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Refactor DisassemblerObjdump.
This change removes ScopedTmpFile from DisassemblerObjdump, and replaces it with the use of the implementation in linux/common. It also switches to using ScopedPipe to read the output from objdump, and directly execing objdump instead of using system. Change-Id: I6d425190fb4a20d6b265c72aa7315026687cb86a Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/3971919 Reviewed-by: Ivan Penkov <ivanpe@chromium.org>
This commit is contained in:
Mark Brand
Ivan Penkov
parent
5daa41904a
commit
38115b0c5f
3 changed files with 178 additions and 137 deletions
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@ -33,6 +33,9 @@
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#include "processor/disassembler_objdump.h"
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#include <unistd.h>
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#include <sys/wait.h>
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#include <array>
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#include <fstream>
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#include <iostream>
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#include <iterator>
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@ -40,77 +43,16 @@
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#include <sstream>
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#include <vector>
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#include "common/linux/eintr_wrapper.h"
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#include "common/linux/scoped_pipe.h"
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#include "common/linux/scoped_tmpfile.h"
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#include "processor/logging.h"
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namespace google_breakpad {
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namespace {
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const size_t kMaxX86InstructionLength = 15;
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// Small RAII wrapper for temporary files.
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//
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// Example:
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// ScopedTmpFile tmp("/tmp/tmpfile-XXXX");
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// if (tmp.Create()) {
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// std::cerr << tmp.path() << std::endl;
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// }
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class ScopedTmpFile {
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public:
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// Initialize the ScopedTmpFile object - this does not create the temporary
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// file yet.
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ScopedTmpFile(const char* path_format);
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~ScopedTmpFile();
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// Creates the temporary file, returns true on success.
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bool Create();
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// Writes bytes to the temporary file, returns true on success.
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bool Write(const uint8_t* bytes, unsigned int bytes_len);
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// Returns the path of the temporary file.
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string path() const { return path_; }
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private:
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int fd_;
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string path_;
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};
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ScopedTmpFile::ScopedTmpFile(const char* path_format) : path_(path_format) {}
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ScopedTmpFile::~ScopedTmpFile() {
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if (fd_) {
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close(fd_);
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unlink(path_.c_str());
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}
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}
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bool ScopedTmpFile::Create() {
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fd_ = mkstemp(path_.data());
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if (fd_ < 0) {
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unlink(path_.c_str());
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fd_ = 0;
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path_ = "";
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return false;
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}
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return true;
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}
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bool ScopedTmpFile::Write(const uint8_t* bytes, unsigned int bytes_len) {
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if (fd_) {
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do {
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ssize_t result = write(fd_, bytes, bytes_len);
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if (result < 0) {
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break;
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}
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bytes += result;
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bytes_len -= result;
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} while (bytes_len);
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}
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return bytes_len == 0;
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}
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bool IsInstructionPrefix(const string& token) {
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if (token == "lock" || token == "rep" || token == "repz" ||
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token == "repnz") {
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@ -284,47 +226,87 @@ bool DisassemblerObjdump::DisassembleInstruction(uint32_t cpu,
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return false;
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}
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// Create two temporary files, one for the raw instruction bytes to pass to
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// objdump, and one for the output, and write the bytes to the input file.
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ScopedTmpFile raw_bytes_file("/tmp/breakpad_mem_region-raw_bytes-XXXXXX");
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ScopedTmpFile disassembly_file("/tmp/breakpad_mem_region-disassembly-XXXXXX");
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if (!raw_bytes_file.Create() || !disassembly_file.Create() ||
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!raw_bytes_file.Write(raw_bytes, raw_bytes_len)) {
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BPLOG(ERROR) << "Failed creating temporary files.";
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// Create a temporary file for the raw instruction bytes to pass to
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// objdump, and write the bytes to the input file.
