Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 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 | |
| 18 | #include "fault_handler.h" |
| 19 | #include <sys/ucontext.h> |
| 20 | #include "base/macros.h" |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 21 | #include "base/hex_dump.h" |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 22 | #include "globals.h" |
| 23 | #include "base/logging.h" |
| 24 | #include "base/hex_dump.h" |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 25 | #include "mirror/art_method.h" |
| 26 | #include "mirror/art_method-inl.h" |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 27 | #include "thread.h" |
| 28 | #include "thread-inl.h" |
| 29 | |
| 30 | // |
| 31 | // ARM specific fault handler functions. |
| 32 | // |
| 33 | |
| 34 | namespace art { |
| 35 | |
| 36 | extern "C" void art_quick_throw_null_pointer_exception(); |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 37 | extern "C" void art_quick_throw_stack_overflow(void*); |
Dave Allison | 8325296 | 2014-04-03 16:33:48 -0700 | [diff] [blame] | 38 | extern "C" void art_quick_implicit_suspend(); |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 39 | |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 40 | // Get the size of a thumb2 instruction in bytes. |
| 41 | static uint32_t GetInstructionSize(uint8_t* pc) { |
| 42 | uint16_t instr = pc[0] | pc[1] << 8; |
| 43 | bool is_32bit = ((instr & 0xF000) == 0xF000) || ((instr & 0xF800) == 0xE800); |
| 44 | uint32_t instr_size = is_32bit ? 4 : 2; |
| 45 | return instr_size; |
| 46 | } |
| 47 | |
Mathieu Chartier | c751fdc | 2014-03-30 15:25:44 -0700 | [diff] [blame] | 48 | void FaultManager::GetMethodAndReturnPCAndSP(void* context, mirror::ArtMethod** out_method, |
| 49 | uintptr_t* out_return_pc, uintptr_t* out_sp) { |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 50 | struct ucontext *uc = (struct ucontext *)context; |
| 51 | struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); |
Mathieu Chartier | c751fdc | 2014-03-30 15:25:44 -0700 | [diff] [blame] | 52 | *out_sp = static_cast<uintptr_t>(sc->arm_sp); |
| 53 | LOG(DEBUG) << "sp: " << *out_sp; |
| 54 | if (*out_sp == 0) { |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 55 | return; |
| 56 | } |
| 57 | |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 58 | // In the case of a stack overflow, the stack is not valid and we can't |
| 59 | // get the method from the top of the stack. However it's in r0. |
| 60 | uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(sc->fault_address); |
| 61 | uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>( |
Mathieu Chartier | c751fdc | 2014-03-30 15:25:44 -0700 | [diff] [blame] | 62 | reinterpret_cast<uint8_t*>(*out_sp) - Thread::kStackOverflowReservedBytes); |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 63 | if (overflow_addr == fault_addr) { |
Mathieu Chartier | c751fdc | 2014-03-30 15:25:44 -0700 | [diff] [blame] | 64 | *out_method = reinterpret_cast<mirror::ArtMethod*>(sc->arm_r0); |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 65 | } else { |
| 66 | // The method is at the top of the stack. |
Mathieu Chartier | c751fdc | 2014-03-30 15:25:44 -0700 | [diff] [blame] | 67 | *out_method = reinterpret_cast<mirror::ArtMethod*>(reinterpret_cast<uintptr_t*>(*out_sp)[0]); |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 68 | } |
| 69 | |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 70 | // Work out the return PC. This will be the address of the instruction |
| 71 | // following the faulting ldr/str instruction. This is in thumb mode so |
| 72 | // the instruction might be a 16 or 32 bit one. Also, the GC map always |
| 73 | // has the bottom bit of the PC set so we also need to set that. |
| 74 | |
| 75 | // Need to work out the size of the instruction that caused the exception. |
