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platform_system_core/libunwindstack/Unwinder.cpp
Christopher Ferris 4568f4bc0f Verify that the elf matches the expected arch. 
To avoid a case where a malicious app might try and trick the system to
create an elf and register object that mismatches, always verify that they
are the same arch.

Test: Ran unit tests.
Change-Id: I66978e9e02f8e4f396856912e7019528ead4838e
2018-10-29 18:08:09 -07:00

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9.6 KiB
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/*
* 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.
*/
#define _GNU_SOURCE 1
#include <elf.h>
#include <inttypes.h>
#include <stdint.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <algorithm>
#include <android-base/stringprintf.h>
#include <unwindstack/Elf.h>
#include <unwindstack/JitDebug.h>
#include <unwindstack/MapInfo.h>
#include <unwindstack/Maps.h>
#include <unwindstack/Unwinder.h>
#if !defined(NO_LIBDEXFILE_SUPPORT)
#include <unwindstack/DexFiles.h>
#endif
namespace unwindstack {
// Inject extra 'virtual' frame that represents the dex pc data.
// The dex pc is a magic register defined in the Mterp interpreter,
// and thus it will be restored/observed in the frame after it.
// Adding the dex frame first here will create something like:
// #7 pc 0015fa20 core.vdex java.util.Arrays.binarySearch+8
// #8 pc 006b1ba1 libartd.so ExecuteMterpImpl+14625
// #9 pc 0039a1ef libartd.so art::interpreter::Execute+719
void Unwinder::FillInDexFrame() {
size_t frame_num = frames_.size();
frames_.resize(frame_num + 1);
FrameData* frame = &frames_.at(frame_num);
frame->num = frame_num;
uint64_t dex_pc = regs_->dex_pc();
frame->pc = dex_pc;
frame->sp = regs_->sp();
MapInfo* info = maps_->Find(dex_pc);
if (info != nullptr) {
frame->map_start = info->start;
frame->map_end = info->end;
frame->map_offset = info->offset;
frame->map_load_bias = info->load_bias;
frame->map_flags = info->flags;
if (resolve_names_) {
frame->map_name = info->name;
}
frame->rel_pc = dex_pc - info->start;
} else {
frame->rel_pc = dex_pc;
return;
}
if (!resolve_names_) {
return;
}
#if !defined(NO_LIBDEXFILE_SUPPORT)
if (dex_files_ == nullptr) {
return;
}
dex_files_->GetMethodInformation(maps_, info, dex_pc, &frame->function_name,
&frame->function_offset);
#endif
}
void Unwinder::FillInFrame(MapInfo* map_info, Elf* elf, uint64_t rel_pc, uint64_t func_pc,
uint64_t pc_adjustment) {
size_t frame_num = frames_.size();
frames_.resize(frame_num + 1);
FrameData* frame = &frames_.at(frame_num);
frame->num = frame_num;
frame->sp = regs_->sp();
frame->rel_pc = rel_pc - pc_adjustment;
frame->pc = regs_->pc() - pc_adjustment;
if (map_info == nullptr) {
return;
}
if (resolve_names_) {
frame->map_name = map_info->name;
}
frame->map_offset = map_info->offset;
frame->map_start = map_info->start;
frame->map_end = map_info->end;
frame->map_flags = map_info->flags;
frame->map_load_bias = elf->GetLoadBias();
if (!resolve_names_ ||
!elf->GetFunctionName(func_pc, &frame->function_name, &frame->function_offset)) {
frame->function_name = "";
frame->function_offset = 0;
}
}
static bool ShouldStop(const std::vector<std::string>* map_suffixes_to_ignore,
std::string& map_name) {
if (map_suffixes_to_ignore == nullptr) {
return false;
}
auto pos = map_name.find_last_of('.');
if (pos == std::string::npos) {
return false;
}
return std::find(map_suffixes_to_ignore->begin(), map_suffixes_to_ignore->end(),
map_name.substr(pos + 1)) != map_suffixes_to_ignore->end();
}
void Unwinder::Unwind(const std::vector<std::string>* initial_map_names_to_skip,
const std::vector<std::string>* map_suffixes_to_ignore) {
frames_.clear();
last_error_.code = ERROR_NONE;
last_error_.address = 0;
ArchEnum arch = regs_->Arch();
bool return_address_attempt = false;
bool adjust_pc = false;
std::unique_ptr<JitDebug> jit_debug;
for (; frames_.size() < max_frames_;) {
uint64_t cur_pc = regs_->pc();
uint64_t cur_sp = regs_->sp();
MapInfo* map_info = maps_->Find(regs_->pc());
uint64_t pc_adjustment = 0;
uint64_t step_pc;
uint64_t rel_pc;
Elf* elf;
if (map_info == nullptr) {
step_pc = regs_->pc();
rel_pc = step_pc;
last_error_.code = ERROR_INVALID_MAP;
} else {
if (ShouldStop(map_suffixes_to_ignore, map_info->name)) {
break;
}
elf = map_info->GetElf(process_memory_, arch);
step_pc = regs_->pc();
rel_pc = elf->GetRelPc(step_pc, map_info);
// Everyone except elf data in gdb jit debug maps uses the relative pc.
