1 // Copyright 2017 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 // PLEASE READ BEFORE CHANGING THIS FILE! 6 // 7 // This file contains code that is used both inside and outside the out of 8 // bounds signal handler. Because this code runs in a signal handler context, 9 // use extra care when modifying this file. Here are some rules to follow. 10 // 11 // 1. Do not introduce any new external dependencies. This file needs 12 // to be self contained so it is easy to audit everything that a 13 // signal handler might do. 14 // 15 // 2. Any changes must be reviewed by someone from the crash reporting 16 // or security team. See OWNERS for suggested reviewers. 17 // 18 // For more information, see https://goo.gl/yMeyUY. 19 20 #include "src/trap-handler/trap-handler-internal.h" 21 22 namespace v8 { 23 namespace internal { 24 namespace trap_handler { 25 26 // We declare this as int rather than bool as a workaround for a glibc bug, in 27 // which the dynamic loader cannot handle executables whose TLS area is only 28 // 1 byte in size; see https://sourceware.org/bugzilla/show_bug.cgi?id=14898. 29 THREAD_LOCAL int g_thread_in_wasm_code; 30 31 #if V8_TRAP_HANDLER_SUPPORTED 32 // When using the default signal handler, we save the old one to restore in case 33 // V8 chooses not to handle the signal. 34 struct sigaction g_old_handler; 35 bool g_is_default_signal_handler_registered; 36 #endif 37 38 V8_EXPORT_PRIVATE void RestoreOriginalSignalHandler() { 39 #if V8_TRAP_HANDLER_SUPPORTED 40 if (sigaction(SIGSEGV, &g_old_handler, nullptr) == 0) { 41 g_is_default_signal_handler_registered = false; 42 } 43 #endif 44 } 45 46 static_assert(sizeof(g_thread_in_wasm_code) > 1, 47 "sizeof(thread_local_var) must be > 1, see " 48 "https://sourceware.org/bugzilla/show_bug.cgi?id=14898"); 49 50 size_t gNumCodeObjects = 0; 51 CodeProtectionInfoListEntry* gCodeObjects = nullptr; 52 std::atomic_size_t gRecoveredTrapCount = {0}; 53 54 std::atomic_flag MetadataLock::spinlock_ = ATOMIC_FLAG_INIT; 55 56 MetadataLock::MetadataLock() { 57 if (g_thread_in_wasm_code) { 58 abort(); 59 } 60 61 while (spinlock_.test_and_set(std::memory_order::memory_order_acquire)) { 62 } 63 } 64 65 MetadataLock::~MetadataLock() { 66 if (g_thread_in_wasm_code) { 67 abort(); 68 } 69 70 spinlock_.clear(std::memory_order::memory_order_release); 71 } 72 73 } // namespace trap_handler 74 } // namespace internal 75 } // namespace v8 76
