debuggerd: advance our amazing bet.
Remove debuggerd in favor of a helper process that gets execed by
crashing processes.
Bug: http://b/30705528
Test: debuggerd_test
Change-Id: I9906c69473989cbf7fe5ea6cccf9a9c563d75906
diff --git a/debuggerd/debuggerd.cpp b/debuggerd/debuggerd.cpp
index 893adc8..3208230 100644
--- a/debuggerd/debuggerd.cpp
+++ b/debuggerd/debuggerd.cpp
@@ -1,5 +1,5 @@
/*
- * Copyright 2006, The Android Open Source Project
+ * Copyright 2016, 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.
@@ -14,937 +14,68 @@
* limitations under the License.
*/
-#define LOG_TAG "debuggerd"
-
-#include <arpa/inet.h>
-#include <dirent.h>
-#include <elf.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <linux/input.h>
-#include <pthread.h>
-#include <signal.h>
-#include <stdarg.h>
+#include <err.h>
#include <stdio.h>
-#include <sys/poll.h>
-#include <sys/prctl.h>
-#include <sys/ptrace.h>
-#include <sys/socket.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <sys/wait.h>
-#include <sys/un.h>
-#include <time.h>
+#include <stdlib.h>
+#include <string.h>
-#include <memory>
-#include <set>
-#include <string>
-
-#include <selinux/android.h>
+#include <limits>
+#include <thread>
#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/parseint.h>
#include <android-base/unique_fd.h>
-#include <cutils/debugger.h>
-#include <cutils/properties.h>
-#include <cutils/sockets.h>
-#include <log/log.h>
-
-#include <private/android_filesystem_config.h>
-
#include <debuggerd/client.h>
+#include <debuggerd/util.h>
+#include <selinux/selinux.h>
-#include "backtrace.h"
-#include "getevent.h"
-#include "open_files_list.h"
-#include "signal_sender.h"
-#include "tombstone.h"
-#include "utility.h"
+using android::base::unique_fd;
-// If the 32 bit executable is compiled on a 64 bit system,
-// use the 32 bit socket name.
-#if defined(TARGET_IS_64_BIT) && !defined(__LP64__)
-#define SOCKET_NAME DEBUGGER32_SOCKET_NAME
-#else
-#define SOCKET_NAME DEBUGGER_SOCKET_NAME
-#endif
+static void usage(int exit_code) {
+ fprintf(stderr, "usage: debuggerd [-b] PID\n");
+ _exit(exit_code);
+}
-struct debugger_request_t {
- debugger_action_t action;
- pid_t pid, tid;
- uid_t uid, gid;
- pid_t ignore_tid;
- uintptr_t abort_msg_address;
-};
+static std::thread spawn_redirect_thread(unique_fd fd) {
+ return std::thread([fd{ std::move(fd) }]() {
+ while (true) {
+ char buf[BUFSIZ];
+ ssize_t rc = TEMP_FAILURE_RETRY(read(fd.get(), buf, sizeof(buf)));
+ if (rc <= 0) {
+ return;
+ }
-static void wait_for_user_action(const debugger_request_t& request) {
- // Explain how to attach the debugger.
- ALOGI("***********************************************************\n"
- "* Process %d has been suspended while crashing.\n"
- "* To attach gdbserver and start gdb, run this on the host:\n"
- "*\n"
- "* gdbclient.py -p %d\n"
- "*\n"
- "* Wait for gdb to start, then press the VOLUME DOWN key\n"
- "* to let the process continue crashing.\n"
- "***********************************************************",
- request.pid, request.tid);
-
- // Wait for VOLUME DOWN.
