Refactor the code.

The object hierarchy was confusing and convoluted. This removes
a lot of unnecessary code, and consolidates the BacktraceCurrent
and BacktraceThread code into BacktraceCurrent.

Change-Id: I01c8407d493712a48169df49dd3ff46db4a7c3ae

1 files changed, 144 insertions, 0 deletions

diff --git a/libbacktrace/BacktraceCurrent.cpp b/libbacktrace/BacktraceCurrent.cpp
new file mode 100644
index 000000000..b7190e256
--- /dev/null
+++ b/libbacktrace/BacktraceCurrent.cpp
@@ -0,0 +1,144 @@
+/*
+ * 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.
+ */
+
+#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 <string>
+
+#include <backtrace/Backtrace.h>
+#include <backtrace/BacktraceMap.h>
+
+#include "BacktraceCurrent.h"
+#include "BacktraceLog.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_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 (ucontext) {
+    return UnwindFromContext(num_ignore_frames, ucontext);
+  }
+
+  if (Tid() != gettid()) {
+    return UnwindThread(num_ignore_frames);
+  }
+
+  return UnwindFromContext(num_ignore_frames, nullptr);
+}
+
+static pthread_mutex_t g_sigaction_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+static void SignalHandler(int, siginfo_t*, void* sigcontext) {
+  ThreadEntry* entry = ThreadEntry::Get(getpid(), gettid(), false);
+  if (!entry) {
+    BACK_LOGW("Unable to find pid %d tid %d information", 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.
+  entry->Wait(2);
+
+  ThreadEntry::Remove(entry);
+}
+
+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_LOGW("sigaction failed %s", strerror(errno));
+    entry->Unlock();
+    ThreadEntry::Remove(entry);
+    pthread_mutex_unlock(&g_sigaction_mutex);
+    return false;
+  }
+
+  if (tgkill(Pid(), Tid(), THREAD_SIGNAL) != 0) {
+    BACK_LOGW("tgkill %d failed: %s", Tid(), strerror(errno));
+    sigaction(THREAD_SIGNAL, &oldact, nullptr);
+    entry->Unlock();
+    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.
+  entry->Wait(1);
+
+  // After the thread has received the signal, allow other unwinders to
+  // continue.
+  sigaction(THREAD_SIGNAL, &oldact, nullptr);
+  pthread_mutex_unlock(&g_sigaction_mutex);
+
+  bool unwind_done = UnwindFromContext(num_ignore_frames, entry->GetUcontext());
+
+  // Tell the signal handler to exit and release the entry.
+  entry->Wake();
+
+  return unwind_done;
+}