03dca28def
ELF said that padding is present, if necessary, to ensure 4-byte alignment for the descriptor and next note entry, but such padding is not included in namesz and descsz. Change-Id: I7896783f3d9a787772d56c49905f52a493c9fba1
121 lines
3.8 KiB
C++
121 lines
3.8 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#define LOG_TAG "DEBUG"
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#include <elf.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <string>
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#include <backtrace/Backtrace.h>
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#include <base/stringprintf.h>
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#include <log/log.h>
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#include "elf_utils.h"
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#define NOTE_ALIGN(size) ((size + 3) & ~3)
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template <typename HdrType, typename PhdrType, typename NhdrType>
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static bool get_build_id(
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Backtrace* backtrace, uintptr_t base_addr, uint8_t* e_ident, std::string* build_id) {
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HdrType hdr;
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memcpy(&hdr.e_ident[0], e_ident, EI_NIDENT);
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// First read the rest of the header.
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if (backtrace->Read(base_addr + EI_NIDENT, reinterpret_cast<uint8_t*>(&hdr) + EI_NIDENT,
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sizeof(HdrType) - EI_NIDENT) != sizeof(HdrType) - EI_NIDENT) {
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return false;
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}
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for (size_t i = 0; i < hdr.e_phnum; i++) {
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PhdrType phdr;
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if (backtrace->Read(base_addr + hdr.e_phoff + i * hdr.e_phentsize,
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reinterpret_cast<uint8_t*>(&phdr), sizeof(phdr)) != sizeof(phdr)) {
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return false;
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}
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// Looking for the .note.gnu.build-id note.
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if (phdr.p_type == PT_NOTE) {
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size_t hdr_size = phdr.p_filesz;
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uintptr_t addr = base_addr + phdr.p_offset;
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while (hdr_size >= sizeof(NhdrType)) {
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NhdrType nhdr;
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if (backtrace->Read(addr, reinterpret_cast<uint8_t*>(&nhdr), sizeof(nhdr)) != sizeof(nhdr)) {
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return false;
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}
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addr += sizeof(nhdr);
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if (nhdr.n_type == NT_GNU_BUILD_ID) {
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// Skip the name (which is the owner and should be "GNU").
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addr += NOTE_ALIGN(nhdr.n_namesz);
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uint8_t build_id_data[128];
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if (nhdr.n_namesz > sizeof(build_id_data)) {
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ALOGE("Possible corrupted note, name size value is too large: %u",
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nhdr.n_namesz);
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return false;
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}
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if (backtrace->Read(addr, build_id_data, nhdr.n_descsz) != nhdr.n_descsz) {
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return false;
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}
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build_id->clear();
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for (size_t bytes = 0; bytes < nhdr.n_descsz; bytes++) {
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*build_id += android::base::StringPrintf("%02x", build_id_data[bytes]);
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}
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return true;
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} else {
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// Move past the extra note data.
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hdr_size -= sizeof(nhdr);
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size_t skip_bytes = NOTE_ALIGN(nhdr.n_namesz) + NOTE_ALIGN(nhdr.n_descsz);
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addr += skip_bytes;
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if (hdr_size < skip_bytes) {
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break;
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}
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hdr_size -= skip_bytes;
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}
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}
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}
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}
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return false;
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}
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bool elf_get_build_id(Backtrace* backtrace, uintptr_t addr, std::string* build_id) {
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// Read and verify the elf magic number first.
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uint8_t e_ident[EI_NIDENT];
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if (backtrace->Read(addr, e_ident, SELFMAG) != SELFMAG) {
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return false;
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}
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if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) {
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return false;
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}
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// Read the rest of EI_NIDENT.
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if (backtrace->Read(addr + SELFMAG, e_ident + SELFMAG, EI_NIDENT - SELFMAG) != EI_NIDENT - SELFMAG) {
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return false;
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}
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if (e_ident[EI_CLASS] == ELFCLASS32) {
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return get_build_id<Elf32_Ehdr, Elf32_Phdr, Elf32_Nhdr>(backtrace, addr, e_ident, build_id);
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} else if (e_ident[EI_CLASS] == ELFCLASS64) {
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return get_build_id<Elf64_Ehdr, Elf64_Phdr, Elf64_Nhdr>(backtrace, addr, e_ident, build_id);
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}
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return false;
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}
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