- while (true) {
- input_event e;
- if (get_event(&e, -1) == 0) {
- if (e.type == EV_KEY && e.code == KEY_VOLUMEDOWN && e.value == 0) {
- break;
+ if (!android::base::WriteFully(STDOUT_FILENO, buf, rc)) {
+ return;
}
}
- }
-
- 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);
+int main(int argc, char* argv[]) {
+ if (argc <= 1) usage(0);
+ if (argc > 3) usage(1);
+ if (argc == 3 && strcmp(argv[1], "-b") != 0) usage(1);
- FILE* fp = fopen(path, "r");
- if (!fp) {
- return -1;
+ pid_t pid;
+ if (!android::base::ParseInt(argv[argc - 1], &pid, 1, std::numeric_limits<pid_t>::max())) {
+ usage(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;
-}
-
-/*
- * Corresponds with debugger_action_t enum type in
- * include/cutils/debugger.h.
- */
-static const char *debuggerd_perms[] = {
- NULL, /* crash is only used on self, no check applied */
- "dump_tombstone",
- "dump_backtrace"
-};
-
-static int audit_callback(void* data, security_class_t /* cls */, char* buf, size_t len)
-{
- struct debugger_request_t* req = reinterpret_cast<debugger_request_t*>(data);
-
- if (!req) {
- ALOGE("No debuggerd request audit data");
- return 0;
- }
-
- snprintf(buf, len, "pid=%d uid=%d gid=%d", req->pid, req->uid, req->gid);
- return 0;
-}
-
-static bool selinux_action_allowed(int s, debugger_request_t* request)
-{
- char *scon = NULL, *tcon = NULL;
- const char *tclass = "debuggerd";
- const char *perm;
- bool allowed = false;
-
- if (request->action <= 0 || request->action >= (sizeof(debuggerd_perms)/sizeof(debuggerd_perms[0]))) {
- ALOGE("SELinux: No permission defined for debugger action %d", request->action);
- return false;
+ unique_fd piperead, pipewrite;
+ if (!Pipe(&piperead, &pipewrite)) {
+ err(1, "failed to create pipe");
}
- perm = debuggerd_perms[request->action];
-
- if (getpeercon(s, &scon) < 0) {
- ALOGE("Cannot get peer context from socket\n");
- goto out;
+ std::thread redirect_thread = spawn_redirect_thread(std::move(piperead));
+ bool backtrace = argc == 3;
+ if (!debuggerd_trigger_dump(pid, std::move(pipewrite),
+ backtrace ? kDebuggerdBacktrace : kDebuggerdBacktrace, 0)) {
+ redirect_thread.join();
+ errx(1, "failed to dump process %d", pid);
}
- if (getpidcon(request->tid, &tcon) < 0) {
- ALOGE("Cannot get context for tid %d\n", request->tid);
- goto out;
- }
-
- allowed = (selinux_check_access(scon, tcon, tclass, perm, reinterpret_cast<void*>(request)) == 0);
-
-out:
- freecon(scon);
- freecon(tcon);
- return allowed;
-}
-
-static bool pid_contains_tid(pid_t pid, pid_t tid) {
- char task_path[PATH_MAX];
- if (snprintf(task_path, PATH_MAX, "/proc/%d/task/%d", pid, tid) >= PATH_MAX) {
- ALOGE("debuggerd: task path overflow (pid = %d, tid = %d)\n", pid, tid);
- exit(1);
- }
-
- return access(task_path, F_OK) == 0;
-}
-
-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");
- 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 = static_cast<debugger_action_t>(msg.action);
- out_request->tid = msg.tid;
- out_request->ignore_tid = msg.ignore_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;
-
- 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;
- }
-
- if (!selinux_action_allowed(fd, out_request))
- return -1;
- } else {
- // No one else is allowed to dump arbitrary processes.
- return -1;
- }
+ redirect_thread.join();
return 0;
}
-
-static int activity_manager_connect() {
- android::base::unique_fd amfd(socket(PF_UNIX, SOCK_STREAM, 0));
- if (amfd.get() < -1) {
- ALOGE("debuggerd: Unable to connect to activity manager (socket failed: %s)", strerror(errno));
- return -1;
- }
-
- struct sockaddr_un address;
- memset(&address, 0, sizeof(address));
- address.sun_family = AF_UNIX;
- // The path used here must match the value defined in NativeCrashListener.java.
