upload android base code part6

android/system/core/libbacktrace/BacktraceCurrent.cpp

@@ -0,0 +1,231 @@
+/*
+ * Copyright (C) 2013 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 _GNU_SOURCE 1
+#include <errno.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/param.h>
+#include <sys/ptrace.h>
+#include <sys/types.h>
+#include <ucontext.h>
+#include <unistd.h>
+
+#include <stdlib.h>
+
+#include <string>
+
+#include <backtrace/Backtrace.h>
+#include <backtrace/BacktraceMap.h>
+
+#include "BacktraceAsyncSafeLog.h"
+#include "BacktraceCurrent.h"
+#include "ThreadEntry.h"
+#include "thread_utils.h"
+
+bool BacktraceCurrent::ReadWord(uintptr_t ptr, word_t* out_value) {
+  if (!VerifyReadWordArgs(ptr, out_value)) {
+    return false;
+  }
+
+  backtrace_map_t map;
+  FillInMap(ptr, &map);
+  if (BacktraceMap::IsValid(map) && map.flags & PROT_READ) {
+    *out_value = *reinterpret_cast<word_t*>(ptr);
+    return true;
+  } else {
+    BACK_ASYNC_SAFE_LOGW("pointer %p not in a readable map", reinterpret_cast<void*>(ptr));
+    *out_value = static_cast<word_t>(-1);
+    return false;
+  }
+}
+
+size_t BacktraceCurrent::Read(uintptr_t addr, uint8_t* buffer, size_t bytes) {
+  backtrace_map_t map;
+  FillInMap(addr, &map);
+  if (!BacktraceMap::IsValid(map) || !(map.flags & PROT_READ)) {
+    return 0;
+  }
+  bytes = MIN(map.end - addr, bytes);
+  memcpy(buffer, reinterpret_cast<uint8_t*>(addr), bytes);
+  return bytes;
+}
+
+bool BacktraceCurrent::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
+  if (GetMap() == nullptr) {
+    // Without a map object, we can't do anything.
+    error_ = BACKTRACE_UNWIND_ERROR_MAP_MISSING;
+    return false;
+  }
+
+  error_ = BACKTRACE_UNWIND_NO_ERROR;
+  if (ucontext) {
+    return UnwindFromContext(num_ignore_frames, ucontext);
+  }
+
+  if (Tid() != gettid()) {
+    return UnwindThread(num_ignore_frames);
+  }
+
+  return UnwindFromContext(num_ignore_frames, nullptr);
+}
+
+bool BacktraceCurrent::DiscardFrame(const backtrace_frame_data_t& frame) {
+  if (BacktraceMap::IsValid(frame.map)) {
+    const std::string library = basename(frame.map.name.c_str());
+    if (library == "libunwind.so" || library == "libbacktrace.so") {
+      return true;
+    }
+  }
+  return false;
+}
+
+static pthread_mutex_t g_sigaction_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+// Since errno is stored per thread, changing it in the signal handler
+// modifies the value on the thread in which the signal handler executes.
+// If a signal occurs between a call and an errno check, it's possible
+// to get the errno set here. Always save and restore it just in case
+// code would modify it.
+class ErrnoRestorer {
+ public:
+  ErrnoRestorer() : saved_errno_(errno) {}
+  ~ErrnoRestorer() {
+    errno = saved_errno_;
+  }
+
+ private:
+  int saved_errno_;
+};
+
+static void SignalLogOnly(int, siginfo_t*, void*) {
+  ErrnoRestorer restore;
+
+  BACK_ASYNC_SAFE_LOGE("pid %d, tid %d: Received a spurious signal %d\n", getpid(), gettid(),
+                       THREAD_SIGNAL);
+}
+
+static void SignalHandler(int, siginfo_t*, void* sigcontext) {
+  ErrnoRestorer restore;
+
+  ThreadEntry* entry = ThreadEntry::Get(getpid(), gettid(), false);
+  if (!entry) {
+    BACK_ASYNC_SAFE_LOGE("pid %d, tid %d entry not found", getpid(), gettid());
+    return;
+  }
+
+  entry->CopyUcontextFromSigcontext(sigcontext);
+
+  // Indicate the ucontext is now valid.
