/*

* 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 <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <signal.h>

#include <sys/prctl.h>

#include <errno.h>

#include <sys/socket.h>

#include <sys/un.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 logSignalSummary(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 haveSiginfo(int signum) {

struct sigaction oldact, newact;

memset(&newact, 0, sizeof(newact));

newact.sa_handler = SIG_DFL;

newact.sa_flags = SA_RESTART;

sigemptyset(&newact.sa_mask);

if (sigaction(signum, &newact, &oldact) < 0) {

__libc_format_log(ANDROID_LOG_WARN, "libc", "Failed testing for SA_SIGINFO: %s",

strerror(errno));

return false;

}

bool ret = (oldact.sa_flags & SA_SIGINFO) != 0;

if (sigaction(signum, &oldact, NULL) == -1) {

__libc_format_log(ANDROID_LOG_WARN, "libc", "Restore failed in test for SA_SIGINFO: %s",

strerror(errno));

}

return ret;

}

/*

* 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 (!haveSiginfo(n)) {

info = NULL;

}

logSignalSummary(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 act;

memset(&act, 0, sizeof(act));

act.sa_sigaction = debuggerd_signal_handler;

act.sa_flags = SA_RESTART | SA_SIGINFO;

sigemptyset(&act.sa_mask);

sigaction(SIGILL, &act, NULL);

sigaction(SIGABRT, &act, NULL);

sigaction(SIGBUS, &act, NULL);

sigaction(SIGFPE, &act, NULL);

sigaction(SIGSEGV, &act, NULL);

#if defined(SIGSTKFLT)

sigaction(SIGSTKFLT, &act, NULL);

#endif

sigaction(SIGPIPE, &act, NULL);

}