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/*
* Copyright (C) 2014 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 "libbacktrace"
#include <pthread.h>
#include <sys/types.h>
#include <unistd.h>
#include <backtrace/BacktraceMap.h>
#include <libunwind.h>
#include "UnwindMap.h"
//-------------------------------------------------------------------------
// libunwind has a single shared address space for the current process
// aka local. If multiple maps are created for the current pid, then
// only update the local address space once, and keep a reference count
// of maps using the same map cursor.
//-------------------------------------------------------------------------
static pthread_mutex_t g_map_mutex = PTHREAD_MUTEX_INITIALIZER;
static unw_map_cursor_t g_map_cursor;
static int g_map_references = 0;
UnwindMap::UnwindMap(pid_t pid) : BacktraceMap(pid) {
map_cursor_.map_list = NULL;
}
UnwindMap::~UnwindMap() {
if (pid_ == getpid()) {
pthread_mutex_lock(&g_map_mutex);
if (--g_map_references == 0) {
// Clear the local address space map.
unw_map_local_set(NULL);
unw_map_cursor_destroy(&map_cursor_);
}
pthread_mutex_unlock(&g_map_mutex);
} else {
unw_map_cursor_destroy(&map_cursor_);
}
}
bool UnwindMap::Build() {
bool return_value = true;
if (pid_ == getpid()) {
pthread_mutex_lock(&g_map_mutex);
if (g_map_references == 0) {
return_value = (unw_map_cursor_create(&map_cursor_, pid_) == 0);
if (return_value) {
// Set the local address space map to our new map.
unw_map_local_set(&map_cursor_);
g_map_references = 1;
g_map_cursor = map_cursor_;
}
} else {
g_map_references++;
map_cursor_ = g_map_cursor;
}
pthread_mutex_unlock(&g_map_mutex);
} else {
return_value = (unw_map_cursor_create(&map_cursor_, pid_) == 0);
}
if (!return_value)
return false;
// Use the map_cursor information to construct the BacktraceMap data
// rather than reparsing /proc/self/maps.
unw_map_cursor_reset(&map_cursor_);
unw_map_t unw_map;
while (unw_map_cursor_get(&map_cursor_, &unw_map)) {
backtrace_map_t map;
map.start = unw_map.start;
map.end = unw_map.end;
map.flags = unw_map.flags;
map.name = unw_map.path;
// The maps are in descending order, but we want them in ascending order.
maps_.push_front(map);
}
return true;
}
//-------------------------------------------------------------------------
// BacktraceMap create function.
//-------------------------------------------------------------------------
BacktraceMap* BacktraceMap::Create(pid_t pid) {
BacktraceMap* map = new UnwindMap(pid);
if (!map->Build()) {
delete map;
return NULL;
}
return map;
}
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