1 /* 2 * Copyright (C) 2014 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 18 #include "fault_handler.h" 19 #include <sys/ucontext.h> 20 #include "art_method-inl.h" 21 #include "base/macros.h" 22 #include "globals.h" 23 #include "base/logging.h" 24 #include "base/hex_dump.h" 25 #include "registers_mips64.h" 26 #include "thread.h" 27 #include "thread-inl.h" 28 29 extern "C" void art_quick_throw_stack_overflow(); 30 extern "C" void art_quick_throw_null_pointer_exception(); 31 32 // 33 // Mips64 specific fault handler functions. 34 // 35 36 namespace art { 37 38 void FaultManager::HandleNestedSignal(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED, 39 void* context ATTRIBUTE_UNUSED) { 40 } 41 42 void FaultManager::GetMethodAndReturnPcAndSp(siginfo_t* siginfo, void* context, 43 ArtMethod** out_method, 44 uintptr_t* out_return_pc, uintptr_t* out_sp) { 45 struct ucontext* uc = reinterpret_cast<struct ucontext*>(context); 46 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); 47 *out_sp = static_cast<uintptr_t>(sc->sc_regs[29]); // SP register 48 VLOG(signals) << "sp: " << *out_sp; 49 if (*out_sp == 0) { 50 return; 51 } 52 53 // In the case of a stack overflow, the stack is not valid and we can't 54 // get the method from the top of the stack. However it's in r0. 55 uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(siginfo->si_addr); // BVA addr 56 uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>( 57 reinterpret_cast<uint8_t*>(*out_sp) - GetStackOverflowReservedBytes(kMips64)); 58 if (overflow_addr == fault_addr) { 59 *out_method = reinterpret_cast<ArtMethod*>(sc->sc_regs[4]); // A0 register 60 } else { 61 // The method is at the top of the stack. 62 *out_method = *reinterpret_cast<ArtMethod**>(*out_sp); 63 } 64 65 // Work out the return PC. This will be the address of the instruction 66 // following the faulting ldr/str instruction. 67 68 VLOG(signals) << "pc: " << std::hex 69 << static_cast<void*>(reinterpret_cast<uint8_t*>(sc->sc_pc)); 70 71 *out_return_pc = sc->sc_pc + 4; 72 } 73 74 bool NullPointerHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED, 75 void* context) { 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 sc->sc_regs[31] = sc->sc_pc + 4; // RA needs to point to gc map location 84 sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception); 85 sc->sc_regs[25] = sc->sc_pc; // make sure T9 points to the function 86 VLOG(signals) << "Generating null pointer exception"; 87 return true; 88 } 89 90 bool SuspensionHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED, 91 void* context ATTRIBUTE_UNUSED) { 92 return false; 93 } 94 95 // Stack overflow fault handler. 96 // 97 // This checks that the fault address is equal to the current stack pointer 98 // minus the overflow region size (16K typically). The instruction that 99 // generates this signal is: 100 // 101 // lw zero, -16384(sp) 102 // 103 // It will fault if sp is inside the protected region on the stack. 104 // 105 // If we determine this is a stack overflow we need to move the stack pointer 106 // to the overflow region below the protected region. 107 108 bool StackOverflowHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) { 109 struct ucontext* uc = reinterpret_cast<struct ucontext*>(context); 110 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); 111 VLOG(signals) << "stack overflow handler with sp at " << std::hex << &uc; 112 VLOG(signals) << "sigcontext: " << std::hex << sc; 113 114 uintptr_t sp = sc->sc_regs[29]; // SP register 115 VLOG(signals) << "sp: " << std::hex << sp; 116 117 uintptr_t fault_addr = reinterpret_cast<uintptr_t>(info->si_addr); // BVA addr 118 VLOG(signals) << "fault_addr: " << std::hex << fault_addr; 119 VLOG(signals) << "checking for stack overflow, sp: " << std::hex << sp << 120 ", fault_addr: " << fault_addr; 121 122 uintptr_t overflow_addr = sp - GetStackOverflowReservedBytes(kMips64); 123 124 // Check that the fault address is the value expected for a stack overflow. 125 if (fault_addr != overflow_addr) { 126 VLOG(signals) << "Not a stack overflow"; 127 return false; 128 } 129 130 VLOG(signals) << "Stack overflow found"; 131 132 // Now arrange for the signal handler to return to art_quick_throw_stack_overflow_from. 133 // The value of RA must be the same as it was when we entered the code that 134 // caused this fault. This will be inserted into a callee save frame by 135 // the function to which this handler returns (art_quick_throw_stack_overflow). 136 sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow); 137 sc->sc_regs[25] = sc->sc_pc; // make sure T9 points to the function 138 139 // The kernel will now return to the address in sc->arm_pc. 140 return true; 141 } 142 } // namespace art 143
