Snap for 4422658 from d85553c0 to pi-release

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/*

 * Copyright (C) 2016 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.

 */

#define LOG_TAG "debuggerd-signal"

#include <errno.h>

#include <pthread.h>

#include <signal.h>

#include <stdlib.h>

#include <string.h>

#include <sys/socket.h>

#include <sys/syscall.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <unistd.h>

#include <log/log.h>

#include "signal_sender.h"

static int signal_fd = -1;

static pid_t signal_pid;

struct signal_message {

  pid_t pid;

  pid_t tid;

  int signal;

};

static void set_signal_sender_process_name() {

#if defined(__LP64__)

  static constexpr char long_process_name[] = "debuggerd64:signaller";

  static constexpr char short_process_name[] = "debuggerd64:sig";

  static_assert(sizeof(long_process_name) <= sizeof("/system/bin/debuggerd64"), "");

#else

  static constexpr char long_process_name[] = "debuggerd:signaller";

  static constexpr char short_process_name[] = "debuggerd:sig";

  static_assert(sizeof(long_process_name) <= sizeof("/system/bin/debuggerd"), "");

#endif

  // pthread_setname_np has a maximum length of 16 chars, including null terminator.

  static_assert(sizeof(short_process_name) <= 16, "");

  pthread_setname_np(pthread_self(), short_process_name);

  char* progname = const_cast<char*>(getprogname());

  if (strlen(progname) <= strlen(long_process_name)) {

    ALOGE("debuggerd: unexpected progname %s", progname);

    return;

  }

  memset(progname, 0, strlen(progname));

  strcpy(progname, long_process_name);

}

// Fork a process to send signals for the worker processes to use after they've dropped privileges.

bool start_signal_sender() {

  if (signal_pid != 0) {

    ALOGE("debuggerd: attempted to start signal sender multiple times");

    return false;

  }

  int sfd[2];

  if (socketpair(AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC, 0, sfd) != 0) {

    ALOGE("debuggerd: failed to create socketpair for signal sender: %s", strerror(errno));

    return false;

  }

  pid_t parent = getpid();

  pid_t fork_pid = fork();

  if (fork_pid == -1) {

    ALOGE("debuggerd: failed to initialize signal sender: fork failed: %s", strerror(errno));

    return false;

  } else if (fork_pid == 0) {

    close(sfd[1]);

    set_signal_sender_process_name();

    while (true) {

      signal_message msg;

      int rc = TEMP_FAILURE_RETRY(read(sfd[0], &msg, sizeof(msg)));

      if (rc < 0) {

        ALOGE("debuggerd: signal sender failed to read from socket");

        break;

      } else if (rc != sizeof(msg)) {

        ALOGE("debuggerd: signal sender read unexpected number of bytes: %d", rc);

        break;

      }

      // Report success after sending a signal

      int err = 0;

      if (msg.tid > 0) {

        if (syscall(SYS_tgkill, msg.pid, msg.tid, msg.signal) != 0) {

          err = errno;

        }

      } else {

        if (kill(msg.pid, msg.signal) != 0) {

          err = errno;

        }

      }

      if (TEMP_FAILURE_RETRY(write(sfd[0], &err, sizeof(err))) < 0) {

        ALOGE("debuggerd: signal sender failed to write: %s", strerror(errno));

      }

    }

    // Our parent proably died, but if not, kill them.

    if (getppid() == parent) {

      kill(parent, SIGKILL);

    }

    _exit(1);

  } else {

    close(sfd[0]);

    signal_fd = sfd[1];

    signal_pid = fork_pid;

    return true;

  }

}

bool stop_signal_sender() {

  if (signal_pid <= 0) {

    return false;

  }

  if (kill(signal_pid, SIGKILL) != 0) {

    ALOGE("debuggerd: failed to kill signal sender: %s", strerror(errno));

    return false;

  }

  close(signal_fd);

  signal_fd = -1;

  int status;

  waitpid(signal_pid, &status, 0);

  signal_pid = 0;

  return true;

}

bool send_signal(pid_t pid, pid_t tid, int signal) {

  if (signal_fd == -1) {

    ALOGE("debuggerd: attempted to send signal before signal sender was started");

    errno = EHOSTUNREACH;

    return false;

  }

  signal_message msg = {.pid = pid, .tid = tid, .signal = signal };

  if (TEMP_FAILURE_RETRY(write(signal_fd, &msg, sizeof(msg))) < 0) {

    ALOGE("debuggerd: failed to send message to signal sender: %s", strerror(errno));

    errno = EHOSTUNREACH;

    return false;

  }

  int response;

  ssize_t rc = TEMP_FAILURE_RETRY(read(signal_fd, &response, sizeof(response)));

  if (rc == 0) {

    ALOGE("debuggerd: received EOF from signal sender");

    errno = EHOSTUNREACH;

    return false;

  } else if (rc < 0) {

    ALOGE("debuggerd: failed to receive response from signal sender: %s", strerror(errno));

    errno = EHOSTUNREACH;

    return false;

  }

  if (response == 0) {

    return true;

  }

  errno = response;

  return false;

}

    defaults: ["libbacktrace_common"],

    host_supported: true,

    cflags: [

        "-Wexit-time-destructors",

    ],

    srcs: [

        "BacktraceMap.cpp",

    ],

    shared_libs: [

        "libbacktrace",

        "libbase",

        "libunwindstack",

    ],

}

bool Backtrace::Unwind(unwindstack::Regs* regs, BacktraceMap* back_map,

                       std::vector<backtrace_frame_data_t>* frames, size_t num_ignore_frames) {

  static std::vector<std::string> skip_names{"libunwindstack.so", "libbacktrace.so"};

  std::vector<std::string> skip_names{"libunwindstack.so", "libbacktrace.so"};

  UnwindStackMap* stack_map = reinterpret_cast<UnwindStackMap*>(back_map);

  auto process_memory = stack_map->process_memory();

  unwindstack::Unwinder unwinder(MAX_BACKTRACE_FRAMES + num_ignore_frames, stack_map->stack_maps(),