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platform_system_core/debuggerd/debuggerd.c

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/* system/debuggerd/debuggerd.c
**
** 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 <sys/exec_elf.h>
#include <sys/stat.h>
#include <sys/poll.h>
#include <cutils/sockets.h>
#include <cutils/logd.h>
#include <cutils/logger.h>
#include <cutils/properties.h>
#include <cutils/debugger.h>
#include <corkscrew/backtrace.h>
#include <linux/input.h>
#include <private/android_filesystem_config.h>
#include "backtrace.h"
#include "getevent.h"
#include "tombstone.h"
#include "utility.h"
typedef struct {
debugger_action_t action;
pid_t pid, tid;
uid_t uid, gid;
} debugger_request_t;
static int
write_string(const char* file, const char* string)
{
int len;
int fd;
ssize_t amt;
fd = open(file, O_RDWR);
len = strlen(string);
if (fd < 0)
return -errno;
amt = write(fd, string, len);
close(fd);
return amt >= 0 ? 0 : -errno;
}
static
void init_debug_led(void)
{
// trout leds
write_string("/sys/class/leds/red/brightness", "0");
write_string("/sys/class/leds/green/brightness", "0");
write_string("/sys/class/leds/blue/brightness", "0");
write_string("/sys/class/leds/red/device/blink", "0");
// sardine leds
write_string("/sys/class/leds/left/cadence", "0,0");
}
static
void enable_debug_led(void)
{
// trout leds
write_string("/sys/class/leds/red/brightness", "255");
// sardine leds
write_string("/sys/class/leds/left/cadence", "1,0");
}
static
void disable_debug_led(void)
{
// trout leds
write_string("/sys/class/leds/red/brightness", "0");
// sardine leds
write_string("/sys/class/leds/left/cadence", "0,0");
}
static void wait_for_user_action(pid_t pid) {
/* First log a helpful message */
LOG( "********************************************************\n"
"* Process %d has been suspended while crashing. To\n"
"* attach gdbserver for a gdb connection on port 5039\n"
"* and start gdbclient:\n"
"*\n"
"* gdbclient app_process :5039 %d\n"
"*\n"
"* Wait for gdb to start, then press HOME or VOLUME DOWN key\n"
"* to let the process continue crashing.\n"
"********************************************************\n",
pid, pid);
/* wait for HOME or VOLUME DOWN key */
if (init_getevent() == 0) {
int ms = 1200 / 10;
int dit = 1;
int dah = 3*dit;
int _ = -dit;
int ___ = 3*_;
int _______ = 7*_;
const signed char codes[] = {
dit,_,dit,_,dit,___,dah,_,dah,_,dah,___,dit,_,dit,_,dit,_______
};
size_t s = 0;
struct input_event e;
bool done = false;
init_debug_led();
enable_debug_led();
do {
int timeout = abs((int)(codes[s])) * ms;
int res = get_event(&e, timeout);
if (res == 0) {
if (e.type == EV_KEY
&& (e.code == KEY_HOME || e.code == KEY_VOLUMEDOWN)
&& e.value == 0) {
done = true;
}
} else if (res == 1) {
if (++s >= sizeof(codes)/sizeof(*codes))
s = 0;
if (codes[s] > 0) {
enable_debug_led();
} else {
disable_debug_led();
}
}
} while (!done);
uninit_getevent();
}
/* don't forget to turn debug led off */
disable_debug_led();
LOG("debuggerd resuming process %d", 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) {
struct ucred cr;
int len = sizeof(cr);
int status = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cr, &len);
if (status != 0) {
LOG("cannot get credentials\n");
return -1;
}
XLOG("reading tid\n");
fcntl(fd, F_SETFL, O_NONBLOCK);
struct 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) {
LOG("timed out reading tid\n");
return -1;
}
debugger_msg_t msg;
status = TEMP_FAILURE_RETRY(read(fd, &msg, sizeof(msg)));
if (status < 0) {
LOG("read failure? %s\n", strerror(errno));
return -1;
}
if (status != sizeof(msg)) {
LOG("invalid crash request of size %d\n", status);
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;
