1 /*
2  * Copyright (C) 2017 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <signal.h>
20 
21 #include "platform/bionic/macros.h"
22 
23 // This code needs to really block all the signals, not just the user-visible
24 // ones. We call __rt_sigprocmask(2) directly so we don't mask out our own
25 // signals (https://issuetracker.google.com/153624226 was a pthread_exit(3)
26 // crash because a request to dump the thread's stack came in as it was exiting).
27 extern "C" int __rt_sigprocmask(int, const sigset64_t*, sigset64_t*, size_t);
28 
29 class ScopedSignalBlocker {
30  public:
31   // Block all signals.
ScopedSignalBlocker()32   explicit ScopedSignalBlocker() {
33     sigset64_t set;
34     sigfillset64(&set);
35     __rt_sigprocmask(SIG_BLOCK, &set, &old_set_, sizeof(sigset64_t));
36   }
37 
38   // Block just the specified signal.
ScopedSignalBlocker(int signal)39   explicit ScopedSignalBlocker(int signal) {
40     sigset64_t set = {};
41     sigaddset64(&set, signal);
42     __rt_sigprocmask(SIG_BLOCK, &set, &old_set_, sizeof(sigset64_t));
43   }
44 
~ScopedSignalBlocker()45   ~ScopedSignalBlocker() {
46     reset();
47   }
48 
reset()49   void reset() {
50     __rt_sigprocmask(SIG_SETMASK, &old_set_, nullptr, sizeof(sigset64_t));
51   }
52 
53   sigset64_t old_set_;
54 
55   BIONIC_DISALLOW_COPY_AND_ASSIGN(ScopedSignalBlocker);
56 };
57