/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "linker.h"
#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
extern "C" int tgkill(int tgid, int tid, int sig);
#define DEBUGGER_SOCKET_NAME "android:debuggerd"
enum debugger_action_t {
// dump a crash
DEBUGGER_ACTION_CRASH,
// dump a tombstone file
DEBUGGER_ACTION_DUMP_TOMBSTONE,
// dump a backtrace only back to the socket
DEBUGGER_ACTION_DUMP_BACKTRACE,
};
/* message sent over the socket */
struct debugger_msg_t {
// version 1 included:
debugger_action_t action;
pid_t tid;
// version 2 added:
uintptr_t abort_msg_address;
};
// see man(2) prctl, specifically the section about PR_GET_NAME
#define MAX_TASK_NAME_LEN (16)
static int socket_abstract_client(const char* name, int type) {
sockaddr_un addr;
// Test with length +1 for the *initial* '\0'.
size_t namelen = strlen(name);
if ((namelen + 1) > sizeof(addr.sun_path)) {
errno = EINVAL;
return -1;
}
/* This is used for abstract socket namespace, we need
* an initial '\0' at the start of the Unix socket path.
*
* Note: The path in this case is *not* supposed to be
* '\0'-terminated. ("man 7 unix" for the gory details.)
*/
memset(&addr, 0, sizeof(addr));
addr.sun_family = AF_LOCAL;
addr.sun_path[0] = 0;
memcpy(addr.sun_path + 1, name, namelen);
socklen_t alen = namelen + offsetof(sockaddr_un, sun_path) + 1;
int s = socket(AF_LOCAL, type, 0);
if (s == -1) {
return -1;
}
int err = TEMP_FAILURE_RETRY(connect(s, (sockaddr*) &addr, alen));
if (err == -1) {
close(s);
s = -1;
}
return s;
}
/*
* Writes a summary of the signal to the log file. We do this so that, if
* for some reason we're not able to contact debuggerd, there is still some
* indication of the failure in the log.
*
* We could be here as a result of native heap corruption, or while a
* mutex is being held, so we don't want to use any libc functions that
* could allocate memory or hold a lock.
*/
static void log_signal_summary(int signum, const siginfo_t* info) {
const char* signal_name;
switch (signum) {
case SIGILL: signal_name = "SIGILL"; break;
case SIGABRT: signal_name = "SIGABRT"; break;
case SIGBUS: signal_name = "SIGBUS"; break;
case SIGFPE: signal_name = "SIGFPE"; break;
case SIGSEGV: signal_name = "SIGSEGV"; break;
#if defined(SIGSTKFLT)
case SIGSTKFLT: signal_name = "SIGSTKFLT"; break;
#endif
case SIGPIPE: signal_name = "SIGPIPE"; break;
default: signal_name = "???"; break;
}
char thread_name[MAX_TASK_NAME_LEN + 1]; // one more for termination
if (prctl(PR_GET_NAME, (unsigned long)thread_name, 0, 0, 0) != 0) {
strcpy(thread_name, "<name unknown>");
} else {
// short names are null terminated by prctl, but the man page
// implies that 16 byte names are not.
thread_name[MAX_TASK_NAME_LEN] = 0;
}
// "info" will be NULL if the siginfo_t information was not available.
if (info != NULL) {
__libc_format_log(ANDROID_LOG_FATAL, "libc",
"Fatal signal %d (%s) at 0x%08x (code=%d), thread %d (%s)",
signum, signal_name, reinterpret_cast<uintptr_t>(info->si_addr),
info->si_code, gettid(), thread_name);
} else {
__libc_format_log(ANDROID_LOG_FATAL, "libc",
"Fatal signal %d (%s), thread %d (%s)",
signum, signal_name, gettid(), thread_name);
}
}
/*
* Returns true if the handler for signal "signum" has SA_SIGINFO set.
