| /* |
| * Copyright (C) 2014 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/ucontext.h> |
| |
| #include "art_method.h" |
| #include "base/enums.h" |
| #include "base/globals.h" |
| #include "base/hex_dump.h" |
| #include "base/logging.h" // For VLOG. |
| #include "base/macros.h" |
| #include "registers_arm64.h" |
| #include "thread-current-inl.h" |
| |
| extern "C" void art_quick_throw_stack_overflow(); |
| extern "C" void art_quick_throw_null_pointer_exception_from_signal(); |
| extern "C" void art_quick_implicit_suspend(); |
| |
| // |
| // ARM64 specific fault handler functions. |
| // |
| |
| namespace art { |
| |
| void FaultManager::GetMethodAndReturnPcAndSp(siginfo_t* siginfo ATTRIBUTE_UNUSED, void* context, |
| ArtMethod** out_method, |
| uintptr_t* out_return_pc, uintptr_t* out_sp) { |
| struct ucontext *uc = reinterpret_cast<struct ucontext *>(context); |
| struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); |
| *out_sp = static_cast<uintptr_t>(sc->sp); |
| VLOG(signals) << "sp: " << *out_sp; |
| if (*out_sp == 0) { |
| return; |
| } |
| |
| // In the case of a stack overflow, the stack is not valid and we can't |
| // get the method from the top of the stack. However it's in x0. |
| uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(sc->fault_address); |
| uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>( |
| reinterpret_cast<uint8_t*>(*out_sp) - GetStackOverflowReservedBytes(InstructionSet::kArm64)); |
| if (overflow_addr == fault_addr) { |
| *out_method = reinterpret_cast<ArtMethod*>(sc->regs[0]); |
| } else { |
| // The method is at the top of the stack. |
| *out_method = *reinterpret_cast<ArtMethod**>(*out_sp); |
| } |
| |
| // Work out the return PC. This will be the address of the instruction |
| // following the faulting ldr/str instruction. |
| VLOG(signals) << "pc: " << std::hex |
| << static_cast<void*>(reinterpret_cast<uint8_t*>(sc->pc)); |
| |
| *out_return_pc = sc->pc + 4; |
| } |
| |
| bool NullPointerHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) { |
| if (!IsValidImplicitCheck(info)) { |
| return false; |
| } |
| // The code that looks for the catch location needs to know the value of the |
| // PC at the point of call. For Null checks we insert a GC map that is immediately after |
| // the load/store instruction that might cause the fault. |
| |
| struct ucontext *uc = reinterpret_cast<struct ucontext*>(context); |
| struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); |
| |
| // Push the gc map location to the stack and pass the fault address in LR. |
| sc->sp -= sizeof(uintptr_t); |
| *reinterpret_cast<uintptr_t*>(sc->sp) = sc->pc + 4; |
| sc->regs[30] = reinterpret_cast<uintptr_t>(info->si_addr); |
| |
| sc->pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception_from_signal); |
| VLOG(signals) << "Generating null pointer exception"; |
| return true; |
| } |
| |
| // A suspend check is done using the following instruction sequence: |
| // 0xf7223228: f9405640 ldr x0, [x18, #168] |
| // .. some intervening instructions |
| // 0xf7223230: f9400000 ldr x0, [x0] |
| |
| // The offset from r18 is Thread::ThreadSuspendTriggerOffset(). |
| // To check for a suspend check, we examine the instructions that caused |
| // the fault (at PC-4 and PC). |
| bool SuspensionHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED, |
| void* context) { |
| // These are the instructions to check for. The first one is the ldr x0,[r18,#xxx] |
| // where xxx is the offset of the suspend trigger. |
| uint32_t checkinst1 = 0xf9400240 | |
| (Thread::ThreadSuspendTriggerOffset<PointerSize::k64>().Int32Value() << 7); |
| uint32_t checkinst2 = 0xf9400000; |
| |
| struct ucontext *uc = reinterpret_cast<struct ucontext *>(context); |
| struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); |
| uint8_t* ptr2 = reinterpret_cast<uint8_t*>(sc->pc); |
| uint8_t* ptr1 = ptr2 - 4; |
| VLOG(signals) << "checking suspend"; |
| |
| uint32_t inst2 = *reinterpret_cast<uint32_t*>(ptr2); |
| VLOG(signals) << "inst2: " << std::hex << inst2 << " checkinst2: " << checkinst2; |
| if (inst2 != checkinst2) { |
| // Second instruction is not good, not ours. |
| return false; |
| } |
| |
| // The first instruction can a little bit up the stream due to load hoisting |
| // in the compiler. |
| uint8_t* limit = ptr1 - 80; // Compiler will hoist to a max of 20 instructions. |
| bool found = false; |
| while (ptr1 > limit) { |
| uint32_t inst1 = *reinterpret_cast<uint32_t*>(ptr1); |
| VLOG(signals) << "inst1: " << std::hex << inst1 << " checkinst1: " << checkinst1; |
| if (inst1 == checkinst1) { |
| found = true; |
| break; |
| } |
| ptr1 -= 4; |
| } |
| if (found) { |
| VLOG(signals) << "suspend check match"; |
| // This is a suspend check. Arrange for the signal handler to return to |
| // art_quick_implicit_suspend. Also set LR so that after the suspend check it |
| // will resume the instruction (current PC + 4). PC points to the |
| // ldr x0,[x0,#0] instruction (r0 will be 0, set by the trigger). |
| |
| sc->regs[30] = sc->pc + 4; |
| sc->pc = reinterpret_cast<uintptr_t>(art_quick_implicit_suspend); |
| |
| // Now remove the suspend trigger that caused this fault. |
| Thread::Current()->RemoveSuspendTrigger(); |
| VLOG(signals) << "removed suspend trigger invoking test suspend"; |
| return true; |
| } |
| return false; |
| } |
| |
| bool StackOverflowHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED, |
| void* context) { |
| struct ucontext *uc = reinterpret_cast<struct ucontext *>(context); |
| struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); |
| VLOG(signals) << "stack overflow handler with sp at " << std::hex << &uc; |
| VLOG(signals) << "sigcontext: " << std::hex << sc; |
| |
| uintptr_t sp = sc->sp; |
| VLOG(signals) << "sp: " << std::hex << sp; |
| |
| uintptr_t fault_addr = sc->fault_address; |
| VLOG(signals) << "fault_addr: " << std::hex << fault_addr; |
| VLOG(signals) << "checking for stack overflow, sp: " << std::hex << sp << |
| ", fault_addr: " << fault_addr; |
| |
| uintptr_t overflow_addr = sp - GetStackOverflowReservedBytes(InstructionSet::kArm64); |
| |
| // Check that the fault address is the value expected for a stack overflow. |
| if (fault_addr != overflow_addr) { |
| VLOG(signals) << "Not a stack overflow"; |
| return false; |
| } |
| |
| VLOG(signals) << "Stack overflow found"; |
| |
| // Now arrange for the signal handler to return to art_quick_throw_stack_overflow. |
| // The value of LR must be the same as it was when we entered the code that |
| // caused this fault. This will be inserted into a callee save frame by |
| // the function to which this handler returns (art_quick_throw_stack_overflow). |
| sc->pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow); |
| |
| // The kernel will now return to the address in sc->pc. |
| return true; |
| } |
| } // namespace art |
| |