- strncpy(address.sun_path, "/data/system/ndebugsocket", sizeof(address.sun_path));
- if (TEMP_FAILURE_RETRY(connect(amfd.get(), reinterpret_cast<struct sockaddr*>(&address),
- sizeof(address))) == -1) {
- ALOGE("debuggerd: Unable to connect to activity manager (connect failed: %s)", strerror(errno));
- return -1;
- }
-
- struct timeval tv;
- memset(&tv, 0, sizeof(tv));
- tv.tv_sec = 1; // tight leash
- if (setsockopt(amfd.get(), SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv)) == -1) {
- ALOGE("debuggerd: Unable to connect to activity manager (setsockopt SO_SNDTIMEO failed: %s)",
- strerror(errno));
- return -1;
- }
-
- tv.tv_sec = 3; // 3 seconds on handshake read
- if (setsockopt(amfd.get(), SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) == -1) {
- ALOGE("debuggerd: Unable to connect to activity manager (setsockopt SO_RCVTIMEO failed: %s)",
- strerror(errno));
- return -1;
- }
-
- return amfd.release();
-}
-
-static void activity_manager_write(int pid, int signal, int amfd, const std::string& amfd_data) {
- if (amfd == -1) {
- return;
- }
-
- // Activity Manager protocol: binary 32-bit network-byte-order ints for the
- // pid and signal number, followed by the raw text of the dump, culminating
- // in a zero byte that marks end-of-data.
- uint32_t datum = htonl(pid);
- if (!android::base::WriteFully(amfd, &datum, 4)) {
- ALOGE("AM pid write failed: %s\n", strerror(errno));
- return;
- }
- datum = htonl(signal);
- if (!android::base::WriteFully(amfd, &datum, 4)) {
- ALOGE("AM signal write failed: %s\n", strerror(errno));
- return;
- }
-
- if (!android::base::WriteFully(amfd, amfd_data.c_str(), amfd_data.size())) {
- ALOGE("AM data write failed: %s\n", strerror(errno));
- return;
- }
-
- // Send EOD to the Activity Manager, then wait for its ack to avoid racing
- // ahead and killing the target out from under it.
- uint8_t eodMarker = 0;
- if (!android::base::WriteFully(amfd, &eodMarker, 1)) {
- ALOGE("AM eod write failed: %s\n", strerror(errno));
- return;
- }
- // 3 sec timeout reading the ack; we're fine if the read fails.
- android::base::ReadFully(amfd, &eodMarker, 1);
-}
-
-static bool should_attach_gdb(const debugger_request_t& request) {
- if (request.action == DEBUGGER_ACTION_CRASH) {
- return property_get_bool("debug.debuggerd.wait_for_gdb", false);
- }
- return false;
-}
-
-#if defined(__LP64__)
-static bool is32bit(pid_t tid) {
- char* exeline;
- if (asprintf(&exeline, "/proc/%d/exe", tid) == -1) {
- return false;
- }
- int fd = TEMP_FAILURE_RETRY(open(exeline, O_RDONLY | O_CLOEXEC));
- int saved_errno = errno;
- free(exeline);
- if (fd == -1) {
- ALOGW("Failed to open /proc/%d/exe %s", tid, strerror(saved_errno));
- return false;
- }
-
- char ehdr[EI_NIDENT];
- ssize_t bytes = TEMP_FAILURE_RETRY(read(fd, &ehdr, sizeof(ehdr)));
