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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 <sys/ucontext.h>
#include "fault_handler.h"
#include "arch/instruction_set.h"
#include "arch/mips/callee_save_frame_mips.h"
#include "art_method.h"
#include "base/callee_save_type.h"
#include "base/hex_dump.h"
#include "base/logging.h" // For VLOG.
#include "base/macros.h"
#include "registers_mips.h"
#include "runtime_globals.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();
//
// Mips specific fault handler functions.
//
namespace art {
void FaultManager::GetMethodAndReturnPcAndSp(siginfo_t* siginfo, void* context,
ArtMethod** out_method,
uintptr_t* out_return_pc, uintptr_t* out_sp) {
struct ucontext_t* uc = reinterpret_cast<struct ucontext_t*>(context);
struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
*out_sp = static_cast<uintptr_t>(sc->sc_regs[mips::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 r0.
uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(siginfo->si_addr); // BVA addr
uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>(
reinterpret_cast<uint8_t*>(*out_sp) - GetStackOverflowReservedBytes(InstructionSet::kMips));
if (overflow_addr == fault_addr) {
*out_method = reinterpret_cast<ArtMethod*>(sc->sc_regs[mips::A0]);
} 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->sc_pc));
*out_return_pc = sc->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_t *uc = reinterpret_cast<struct ucontext_t*>(context);
struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
// Decrement $sp by the frame size of the kSaveEverything method and store
// the fault address in the padding right after the ArtMethod*.
sc->sc_regs[mips::SP] -= mips::MipsCalleeSaveFrameSize(CalleeSaveType::kSaveEverything);
uintptr_t* padding = reinterpret_cast<uintptr_t*>(sc->sc_regs[mips::SP]) + /* ArtMethod* */ 1;
*padding = reinterpret_cast<uintptr_t>(info->si_addr);
sc->sc_regs[mips::RA] = sc->sc_pc + 4; // RA needs to point to gc map location
sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception_from_signal);
// Note: This entrypoint does not rely on T9 pointing to it, so we may as well preserve T9.
VLOG(signals) << "Generating null pointer exception";
return true;
}
bool SuspensionHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
void* context ATTRIBUTE_UNUSED) {
return false;
}
// Stack overflow fault handler.
//
// This checks that the fault address is equal to the current stack pointer
// minus the overflow region size (16K typically). The instruction that
// generates this signal is:
//
// lw zero, -16384(sp)
//
// It will fault if sp is inside the protected region on the stack.
//
// If we determine this is a stack overflow we need to move the stack pointer
// to the overflow region below the protected region.
bool StackOverflowHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) {
struct ucontext_t* uc = reinterpret_cast<struct ucontext_t*>(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->sc_regs[mips::SP];
VLOG(signals) << "sp: " << std::hex << sp;
uintptr_t fault_addr = reinterpret_cast<uintptr_t>(info->si_addr); // BVA addr
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::kMips);
// 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_from.
// The value of RA 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->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow);
sc->sc_regs[mips::T9] = sc->sc_pc; // make sure T9 points to the function
// The kernel will now return to the address in sc->arm_pc.
return true;
}
} // namespace art
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