| 76 | uint8_t* ptr = reinterpret_cast<uint8_t*>(sc->arm_pc); |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 77 | LOG(DEBUG) << "pc: " << std::hex << static_cast<void*>(ptr); |
| 78 | uint32_t instr_size = GetInstructionSize(ptr); |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 79 | |
Mathieu Chartier | c751fdc | 2014-03-30 15:25:44 -0700 | [diff] [blame] | 80 | *out_return_pc = (sc->arm_pc + instr_size) | 1; |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 81 | } |
| 82 | |
| 83 | bool NullPointerHandler::Action(int sig, siginfo_t* info, void* context) { |
| 84 | // The code that looks for the catch location needs to know the value of the |
| 85 | // ARM PC at the point of call. For Null checks we insert a GC map that is immediately after |
| 86 | // the load/store instruction that might cause the fault. However the mapping table has |
| 87 | // the low bits set for thumb mode so we need to set the bottom bit for the LR |
| 88 | // register in order to find the mapping. |
| 89 | |
| 90 | // Need to work out the size of the instruction that caused the exception. |
Mathieu Chartier | c751fdc | 2014-03-30 15:25:44 -0700 | [diff] [blame] | 91 | struct ucontext *uc = reinterpret_cast<struct ucontext*>(context); |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 92 | struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); |
| 93 | uint8_t* ptr = reinterpret_cast<uint8_t*>(sc->arm_pc); |
| 94 | |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 95 | uint32_t instr_size = GetInstructionSize(ptr); |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 96 | sc->arm_lr = (sc->arm_pc + instr_size) | 1; // LR needs to point to gc map location |
| 97 | sc->arm_pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception); |
| 98 | LOG(DEBUG) << "Generating null pointer exception"; |
| 99 | return true; |
| 100 | } |
| 101 | |
| 102 | // A suspend check is done using the following instruction sequence: |
| 103 | // 0xf723c0b2: f8d902c0 ldr.w r0, [r9, #704] ; suspend_trigger_ |
| 104 | // .. some intervening instruction |
| 105 | // 0xf723c0b6: 6800 ldr r0, [r0, #0] |
| 106 | |
| 107 | // The offset from r9 is Thread::ThreadSuspendTriggerOffset(). |
| 108 | // To check for a suspend check, we examine the instructions that caused |
| 109 | // the fault (at PC-4 and PC). |
| 110 | bool SuspensionHandler::Action(int sig, siginfo_t* info, void* context) { |
| 111 | // These are the instructions to check for. The first one is the ldr r0,[r9,#xxx] |
| 112 | // where xxx is the offset of the suspend trigger. |
Ian Rogers | dd7624d | 2014-03-14 17:43:00 -0700 | [diff] [blame] | 113 | uint32_t checkinst1 = 0xf8d90000 + Thread::ThreadSuspendTriggerOffset<4>().Int32Value(); |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 114 | uint16_t checkinst2 = 0x6800; |
| 115 | |
| 116 | struct ucontext *uc = (struct ucontext *)context; |
| 117 | struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); |
| 118 | uint8_t* ptr2 = reinterpret_cast<uint8_t*>(sc->arm_pc); |
| 119 | uint8_t* ptr1 = ptr2 - 4; |
| 120 | LOG(DEBUG) << "checking suspend"; |
| 121 | |
| 122 | uint16_t inst2 = ptr2[0] | ptr2[1] << 8; |
| 123 | LOG(DEBUG) << "inst2: " << std::hex << inst2 << " checkinst2: " << checkinst2; |
| 124 | if (inst2 != checkinst2) { |
| 125 | // Second instruction is not good, not ours. |
| 126 | return false; |
| 127 | } |
| 128 | |
| 129 | // The first instruction can a little bit up the stream due to load hoisting |
| 130 | // in the compiler. |
| 131 | uint8_t* limit = ptr1 - 40; // Compiler will hoist to a max of 20 instructions. |
| 132 | bool found = false; |
| 133 | while (ptr1 > limit) { |
| 134 | uint32_t inst1 = ((ptr1[0] | ptr1[1] << 8) << 16) | (ptr1[2] | ptr1[3] << 8); |
| 135 | LOG(DEBUG) << "inst1: " << std::hex << inst1 << " checkinst1: " << checkinst1; |
| 136 | if (inst1 == checkinst1) { |
| 137 | found = true; |
| 138 | break; |
| 139 | } |
| 140 | ptr1 -= 2; // Min instruction size is 2 bytes. |
| 141 | } |
| 142 | if (found) { |
