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;
}