- close(fd);
- if (bytes != (ssize_t) sizeof(ehdr) || memcmp(ELFMAG, ehdr, SELFMAG) != 0) {
- return false;
- }
- if (ehdr[EI_CLASS] == ELFCLASS32) {
- return true;
- }
- return false;
-}
-
-static void redirect_to_32(int fd, debugger_request_t* request) {
- debugger_msg_t msg;
- memset(&msg, 0, sizeof(msg));
- msg.tid = request->tid;
- msg.action = request->action;
-
- int sock_fd = socket_local_client(DEBUGGER32_SOCKET_NAME, ANDROID_SOCKET_NAMESPACE_ABSTRACT,
- SOCK_STREAM | SOCK_CLOEXEC);
- if (sock_fd < 0) {
- ALOGE("Failed to connect to debuggerd32: %s", strerror(errno));
- return;
- }
-
- if (TEMP_FAILURE_RETRY(write(sock_fd, &msg, sizeof(msg))) != (ssize_t) sizeof(msg)) {
- ALOGE("Failed to write request to debuggerd32 socket: %s", strerror(errno));
- close(sock_fd);
- return;
- }
-
- char ack;
- if (TEMP_FAILURE_RETRY(read(sock_fd, &ack, 1)) == -1) {
- ALOGE("Failed to read ack from debuggerd32 socket: %s", strerror(errno));
- close(sock_fd);
- return;
- }
-
- char buffer[1024];
- ssize_t bytes_read;
- while ((bytes_read = TEMP_FAILURE_RETRY(read(sock_fd, buffer, sizeof(buffer)))) > 0) {
- ssize_t bytes_to_send = bytes_read;
- ssize_t bytes_written;
- do {
- bytes_written = TEMP_FAILURE_RETRY(write(fd, buffer + bytes_read - bytes_to_send,
- bytes_to_send));
- if (bytes_written == -1) {
- if (errno == EAGAIN) {
- // Retry the write.
- continue;
- }
- ALOGE("Error while writing data to fd: %s", strerror(errno));
- break;
- }
- bytes_to_send -= bytes_written;
- } while (bytes_written != 0 && bytes_to_send > 0);
- if (bytes_to_send != 0) {
- ALOGE("Failed to write all data to fd: read %zd, sent %zd", bytes_read, bytes_to_send);
- break;
- }
- }
- close(sock_fd);
-}
-#endif
-
-// Attach to a thread, and verify that it's still a member of the given process
-static bool ptrace_attach_thread(pid_t pid, pid_t tid) {
- if (ptrace(PTRACE_ATTACH, tid, 0, 0) != 0) {
- return false;
- }
-
- // Make sure that the task we attached to is actually part of the pid we're dumping.
- if (!pid_contains_tid(pid, tid)) {
- if (ptrace(PTRACE_DETACH, tid, 0, 0) != 0) {
- ALOGE("debuggerd: failed to detach from thread '%d'", tid);
- exit(1);
- }
- return false;
- }
-
- return true;
-}
-
-static void ptrace_siblings(pid_t pid, pid_t main_tid, pid_t ignore_tid, std::set<pid_t>& tids) {
- char task_path[PATH_MAX];
-
- if (snprintf(task_path, PATH_MAX, "/proc/%d/task", pid) >= PATH_MAX) {
- ALOGE("debuggerd: task path overflow (pid = %d)\n", pid);
- abort();
- }
-
- std::unique_ptr<DIR, int (*)(DIR*)> d(opendir(task_path), closedir);
-
- // Bail early if the task directory cannot be opened.
- if (!d) {
- ALOGE("debuggerd: failed to open /proc/%d/task: %s", pid, strerror(errno));
- return;
- }
-
- struct dirent* de;
- while ((de = readdir(d.get())) != NULL) {
- // Ignore "." and "..".
