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platform_system_core/debuggerd/debuggerd.cpp

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/*
* 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 <arpa/inet.h>
#include <dirent.h>
#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <signal.h>
#include <stdarg.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 <memory>
#include <set>
#include <string>
#include <selinux/android.h>
#include <log/logger.h>
#include <android-base/file.h>
#include <android-base/unique_fd.h>
#include <cutils/debugger.h>
#include <cutils/properties.h>
#include <cutils/sockets.h>
#include <nativehelper/ScopedFd.h>
#include <linux/input.h>
#include <private/android_filesystem_config.h>
#include "backtrace.h"
#include "getevent.h"
#include "signal_sender.h"
#include "tombstone.h"
#include "utility.h"
// 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
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) {
// 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;
}
}
}
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;
}
/*
* 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;
}
perm = debuggerd_perms[request->action];
if (getpeercon(s, &scon) < 0) {
ALOGE("Cannot get peer context from socket\n");
goto out;
}
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 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 = static_cast<debugger_action_t>(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.
char buf[64];
struct stat s;
snprintf(buf, sizeof buf, "/proc/%d/task/%d", out_request->pid, out_request->tid);
if (stat(buf, &s)) {
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;
}
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
static void ptrace_siblings(pid_t pid, pid_t main_tid, std::set<pid_t>& tids) {
char task_path[64];
snprintf(task_path, sizeof(task_path), "/proc/%d/task", pid);
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) {
continue;
}
if (ptrace(PTRACE_ATTACH, tid, 0, 0) < 0) {
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 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;
}
int total_sleep_time_usec = 0;
while (true) {
int signal = wait_for_signal(request.tid, &total_sleep_time_usec);
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, request.pid, request.tid, siblings, signal,
request.original_si_code, 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, request.pid, request.tid, siblings, signal,
request.original_si_code, 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 bionic/libc/linker/debugger.c, in function
// debugger_signal_handler().
// Attach to the target process.
if (ptrace(PTRACE_ATTACH, request.tid, 0, 0) != 0) {
ALOGE("debuggerd: ptrace attach failed: %s", strerror(errno));
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, siblings);
}
// Generate the backtrace map before dropping privileges.
std::unique_ptr<BacktraceMap> backtrace_map(BacktraceMap::Create(request.pid));
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(), 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);
ScopedFd 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 (;;) {
sockaddr_storage ss;
sockaddr* addrp = reinterpret_cast<sockaddr*>(&ss);
socklen_t alen = sizeof(ss);
ALOGV("waiting for connection\n");
int fd = accept4(s, addrp, &alen, SOCK_CLOEXEC);
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);
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) {
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;
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);
}
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