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 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           2 : V8_EXPORT_PRIVATE void RestoreOriginalSignalHandler() {
      39             : #if V8_TRAP_HANDLER_SUPPORTED
      40           2 :   if (sigaction(SIGSEGV, &g_old_handler, nullptr) == 0) {
      41           2 :     g_is_default_signal_handler_registered = false;
      42             :   }
      43             : #endif
      44           2 : }
      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        3926 : MetadataLock::MetadataLock() {
      57        3926 :   if (g_thread_in_wasm_code) {
      58           0 :     abort();
      59             :   }
      60             : 
      61        3926 :   while (spinlock_.test_and_set(std::memory_order::memory_order_acquire)) {
      62             :   }
      63        3926 : }
      64             : 
      65        3926 : MetadataLock::~MetadataLock() {
      66        3926 :   if (g_thread_in_wasm_code) {
      67           0 :     abort();
      68             :   }
      69             : 
      70             :   spinlock_.clear(std::memory_order::memory_order_release);
      71        3926 : }
      72             : 
      73             : }  // namespace trap_handler
      74             : }  // namespace internal
      75             : }  // namespace v8