*/
static bool have_siginfo(int signum) {
struct sigaction old_action, new_action;
memset(&new_action, 0, sizeof(new_action));
new_action.sa_handler = SIG_DFL;
new_action.sa_flags = SA_RESTART;
sigemptyset(&new_action.sa_mask);
if (sigaction(signum, &new_action, &old_action) < 0) {
__libc_format_log(ANDROID_LOG_WARN, "libc", "Failed testing for SA_SIGINFO: %s",
strerror(errno));
return false;
}
bool result = (old_action.sa_flags & SA_SIGINFO) != 0;
if (sigaction(signum, &old_action, NULL) == -1) {
__libc_format_log(ANDROID_LOG_WARN, "libc", "Restore failed in test for SA_SIGINFO: %s",
strerror(errno));
}
return result;
}
/*
* Catches fatal signals so we can ask debuggerd to ptrace us before
* we crash.
*/
void debuggerd_signal_handler(int n, siginfo_t* info, void*) {
/*
* It's possible somebody cleared the SA_SIGINFO flag, which would mean
* our "info" arg holds an undefined value.
*/
if (!have_siginfo(n)) {
info = NULL;
}
log_signal_summary(n, info);
pid_t tid = gettid();
int s = socket_abstract_client(DEBUGGER_SOCKET_NAME, SOCK_STREAM);
if (s >= 0) {
// debuggerd knows our pid from the credentials on the
// local socket but we need to tell it the tid of the crashing thread.
// debuggerd will be paranoid and verify that we sent a tid
// that's actually in our process.
debugger_msg_t msg;
msg.action = DEBUGGER_ACTION_CRASH;
msg.tid = tid;
msg.abort_msg_address = reinterpret_cast<uintptr_t>(gAbortMessage);
int ret = TEMP_FAILURE_RETRY(write(s, &msg, sizeof(msg)));
if (ret == sizeof(msg)) {
// if the write failed, there is no point trying to read a response.
ret = TEMP_FAILURE_RETRY(read(s, &tid, 1));
int saved_errno = errno;
notify_gdb_of_libraries();
errno = saved_errno;
}
if (ret < 0) {
/* read or write failed -- broken connection? */
__libc_format_log(ANDROID_LOG_FATAL, "libc", "Failed while talking to debuggerd: %s",
strerror(errno));
}
close(s);
} else {
/* socket failed; maybe process ran out of fds */
__libc_format_log(ANDROID_LOG_FATAL, "libc", "Unable to open connection to debuggerd: %s",
strerror(errno));
}
/* remove our net so we fault for real when we return */
signal(n, SIG_DFL);
/*
* These signals are not re-thrown when we resume. This means that
* crashing due to (say) SIGPIPE doesn't work the way you'd expect it
* to. We work around this by throwing them manually. We don't want
* to do this for *all* signals because it'll screw up the address for
* faults like SIGSEGV.
*/
switch (n) {
case SIGABRT:
case SIGFPE:
case SIGPIPE:
#ifdef SIGSTKFLT
case SIGSTKFLT:
#endif
(void) tgkill(getpid(), gettid(), n);
break;
default: // SIGILL, SIGBUS, SIGSEGV
break;
}
}
void debuggerd_init() {
struct sigaction action;
memset(&action, 0, sizeof(action));
sigemptyset(&action.sa_mask);
action.sa_sigaction = debuggerd_signal_handler;
action.sa_flags = SA_RESTART | SA_SIGINFO;
// Use the alternate signal stack if available so we can catch stack overflows.
action.sa_flags |= SA_ONSTACK;
sigaction(SIGABRT, &action, NULL);
sigaction(SIGBUS, &action, NULL);
sigaction(SIGFPE, &action, NULL);
sigaction(SIGILL, &action, NULL);
sigaction(SIGPIPE, &action, NULL);
sigaction(SIGSEGV, &action, NULL);
#if defined(SIGSTKFLT)
sigaction(SIGSTKFLT, &action, NULL);
#endif
sigaction(SIGTRAP, &action, NULL);
}