if (!(map_info->flags & MAPS_FLAGS_JIT_SYMFILE_MAP)) {
step_pc = rel_pc;
}
if (adjust_pc) {
pc_adjustment = regs_->GetPcAdjustment(rel_pc, elf);
} else {
pc_adjustment = 0;
}
step_pc -= pc_adjustment;
// If the pc is in an invalid elf file, try and get an Elf object
// using the jit debug information.
if (!elf->valid() && jit_debug_ != nullptr) {
uint64_t adjusted_jit_pc = regs_->pc() - pc_adjustment;
Elf* jit_elf = jit_debug_->GetElf(maps_, adjusted_jit_pc);
if (jit_elf != nullptr) {
// The jit debug information requires a non relative adjusted pc.
step_pc = adjusted_jit_pc;
elf = jit_elf;
}
}
}
if (map_info == nullptr || initial_map_names_to_skip == nullptr ||
std::find(initial_map_names_to_skip->begin(), initial_map_names_to_skip->end(),
basename(map_info->name.c_str())) == initial_map_names_to_skip->end()) {
if (regs_->dex_pc() != 0) {
// Add a frame to represent the dex file.
FillInDexFrame();
// Clear the dex pc so that we don't repeat this frame later.
regs_->set_dex_pc(0);
// Make sure there is enough room for the real frame.
if (frames_.size() == max_frames_) {
last_error_.code = ERROR_MAX_FRAMES_EXCEEDED;
break;
}
}
FillInFrame(map_info, elf, rel_pc, step_pc, pc_adjustment);
// Once a frame is added, stop skipping frames.
initial_map_names_to_skip = nullptr;
}
adjust_pc = true;
bool stepped;
bool in_device_map = false;
if (map_info == nullptr) {
stepped = false;
} else {
if (map_info->flags & MAPS_FLAGS_DEVICE_MAP) {
// Do not stop here, fall through in case we are
// in the speculative unwind path and need to remove
// some of the speculative frames.
stepped = false;
in_device_map = true;
} else {
MapInfo* sp_info = maps_->Find(regs_->sp());
if (sp_info != nullptr && sp_info->flags & MAPS_FLAGS_DEVICE_MAP) {
// Do not stop here, fall through in case we are
// in the speculative unwind path and need to remove
// some of the speculative frames.
stepped = false;
in_device_map = true;
} else {
bool finished;
stepped = elf->Step(rel_pc, step_pc, regs_, process_memory_.get(), &finished);
elf->GetLastError(&last_error_);
if (stepped && finished) {
break;
}
}
}
}
if (!stepped) {
if (return_address_attempt) {
// Remove the speculative frame.
frames_.pop_back();
break;
} else if (in_device_map) {
// Do not attempt any other unwinding, pc or sp is in a device
// map.
break;
} else {
// Steping didn't work, try this secondary method.
if (!regs_->SetPcFromReturnAddress(process_memory_.get())) {
break;
}
return_address_attempt = true;
}
} else {
return_address_attempt = false;
if (max_frames_ == frames_.size()) {
last_error_.code = ERROR_MAX_FRAMES_EXCEEDED;
}
}
// If the pc and sp didn't change, then consider everything stopped.
if (cur_pc == regs_->pc() && cur_sp == regs_->sp()) {
last_error_.code = ERROR_REPEATED_FRAME;
break;
}
}
}
std::string Unwinder::FormatFrame(size_t frame_num) {
if (frame_num >= frames_.size()) {
return "";
}
return FormatFrame(frames_[frame_num], regs_->Is32Bit());
}
std::string Unwinder::FormatFrame(const FrameData& frame, bool is32bit) {
std::string data;
if (is32bit) {
data += android::base::StringPrintf(" #%02zu pc %08" PRIx64, frame.num, frame.rel_pc);
} else {
data += android::base::StringPrintf(" #%02zu pc %016" PRIx64, frame.num, frame.rel_pc);
}
if (frame.map_offset != 0) {
data += android::base::StringPrintf(" (offset 0x%" PRIx64 ")", frame.map_offset);
}
if (frame.map_start == frame.map_end) {
// No valid map associated with this frame.
data += " <unknown>";
} else if (!frame.map_name.empty()) {
data += " " + frame.map_name;
} else {
data += android::base::StringPrintf(" <anonymous:%" PRIx64 ">", frame.map_start);
}
if (!frame.function_name.empty()) {
data += " (" + frame.function_name;
if (frame.function_offset != 0) {
data += android::base::StringPrintf("+%" PRId64, frame.function_offset);
}
data += ')';
}
return data;
}
void Unwinder::SetJitDebug(JitDebug* jit_debug, ArchEnum arch) {
jit_debug->SetArch(arch);
jit_debug_ = jit_debug;
}
#if !defined(NO_LIBDEXFILE_SUPPORT)
void Unwinder::SetDexFiles(DexFiles* dex_files, ArchEnum arch) {
dex_files->SetArch(arch);
dex_files_ = dex_files;
}
#endif
} // namespace unwindstack
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