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 trap 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 uintptr_t 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 MetadataLock(const MetadataLock&) = delete; 39 void operator=(const MetadataLock&) = delete; 40 }; 41 42 // To enable constant time registration of handler data, we keep a free list of 43 // entries in the gCodeObjects table. Each entry contains a {next_free} field, 44 // which can be used to figure out where the next entry should be inserted. 45 // In order to avoid having to initialize all the links to start with, we use 46 // 0 to indicate that this is a fresh, never-used list entry and that therefore 47 // the next entry is known to be free. If {next_entry} is greater than zero, 48 // then {next_entry - 1} is the index that we should insert into next. 49 struct CodeProtectionInfoListEntry { 50 CodeProtectionInfo* code_info; 51 size_t next_free; 52 }; 53 54 extern size_t gNumCodeObjects; 55 extern CodeProtectionInfoListEntry* gCodeObjects; 56 57 extern std::atomic_size_t gRecoveredTrapCount; 58 59 // Searches the fault location table for an entry matching fault_addr. If found, 60 // returns true and sets landing_pad to the address of a fragment of code that 61 // can recover from this fault. Otherwise, returns false and leaves offset 62 // unchanged. 63 bool TryFindLandingPad(uintptr_t fault_addr, uintptr_t* landing_pad); 64 65 } // namespace trap_handler 66 } // namespace internal 67 } // namespace v8 68 69 #endif // V8_TRAP_HANDLER_TRAP_HANDLER_INTERNAL_H_ 70