| /* |
| * Copyright 2006, 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. |
| */ |
| |
| #include <stdio.h> |
| #include <errno.h> |
| #include <signal.h> |
| #include <pthread.h> |
| #include <stdarg.h> |
| #include <fcntl.h> |
| #include <sys/types.h> |
| #include <dirent.h> |
| #include <time.h> |
| |
| #include <sys/ptrace.h> |
| #include <sys/wait.h> |
| #include <elf.h> |
| #include <sys/stat.h> |
| #include <sys/poll.h> |
| |
| #include <log/logger.h> |
| |
| #include <cutils/sockets.h> |
| #include <cutils/properties.h> |
| #include <cutils/debugger.h> |
| |
| #include <linux/input.h> |
| |
| #include <private/android_filesystem_config.h> |
| |
| #include "backtrace.h" |
| #include "getevent.h" |
| #include "tombstone.h" |
| #include "utility.h" |
| |
| struct debugger_request_t { |
| debugger_action_t action; |
| pid_t pid, tid; |
| uid_t uid, gid; |
| uintptr_t abort_msg_address; |
| int32_t original_si_code; |
| }; |
| |
| static void wait_for_user_action(const debugger_request_t &request) { |
| // Find out the name of the process that crashed. |
| char path[64]; |
| snprintf(path, sizeof(path), "/proc/%d/exe", request.pid); |
| |
| char exe[PATH_MAX]; |
| int count; |
| if ((count = readlink(path, exe, sizeof(exe) - 1)) == -1) { |
| ALOGE("readlink('%s') failed: %s", path, strerror(errno)); |
| strlcpy(exe, "unknown", sizeof(exe)); |
| } else { |
| exe[count] = '\0'; |
| } |
| |
| // Explain how to attach the debugger. |
| ALOGI("********************************************************\n" |
| "* Process %d has been suspended while crashing.\n" |
| "* To attach gdbserver for a gdb connection on port 5039\n" |
| "* and start gdbclient:\n" |
| "*\n" |
| "* gdbclient %s :5039 %d\n" |
| "*\n" |
| "* Wait for gdb to start, then press the VOLUME DOWN key\n" |
| "* to let the process continue crashing.\n" |
| "********************************************************", |
| request.pid, exe, request.tid); |
| |
| // Wait for VOLUME DOWN. |
| if (init_getevent() == 0) { |
| while (true) { |
| input_event e; |
| if (get_event(&e, -1) == 0) { |
| if (e.type == EV_KEY && e.code == KEY_VOLUMEDOWN && e.value == 0) { |
| break; |
| } |
| } |
| } |
| uninit_getevent(); |
| } |
| |
| ALOGI("debuggerd resuming process %d", request.pid); |
| } |
| |
| static int get_process_info(pid_t tid, pid_t* out_pid, uid_t* out_uid, uid_t* out_gid) { |
| char path[64]; |
| snprintf(path, sizeof(path), "/proc/%d/status", tid); |
| |
| FILE* fp = fopen(path, "r"); |
| if (!fp) { |
| return -1; |
| } |
| |
| int fields = 0; |
| char line[1024]; |
| while (fgets(line, sizeof(line), fp)) { |
| size_t len = strlen(line); |
| if (len > 6 && !memcmp(line, "Tgid:\t", 6)) { |
| *out_pid = atoi(line + 6); |
| fields |= 1; |
| } else if (len > 5 && !memcmp(line, "Uid:\t", 5)) { |
| *out_uid = atoi(line + 5); |
| fields |= 2; |
| } else if (len > 5 && !memcmp(line, "Gid:\t", 5)) { |
| *out_gid = atoi(line + 5); |
| fields |= 4; |
| } |
| } |
| fclose(fp); |
| return fields == 7 ? 0 : -1; |
| } |
| |
| static int read_request(int fd, debugger_request_t* out_request) { |
| ucred cr; |
| socklen_t len = sizeof(cr); |
| int status = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cr, &len); |
| if (status != 0) { |
| ALOGE("cannot get credentials"); |
| return -1; |
| } |
| |
| ALOGV("reading tid"); |
| fcntl(fd, F_SETFL, O_NONBLOCK); |
| |
| pollfd pollfds[1]; |
| pollfds[0].fd = fd; |
| pollfds[0].events = POLLIN; |
| pollfds[0].revents = 0; |
| status = TEMP_FAILURE_RETRY(poll(pollfds, 1, 3000)); |
