| /* |
| * 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 <setjmp.h> |
| #include <sys/mman.h> |
| #include <sys/ucontext.h> |
| |
| #include "art_method-inl.h" |
| #include "base/safe_copy.h" |
| #include "base/stl_util.h" |
| #include "mirror/class.h" |
| #include "mirror/object_reference.h" |
| #include "oat_quick_method_header.h" |
| #include "sigchain.h" |
| #include "thread-current-inl.h" |
| #include "verify_object-inl.h" |
| |
| namespace art { |
| // Static fault manger object accessed by signal handler. |
| FaultManager fault_manager; |
| |
| extern "C" __attribute__((visibility("default"))) void art_sigsegv_fault() { |
| // Set a breakpoint here to be informed when a SIGSEGV is unhandled by ART. |
| VLOG(signals)<< "Caught unknown SIGSEGV in ART fault handler - chaining to next handler."; |
| } |
| |
| // Signal handler called on SIGSEGV. |
| static bool art_fault_handler(int sig, siginfo_t* info, void* context) { |
| return fault_manager.HandleFault(sig, info, context); |
| } |
| |
| #if defined(__linux__) |
| |
| // Change to verify the safe implementations against the original ones. |
| constexpr bool kVerifySafeImpls = false; |
| |
| // Provide implementations of ArtMethod::GetDeclaringClass and VerifyClassClass that use SafeCopy |
| // to safely dereference pointers which are potentially garbage. |
| // Only available on Linux due to availability of SafeCopy. |
| |
| static mirror::Class* SafeGetDeclaringClass(ArtMethod* method) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| char* method_declaring_class = |
| reinterpret_cast<char*>(method) + ArtMethod::DeclaringClassOffset().SizeValue(); |
| |
| // ArtMethod::declaring_class_ is a GcRoot<mirror::Class>. |
| // Read it out into as a CompressedReference directly for simplicity's sake. |
| mirror::CompressedReference<mirror::Class> cls; |
| ssize_t rc = SafeCopy(&cls, method_declaring_class, sizeof(cls)); |
| CHECK_NE(-1, rc); |
| |
| if (kVerifySafeImpls) { |
| mirror::Class* actual_class = method->GetDeclaringClassUnchecked<kWithoutReadBarrier>(); |
| CHECK_EQ(actual_class, cls.AsMirrorPtr()); |
| } |
| |
| if (rc != sizeof(cls)) { |
| return nullptr; |
| } |
| |
| return cls.AsMirrorPtr(); |
| } |
| |
| static mirror::Class* SafeGetClass(mirror::Object* obj) REQUIRES_SHARED(Locks::mutator_lock_) { |
| char* obj_cls = reinterpret_cast<char*>(obj) + mirror::Object::ClassOffset().SizeValue(); |
| |
| mirror::HeapReference<mirror::Class> cls = |
| mirror::HeapReference<mirror::Class>::FromMirrorPtr(nullptr); |
| ssize_t rc = SafeCopy(&cls, obj_cls, sizeof(cls)); |
| CHECK_NE(-1, rc); |
| |
| if (kVerifySafeImpls) { |
| mirror::Class* actual_class = obj->GetClass<kVerifyNone>(); |
| CHECK_EQ(actual_class, cls.AsMirrorPtr()); |
| } |
| |
| if (rc != sizeof(cls)) { |
| return nullptr; |
| } |
| |
| return cls.AsMirrorPtr(); |
| } |
| |
| static bool SafeVerifyClassClass(mirror::Class* cls) REQUIRES_SHARED(Locks::mutator_lock_) { |
| mirror::Class* c_c = SafeGetClass(cls); |
| bool result = c_c != nullptr && c_c == SafeGetClass(c_c); |
| |
| if (kVerifySafeImpls) { |
| CHECK_EQ(VerifyClassClass(cls), result); |
| } |
| |
| return result; |
| } |
| |
| #else |
| |
| static mirror::Class* SafeGetDeclaringClass(ArtMethod* method_obj) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| return method_obj->GetDeclaringClassUnchecked<kWithoutReadBarrier>(); |
| } |
| |
| static bool SafeVerifyClassClass(mirror::Class* cls) REQUIRES_SHARED(Locks::mutator_lock_) { |
| return VerifyClassClass(cls); |
| } |
| #endif |
| |
| |
| FaultManager::FaultManager() : initialized_(false) { |
| sigaction(SIGSEGV, nullptr, &oldaction_); |
| } |
| |
| FaultManager::~FaultManager() { |
| } |
| |
| void FaultManager::Init() { |
| CHECK(!initialized_); |
| sigset_t mask; |
| sigfillset(&mask); |
| sigdelset(&mask, SIGABRT); |
| sigdelset(&mask, SIGBUS); |
| sigdelset(&mask, SIGFPE); |
| sigdelset(&mask, SIGILL); |
| sigdelset(&mask, SIGSEGV); |
| |
| SigchainAction sa = { |
| .sc_sigaction = art_fault_handler, |
| .sc_mask = mask, |
| .sc_flags = 0UL, |
| }; |
| |
| AddSpecialSignalHandlerFn(SIGSEGV, &sa); |
| initialized_ = true; |
| } |
| |
| void FaultManager::Release() { |
| if (initialized_) { |
| RemoveSpecialSignalHandlerFn(SIGSEGV, art_fault_handler); |
| initialized_ = false; |
| } |
| } |
| |
| void FaultManager::Shutdown() { |
| if (initialized_) { |
| Release(); |
| |
| // Free all handlers. |
| STLDeleteElements(&generated_code_handlers_); |
| STLDeleteElements(&other_handlers_); |
| } |
| } |
| |
| bool FaultManager::HandleFaultByOtherHandlers(int sig, siginfo_t* info, void* context) { |
| if (other_handlers_.empty()) { |
