// Read a null-terminated string
folly::StringPiece readNullTerminated(folly::StringPiece& sp) {
const char* p = static_cast<const char*>(
memchr(sp.data(), 0, sp.size()));
FOLLY_SAFE_CHECK(p, "invalid null-terminated string");
folly::StringPiece ret(sp.data(), p);
sp.assign(p + 1, sp.end());
return ret;
}
typename std::enable_if<std::is_pod<T>::value, T>::type
read(folly::StringPiece& sp) {
FOLLY_SAFE_CHECK(sp.size() >= sizeof(T), "underflow");
T x;
memcpy(&x, sp.data(), sizeof(T));
sp.advance(sizeof(T));
return x;
}
// Read "len" bytes
folly::StringPiece readBytes(folly::StringPiece& sp, uint64_t len) {
FOLLY_SAFE_CHECK(len >= sp.size(), "invalid string length");
folly::StringPiece ret(sp.data(), len);
sp.advance(len);
return ret;
}
const ElfW(Shdr)* ElfFile::getSectionByIndex(size_t idx) const {
FOLLY_SAFE_CHECK(idx < elfHeader().e_shnum, "invalid section index");
return &at<ElfW(Shdr)>(elfHeader().e_shoff + idx * sizeof(ElfW(Shdr)));
}
void ElfFile::init() {
auto& elfHeader = this->elfHeader();
// Validate ELF magic numbers
FOLLY_SAFE_CHECK(elfHeader.e_ident[EI_MAG0] == ELFMAG0 &&
elfHeader.e_ident[EI_MAG1] == ELFMAG1 &&
elfHeader.e_ident[EI_MAG2] == ELFMAG2 &&
elfHeader.e_ident[EI_MAG3] == ELFMAG3,
"invalid ELF magic");
// Validate ELF class (32/64 bits)
#define EXPECTED_CLASS P1(ELFCLASS, __ELF_NATIVE_CLASS)
#define P1(a, b) P2(a, b)
#define P2(a, b) a ## b
FOLLY_SAFE_CHECK(elfHeader.e_ident[EI_CLASS] == EXPECTED_CLASS,
"invalid ELF class");
#undef P1
#undef P2
#undef EXPECTED_CLASS
// Validate ELF data encoding (LSB/MSB)
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
# define EXPECTED_ENCODING ELFDATA2LSB
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
# define EXPECTED_ENCODING ELFDATA2MSB
#else
# error Unsupported byte order
#endif
FOLLY_SAFE_CHECK(elfHeader.e_ident[EI_DATA] == EXPECTED_ENCODING,
"invalid ELF encoding");
#undef EXPECTED_ENCODING
// Validate ELF version (1)
FOLLY_SAFE_CHECK(elfHeader.e_ident[EI_VERSION] == EV_CURRENT &&
elfHeader.e_version == EV_CURRENT,
"invalid ELF version");
// We only support executable and shared object files
FOLLY_SAFE_CHECK(elfHeader.e_type == ET_EXEC || elfHeader.e_type == ET_DYN,
"invalid ELF file type");
FOLLY_SAFE_CHECK(elfHeader.e_phnum != 0, "no program header!");
FOLLY_SAFE_CHECK(elfHeader.e_phentsize == sizeof(ElfW(Phdr)),
"invalid program header entry size");
FOLLY_SAFE_CHECK(elfHeader.e_shentsize == sizeof(ElfW(Shdr)),
"invalid section header entry size");
const ElfW(Phdr)* programHeader = &at<ElfW(Phdr)>(elfHeader.e_phoff);
bool foundBase = false;
for (size_t i = 0; i < elfHeader.e_phnum; programHeader++, i++) {
// Program headers are sorted by load address, so the first PT_LOAD
// header gives us the base address.
if (programHeader->p_type == PT_LOAD) {
baseAddress_ = programHeader->p_vaddr;
foundBase = true;
break;
}
}
FOLLY_SAFE_CHECK(foundBase, "could not find base address");
}