| if (status != 1) { |
| ALOGE("timed out reading tid (from pid=%d uid=%d)\n", cr.pid, cr.uid); |
| return -1; |
| } |
| |
| debugger_msg_t msg; |
| memset(&msg, 0, sizeof(msg)); |
| status = TEMP_FAILURE_RETRY(read(fd, &msg, sizeof(msg))); |
| if (status < 0) { |
| ALOGE("read failure? %s (pid=%d uid=%d)\n", strerror(errno), cr.pid, cr.uid); |
| return -1; |
| } |
| if (status != sizeof(debugger_msg_t)) { |
| ALOGE("invalid crash request of size %d (from pid=%d uid=%d)\n", status, cr.pid, cr.uid); |
| return -1; |
| } |
| |
| out_request->action = msg.action; |
| out_request->tid = msg.tid; |
| out_request->pid = cr.pid; |
| out_request->uid = cr.uid; |
| out_request->gid = cr.gid; |
| out_request->abort_msg_address = msg.abort_msg_address; |
| out_request->original_si_code = msg.original_si_code; |
| |
| if (msg.action == DEBUGGER_ACTION_CRASH) { |
| // Ensure that the tid reported by the crashing process is valid. |
| // This check needs to happen again after ptracing the requested thread to prevent a race. |
| if (!pid_contains_tid(out_request->pid, out_request->tid)) { |
| ALOGE("tid %d does not exist in pid %d. ignoring debug request\n", out_request->tid, |
| out_request->pid); |
| return -1; |
| } |
| } else if (cr.uid == 0 |
| || (cr.uid == AID_SYSTEM && msg.action == DEBUGGER_ACTION_DUMP_BACKTRACE)) { |
| // Only root or system can ask us to attach to any process and dump it explicitly. |
| // However, system is only allowed to collect backtraces but cannot dump tombstones. |
| status = get_process_info(out_request->tid, &out_request->pid, |
| &out_request->uid, &out_request->gid); |
| if (status < 0) { |
| ALOGE("tid %d does not exist. ignoring explicit dump request\n", out_request->tid); |
| return -1; |
| } |
| } else { |
| // No one else is allowed to dump arbitrary processes. |
| return -1; |
| } |
| return 0; |
| } |
| |
| static bool should_attach_gdb(debugger_request_t* request) { |
| if (request->action == DEBUGGER_ACTION_CRASH) { |
| char value[PROPERTY_VALUE_MAX]; |
| property_get("debug.db.uid", value, "-1"); |
| int debug_uid = atoi(value); |
| return debug_uid >= 0 && request->uid <= (uid_t)debug_uid; |
| } |
| return false; |
| } |
| |
| static void handle_request(int fd) { |
| ALOGV("handle_request(%d)\n", fd); |
| |
| debugger_request_t request; |
| memset(&request, 0, sizeof(request)); |
| int status = read_request(fd, &request); |
| if (!status) { |
| ALOGV("BOOM: pid=%d uid=%d gid=%d tid=%d\n", |
| request.pid, request.uid, request.gid, request.tid); |
| |
| // At this point, the thread that made the request is blocked in |
| // a read() call. If the thread has crashed, then this gives us |
| // time to PTRACE_ATTACH to it before it has a chance to really fault. |
| // |
| // The PTRACE_ATTACH sends a SIGSTOP to the target process, but it |
| // won't necessarily have stopped by the time ptrace() returns. (We |
| // currently assume it does.) We write to the file descriptor to |
| // ensure that it can run as soon as we call PTRACE_CONT below. |
| // See details in bionic/libc/linker/debugger.c, in function |
| // debugger_signal_handler(). |
| if (!ptrace_attach_thread(request.pid, request.tid)) { |
| ALOGE("ptrace attach failed: %s\n", strerror(errno)); |
| } else { |
| // DEBUGGER_ACTION_CRASH requests can come from arbitrary processes and the tid field in |
| // the request is sent from the other side. If an attacker can cause a process to be |
| // spawned with the pid of their process, they could trick debuggerd into dumping that |