| 143 | LOG(DEBUG) << "suspend check match"; |
| 144 | // This is a suspend check. Arrange for the signal handler to return to |
Dave Allison | 8325296 | 2014-04-03 16:33:48 -0700 | [diff] [blame] | 145 | // art_quick_implicit_suspend. Also set LR so that after the suspend check it |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 146 | // will resume the instruction (current PC + 2). PC points to the |
| 147 | // ldr r0,[r0,#0] instruction (r0 will be 0, set by the trigger). |
| 148 | |
| 149 | // NB: remember that we need to set the bottom bit of the LR register |
| 150 | // to switch to thumb mode. |
| 151 | LOG(DEBUG) << "arm lr: " << std::hex << sc->arm_lr; |
| 152 | LOG(DEBUG) << "arm pc: " << std::hex << sc->arm_pc; |
| 153 | sc->arm_lr = sc->arm_pc + 3; // +2 + 1 (for thumb) |
Dave Allison | 8325296 | 2014-04-03 16:33:48 -0700 | [diff] [blame] | 154 | sc->arm_pc = reinterpret_cast<uintptr_t>(art_quick_implicit_suspend); |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 155 | |
| 156 | // Now remove the suspend trigger that caused this fault. |
Dave Allison | d6ed642 | 2014-04-09 23:36:15 +0000 | [diff] [blame^] | 157 | Thread::Current()->RemoveSuspendTrigger(); |
| 158 | LOG(DEBUG) << "removed suspend trigger invoking test suspend"; |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 159 | return true; |
| 160 | } |
| 161 | return false; |
| 162 | } |
| 163 | |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 164 | // Stack overflow fault handler. |
| 165 | // |
| 166 | // This checks that the fault address is equal to the current stack pointer |
| 167 | // minus the overflow region size (16K typically). The instruction sequence |
| 168 | // that generates this signal is: |
| 169 | // |
| 170 | // sub r12,sp,#16384 |
| 171 | // ldr.w r12,[r12,#0] |
| 172 | // |
| 173 | // The second instruction will fault if r12 is inside the protected region |
| 174 | // on the stack. |
| 175 | // |
| 176 | // If we determine this is a stack overflow we need to move the stack pointer |
| 177 | // to the overflow region below the protected region. Because we now have |
| 178 | // a gap in the stack (skips over protected region), we need to arrange |
| 179 | // for the rest of the system to be unaware of the new stack arrangement |
| 180 | // and behave as if there is a fully valid stack. We do this by placing |
| 181 | // a unique address onto the stack followed by |
| 182 | // the size of the gap. The stack walker will detect this and skip over the |
| 183 | // gap. |
| 184 | |
| 185 | // NB. We also need to be careful of stack alignment as the ARM EABI specifies that |
| 186 | // stack must be 8 byte aligned when making any calls. |
| 187 | |
| 188 | // NB. The size of the gap is the difference between the previous frame's SP and |
| 189 | // the SP at which the size word is pushed. |
| 190 | |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 191 | bool StackOverflowHandler::Action(int sig, siginfo_t* info, void* context) { |
Dave Allison | f943914 | 2014-03-27 15:10:22 -0700 | [diff] [blame] | 192 | struct ucontext *uc = (struct ucontext *)context; |
| 193 | struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext); |
| 194 | LOG(DEBUG) << "stack overflow handler with sp at " << std::hex << &uc; |
| 195 | LOG(DEBUG) << "sigcontext: " << std::hex << sc; |
| 196 | |
| 197 | uint8_t* sp = reinterpret_cast<uint8_t*>(sc->arm_sp); |
| 198 | LOG(DEBUG) << "sp: " << static_cast<void*>(sp); |
| 199 | |
| 200 | uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(sc->fault_address); |
| 201 | LOG(DEBUG) << "fault_addr: " << std::hex << fault_addr; |
| 202 | LOG(DEBUG) << "checking for stack overflow, sp: " << std::hex << static_cast<void*>(sp) << |
| 203 | ", fault_addr: " << fault_addr; |
| 204 | uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>(sp - Thread::kStackOverflowReservedBytes); |
| 205 | |
| 206 | // Check that the fault address is the value expected for a stack overflow. |
