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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.
*/
#include <pthread.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <backtrace/BacktraceMap.h>
#include <libunwind.h>
#include "BacktraceLog.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.
//-------------------------------------------------------------------------
UnwindMap::UnwindMap(pid_t pid) : BacktraceMap(pid) {
unw_map_cursor_clear(&map_cursor_);
}
UnwindMapRemote::UnwindMapRemote(pid_t pid) : UnwindMap(pid) {
}
UnwindMapRemote::~UnwindMapRemote() {
unw_map_cursor_destroy(&map_cursor_);
unw_map_cursor_clear(&map_cursor_);
}
bool UnwindMapRemote::GenerateMap() {
// 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_next(&map_cursor_, &unw_map)) {
backtrace_map_t map;
map.start = unw_map.start;
map.end = unw_map.end;
map.offset = unw_map.offset;
map.load_bias = unw_map.load_base;
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;
}
bool UnwindMapRemote::Build() {
return (unw_map_cursor_create(&map_cursor_, pid_) == 0) && GenerateMap();
}
UnwindMapLocal::UnwindMapLocal() : UnwindMap(getpid()), map_created_(false) {
pthread_rwlock_init(&map_lock_, nullptr);
}
UnwindMapLocal::~UnwindMapLocal() {
if (map_created_) {
unw_map_local_destroy();
unw_map_cursor_clear(&map_cursor_);
}
}
bool UnwindMapLocal::GenerateMap() {
// Lock so that multiple threads cannot modify the maps data at the
// same time.
pthread_rwlock_wrlock(&map_lock_);
// It's possible for the map to be regenerated while this loop is occurring.
// If that happens, get the map again, but only try at most three times
// before giving up.
bool generated = false;
for (int i = 0; i < 3; i++) {
maps_.clear();
// Save the map data retrieved so we can tell if it changes.
unw_map_local_cursor_get(&map_cursor_);
unw_map_t unw_map;
int ret;
while ((ret = unw_map_local_cursor_get_next(&map_cursor_, &unw_map)) > 0) {
backtrace_map_t map;
map.start = unw_map.start;
map.end = unw_map.end;
map.offset = unw_map.offset;
map.load_bias = unw_map.load_base;
map.flags = unw_map.flags;
map.name = unw_map.path;
free(unw_map.path);
// The maps are in descending order, but we want them in ascending order.
maps_.push_front(map);
}
// Check to see if the map changed while getting the data.
if (ret != -UNW_EINVAL) {
generated = true;
break;
}
}
pthread_rwlock_unlock(&map_lock_);
if (!generated) {
BACK_LOGW("Unable to generate the map.");
}
return generated;
}
bool UnwindMapLocal::Build() {
return (map_created_ = (unw_map_local_create() == 0)) && GenerateMap();;
}
void UnwindMapLocal::FillIn(uintptr_t addr, backtrace_map_t* map) {
BacktraceMap::FillIn(addr, map);
if (!IsValid(*map)) {
// Check to see if the underlying map changed and regenerate the map
// if it did.
if (unw_map_local_cursor_valid(&map_cursor_) < 0) {
if (GenerateMap()) {
BacktraceMap::FillIn(addr, map);
}
}
}
}
//-------------------------------------------------------------------------
// BacktraceMap create function.
//-------------------------------------------------------------------------
BacktraceMap* BacktraceMap::Create(pid_t pid, bool uncached) {
BacktraceMap* map;
if (uncached) {
// Force use of the base class to parse the maps when this call is made.
map = new BacktraceMap(pid);
} else if (pid == getpid()) {
map = new UnwindMapLocal();
} else {
map = new UnwindMapRemote(pid);
}
if (!map->Build()) {
delete map;
return nullptr;
}
return map;
}
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