| // process by exiting after sending the request. Validate the trusted request.uid/gid |
| // to defend against this. |
| if (request.action == DEBUGGER_ACTION_CRASH) { |
| pid_t pid; |
| uid_t uid; |
| gid_t gid; |
| if (get_process_info(request.tid, &pid, &uid, &gid) != 0) { |
| ALOGE("debuggerd: failed to get process info for tid '%d'", request.tid); |
| exit(1); |
| } |
| |
| if (pid != request.pid || uid != request.uid || gid != request.gid) { |
| ALOGE( |
| "debuggerd: attached task %d does not match request: " |
| "expected pid=%d,uid=%d,gid=%d, actual pid=%d,uid=%d,gid=%d", |
| request.tid, request.pid, request.uid, request.gid, pid, uid, gid); |
| exit(1); |
| } |
| } |
| |
| bool detach_failed = false; |
| bool tid_unresponsive = false; |
| bool attach_gdb = should_attach_gdb(&request); |
| if (TEMP_FAILURE_RETRY(write(fd, "\0", 1)) != 1) { |
| ALOGE("failed responding to client: %s\n", strerror(errno)); |
| } else { |
| char* tombstone_path = NULL; |
| |
| if (request.action == DEBUGGER_ACTION_CRASH) { |
| close(fd); |
| fd = -1; |
| } |
| |
| int total_sleep_time_usec = 0; |
| for (;;) { |
| int signal = wait_for_sigstop(request.tid, &total_sleep_time_usec, &detach_failed); |
| if (signal == -1) { |
| tid_unresponsive = true; |
| break; |
| } |
| |
| switch (signal) { |
| case SIGSTOP: |
| if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) { |
| ALOGV("stopped -- dumping to tombstone\n"); |
| tombstone_path = engrave_tombstone(request.pid, request.tid, |
| signal, request.original_si_code, |
| request.abort_msg_address, true, |
| &detach_failed, &total_sleep_time_usec); |
| } else if (request.action == DEBUGGER_ACTION_DUMP_BACKTRACE) { |
| ALOGV("stopped -- dumping to fd\n"); |
| dump_backtrace(fd, -1, request.pid, request.tid, &detach_failed, |
| &total_sleep_time_usec); |
| } else { |
| ALOGV("stopped -- continuing\n"); |
| status = ptrace(PTRACE_CONT, request.tid, 0, 0); |
| if (status) { |
| ALOGE("ptrace continue failed: %s\n", strerror(errno)); |
| } |
| continue; // loop again |
| } |
| break; |
| |
| case SIGABRT: |
| case SIGBUS: |
| case SIGFPE: |
| case SIGILL: |
| case SIGPIPE: |
| case SIGSEGV: |
| #ifdef SIGSTKFLT |
| case SIGSTKFLT: |
| #endif |
| case SIGTRAP: |
| ALOGV("stopped -- fatal signal\n"); |
| // Send a SIGSTOP to the process to make all of |
| // the non-signaled threads stop moving. Without |
| // this we get a lot of "ptrace detach failed: |
| // No such process". |
| kill(request.pid, SIGSTOP); |
| // don't dump sibling threads when attaching to GDB because it |
| // makes the process less reliable, apparently... |
| tombstone_path = engrave_tombstone(request.pid, request.tid, |
| signal, request.original_si_code, |
| request.abort_msg_address, !attach_gdb, |
| &detach_failed, &total_sleep_time_usec); |
| break; |
| |
| default: |
| ALOGE("process stopped due to unexpected signal %d\n", signal); |
| break; |
| } |
| break; |
| } |
| |
| if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) { |
| if (tombstone_path) { |
| write(fd, tombstone_path, strlen(tombstone_path)); |
| } |
| close(fd); |
| fd = -1; |
| } |
| free(tombstone_path); |
| } |
| |
| if (!tid_unresponsive) { |
| ALOGV("detaching"); |
| if (attach_gdb) { |
| // stop the process so we can debug |
| kill(request.pid, SIGSTOP); |
| } |
| if (ptrace(PTRACE_DETACH, request.tid, 0, 0)) { |
| ALOGE("ptrace detach from %d failed: %s", request.tid, strerror(errno)); |
| detach_failed = true; |
| } else if (attach_gdb) { |
| // if debug.db.uid is set, its value indicates if we should wait |
