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194 lines
7.5 KiB
194 lines
7.5 KiB
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "fault_handler.h"
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#include <sys/ucontext.h>
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#include "arch/instruction_set.h"
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#include "art_method.h"
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#include "base/enums.h"
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#include "base/hex_dump.h"
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#include "base/logging.h" // For VLOG.
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#include "base/macros.h"
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#include "registers_arm64.h"
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#include "runtime_globals.h"
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#include "thread-current-inl.h"
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extern "C" void art_quick_throw_stack_overflow();
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extern "C" void art_quick_throw_null_pointer_exception_from_signal();
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extern "C" void art_quick_implicit_suspend();
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//
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// ARM64 specific fault handler functions.
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//
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namespace art {
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void FaultManager::GetMethodAndReturnPcAndSp(siginfo_t* siginfo ATTRIBUTE_UNUSED,
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void* context,
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ArtMethod** out_method,
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uintptr_t* out_return_pc,
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uintptr_t* out_sp,
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bool* out_is_stack_overflow) {
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struct ucontext *uc = reinterpret_cast<struct ucontext *>(context);
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struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
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*out_sp = static_cast<uintptr_t>(sc->sp);
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VLOG(signals) << "sp: " << *out_sp;
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if (*out_sp == 0) {
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return;
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}
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// In the case of a stack overflow, the stack is not valid and we can't
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// get the method from the top of the stack. However it's in x0.
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uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(sc->fault_address);
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uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>(
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reinterpret_cast<uint8_t*>(*out_sp) - GetStackOverflowReservedBytes(InstructionSet::kArm64));
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if (overflow_addr == fault_addr) {
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*out_method = reinterpret_cast<ArtMethod*>(sc->regs[0]);
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*out_is_stack_overflow = true;
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} else {
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// The method is at the top of the stack.
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*out_method = *reinterpret_cast<ArtMethod**>(*out_sp);
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*out_is_stack_overflow = false;
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}
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// Work out the return PC. This will be the address of the instruction
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// following the faulting ldr/str instruction.
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VLOG(signals) << "pc: " << std::hex
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<< static_cast<void*>(reinterpret_cast<uint8_t*>(sc->pc));
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*out_return_pc = sc->pc + 4;
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}
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bool NullPointerHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) {
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if (!IsValidImplicitCheck(info)) {
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return false;
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}
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// The code that looks for the catch location needs to know the value of the
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// PC at the point of call. For Null checks we insert a GC map that is immediately after
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// the load/store instruction that might cause the fault.
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struct ucontext *uc = reinterpret_cast<struct ucontext*>(context);
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struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
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// Push the gc map location to the stack and pass the fault address in LR.
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sc->sp -= sizeof(uintptr_t);
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*reinterpret_cast<uintptr_t*>(sc->sp) = sc->pc + 4;
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sc->regs[30] = reinterpret_cast<uintptr_t>(info->si_addr);
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sc->pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception_from_signal);
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VLOG(signals) << "Generating null pointer exception";
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return true;
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}
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// A suspend check is done using the following instruction sequence:
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// 0xf7223228: f9405640 ldr x0, [x18, #168]
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// .. some intervening instructions
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// 0xf7223230: f9400000 ldr x0, [x0]
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// The offset from r18 is Thread::ThreadSuspendTriggerOffset().
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// To check for a suspend check, we examine the instructions that caused
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// the fault (at PC-4 and PC).
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bool SuspensionHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
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void* context) {
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// These are the instructions to check for. The first one is the ldr x0,[r18,#xxx]
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// where xxx is the offset of the suspend trigger.
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uint32_t checkinst1 = 0xf9400240 |
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(Thread::ThreadSuspendTriggerOffset<PointerSize::k64>().Int32Value() << 7);
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uint32_t checkinst2 = 0xf9400000;
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struct ucontext *uc = reinterpret_cast<struct ucontext *>(context);
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struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
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uint8_t* ptr2 = reinterpret_cast<uint8_t*>(sc->pc);
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uint8_t* ptr1 = ptr2 - 4;
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VLOG(signals) << "checking suspend";
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uint32_t inst2 = *reinterpret_cast<uint32_t*>(ptr2);
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VLOG(signals) << "inst2: " << std::hex << inst2 << " checkinst2: " << checkinst2;
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if (inst2 != checkinst2) {
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// Second instruction is not good, not ours.
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return false;
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}
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// The first instruction can a little bit up the stream due to load hoisting
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// in the compiler.
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uint8_t* limit = ptr1 - 80; // Compiler will hoist to a max of 20 instructions.
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bool found = false;
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while (ptr1 > limit) {
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uint32_t inst1 = *reinterpret_cast<uint32_t*>(ptr1);
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VLOG(signals) << "inst1: " << std::hex << inst1 << " checkinst1: " << checkinst1;
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if (inst1 == checkinst1) {
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found = true;
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break;
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}
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ptr1 -= 4;
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}
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if (found) {
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VLOG(signals) << "suspend check match";
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// This is a suspend check. Arrange for the signal handler to return to
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// art_quick_implicit_suspend. Also set LR so that after the suspend check it
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// will resume the instruction (current PC + 4). PC points to the
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// ldr x0,[x0,#0] instruction (r0 will be 0, set by the trigger).
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sc->regs[30] = sc->pc + 4;
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sc->pc = reinterpret_cast<uintptr_t>(art_quick_implicit_suspend);
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// Now remove the suspend trigger that caused this fault.
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Thread::Current()->RemoveSuspendTrigger();
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VLOG(signals) << "removed suspend trigger invoking test suspend";
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return true;
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}
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return false;
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}
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bool StackOverflowHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
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void* context) {
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struct ucontext *uc = reinterpret_cast<struct ucontext *>(context);
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struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
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VLOG(signals) << "stack overflow handler with sp at " << std::hex << &uc;
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VLOG(signals) << "sigcontext: " << std::hex << sc;
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uintptr_t sp = sc->sp;
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VLOG(signals) << "sp: " << std::hex << sp;
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uintptr_t fault_addr = sc->fault_address;
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VLOG(signals) << "fault_addr: " << std::hex << fault_addr;
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VLOG(signals) << "checking for stack overflow, sp: " << std::hex << sp <<
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", fault_addr: " << fault_addr;
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uintptr_t overflow_addr = sp - GetStackOverflowReservedBytes(InstructionSet::kArm64);
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// Check that the fault address is the value expected for a stack overflow.
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if (fault_addr != overflow_addr) {
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VLOG(signals) << "Not a stack overflow";
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return false;
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}
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VLOG(signals) << "Stack overflow found";
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// Now arrange for the signal handler to return to art_quick_throw_stack_overflow.
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// The value of LR must be the same as it was when we entered the code that
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// caused this fault. This will be inserted into a callee save frame by
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// the function to which this handler returns (art_quick_throw_stack_overflow).
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sc->pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow);
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// The kernel will now return to the address in sc->pc.
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return true;
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}
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} // namespace art
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