+  entry->Wake();
+
+  // Pause the thread until the unwind is complete. This avoids having
+  // the thread run ahead causing problems.
+  // The number indicates that we are waiting for the second Wake() call
+  // overall which is made by the thread requesting an unwind.
+  if (entry->Wait(2)) {
+    // Do not remove the entry here because that can result in a deadlock
+    // if the code cannot properly send a signal to the thread under test.
+    entry->Wake();
+  } else {
+    // At this point, it is possible that entry has been freed, so just exit.
+    BACK_ASYNC_SAFE_LOGE("Timed out waiting for unwind thread to indicate it completed.");
+  }
+}
+
+bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {
+  // Prevent multiple threads trying to set the trigger action on different
+  // threads at the same time.
+  pthread_mutex_lock(&g_sigaction_mutex);
+
+  ThreadEntry* entry = ThreadEntry::Get(Pid(), Tid());
+  entry->Lock();
+
+  struct sigaction act, oldact;
+  memset(&act, 0, sizeof(act));
+  act.sa_sigaction = SignalHandler;
+  act.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
+  sigemptyset(&act.sa_mask);
+  if (sigaction(THREAD_SIGNAL, &act, &oldact) != 0) {
+    BACK_ASYNC_SAFE_LOGE("sigaction failed: %s", strerror(errno));
+    ThreadEntry::Remove(entry);
+    pthread_mutex_unlock(&g_sigaction_mutex);
+    error_ = BACKTRACE_UNWIND_ERROR_INTERNAL;
+    return false;
+  }
+
+  if (tgkill(Pid(), Tid(), THREAD_SIGNAL) != 0) {
+    // Do not emit an error message, this might be expected. Set the
+    // error and let the caller decide.
+    if (errno == ESRCH) {
+      error_ = BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST;
+    } else {
+      error_ = BACKTRACE_UNWIND_ERROR_INTERNAL;
+    }
+
+    sigaction(THREAD_SIGNAL, &oldact, nullptr);
+    ThreadEntry::Remove(entry);
+    pthread_mutex_unlock(&g_sigaction_mutex);
+    return false;
+  }
+
+  // Wait for the thread to get the ucontext. The number indicates
+  // that we are waiting for the first Wake() call made by the thread.
+  bool wait_completed = entry->Wait(1);
+
+  if (!wait_completed && oldact.sa_sigaction == nullptr) {
+    // If the wait failed, it could be that the signal could not be delivered
+    // within the timeout. Add a signal handler that's simply going to log
+    // something so that we don't crash if the signal eventually gets
+    // delivered. Only do this if there isn't already an action set up.
+    memset(&act, 0, sizeof(act));
+    act.sa_sigaction = SignalLogOnly;
+    act.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
+    sigemptyset(&act.sa_mask);
+    sigaction(THREAD_SIGNAL, &act, nullptr);
+  } else {
+    sigaction(THREAD_SIGNAL, &oldact, nullptr);
+  }
+  // After the thread has received the signal, allow other unwinders to
+  // continue.
+  pthread_mutex_unlock(&g_sigaction_mutex);
+
+  bool unwind_done = false;
+  if (wait_completed) {
+    unwind_done = UnwindFromContext(num_ignore_frames, entry->GetUcontext());
+
+    // Tell the signal handler to exit and release the entry.
+    entry->Wake();
+
+    // Wait for the thread to indicate it is done with the ThreadEntry.
+    if (!entry->Wait(3)) {
+      // Send a warning, but do not mark as a failure to unwind.
+      BACK_ASYNC_SAFE_LOGW("Timed out waiting for signal handler to indicate it finished.");
+    }
+  } else {
+    // Check to see if the thread has disappeared.
+    if (tgkill(Pid(), Tid(), 0) == -1 && errno == ESRCH) {
+      error_ = BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST;
+    } else {
+      error_ = BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT;
+      BACK_ASYNC_SAFE_LOGE("Timed out waiting for signal handler to get ucontext data.");
+    }
+  }
+
+  ThreadEntry::Remove(entry);
+
+  return unwind_done;
+}