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
diff --git a/libbacktrace/BacktraceCurrent.cpp b/libbacktrace/BacktraceCurrent.cpp
new file mode 100644
index 0000000..b7190e2
--- /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;
+}