Line data    Source code

       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 trap handler. Because this code runs in a trap 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             : //    trap 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             : static_assert(sizeof(g_thread_in_wasm_code) > 1,
      32             :               "sizeof(thread_local_var) must be > 1, see "
      33             :               "https://sourceware.org/bugzilla/show_bug.cgi?id=14898");
      34             : 
      35             : size_t gNumCodeObjects = 0;
      36             : CodeProtectionInfoListEntry* gCodeObjects = nullptr;
      37             : std::atomic_size_t gRecoveredTrapCount = {0};
      38             : 
      39             : std::atomic_flag MetadataLock::spinlock_ = ATOMIC_FLAG_INIT;
      40             : 
      41      269185 : MetadataLock::MetadataLock() {
      42      269185 :   if (g_thread_in_wasm_code) {
      43           0 :     abort();
      44             :   }
      45             : 
      46     1080823 :   while (spinlock_.test_and_set(std::memory_order::memory_order_acquire)) {
      47             :   }
      48      269185 : }
      49             : 
      50      269185 : MetadataLock::~MetadataLock() {
      51      269185 :   if (g_thread_in_wasm_code) {
      52           0 :     abort();
      53             :   }
      54             : 
      55             :   spinlock_.clear(std::memory_order::memory_order_release);
      56      269185 : }
      57             : 
      58             : }  // namespace trap_handler
      59             : }  // namespace internal
      60             : }  // namespace v8