platform_system_core/libbacktrace/UnwindStackMap.cpp
Christopher Ferris be788d891d Allow multiple threads sharing a map to unwind.
Add a mutex in MapInfo, and a mutex in Elf. Lock the creation of an Elf
file using the MapInfo mutex, and lock when calling Step, GetFunctionName,
or GetSoname since they can modify information in the object. It might
be beneficial to use a fine grained lock in the future.

Change the Maps object to contain a vector of MapInfo pointers rather
than the total objects. This avoids copying this data around.

Add a test to libbacktrace to verify that sharing a map while doing
unwinds in different threads works.

Add concurrency tests in libunwindstack to verify the locking works.

Add always inline to the RegsGetLocal arm and aarch64 functions. I had
a case where clang did not inline the code, so make sure this is specified.

Bug: 68813077

Test: New unit tests to cover the case. Passes all unit tests.
Test: Ran a monkey test while dumping bugreports and verified that
Test: no crashes in libunwind.
Test: Remove the locking and verified that all of the concurrenty tests fail.
Change-Id: I769e728c676f6bdae9e64ce4cdc03b6749beae03
2017-11-28 15:20:38 -08:00

122 lines
3.4 KiB
C++

/*
* Copyright (C) 2017 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 <stdint.h>
#include <stdlib.h>
#include <sys/types.h>
#include <backtrace/BacktraceMap.h>
#include <unwindstack/Elf.h>
#include <unwindstack/MapInfo.h>
#include <unwindstack/Maps.h>
#include "UnwindStackMap.h"
//-------------------------------------------------------------------------
UnwindStackMap::UnwindStackMap(pid_t pid) : BacktraceMap(pid) {}
bool UnwindStackMap::Build() {
if (pid_ == 0) {
pid_ = getpid();
stack_maps_.reset(new unwindstack::LocalMaps);
} else {
stack_maps_.reset(new unwindstack::RemoteMaps(pid_));
}
// Create the process memory object.
process_memory_ = unwindstack::Memory::CreateProcessMemory(pid_);
if (!stack_maps_->Parse()) {
return false;
}
// Iterate through the maps and fill in the backtrace_map_t structure.
for (auto* map_info : *stack_maps_) {
backtrace_map_t map;
map.start = map_info->start;
map.end = map_info->end;
map.offset = map_info->offset;
// Set to -1 so that it is demand loaded.
map.load_bias = static_cast<uintptr_t>(-1);
map.flags = map_info->flags;
map.name = map_info->name;
maps_.push_back(map);
}
return true;
}
void UnwindStackMap::FillIn(uintptr_t addr, backtrace_map_t* map) {
BacktraceMap::FillIn(addr, map);
if (map->load_bias != static_cast<uintptr_t>(-1)) {
return;
}
// Fill in the load_bias.
unwindstack::MapInfo* map_info = stack_maps_->Find(addr);
if (map_info == nullptr) {
return;
}
unwindstack::Elf* elf = map_info->GetElf(process_memory_, true);
map->load_bias = elf->GetLoadBias();
}
std::string UnwindStackMap::GetFunctionName(uintptr_t pc, uintptr_t* offset) {
*offset = 0;
unwindstack::Maps* maps = stack_maps();
// Get the map for this
unwindstack::MapInfo* map_info = maps->Find(pc);
if (map_info == nullptr || map_info->flags & PROT_DEVICE_MAP) {
return "";
}
unwindstack::Elf* elf = map_info->GetElf(process_memory(), true);
std::string name;
uint64_t func_offset;
if (!elf->GetFunctionName(elf->GetRelPc(pc, map_info), &name, &func_offset)) {
return "";
}
*offset = func_offset;
return name;
}
std::shared_ptr<unwindstack::Memory> UnwindStackMap::GetProcessMemory() {
return process_memory_;
}
//-------------------------------------------------------------------------
// 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 UnwindStackMap(0);
} else {
map = new UnwindStackMap(pid);
}
if (!map->Build()) {
delete map;
return nullptr;
}
return map;
}