| 207 | if (fault_addr != overflow_addr) { |
| 208 | LOG(DEBUG) << "Not a stack overflow"; |
| 209 | return false; |
| 210 | } |
| 211 | |
| 212 | // We know this is a stack overflow. We need to move the sp to the overflow region |
| 213 | // the exists below the protected region. R9 contains the current Thread* so |
| 214 | // we can read the stack_end from that and subtract the size of the |
| 215 | // protected region. This creates a gap in the stack that needs to be marked. |
| 216 | Thread* self = reinterpret_cast<Thread*>(sc->arm_r9); |
| 217 | |
| 218 | uint8_t* prevsp = sp; |
| 219 | sp = self->GetStackEnd() - Thread::kStackOverflowProtectedSize; |
| 220 | LOG(DEBUG) << "setting sp to overflow region at " << std::hex << static_cast<void*>(sp); |
| 221 | |
| 222 | // We need to find the previous frame. Remember that |
| 223 | // this has not yet been fully constructed because the SP has not been |
| 224 | // decremented. So we need to work out the size of the spill portion of the |
| 225 | // frame. This consists of something like: |
| 226 | // |
| 227 | // 0xb6a1d49c: e92d40e0 push {r5, r6, r7, lr} |
| 228 | // 0xb6a1d4a0: ed2d8a06 vpush.f32 {s16-s21} |
| 229 | // |
| 230 | // The first is encoded in the ArtMethod as the spill_mask, the second as the |
| 231 | // fp_spill_mask. A population count on each will give the number of registers |
| 232 | // in each mask. Each register is 4 bytes on ARM32. |
| 233 | |
| 234 | mirror::ArtMethod* method = reinterpret_cast<mirror::ArtMethod*>(sc->arm_r0); |
| 235 | uint32_t spill_mask = method->GetCoreSpillMask(); |
| 236 | uint32_t numcores = __builtin_popcount(spill_mask); |
| 237 | uint32_t fp_spill_mask = method->GetFpSpillMask(); |
| 238 | uint32_t numfps = __builtin_popcount(fp_spill_mask); |
| 239 | uint32_t spill_size = (numcores + numfps) * 4; |
| 240 | LOG(DEBUG) << "spill size: " << spill_size; |
| 241 | uint8_t* prevframe = prevsp + spill_size; |
| 242 | LOG(DEBUG) << "previous frame: " << static_cast<void*>(prevframe); |
| 243 | |
| 244 | // NOTE: the ARM EABI needs an 8 byte alignment. In the case of ARM32 a pointer |
| 245 | // is 4 bytes so that, together with the offset to the previous frame is 8 |
| 246 | // bytes. On other architectures we will need to align the stack. |
| 247 | |
| 248 | // Push a marker onto the stack to tell the stack walker that there is a stack |
| 249 | // overflow and the stack is not contiguous. |
| 250 | |
| 251 | // First the offset from SP to the previous frame. |
| 252 | sp -= sizeof(uint32_t); |
| 253 | LOG(DEBUG) << "push gap of " << static_cast<uint32_t>(prevframe - sp); |
| 254 | *reinterpret_cast<uint32_t*>(sp) = static_cast<uint32_t>(prevframe - sp); |
| 255 | |
| 256 | // Now the gap marker (pointer sized). |
| 257 | sp -= sizeof(mirror::ArtMethod*); |
| 258 | *reinterpret_cast<void**>(sp) = stack_overflow_gap_marker; |
| 259 | |
| 260 | // Now establish the stack pointer for the signal return. |
| 261 | sc->arm_sp = reinterpret_cast<uintptr_t>(sp); |
| 262 | |
| 263 | // Now arrange for the signal handler to return to art_quick_throw_stack_overflow. |
| 264 | // We need the LR to point to the GC map just after the fault instruction. |
| 265 | uint8_t* ptr = reinterpret_cast<uint8_t*>(sc->arm_pc); |
| 266 | uint32_t instr_size = GetInstructionSize(ptr); |
| 267 | sc->arm_lr = (sc->arm_pc + instr_size) | 1; // LR needs to point to gc map location |
| 268 | sc->arm_pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow); |
| 269 | |
| 270 | // The kernel will now return to the address in sc->arm_pc. We have arranged the |
| 271 | // stack pointer to be in the overflow region. Throwing the exception will perform |
| 272 | // a longjmp which will restore the stack pointer to the correct location for the |
| 273 | // exception catch. |
| 274 | return true; |
Dave Allison | b373e09 | 2014-02-20 16:06:36 -0800 | [diff] [blame] | 275 | } |
| 276 | } // namespace art |