- if (!strcmp(de->d_name, ".") || !strcmp(de->d_name, "..")) {
- continue;
- }
-
- char* end;
- pid_t tid = strtoul(de->d_name, &end, 10);
- if (*end) {
- continue;
- }
-
- if (tid == main_tid || tid == ignore_tid) {
- continue;
- }
-
- if (!ptrace_attach_thread(pid, tid)) {
- ALOGE("debuggerd: ptrace attach to %d failed: %s", tid, strerror(errno));
- continue;
- }
-
- tids.insert(tid);
- }
-}
-
-static bool perform_dump(const debugger_request_t& request, int fd, int tombstone_fd,
- BacktraceMap* backtrace_map, const OpenFilesList& open_files,
- const std::set<pid_t>& siblings,
- int* crash_signal, std::string* amfd_data) {
- if (TEMP_FAILURE_RETRY(write(fd, "\0", 1)) != 1) {
- ALOGE("debuggerd: failed to respond to client: %s\n", strerror(errno));
- return false;
- }
-
- while (true) {
- // wait_for_signal waits for forever, but the watchdog process will kill us
- // if it takes too long.
- int signal = wait_for_signal(request.tid);
- switch (signal) {
- case -1:
- ALOGE("debuggerd: timed out waiting for signal");
- return false;
-
- case SIGSTOP:
- if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) {
- ALOGV("debuggerd: stopped -- dumping to tombstone");
- engrave_tombstone(tombstone_fd, backtrace_map, open_files,
- request.pid, request.tid, siblings,
- request.abort_msg_address, amfd_data);
- } else if (request.action == DEBUGGER_ACTION_DUMP_BACKTRACE) {
- ALOGV("debuggerd: stopped -- dumping to fd");
- dump_backtrace(fd, backtrace_map, request.pid, request.tid, siblings, nullptr);
- } else {
- ALOGV("debuggerd: stopped -- continuing");
- if (ptrace(PTRACE_CONT, request.tid, 0, 0) != 0) {
- ALOGE("debuggerd: ptrace continue failed: %s", strerror(errno));
- return false;
- }
- continue; // loop again
- }
- break;
-
- case SIGABRT:
- case SIGBUS:
- case SIGFPE:
- case SIGILL:
- case SIGSEGV:
-#ifdef SIGSTKFLT
- case SIGSTKFLT:
-#endif
- case SIGSYS:
- case SIGTRAP:
- ALOGV("stopped -- fatal signal\n");
- *crash_signal = signal;
- engrave_tombstone(tombstone_fd, backtrace_map, open_files,
- request.pid, request.tid, siblings,
- request.abort_msg_address, amfd_data);
- break;
-
- default:
- ALOGE("debuggerd: process stopped due to unexpected signal %d\n", signal);
- break;
- }
- break;
- }
-
- return true;
-}
-
-static bool drop_privileges() {
- // AID_LOG: for reading the logs data associated with the crashing process.
- // AID_READPROC: for reading /proc/<PID>/{comm,cmdline}.
- gid_t groups[] = { AID_DEBUGGERD, AID_LOG, AID_READPROC };
- if (setgroups(sizeof(groups)/sizeof(groups[0]), groups) != 0) {
- ALOGE("debuggerd: failed to setgroups: %s", strerror(errno));
- return false;
- }
-
- if (setresgid(AID_DEBUGGERD, AID_DEBUGGERD, AID_DEBUGGERD) != 0) {
- ALOGE("debuggerd: failed to setresgid: %s", strerror(errno));
- return false;
- }
-
- if (setresuid(AID_DEBUGGERD, AID_DEBUGGERD, AID_DEBUGGERD) != 0) {
- ALOGE("debuggerd: failed to setresuid: %s", strerror(errno));
- return false;
- }
-
- return true;
-}
-
-static void worker_process(int fd, debugger_request_t& request) {
- // Open the tombstone file if we need it.
- std::string tombstone_path;
- int tombstone_fd = -1;
- switch (request.action) {
- case DEBUGGER_ACTION_DUMP_TOMBSTONE:
- case DEBUGGER_ACTION_CRASH:
- tombstone_fd = open_tombstone(&tombstone_path);
- if (tombstone_fd == -1) {
- ALOGE("debuggerd: failed to open tombstone file: %s\n", strerror(errno));
- exit(1);
- }
- break;
-
- case DEBUGGER_ACTION_DUMP_BACKTRACE:
- break;
-
- default:
- ALOGE("debuggerd: unexpected request action: %d", request.action);
- exit(1);
- }
-
- // 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 client/debuggerd_client.cpp, in function
- // debugger_signal_handler().
