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 "fault_handler.h" 18 #include <sys/ucontext.h> 19 20 #include "art_method.h" 21 #include "base/hex_dump.h" 22 #include "base/logging.h" 23 #include "base/macros.h" 24 #include "globals.h" 25 #include "quick_method_frame_info_mips.h" 26 #include "registers_mips.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_from_signal(); 31 32 // 33 // Mips specific fault handler functions. 34 // 35 36 namespace art { 37 38 void FaultManager::GetMethodAndReturnPcAndSp(siginfo_t* siginfo, void* context, 39 ArtMethod** out_method, 40 uintptr_t* out_return_pc, uintptr_t* out_sp) { 41 struct ucontext* uc = reinterpret_cast<struct ucontext*>(context); 42 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); 43 *out_sp = static_cast<uintptr_t>(sc->sc_regs[mips::SP]); 44 VLOG(signals) << "sp: " << *out_sp; 45 if (*out_sp == 0) { 46 return; 47 } 48 49 // In the case of a stack overflow, the stack is not valid and we can't 50 // get the method from the top of the stack. However it's in r0. 51 uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(siginfo->si_addr); // BVA addr 52 uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>( 53 reinterpret_cast<uint8_t*>(*out_sp) - GetStackOverflowReservedBytes(kMips)); 54 if (overflow_addr == fault_addr) { 55 *out_method = reinterpret_cast<ArtMethod*>(sc->sc_regs[mips::A0]); 56 } else { 57 // The method is at the top of the stack. 58 *out_method = *reinterpret_cast<ArtMethod**>(*out_sp); 59 } 60 61 // Work out the return PC. This will be the address of the instruction 62 // following the faulting ldr/str instruction. 63 64 VLOG(signals) << "pc: " << std::hex 65 << static_cast<void*>(reinterpret_cast<uint8_t*>(sc->sc_pc)); 66 67 *out_return_pc = sc->sc_pc + 4; 68 } 69 70 bool NullPointerHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) { 71 if (!IsValidImplicitCheck(info)) { 72 return false; 73 } 74 // The code that looks for the catch location needs to know the value of the 75 // PC at the point of call. For Null checks we insert a GC map that is immediately after 76 // the load/store instruction that might cause the fault. 77 78 struct ucontext *uc = reinterpret_cast<struct ucontext*>(context); 79 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); 80 81 // Decrement $sp by the frame size of the kSaveEverything method and store 82 // the fault address in the padding right after the ArtMethod*. 83 sc->sc_regs[mips::SP] -= mips::MipsCalleeSaveFrameSize(Runtime::kSaveEverything); 84 uintptr_t* padding = reinterpret_cast<uintptr_t*>(sc->sc_regs[mips::SP]) + /* ArtMethod* */ 1; 85 *padding = reinterpret_cast<uintptr_t>(info->si_addr); 86 87 sc->sc_regs[mips::RA] = sc->sc_pc + 4; // RA needs to point to gc map location 88 sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception_from_signal); 89 // Note: This entrypoint does not rely on T9 pointing to it, so we may as well preserve T9. 90 VLOG(signals) << "Generating null pointer exception"; 91 return true; 92 } 93 94 bool SuspensionHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED, 95 void* context ATTRIBUTE_UNUSED) { 96 return false; 97 } 98 99 // Stack overflow fault handler. 100 // 101 // This checks that the fault address is equal to the current stack pointer 102 // minus the overflow region size (16K typically). The instruction that 103 // generates this signal is: 104 // 105 // lw zero, -16384(sp) 106 // 107 // It will fault if sp is inside the protected region on the stack. 108 // 109 // If we determine this is a stack overflow we need to move the stack pointer 110 // to the overflow region below the protected region. 111 112 bool StackOverflowHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) { 113 struct ucontext* uc = reinterpret_cast<struct ucontext*>(context); 114 struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); 115 VLOG(signals) << "stack overflow handler with sp at " << std::hex << &uc; 116 VLOG(signals) << "sigcontext: " << std::hex << sc; 117 118 uintptr_t sp = sc->sc_regs[mips::SP]; 119 VLOG(signals) << "sp: " << std::hex << sp; 120 121 uintptr_t fault_addr = reinterpret_cast<uintptr_t>(info->si_addr); // BVA addr 122 VLOG(signals) << "fault_addr: " << std::hex << fault_addr; 123 VLOG(signals) << "checking for stack overflow, sp: " << std::hex << sp << 124 ", fault_addr: " << fault_addr; 125 126 uintptr_t overflow_addr = sp - GetStackOverflowReservedBytes(kMips); 127 128 // Check that the fault address is the value expected for a stack overflow. 129 if (fault_addr != overflow_addr) { 130 VLOG(signals) << "Not a stack overflow"; 131 return false; 132 } 133 134 VLOG(signals) << "Stack overflow found"; 135 136 // Now arrange for the signal handler to return to art_quick_throw_stack_overflow_from. 137 // The value of RA must be the same as it was when we entered the code that 138 // caused this fault. This will be inserted into a callee save frame by 139 // the function to which this handler returns (art_quick_throw_stack_overflow). 140 sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow); 141 sc->sc_regs[mips::T9] = sc->sc_pc; // make sure T9 points to the function 142 143 // The kernel will now return to the address in sc->arm_pc. 144 return true; 145 } 146 } // namespace art 147