| return false; |
| } |
| |
| Thread* self = Thread::Current(); |
| |
| DCHECK(self != nullptr); |
| DCHECK(Runtime::Current() != nullptr); |
| DCHECK(Runtime::Current()->IsStarted()); |
| for (const auto& handler : other_handlers_) { |
| if (handler->Action(sig, info, context)) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| bool FaultManager::HandleFault(int sig, siginfo_t* info, void* context) { |
| VLOG(signals) << "Handling fault"; |
| |
| #ifdef TEST_NESTED_SIGNAL |
| // Simulate a crash in a handler. |
| raise(SIGSEGV); |
| #endif |
| |
| if (IsInGeneratedCode(info, context, true)) { |
| VLOG(signals) << "in generated code, looking for handler"; |
| for (const auto& handler : generated_code_handlers_) { |
| VLOG(signals) << "invoking Action on handler " << handler; |
| if (handler->Action(sig, info, context)) { |
| // We have handled a signal so it's time to return from the |
| // signal handler to the appropriate place. |
| return true; |
| } |
| } |
| |
| // We hit a signal we didn't handle. This might be something for which |
| // we can give more information about so call all registered handlers to |
| // see if it is. |
| if (HandleFaultByOtherHandlers(sig, info, context)) { |
| return true; |
| } |
| } |
| |
| // Set a breakpoint in this function to catch unhandled signals. |
| art_sigsegv_fault(); |
| return false; |
| } |
| |
| void FaultManager::AddHandler(FaultHandler* handler, bool generated_code) { |
| DCHECK(initialized_); |
| 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(siginfo_t* siginfo, void* context, bool check_dex_pc) { |
| // We can only be running Java code in the current thread if it |
| // is in Runnable state. |
| VLOG(signals) << "Checking for generated code"; |
| Thread* thread = Thread::Current(); |
| if (thread == nullptr) { |
| VLOG(signals) << "no current thread"; |
| return false; |
| } |
| |
| ThreadState state = thread->GetState(); |
| if (state != kRunnable) { |
| VLOG(signals) << "not runnable"; |
| return false; |
| } |
| |
| // Current thread is runnable. |
| // Make sure it has the mutator lock. |
| if (!Locks::mutator_lock_->IsSharedHeld(thread)) { |
| VLOG(signals) << "no lock"; |
| return false; |
| } |
| |
| ArtMethod* method_obj = nullptr; |
| 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(siginfo, context, &method_obj, &return_pc, &sp); |
| |
| // If we don't have a potential method, we're outta here. |
| VLOG(signals) << "potential method: " << method_obj; |
| // TODO: Check linear alloc and image. |
| DCHECK_ALIGNED(ArtMethod::Size(kRuntimePointerSize), sizeof(void*)) |
| << "ArtMethod is not pointer aligned"; |
| if (method_obj == nullptr || !IsAligned<sizeof(void*)>(method_obj)) { |
| VLOG(signals) << "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. |
| // No read barrier because method_obj may not be a real object. |
| mirror::Class* cls = SafeGetDeclaringClass(method_obj); |
| if (cls == nullptr) { |
| VLOG(signals) << "not a class"; |
| return false; |
| } |
| |
| if (!IsAligned<kObjectAlignment>(cls)) { |
| VLOG(signals) << "not aligned"; |
| return false; |
| } |
| |
| if (!SafeVerifyClassClass(cls)) { |
| VLOG(signals) << "not a class class"; |
| return false; |
| } |
| |
| const OatQuickMethodHeader* method_header = method_obj->GetOatQuickMethodHeader(return_pc); |
| |
| // 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) { |
| VLOG(signals) << "looking for dex pc for return pc " << std::hex << return_pc; |
| uint32_t sought_offset = return_pc - |
| reinterpret_cast<uintptr_t>(method_header->GetEntryPoint()); |
| VLOG(signals) << "pc offset: " << std::hex << sought_offset; |
| } |
| uint32_t dexpc = method_header->ToDexPc(method_obj, return_pc, false); |
| VLOG(signals) << "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 ATTRIBUTE_UNUSED, siginfo_t* siginfo, void* context) { |
| // Make sure that we are in the generated code, but we may not have a dex pc. |
| bool in_generated_code = manager_->IsInGeneratedCode(siginfo, context, false); |
| if (in_generated_code) { |
| LOG(ERROR) << "Dumping java stack trace for crash in generated code"; |
| ArtMethod* method = nullptr; |
| uintptr_t return_pc = 0; |
| uintptr_t sp = 0; |
| Thread* self = Thread::Current(); |
| |
| manager_->GetMethodAndReturnPcAndSp(siginfo, context, &method, &return_pc, &sp); |
| // Inside of generated code, sp[0] is the method, so sp is the frame. |
| self->SetTopOfStack(reinterpret_cast<ArtMethod**>(sp)); |
| self->DumpJavaStack(LOG_STREAM(ERROR)); |
| } |
| |
| return false; // Return false since we want to propagate the fault to the main signal handler. |
| } |
| |
| } // namespace art |