-
- // Attach to the target process.
- if (!ptrace_attach_thread(request.pid, request.tid)) {
- ALOGE("debuggerd: ptrace attach failed: %s", strerror(errno));
- exit(1);
- }
-
- // 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);
- }
- }
-
- // Don't attach to the sibling threads if we want to attach gdb.
- // Supposedly, it makes the process less reliable.
- bool attach_gdb = should_attach_gdb(request);
- if (attach_gdb) {
- // Open all of the input devices we need to listen for VOLUMEDOWN before dropping privileges.
- if (init_getevent() != 0) {
- ALOGE("debuggerd: failed to initialize input device, not waiting for gdb");
- attach_gdb = false;
- }
-
- }
-
- std::set<pid_t> siblings;
- if (!attach_gdb) {
- ptrace_siblings(request.pid, request.tid, request.ignore_tid, siblings);
- }
-
- // Generate the backtrace map before dropping privileges.
- std::unique_ptr<BacktraceMap> backtrace_map(BacktraceMap::Create(request.pid));
-
- // Collect the list of open files before dropping privileges.
- OpenFilesList open_files;
- populate_open_files_list(request.pid, &open_files);
-
- int amfd = -1;
- std::unique_ptr<std::string> amfd_data;
- if (request.action == DEBUGGER_ACTION_CRASH) {
- // Connect to the activity manager before dropping privileges.
- amfd = activity_manager_connect();
- amfd_data.reset(new std::string);
- }
-
- bool succeeded = false;
-
- // Now that we've done everything that requires privileges, we can drop them.
- if (!drop_privileges()) {
- ALOGE("debuggerd: failed to drop privileges, exiting");
- _exit(1);
- }
-
- int crash_signal = SIGKILL;
- succeeded = perform_dump(request, fd, tombstone_fd, backtrace_map.get(), open_files,
- siblings, &crash_signal, amfd_data.get());
- if (succeeded) {
- if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) {
- if (!tombstone_path.empty()) {
- android::base::WriteFully(fd, tombstone_path.c_str(), tombstone_path.length());
- }
- }
- }
-
- if (attach_gdb) {
- // Tell the signal process to send SIGSTOP to the target.
- if (!send_signal(request.pid, 0, SIGSTOP)) {
- ALOGE("debuggerd: failed to stop process for gdb attach: %s", strerror(errno));
- attach_gdb = false;
- }
- }
-
- if (!attach_gdb) {
- // Tell the Activity Manager about the crashing process. If we are
- // waiting for gdb to attach, do not send this or Activity Manager
- // might kill the process before anyone can attach.
- activity_manager_write(request.pid, crash_signal, amfd, *amfd_data.get());
- }
-
- if (ptrace(PTRACE_DETACH, request.tid, 0, 0) != 0) {
- ALOGE("debuggerd: ptrace detach from %d failed: %s", request.tid, strerror(errno));
- }
-
- for (pid_t sibling : siblings) {
- ptrace(PTRACE_DETACH, sibling, 0, 0);
- }
-
- // Send the signal back to the process if it crashed and we're not waiting for gdb.
- if (!attach_gdb && request.action == DEBUGGER_ACTION_CRASH) {
- if (!send_signal(request.pid, request.tid, crash_signal)) {
- ALOGE("debuggerd: failed to kill process %d: %s", request.pid, strerror(errno));
- }
- }
-
- // Wait for gdb, if requested.
- if (attach_gdb) {
- wait_for_user_action(request);
-
- // Now tell the activity manager about this process.
- activity_manager_write(request.pid, crash_signal, amfd, *amfd_data.get());
-
- // Tell the signal process to send SIGCONT to the target.
