}
|