1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include <sys/ucontext.h> 18 #include "fault_handler.h" 19 20 #include "arch/instruction_set.h" 21 #include "arch/mips/callee_save_frame_mips.h" 22 #include "art_method.h" 23 #include "base/callee_save_type.h" 24 #include "base/hex_dump.h" 25 #include "base/logging.h" // For VLOG. 26 #include "base/macros.h" 27 #include "registers_mips.h" 28 #include "runtime_globals.h" 29 #include "thread-current-inl.h" 30 31 extern "C" void art_quick_throw_stack_overflow(); 32 extern "C" void art_quick_throw_null_pointer_exception_from_signal(); 33 34 // 35 // Mips specific fault handler functions. 36 // 37 38 namespace art { 39 40 void FaultManager::GetMethodAndReturnPcAndSp(siginfo_t* siginfo, void* context, 41 ArtMethod** out_method, 42 uintptr_t* out_return_pc, uintptr_t* out_sp) { 43 struct ucontext* uc = reinterpret_cast<struct ucontext*>(context); 44 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); 45 *out_sp = static_cast<uintptr_t>(sc->sc_regs[mips::SP]); 46 VLOG(signals) << "sp: " << *out_sp; 47 if (*out_sp == 0) { 48 return; 49 } 50 51 // In the case of a stack overflow, the stack is not valid and we can't 52 // get the method from the top of the stack. However it's in r0. 53 uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(siginfo->si_addr); // BVA addr 54 uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>( 55 reinterpret_cast<uint8_t*>(*out_sp) - GetStackOverflowReservedBytes(InstructionSet::kMips)); 56 if (overflow_addr == fault_addr) { 57 *out_method = reinterpret_cast<ArtMethod*>(sc->sc_regs[mips::A0]); 58 } else { 59 // The method is at the top of the stack. 60 *out_method = *reinterpret_cast<ArtMethod**>(*out_sp); 61 } 62 63 // Work out the return PC. This will be the address of the instruction 64 // following the faulting ldr/str instruction. 65 66 VLOG(signals) << "pc: " << std::hex 67 << static_cast<void*>(reinterpret_cast<uint8_t*>(sc->sc_pc)); 68 69 *out_return_pc = sc->sc_pc + 4; 70 } 71 72 bool NullPointerHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) { 73 if (!IsValidImplicitCheck(info)) { 74 return false; 75 } 76 // The code that looks for the catch location needs to know the value of the 77 // PC at the point of call. For Null checks we insert a GC map that is immediately after 78 // the load/store instruction that might cause the fault. 79 80 struct ucontext *uc = reinterpret_cast<struct ucontext*>(context); 81 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); 82 83 // Decrement $sp by the frame size of the kSaveEverything method and store 84 // the fault address in the padding right after the ArtMethod*. 85 sc->sc_regs[mips::SP] -= mips::MipsCalleeSaveFrameSize(CalleeSaveType::kSaveEverything); 86 uintptr_t* padding = reinterpret_cast<uintptr_t*>(sc->sc_regs[mips::SP]) + /* ArtMethod* */ 1; 87 *padding = reinterpret_cast<uintptr_t>(info->si_addr); 88 89 sc->sc_regs[mips::RA] = sc->sc_pc + 4; // RA needs to point to gc map location 90 sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception_from_signal); 91 // Note: This entrypoint does not rely on T9 pointing to it, so we may as well preserve T9. 92 VLOG(signals) << "Generating null pointer exception"; 93 return true; 94 } 95 96 bool SuspensionHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED, 97 void* context ATTRIBUTE_UNUSED) { 98 return false; 99 } 100 101 // Stack overflow fault handler. 102 // 103 // This checks that the fault address is equal to the current stack pointer 104 // minus the overflow region size (16K typically). The instruction that 105 // generates this signal is: 106 // 107 // lw zero, -16384(sp) 108 // 109 // It will fault if sp is inside the protected region on the stack. 110 // 111 // If we determine this is a stack overflow we need to move the stack pointer 112 // to the overflow region below the protected region. 113 114 bool StackOverflowHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) { 115 struct ucontext* uc = reinterpret_cast<struct ucontext*>(context); 116 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); 117 VLOG(signals) << "stack overflow handler with sp at " << std::hex << &uc; 118 VLOG(signals) << "sigcontext: " << std::hex << sc; 119 120 uintptr_t sp = sc->sc_regs[mips::SP]; 121 VLOG(signals) << "sp: " << std::hex << sp; 122 123 uintptr_t fault_addr = reinterpret_cast<uintptr_t>(info->si_addr); // BVA addr 124 VLOG(signals) << "fault_addr: " << std::hex << fault_addr; 125 VLOG(signals) << "checking for stack overflow, sp: " << std::hex << sp << 126 ", fault_addr: " << fault_addr; 127 128 uintptr_t overflow_addr = sp - GetStackOverflowReservedBytes(InstructionSet::kMips); 129 130 // Check that the fault address is the value expected for a stack overflow. 131 if (fault_addr != overflow_addr) { 132 VLOG(signals) << "Not a stack overflow"; 133 return false; 134 } 135 136 VLOG(signals) << "Stack overflow found"; 137 138 // Now arrange for the signal handler to return to art_quick_throw_stack_overflow_from. 139 // The value of RA must be the same as it was when we entered the code that 140 // caused this fault. This will be inserted into a callee save frame by 141 // the function to which this handler returns (art_quick_throw_stack_overflow). 142 sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow); 143 sc->sc_regs[mips::T9] = sc->sc_pc; // make sure T9 points to the function 144 145 // The kernel will now return to the address in sc->arm_pc. 146 return true; 147 } 148 } // namespace art 149