- if (!send_signal(request.pid, 0, SIGCONT)) {
- ALOGE("debuggerd: failed to resume process %d: %s", request.pid, strerror(errno));
- }
-
- uninit_getevent();
- }
-
- close(amfd);
-
- exit(!succeeded);
-}
-
-static void monitor_worker_process(int child_pid, const debugger_request_t& request) {
- struct timespec timeout = {.tv_sec = 10, .tv_nsec = 0 };
- if (should_attach_gdb(request)) {
- // If wait_for_gdb is enabled, set the timeout to something large.
- timeout.tv_sec = INT_MAX;
- }
-
- sigset_t signal_set;
- sigemptyset(&signal_set);
- sigaddset(&signal_set, SIGCHLD);
-
- bool kill_worker = false;
- bool kill_target = false;
- bool kill_self = false;
-
- int status;
- siginfo_t siginfo;
- int signal = TEMP_FAILURE_RETRY(sigtimedwait(&signal_set, &siginfo, &timeout));
- if (signal == SIGCHLD) {
- pid_t rc = waitpid(-1, &status, WNOHANG | WUNTRACED);
- if (rc != child_pid) {
- ALOGE("debuggerd: waitpid returned unexpected pid (%d), committing murder-suicide", rc);
-
- if (WIFEXITED(status)) {
- ALOGW("debuggerd: pid %d exited with status %d", rc, WEXITSTATUS(status));
- } else if (WIFSIGNALED(status)) {
- ALOGW("debuggerd: pid %d received signal %d", rc, WTERMSIG(status));
- } else if (WIFSTOPPED(status)) {
- ALOGW("debuggerd: pid %d stopped by signal %d", rc, WSTOPSIG(status));
- } else if (WIFCONTINUED(status)) {
- ALOGW("debuggerd: pid %d continued", rc);
- }
-
- kill_worker = true;
- kill_target = true;
- kill_self = true;
- } else if (WIFSIGNALED(status)) {
- ALOGE("debuggerd: worker process %d terminated due to signal %d", child_pid, WTERMSIG(status));
- kill_worker = false;
- kill_target = true;
- } else if (WIFSTOPPED(status)) {
- ALOGE("debuggerd: worker process %d stopped due to signal %d", child_pid, WSTOPSIG(status));
- kill_worker = true;
- kill_target = true;
- }
- } else {
- ALOGE("debuggerd: worker process %d timed out", child_pid);
- kill_worker = true;
- kill_target = true;
- }
-
- if (kill_worker) {
- // Something bad happened, kill the worker.
- if (kill(child_pid, SIGKILL) != 0) {
- ALOGE("debuggerd: failed to kill worker process %d: %s", child_pid, strerror(errno));
- } else {
- waitpid(child_pid, &status, 0);
- }
- }
-
- int exit_signal = SIGCONT;
- if (kill_target && request.action == DEBUGGER_ACTION_CRASH) {
- ALOGE("debuggerd: killing target %d", request.pid);
- exit_signal = SIGKILL;
- } else {
- ALOGW("debuggerd: resuming target %d", request.pid);
- }
-
- if (kill(request.pid, exit_signal) != 0) {
- ALOGE("debuggerd: failed to send signal %d to target: %s", exit_signal, strerror(errno));
- }
-
- if (kill_self) {
- stop_signal_sender();
- _exit(1);
- }
-}
-
-static void handle_request(int fd) {
- ALOGV("handle_request(%d)\n", fd);
-
- android::base::unique_fd closer(fd);
- debugger_request_t request;
- memset(&request, 0, sizeof(request));
- int status = read_request(fd, &request);
- if (status != 0) {
- return;
- }
-
- ALOGW("debuggerd: handling request: pid=%d uid=%d gid=%d tid=%d\n", request.pid, request.uid,
- request.gid, request.tid);
-
-#if defined(__LP64__)
- // On 64 bit systems, requests to dump 32 bit and 64 bit tids come
- // to the 64 bit debuggerd. If the process is a 32 bit executable,
- // redirect the request to the 32 bit debuggerd.