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)) {
LOG("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) {
LOG("tid %d does not exist. ignoring explicit dump request\n",
out_request->tid);
return -1;
}
} else {
/* No one else is not 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) {
XLOG("handle_request(%d)\n", fd);
debugger_request_t request;
int status = read_request(fd, &request);
if (!status) {
XLOG("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(PTRACE_ATTACH, request.tid, 0, 0)) {
LOG("ptrace attach failed: %s\n", strerror(errno));
} else {
bool detach_failed = false;
bool attach_gdb = should_attach_gdb(&request);
if (TEMP_FAILURE_RETRY(write(fd, "\0", 1)) != 1) {
LOG("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_signal(request.tid, &total_sleep_time_usec);
if (signal < 0) {
break;
}
switch (signal) {
case SIGSTOP:
if (request.action == DEBUGGER_ACTION_DUMP_TOMBSTONE) {
XLOG("stopped -- dumping to tombstone\n");
tombstone_path = engrave_tombstone(request.pid, request.tid,
signal, true, true, &detach_failed,
&total_sleep_time_usec);
} else if (request.action == DEBUGGER_ACTION_DUMP_BACKTRACE) {
XLOG("stopped -- dumping to fd\n");
dump_backtrace(fd, request.pid, request.tid, &detach_failed,
&total_sleep_time_usec);
} else {
XLOG("stopped -- continuing\n");
status = ptrace(PTRACE_CONT, request.tid, 0, 0);
if (status) {
LOG("ptrace continue failed: %s\n", strerror(errno));
}
continue; /* loop again */
}
break;
case SIGILL:
case SIGABRT:
case SIGBUS:
case SIGFPE:
case SIGSEGV:
case SIGPIPE:
#ifdef SIGSTKFLT
case SIGSTKFLT:
#endif
{
XLOG("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, !attach_gdb, false, &detach_failed,
&total_sleep_time_usec);
break;
}
default:
XLOG("stopped -- unexpected signal\n");
LOG("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);
}
XLOG("detaching\n");
if (attach_gdb) {
/* stop the process so we can debug */
kill(request.pid, SIGSTOP);
/* detach so we can attach gdbserver */
if (ptrace(PTRACE_DETACH, request.tid, 0, 0)) {
LOG("ptrace detach from %d failed: %s\n", request.tid, strerror(errno));
detach_failed = true;
}
/*
* 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.pid);
} else {
/* just detach */
if (ptrace(PTRACE_DETACH, request.tid, 0, 0)) {
LOG("ptrace detach from %d failed: %s\n", request.tid, strerror(errno));
detach_failed = true;
}
}
/* 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) {
LOG("debuggerd committing suicide to free the zombie!\n");
kill(getpid(), SIGKILL);
}
}
}
if (fd >= 0) {
close(fd);
}
}
static int do_server() {
int s;
struct sigaction act;
int logsocket = -1;
/*
* debuggerd crashes can't be reported to debuggerd. Reset all of the
* crash handlers.
*/
signal(SIGILL, SIG_DFL);
signal(SIGABRT, SIG_DFL);
signal(SIGBUS, SIG_DFL);
signal(SIGFPE, SIG_DFL);
signal(SIGSEGV, SIG_DFL);
signal(SIGPIPE, SIG_DFL);
#ifdef SIGSTKFLT
signal(SIGSTKFLT, SIG_DFL);
#endif
logsocket = socket_local_client("logd",
ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_DGRAM);
if(logsocket < 0) {
logsocket = -1;
} else {
fcntl(logsocket, F_SETFD, FD_CLOEXEC);
}
act.sa_handler = SIG_DFL;
sigemptyset(&act.sa_mask);
sigaddset(&act.sa_mask,SIGCHLD);
act.sa_flags = SA_NOCLDWAIT;
sigaction(SIGCHLD, &act, 0);
s = socket_local_server(DEBUGGER_SOCKET_NAME,
ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_STREAM);
if(s < 0) return 1;
fcntl(s, F_SETFD, FD_CLOEXEC);
LOG("debuggerd: " __DATE__ " " __TIME__ "\n");
for(;;) {
struct sockaddr addr;
socklen_t alen;
int fd;
alen = sizeof(addr);
XLOG("waiting for connection\n");
fd = accept(s, &addr, &alen);
if(fd < 0) {
XLOG("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);
}
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