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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#define LOG_TAG "DEBUG"
#include <elf.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <backtrace/Backtrace.h>
#include <base/stringprintf.h>
#include <log/log.h>
#include "elf_utils.h"
#define NOTE_ALIGN(size) ((size + 3) & ~3)
template <typename HdrType, typename PhdrType, typename NhdrType>
static bool get_build_id(
Backtrace* backtrace, uintptr_t base_addr, uint8_t* e_ident, std::string* build_id) {
HdrType hdr;
memcpy(&hdr.e_ident[0], e_ident, EI_NIDENT);
// First read the rest of the header.
if (backtrace->Read(base_addr + EI_NIDENT, reinterpret_cast<uint8_t*>(&hdr) + EI_NIDENT,
sizeof(HdrType) - EI_NIDENT) != sizeof(HdrType) - EI_NIDENT) {
return false;
}
for (size_t i = 0; i < hdr.e_phnum; i++) {
PhdrType phdr;
if (backtrace->Read(base_addr + hdr.e_phoff + i * hdr.e_phentsize,
reinterpret_cast<uint8_t*>(&phdr), sizeof(phdr)) != sizeof(phdr)) {
return false;
}
// Looking for the .note.gnu.build-id note.
if (phdr.p_type == PT_NOTE) {
size_t hdr_size = phdr.p_filesz;
uintptr_t addr = base_addr + phdr.p_offset;
while (hdr_size >= sizeof(NhdrType)) {
NhdrType nhdr;
if (backtrace->Read(addr, reinterpret_cast<uint8_t*>(&nhdr), sizeof(nhdr)) != sizeof(nhdr)) {
return false;
}
addr += sizeof(nhdr);
if (nhdr.n_type == NT_GNU_BUILD_ID) {
// Skip the name (which is the owner and should be "GNU").
addr += NOTE_ALIGN(nhdr.n_namesz);
uint8_t build_id_data[160];
if (nhdr.n_descsz > sizeof(build_id_data)) {
ALOGE("Possible corrupted note, desc size value is too large: %u",
nhdr.n_descsz);
return false;
}
if (backtrace->Read(addr, build_id_data, nhdr.n_descsz) != nhdr.n_descsz) {
return false;
}
build_id->clear();
for (size_t bytes = 0; bytes < nhdr.n_descsz; bytes++) {
*build_id += android::base::StringPrintf("%02x", build_id_data[bytes]);
}
return true;
} else {
// Move past the extra note data.
hdr_size -= sizeof(nhdr);
size_t skip_bytes = NOTE_ALIGN(nhdr.n_namesz) + NOTE_ALIGN(nhdr.n_descsz);
addr += skip_bytes;
if (hdr_size < skip_bytes) {
break;
}
hdr_size -= skip_bytes;
}
}
}
}
return false;
}
bool elf_get_build_id(Backtrace* backtrace, uintptr_t addr, std::string* build_id) {
// Read and verify the elf magic number first.
uint8_t e_ident[EI_NIDENT];
if (backtrace->Read(addr, e_ident, SELFMAG) != SELFMAG) {
return false;
}
if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) {
return false;
}
// Read the rest of EI_NIDENT.
if (backtrace->Read(addr + SELFMAG, e_ident + SELFMAG, EI_NIDENT - SELFMAG) != EI_NIDENT - SELFMAG) {
return false;
}
if (e_ident[EI_CLASS] == ELFCLASS32) {
return get_build_id<Elf32_Ehdr, Elf32_Phdr, Elf32_Nhdr>(backtrace, addr, e_ident, build_id);
} else if (e_ident[EI_CLASS] == ELFCLASS64) {
return get_build_id<Elf64_Ehdr, Elf64_Phdr, Elf64_Nhdr>(backtrace, addr, e_ident, build_id);
}
return false;
}
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