- if (is32bit(request.tid)) {
- // Only dump backtrace and dump tombstone requests can be redirected.
- if (request.action == DEBUGGER_ACTION_DUMP_BACKTRACE ||
- request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) {
- redirect_to_32(fd, &request);
- } else {
- ALOGE("debuggerd: Not allowed to redirect action %d to 32 bit debuggerd\n", request.action);
- }
- return;
- }
-#endif
-
- // Fork a child to handle the rest of the request.
- pid_t fork_pid = fork();
- if (fork_pid == -1) {
- ALOGE("debuggerd: failed to fork: %s\n", strerror(errno));
- } else if (fork_pid == 0) {
- worker_process(fd, request);
- } else {
- monitor_worker_process(fork_pid, request);
- }
-}
-
-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);
-
- // Block SIGCHLD so we can sigtimedwait for it.
- sigset_t sigchld;
- sigemptyset(&sigchld);
- sigaddset(&sigchld, SIGCHLD);
- sigprocmask(SIG_SETMASK, &sigchld, nullptr);
-
- int s = socket_local_server(SOCKET_NAME, ANDROID_SOCKET_NAMESPACE_ABSTRACT,
- SOCK_STREAM | SOCK_CLOEXEC);
- if (s == -1) return 1;
-
- // Fork a process that stays root, and listens on a pipe to pause and resume the target.
- if (!start_signal_sender()) {
- ALOGE("debuggerd: failed to fork signal sender");
- return 1;
- }
-
- ALOGI("debuggerd: starting\n");
-
- for (;;) {
- ALOGV("waiting for connection\n");
- int fd = accept4(s, nullptr, nullptr, SOCK_CLOEXEC | SOCK_NONBLOCK);
- if (fd == -1) {
- ALOGE("accept failed: %s\n", strerror(errno));
- continue;
- }
-
- 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);
- fflush(stdout);
-
- // TODO: we could have better error reporting if debuggerd sent an error string back.
- if (dump_backtrace) {
- if (dump_backtrace_to_file(tid, fileno(stdout)) < 0) {
- fputs("Error dumping backtrace (check logcat).\n", stderr);
- return 1;
- }
- } else {
- char tombstone_path[PATH_MAX];
- if (dump_tombstone(tid, tombstone_path, sizeof(tombstone_path)) < 0) {
- fputs("Error dumping tombstone (check logcat).\n", stderr);
- return 1;
- }
- fprintf(stderr, "Tombstone written to: %s\n", tombstone_path);
- }
- return 0;
-}
-
-static int usage() {
- fputs("usage: debuggerd [-b] [<tid>]\n"
- "\n"
- "Given a thread id, sends a request to debuggerd to dump that thread.\n"
- "Otherwise, starts the debuggerd server.\n"
- "\n"
- "-b\tdump backtrace to console, otherwise generate tombstone\n", stderr);
- return EXIT_FAILURE;
-}
-
-int main(int argc, char** argv) {
- union selinux_callback cb;
- if (argc == 1) {
- cb.func_audit = audit_callback;
- selinux_set_callback(SELINUX_CB_AUDIT, cb);
- cb.func_log = selinux_log_callback;
- selinux_set_callback(SELINUX_CB_LOG, cb);
- return do_server();
- }
-
- bool dump_backtrace = false;
- pid_t tid = 0;
- for (int i = 1; i < argc; i++) {
- if (!strcmp(argv[i], "-b")) {
- dump_backtrace = true;
- } else if (tid != 0 || (tid = atoi(argv[i])) == 0) {
- // Only one tid is allowed. (And 0 isn't a valid tid.)
- // atoi(3) returns 0 on failure to parse, so this catches anything else too.
- return usage();
- }
- }
- return (tid != 0) ? do_explicit_dump(tid, dump_backtrace) : usage();
-}