| // for user action for the crashing process. |
| // in this case, we log a message and turn the debug LED on |
| // waiting for a gdb connection (for instance) |
| wait_for_user_action(request); |
| } |
| } |
| |
| // resume stopped process (so it can crash in peace). |
| kill(request.pid, SIGCONT); |
| |
| // If we didn't successfully detach, we're still the parent, and the |
| // actual parent won't receive a death notification via wait(2). At this point |
| // there's not much we can do about that. |
| if (detach_failed) { |
| ALOGE("debuggerd committing suicide to free the zombie!\n"); |
| kill(getpid(), SIGKILL); |
| } |
| } |
| |
| } |
| if (fd >= 0) { |
| close(fd); |
| } |
| } |
| |
| static int do_server() { |
| // debuggerd crashes can't be reported to debuggerd. |
| // Reset all of the crash handlers. |
| signal(SIGABRT, SIG_DFL); |
| signal(SIGBUS, SIG_DFL); |
| signal(SIGFPE, SIG_DFL); |
| signal(SIGILL, SIG_DFL); |
| signal(SIGSEGV, SIG_DFL); |
| #ifdef SIGSTKFLT |
| signal(SIGSTKFLT, SIG_DFL); |
| #endif |
| signal(SIGTRAP, SIG_DFL); |
| |
| // Ignore failed writes to closed sockets |
| signal(SIGPIPE, SIG_IGN); |
| |
| int logsocket = socket_local_client("logd", ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_DGRAM); |
| if (logsocket < 0) { |
| logsocket = -1; |
| } else { |
| fcntl(logsocket, F_SETFD, FD_CLOEXEC); |
| } |
| |
| struct sigaction act; |
| act.sa_handler = SIG_DFL; |
| sigemptyset(&act.sa_mask); |
| sigaddset(&act.sa_mask,SIGCHLD); |
| act.sa_flags = SA_NOCLDWAIT; |
| sigaction(SIGCHLD, &act, 0); |
| |
| int s = socket_local_server(DEBUGGER_SOCKET_NAME, ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_STREAM); |
| if (s < 0) |
| return 1; |
| fcntl(s, F_SETFD, FD_CLOEXEC); |
| |
| ALOGI("debuggerd: " __DATE__ " " __TIME__ "\n"); |
| |
| for (;;) { |
| sockaddr addr; |
| socklen_t alen = sizeof(addr); |
| |
| ALOGV("waiting for connection\n"); |
| int fd = accept(s, &addr, &alen); |
| if (fd < 0) { |
| ALOGV("accept failed: %s\n", strerror(errno)); |
| continue; |
| } |
| |
| fcntl(fd, F_SETFD, FD_CLOEXEC); |
| |
| handle_request(fd); |
| } |
| return 0; |
| } |
| |
| static int do_explicit_dump(pid_t tid, bool dump_backtrace) { |
| fprintf(stdout, "Sending request to dump task %d.\n", tid); |
| |
| if (dump_backtrace) { |
| fflush(stdout); |
| if (dump_backtrace_to_file(tid, fileno(stdout)) < 0) { |
| fputs("Error dumping backtrace.\n", stderr); |
| return 1; |
| } |
| } else { |
| char tombstone_path[PATH_MAX]; |
| if (dump_tombstone(tid, tombstone_path, sizeof(tombstone_path)) < 0) { |
| fputs("Error dumping tombstone.\n", stderr); |
| return 1; |
| } |
| fprintf(stderr, "Tombstone written to: %s\n", tombstone_path); |
| } |
| return 0; |
| } |
| |
| static void usage() { |
| fputs("Usage: -b [<tid>]\n" |
| " -b dump backtrace to console, otherwise dump full tombstone file\n" |
| "\n" |
| "If tid specified, sends a request to debuggerd to dump that task.\n" |
| "Otherwise, starts the debuggerd server.\n", stderr); |
| } |
| |
| int main(int argc, char** argv) { |
| if (argc == 1) { |
| return do_server(); |
| } |
| |
| bool dump_backtrace = false; |
| bool have_tid = false; |
| pid_t tid = 0; |
| for (int i = 1; i < argc; i++) { |
| if (!strcmp(argv[i], "-b")) { |
| dump_backtrace = true; |
| } else if (!have_tid) { |
| tid = atoi(argv[i]); |
| have_tid = true; |
| } else { |
| usage(); |
| return 1; |
| } |
| } |
| if (!have_tid) { |
| usage(); |
| return 1; |
| } |
| return do_explicit_dump(tid, dump_backtrace); |
| } |