1 // Copyright 2016 the V8 project authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef V8_TRAP_HANDLER_TRAP_HANDLER_INTERNAL_H_ 6 #define V8_TRAP_HANDLER_TRAP_HANDLER_INTERNAL_H_ 7 8 // This file should not be included (even transitively) by files outside of 9 // src/trap-handler. 10 11 #include "src/trap-handler/trap-handler.h" 12 13 #include <atomic> 14 15 namespace v8 { 16 namespace internal { 17 namespace trap_handler { 18 19 // This describes a chunk of code that the signal handler will be able to handle 20 // faults in. {base} points to the beginning of the chunk, and {size} is the 21 // number of bytes in the code chunk. The remainder of the struct is a list of 22 // protected memory access instructions and an offset to a landing pad to handle 23 // faults on that instruction. 24 struct CodeProtectionInfo { 25 Address base; 26 size_t size; 27 size_t num_protected_instructions; 28 ProtectedInstructionData instructions[1]; 29 }; 30 31 class MetadataLock { 32 static std::atomic_flag spinlock_; 33 34 public: 35 MetadataLock(); 36 ~MetadataLock(); 37 38 // We'd normally use DISALLOW_COPY_AND_ASSIGN, but we're avoiding a dependency 39 // on base/macros.h 40 MetadataLock(const MetadataLock&) = delete; 41 void operator=(const MetadataLock&) = delete; 42 }; 43 44 #if V8_TRAP_HANDLER_SUPPORTED 45 void HandleSignal(int signum, siginfo_t* info, void* context); 46 #endif 47 48 // To enable constant time registration of handler data, we keep a free list of 49 // entries in the gCodeObjects table. Each entry contains a {next_free} field, 50 // which can be used to figure out where the next entry should be inserted. 51 // In order to avoid having to initialize all the links to start with, we use 52 // 0 to indicate that this is a fresh, never-used list entry and that therefore 53 // the next entry is known to be free. If {next_entry} is greater than zero, 54 // then {next_entry - 1} is the index that we should insert into next. 55 struct CodeProtectionInfoListEntry { 56 CodeProtectionInfo* code_info; 57 size_t next_free; 58 }; 59 60 extern size_t gNumCodeObjects; 61 extern CodeProtectionInfoListEntry* gCodeObjects; 62 63 extern std::atomic_size_t gRecoveredTrapCount; 64 65 // Searches the fault location table for an entry matching fault_addr. If found, 66 // returns true and sets landing_pad to the address of a fragment of code that 67 // can recover from this fault. Otherwise, returns false and leaves offset 68 // unchanged. 69 bool TryFindLandingPad(uintptr_t fault_addr, uintptr_t* landing_pad); 70 71 #if V8_TRAP_HANDLER_SUPPORTED 72 // When using the default signal handler, we save the old one to restore in case 73 // V8 chooses not to handle the signal. 74 extern struct sigaction g_old_handler; 75 extern bool g_is_default_signal_handler_registered; 76 #endif 77 78 } // namespace trap_handler 79 } // namespace internal 80 } // namespace v8 81 82 #endif // V8_TRAP_HANDLER_TRAP_HANDLER_INTERNAL_H_ 83