text: /*
   * 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 "linker_gdb_support.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/syscall.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.
  // NOTE: Any changes to this structure must also be reflected in
  //       system/core/include/cutils/debugger.h.
  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'.
    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 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 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) {
    // 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 contacted debuggerd first; not contacting debuggerd.");
        // 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);
  
    // We need to return from the signal handler so that debuggerd can dump the
    // thread that crashed, but returning here does not guarantee that the signal
    // will be thrown again, even for SIGSEGV and friends, since the signal could
    // have been sent manually. Resend the signal with rt_tgsigqueueinfo(2) to
    // preserve the SA_SIGINFO contents.
    signal(signal_number, SIG_DFL);
  
    struct siginfo si;
    if (!info) {
      memset(&si, 0, sizeof(si));
      si.si_code = SI_USER;
      si.si_pid = getpid();
      si.si_uid = getuid();
      info = &si;
    } else if (info->si_code >= 0 || info->si_code == SI_TKILL) {
      // rt_tgsigqueueinfo(2)'s documentation appears to be incorrect on kernels
      // that contain commit 66dd34a (3.9+). The manpage claims to only allow
      // negative si_code values that are not SI_TKILL, but 66dd34a changed the
      // check to allow all si_code values in calls coming from inside the house.
    }
  
    int rc = syscall(SYS_rt_tgsigqueueinfo, getpid(), gettid(), signal_number, info);
    if (rc != 0) {
      __libc_format_log(ANDROID_LOG_FATAL, "libc", "failed to resend signal during crash: %s",
                        strerror(errno));
      _exit(0);
    }
  }
  
  __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(SIGSEGV, &action, nullptr);
  #if defined(SIGSTKFLT)
    sigaction(SIGSTKFLT, &action, nullptr);
  #endif
    sigaction(SIGTRAP, &action, nullptr);
  }
  