12385e3ad0
The backtrace structure used to include a pointer to a backtrace_map_t that represented the map data for a particular pc. This introduced a race condition where the pointer could be discarded, but the backtrace structure still contained a pointer to garbage memory. Now all of the map information is right in the structure. Bug: 19028453 Change-Id: If7088a73f3c6bf1f3bc8cdd2bb4b62e7cab831c0
148 lines
4.1 KiB
C++
148 lines
4.1 KiB
C++
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <pthread.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <backtrace/BacktraceMap.h>
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#include <libunwind.h>
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#include "BacktraceLog.h"
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#include "UnwindMap.h"
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//-------------------------------------------------------------------------
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// libunwind has a single shared address space for the current process
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// aka local. If multiple maps are created for the current pid, then
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// only update the local address space once, and keep a reference count
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// of maps using the same map cursor.
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//-------------------------------------------------------------------------
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UnwindMap::UnwindMap(pid_t pid) : BacktraceMap(pid) {
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}
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UnwindMap::~UnwindMap() {
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unw_map_cursor_destroy(&map_cursor_);
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unw_map_cursor_clear(&map_cursor_);
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}
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bool UnwindMap::GenerateMap() {
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// Use the map_cursor information to construct the BacktraceMap data
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// rather than reparsing /proc/self/maps.
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unw_map_cursor_reset(&map_cursor_);
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unw_map_t unw_map;
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while (unw_map_cursor_get_next(&map_cursor_, &unw_map)) {
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backtrace_map_t map;
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map.start = unw_map.start;
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map.end = unw_map.end;
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map.flags = unw_map.flags;
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map.name = unw_map.path;
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// The maps are in descending order, but we want them in ascending order.
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maps_.push_front(map);
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}
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return true;
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}
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bool UnwindMap::Build() {
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return (unw_map_cursor_create(&map_cursor_, pid_) == 0) && GenerateMap();
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}
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UnwindMapLocal::UnwindMapLocal() : UnwindMap(getpid()), map_created_(false) {
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}
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UnwindMapLocal::~UnwindMapLocal() {
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if (map_created_) {
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unw_map_local_destroy();
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unw_map_cursor_clear(&map_cursor_);
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}
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}
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bool UnwindMapLocal::GenerateMap() {
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// It's possible for the map to be regenerated while this loop is occurring.
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// If that happens, get the map again, but only try at most three times
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// before giving up.
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for (int i = 0; i < 3; i++) {
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maps_.clear();
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unw_map_local_cursor_get(&map_cursor_);
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unw_map_t unw_map;
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int ret;
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while ((ret = unw_map_local_cursor_get_next(&map_cursor_, &unw_map)) > 0) {
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backtrace_map_t map;
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map.start = unw_map.start;
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map.end = unw_map.end;
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map.flags = unw_map.flags;
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map.name = unw_map.path;
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free(unw_map.path);
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// The maps are in descending order, but we want them in ascending order.
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maps_.push_front(map);
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}
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// Check to see if the map changed while getting the data.
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if (ret != -UNW_EINVAL) {
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return true;
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}
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}
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BACK_LOGW("Unable to generate the map.");
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return false;
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}
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bool UnwindMapLocal::Build() {
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return (map_created_ = (unw_map_local_create() == 0)) && GenerateMap();;
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}
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void UnwindMapLocal::FillIn(uintptr_t addr, backtrace_map_t* map) {
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BacktraceMap::FillIn(addr, map);
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if (!IsValid(*map)) {
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// Check to see if the underlying map changed and regenerate the map
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// if it did.
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if (unw_map_local_cursor_valid(&map_cursor_) < 0) {
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if (GenerateMap()) {
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BacktraceMap::FillIn(addr, map);
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}
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}
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}
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}
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//-------------------------------------------------------------------------
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// BacktraceMap create function.
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//-------------------------------------------------------------------------
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BacktraceMap* BacktraceMap::Create(pid_t pid, bool uncached) {
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BacktraceMap* map;
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if (uncached) {
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// Force use of the base class to parse the maps when this call is made.
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map = new BacktraceMap(pid);
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} else if (pid == getpid()) {
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map = new UnwindMapLocal();
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} else {
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map = new UnwindMap(pid);
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}
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if (!map->Build()) {
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delete map;
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return NULL;
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}
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return map;
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}
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