debuggerd: add libdebuggerd_client.

Bug: http://b/24414818
Change-Id: I079c534d2c952b6975bf0428eb86cc7a55525737

1 files changed, 311 insertions, 0 deletions

diff --git a/debuggerd/client/debuggerd_client.cpp b/debuggerd/client/debuggerd_client.cpp
new file mode 100644
index 000000000..44e92fedd
--- /dev/null
+++ b/debuggerd/client/debuggerd_client.cpp
@@ -0,0 +1,311 @@
+/*
+ * 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 "debuggerd/client.h"
+
+#include <errno.h>
+#include <inttypes.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stddef.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>
+
+#include "private/libc_logging.h"
+
+#if defined(TARGET_IS_64_BIT) && !defined(__LP64__)
+#define SOCKET_NAME "android:debuggerd32"
+#else
+#define SOCKET_NAME "android:debuggerd"
+#endif
+
+// see man(2) prctl, specifically the section about PR_GET_NAME
+#define MAX_TASK_NAME_LEN (16)
+
+static debuggerd_callbacks_t g_callbacks;
+
+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(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 = 0;
+
+  if (g_callbacks.get_abort_message) {
+    msg.abort_msg_address = reinterpret_cast<uintptr_t>(g_callbacks.get_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;
+    if (g_callbacks.post_dump) {
+      g_callbacks.post_dump();
+    }
+    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);
+  }
+}
+
+void debuggerd_init(debuggerd_callbacks_t* callbacks) {
+  if (callbacks) {
+    g_callbacks = *callbacks;
+  }
+
+  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);
+}