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/*
* Copyright (C) 2008 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 "fault_handler.h"
#include <sys/mman.h>
#include <sys/ucontext.h>
#include "base/macros.h"
#include "globals.h"
#include "base/logging.h"
#include "base/hex_dump.h"
#include "thread.h"
#include "mirror/art_method-inl.h"
#include "mirror/class-inl.h"
#include "mirror/dex_cache.h"
#include "mirror/object_array-inl.h"
#include "mirror/object-inl.h"
#include "object_utils.h"
#include "scoped_thread_state_change.h"
#include "verify_object-inl.h"
namespace art {
// Static fault manger object accessed by signal handler.
FaultManager fault_manager;
// Signal handler called on SIGSEGV.
static void art_fault_handler(int sig, siginfo_t* info, void* context) {
fault_manager.HandleFault(sig, info, context);
}
FaultManager::FaultManager() {
sigaction(SIGSEGV, nullptr, &oldaction_);
}
FaultManager::~FaultManager() {
sigaction(SIGSEGV, &oldaction_, nullptr); // Restore old handler.
}
void FaultManager::Init() {
struct sigaction action;
action.sa_sigaction = art_fault_handler;
sigemptyset(&action.sa_mask);
action.sa_flags = SA_SIGINFO | SA_ONSTACK;
#if !defined(__mips__)
action.sa_restorer = nullptr;
#endif
sigaction(SIGSEGV, &action, &oldaction_);
}
void FaultManager::HandleFault(int sig, siginfo_t* info, void* context) {
LOG(DEBUG) << "Handling fault";
if (IsInGeneratedCode(context, true)) {
LOG(DEBUG) << "in generated code, looking for handler";
for (const auto& handler : generated_code_handlers_) {
LOG(DEBUG) << "invoking Action on handler " << handler;
if (handler->Action(sig, info, context)) {
return;
}
}
}
for (const auto& handler : other_handlers_) {
if (handler->Action(sig, info, context)) {
return;
}
}
LOG(ERROR)<< "Caught unknown SIGSEGV in ART fault handler";
oldaction_.sa_sigaction(sig, info, context);
}
void FaultManager::AddHandler(FaultHandler* handler, bool generated_code) {
if (generated_code) {
generated_code_handlers_.push_back(handler);
} else {
other_handlers_.push_back(handler);
}
}
void FaultManager::RemoveHandler(FaultHandler* handler) {
auto it = std::find(generated_code_handlers_.begin(), generated_code_handlers_.end(), handler);
if (it != generated_code_handlers_.end()) {
generated_code_handlers_.erase(it);
return;
}
auto it2 = std::find(other_handlers_.begin(), other_handlers_.end(), handler);
if (it2 != other_handlers_.end()) {
other_handlers_.erase(it);
return;
}
LOG(FATAL) << "Attempted to remove non existent handler " << handler;
}
// This function is called within the signal handler. It checks that
// the mutator_lock is held (shared). No annotalysis is done.
bool FaultManager::IsInGeneratedCode(void* context, bool check_dex_pc) {
// We can only be running Java code in the current thread if it
// is in Runnable state.
LOG(DEBUG) << "Checking for generated code";
Thread* thread = Thread::Current();
if (thread == nullptr) {
LOG(DEBUG) << "no current thread";
return false;
}
ThreadState state = thread->GetState();
if (state != kRunnable) {
LOG(DEBUG) << "not runnable";
return false;
}
// Current thread is runnable.
// Make sure it has the mutator lock.
if (!Locks::mutator_lock_->IsSharedHeld(thread)) {
LOG(DEBUG) << "no lock";
return false;
}
mirror::ArtMethod* method_obj = 0;
uintptr_t return_pc = 0;
uintptr_t sp = 0;
// Get the architecture specific method address and return address. These
// are in architecture specific files in arch/<arch>/fault_handler_<arch>.
GetMethodAndReturnPCAndSP(context, &method_obj, &return_pc, &sp);
// If we don't have a potential method, we're outta here.
LOG(DEBUG) << "potential method: " << method_obj;
if (method_obj == 0 || !IsAligned<kObjectAlignment>(method_obj)) {
LOG(DEBUG) << "no method";
return false;
}
// Verify that the potential method is indeed a method.
// TODO: check the GC maps to make sure it's an object.
// Check that the class pointer inside the object is not null and is aligned.
// TODO: Method might be not a heap address, and GetClass could fault.
mirror::Class* cls = method_obj->GetClass<kVerifyNone>();
if (cls == nullptr) {
LOG(DEBUG) << "not a class";
return false;
}
if (!IsAligned<kObjectAlignment>(cls)) {
LOG(DEBUG) << "not aligned";
return false;
}
if (!VerifyClassClass(cls)) {
LOG(DEBUG) << "not a class class";
return false;
}
// Now make sure the class is a mirror::ArtMethod.
if (!cls->IsArtMethodClass()) {
LOG(DEBUG) << "not a method";
return false;
}
// We can be certain that this is a method now. Check if we have a GC map
// at the return PC address.
if (true || kIsDebugBuild) {
LOG(DEBUG) << "looking for dex pc for return pc " << std::hex << return_pc;
const void* code = Runtime::Current()->GetInstrumentation()->GetQuickCodeFor(method_obj);
uint32_t sought_offset = return_pc - reinterpret_cast<uintptr_t>(code);
LOG(DEBUG) << "pc offset: " << std::hex << sought_offset;
}
uint32_t dexpc = method_obj->ToDexPc(return_pc, false);
LOG(DEBUG) << "dexpc: " << dexpc;
return !check_dex_pc || dexpc != DexFile::kDexNoIndex;
}
FaultHandler::FaultHandler(FaultManager* manager) : manager_(manager) {
}
//
// Null pointer fault handler
//
NullPointerHandler::NullPointerHandler(FaultManager* manager) : FaultHandler(manager) {
manager_->AddHandler(this, true);
}
//
// Suspension fault handler
//
SuspensionHandler::SuspensionHandler(FaultManager* manager) : FaultHandler(manager) {
manager_->AddHandler(this, true);
}
//
// Stack overflow fault handler
//
StackOverflowHandler::StackOverflowHandler(FaultManager* manager) : FaultHandler(manager) {
manager_->AddHandler(this, true);
}
//
// Stack trace handler, used to help get a stack trace from SIGSEGV inside of compiled code.
//
JavaStackTraceHandler::JavaStackTraceHandler(FaultManager* manager) : FaultHandler(manager) {
manager_->AddHandler(this, false);
}
bool JavaStackTraceHandler::Action(int sig, siginfo_t* siginfo, void* context) {
// Make sure that we are in the generated code, but we may not have a dex pc.
if (manager_->IsInGeneratedCode(context, false)) {
LOG(ERROR) << "Dumping java stack trace for crash in generated code";
mirror::ArtMethod* method = nullptr;
uintptr_t return_pc = 0;
uintptr_t sp = 0;
manager_->GetMethodAndReturnPCAndSP(context, &method, &return_pc, &sp);
Thread* self = Thread::Current();
// Inside of generated code, sp[0] is the method, so sp is the frame.
mirror::ArtMethod** frame = reinterpret_cast<mirror::ArtMethod**>(sp);
self->SetTopOfStack(frame, 0); // Since we don't necessarily have a dex pc, pass in 0.
self->DumpJavaStack(LOG(ERROR));
}
return false; // Return false since we want to propagate the fault to the main signal handler.
}
} // namespace art
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