/*
 * 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 <inttypes.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.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);

// Crash actions have to be sent to the proper debuggerd.
// On 64 bit systems, the 32 bit debuggerd is named differently.
#if defined(TARGET_IS_64_BIT) && !defined(__LP64__)
#define DEBUGGER_SOCKET_NAME "android:debuggerd32"
#else
#define DEBUGGER_SOCKET_NAME "android:debuggerd"
#endif

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 __attribute__((packed)) debugger_msg_t {
 int32_t action;
 pid_t tid;
 uint64_t abort_msg_address;
 int32_t original_si_code;
};

// 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円'.
 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円' at the start of the Unix socket path.
 //
 // Note: The path in this case is *not* supposed to be
 // '0円'-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 rc = TEMP_FAILURE_RETRY(connect(s, reinterpret_cast<sockaddr*>(&addr), alen));
 if (rc == -1) {
 close(s);
 return -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 = "???";
 bool has_address = false;
 switch (signum) {
 case SIGABRT:
 signal_name = "SIGABRT";
 break;
 case SIGBUS:
 signal_name = "SIGBUS";
 has_address = true;
 break;
 case SIGFPE:
 signal_name = "SIGFPE";
 has_address = true;
 break;
 case SIGILL:
 signal_name = "SIGILL";
 has_address = true;
 break;
 case SIGPIPE:
 signal_name = "SIGPIPE";
 break;
 case SIGSEGV:
 signal_name = "SIGSEGV";
 has_address = true;
 break;
#if defined(SIGSTKFLT)
 case SIGSTKFLT:
 signal_name = "SIGSTKFLT";
 break;
#endif
 case SIGTRAP:
 signal_name = "SIGTRAP";
 break;
 }

 char thread_name[MAX_TASK_NAME_LEN + 1]; // one more for termination
 if (prctl(PR_GET_NAME, reinterpret_cast<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.
 // Many signals don't have an address or a code.
 char code_desc[32]; // ", code -6"
 char addr_desc[32]; // ", fault addr 0x1234"
 addr_desc[0] = code_desc[0] = 0;
 if (info != nullptr) {
 // For a rethrown signal, this si_code will be right and the one debuggerd shows will
 // always be SI_TKILL.
 __libc_format_buffer(code_desc, sizeof(code_desc), ", code %d", info->si_code);
 if (has_address) {
 __libc_format_buffer(addr_desc, sizeof(addr_desc), ", fault addr %p", info->si_addr);
 }
 }
 __libc_format_log(ANDROID_LOG_FATAL, "libc",
 "Fatal signal %d (%s)%s%s in tid %d (%s)",
 signum, signal_name, code_desc, addr_desc, 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, nullptr) == -1) {
 __libc_format_log(ANDROID_LOG_WARN, "libc", "Restore failed in test for SA_SIGINFO: %s",
 strerror(errno));
 }
 return result;
}

static void send_debuggerd_packet(siginfo_t* info) {
 if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0) {
 // process has disabled core dumps and PTRACE_ATTACH, and does not want to be dumped.
 // Honor that intention by not connecting to debuggerd and asking it
 // to dump our internal state.
 __libc_format_log(ANDROID_LOG_INFO, "libc",
 "Suppressing debuggerd output because prctl(PR_GET_DUMPABLE)==0");
 return;
 }

 // Mutex to prevent multiple crashing threads from trying to talk
 // to debuggerd at the same time.
 static pthread_mutex_t crash_mutex = PTHREAD_MUTEX_INITIALIZER;
 int ret = pthread_mutex_trylock(&crash_mutex);
 if (ret != 0) {
 if (ret == EBUSY) {
 __libc_format_log(ANDROID_LOG_INFO, "libc",
 "Another thread has contacted debuggerd first, stop and wait for process to die.");
 // This will never complete since the lock is never released.
 pthread_mutex_lock(&crash_mutex);
 } else {
 __libc_format_log(ANDROID_LOG_INFO, "libc",
 "pthread_mutex_trylock failed: %s", strerror(ret));
 }
 return;
 }

 int s = socket_abstract_client(DEBUGGER_SOCKET_NAME, SOCK_STREAM | SOCK_CLOEXEC);
 if (s == -1) {
 __libc_format_log(ANDROID_LOG_FATAL, "libc", "Unable to open connection to debuggerd: %s",
 strerror(errno));
 return;
 }

 // 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 = gettid();
 msg.abort_msg_address = reinterpret_cast<uintptr_t>(g_abort_message);
 msg.original_si_code = (info != nullptr) ? info->si_code : 0;
 ret = TEMP_FAILURE_RETRY(write(s, &msg, sizeof(msg)));
 if (ret == sizeof(msg)) {
 char debuggerd_ack;
 ret = TEMP_FAILURE_RETRY(read(s, &debuggerd_ack, 1));
 int saved_errno = errno;
 notify_gdb_of_libraries();
 errno = saved_errno;
 } else {
 // read or write failed -- broken connection?
 __libc_format_log(ANDROID_LOG_FATAL, "libc", "Failed while talking to debuggerd: %s",
 strerror(errno));
 }

 close(s);
}

/*
 * Catches fatal signals so we can ask debuggerd to ptrace us before
 * we crash.
 */
static void debuggerd_signal_handler(int signal_number, 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(signal_number)) {
 info = nullptr;
 }

 log_signal_summary(signal_number, info);

 send_debuggerd_packet(info);

 // Remove our net so we fault for real when we return.
 signal(signal_number, 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 si_addr for
 // faults like SIGSEGV. It does screw up the si_code, which is why we
 // passed that to debuggerd above.
 switch (signal_number) {
 case SIGABRT:
 case SIGFPE:
 case SIGPIPE:
#if defined(SIGSTKFLT)
 case SIGSTKFLT:
#endif
 case SIGTRAP:
 tgkill(getpid(), gettid(), signal_number);
 break;
 default: // SIGILL, SIGBUS, SIGSEGV
 break;
 }
}

__LIBC_HIDDEN__ 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, nullptr);
 sigaction(SIGBUS, &action, nullptr);
 sigaction(SIGFPE, &action, nullptr);
 sigaction(SIGILL, &action, nullptr);
 sigaction(SIGPIPE, &action, nullptr);
 sigaction(SIGSEGV, &action, nullptr);
#if defined(SIGSTKFLT)
 sigaction(SIGSTKFLT, &action, nullptr);
#endif
 sigaction(SIGTRAP, &action, nullptr);
}