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ScopedTmpFile raw_bytes_file;
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if (!raw_bytes_file.InitData(raw_bytes, raw_bytes_len)) {
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BPLOG(ERROR) << "Failed creating temporary file.";
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return false;
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}
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char cmd[1024] = {0};
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snprintf(cmd, 1024,
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"objdump -D --no-show-raw-insn -b binary -M intel -m %s %s > %s",
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architecture.c_str(), raw_bytes_file.path().c_str(),
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disassembly_file.path().c_str());
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if (system(cmd)) {
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BPLOG(ERROR) << "Failed to call objdump.";
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// Create a pipe to use to read the disassembly back from objdump.
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ScopedPipe disassembly_pipe;
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if (!disassembly_pipe.Init()) {
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BPLOG(ERROR) << "Failed creating pipe for output.";
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return false;
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}
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// Pipe each output line into the string until the string contains the first
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// instruction from objdump.
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std::ifstream objdump_stream(disassembly_file.path());
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pid_t child_pid = fork();
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if (child_pid < 0) {
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BPLOG(ERROR) << "Fork failed.";
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return false;
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}
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// Match the instruction line, from:
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// 0: lock cmpxchg DWORD PTR [esi+0x10],eax
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// extract the string "lock cmpxchg DWORD PTR [esi+0x10],eax"
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std::regex instruction_regex(
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"^\\s+[0-9a-f]+:\\s+" // " 0:"
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"((?:\\s*\\S*)+)$"); // "lock cmpxchg..."
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if (child_pid == 0) {
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// In the child process, set up the input and output file descriptors.
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if (dup2(raw_bytes_file.GetFd(), STDIN_FILENO) < 0 ||
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disassembly_pipe.Dup2WriteFd(STDOUT_FILENO) < 0 ||
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disassembly_pipe.Dup2WriteFd(STDERR_FILENO) < 0) {
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BPLOG(ERROR) << "Failed dup'ing file descriptors.";
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exit(-1);
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}
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std::string line;
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std::smatch match;
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do {
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if (!getline(objdump_stream, line)) {
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BPLOG(INFO) << "Failed to find instruction in objdump output.";
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// We need to close the read end of the pipe in the child process so that
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// when the parent closes it, the pipe is disconnected.
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disassembly_pipe.CloseReadFd();
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// We use "/proc/self/fd/0" here to allow objdump to parse an unnamed file,
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// since objdump does not have a mode to read from stdin. This cannot be
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// used with a pipe, since objdump requires that the input is a standard
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// file.
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execlp("objdump", "objdump", "-D", "--no-show-raw-insn", "-b", "binary",
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"-M", "intel", "-m", architecture.c_str(), "/proc/self/fd/0",
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nullptr);
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BPLOG(ERROR) << "Failed to exec objdump.";
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exit(-1);
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} else {
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// In the parent process, parse the objdump output.
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// Match the instruction line, from:
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// 0: lock cmpxchg DWORD PTR [esi+0x10],eax
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// extract the string "lock cmpxchg DWORD PTR [esi+0x10],eax"
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std::regex instruction_regex(
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"^\\s+[0-9a-f]+:\\s+" // " 0:"
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"((?:\\s*\\S*)+)$"); // "lock cmpxchg..."
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std::string line;
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std::smatch match;
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while (disassembly_pipe.ReadLine(line)) {
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if (std::regex_match(line, match, instruction_regex)) {
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instruction = match[1].str();
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break;
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}
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}
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// Close the read pipe so that objdump will exit (in case we broke out of
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// the loop above before reading all of the output).
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disassembly_pipe.CloseReadFd();
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// Now wait for objdump to exit.
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int status = 0;
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HANDLE_EINTR(waitpid(child_pid, &status, 0));
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if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
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BPLOG(ERROR) << "objdump didn't run successfully.";
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return false;
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}
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} while (!std::regex_match(line, match, instruction_regex));
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instruction = match[1].str();
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if (instruction == "") {
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BPLOG(ERROR) << "Failed to find instruction in objdump output.";
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return false;
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}
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}
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return true;
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}
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