1 /*
2 * Copyright (C) 2011 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 #include <signal.h>
18
19 #include "thread.h"
20 #include "utils.h"
21
22 namespace art {
23
SetNativePriority(int)24 void Thread::SetNativePriority(int) {
25 // Do nothing.
26 }
27
GetNativePriority()28 int Thread::GetNativePriority() {
29 return kNormThreadPriority;
30 }
31
SigAltStack(stack_t * new_stack,stack_t * old_stack)32 static void SigAltStack(stack_t* new_stack, stack_t* old_stack) {
33 if (sigaltstack(new_stack, old_stack) == -1) {
34 PLOG(FATAL) << "sigaltstack failed";
35 }
36 }
37
38 // The default SIGSTKSZ on linux is 8K. If we do any logging in a signal
39 // handler or do a stack unwind, this is too small. We allocate 32K
40 // instead of the minimum signal stack size.
41 // TODO: We shouldn't do logging (with locks) in signal handlers.
42 static constexpr int kHostAltSigStackSize =
43 32 * KB < MINSIGSTKSZ ? MINSIGSTKSZ : 32 * KB;
44
SetUpAlternateSignalStack()45 void Thread::SetUpAlternateSignalStack() {
46 // Create and set an alternate signal stack.
47 #ifdef ART_TARGET_ANDROID
48 LOG(FATAL) << "Invalid use of alternate signal stack on Android";
49 #endif
50 stack_t ss;
51 ss.ss_sp = new uint8_t[kHostAltSigStackSize];
52 ss.ss_size = kHostAltSigStackSize;
53 ss.ss_flags = 0;
54 CHECK(ss.ss_sp != nullptr);
55 SigAltStack(&ss, nullptr);
56
57 // Double-check that it worked.
58 ss.ss_sp = nullptr;
59 SigAltStack(nullptr, &ss);
60 VLOG(threads) << "Alternate signal stack is " << PrettySize(ss.ss_size) << " at " << ss.ss_sp;
61 }
62
TearDownAlternateSignalStack()63 void Thread::TearDownAlternateSignalStack() {
64 // Get the pointer so we can free the memory.
65 stack_t ss;
66 SigAltStack(nullptr, &ss);
67 uint8_t* allocated_signal_stack = reinterpret_cast<uint8_t*>(ss.ss_sp);
68
69 // Tell the kernel to stop using it.
70 ss.ss_sp = nullptr;
71 ss.ss_flags = SS_DISABLE;
72 ss.ss_size = kHostAltSigStackSize; // Avoid ENOMEM failure with Mac OS' buggy libc.
73 SigAltStack(&ss, nullptr);
74
75 // Free it.
76 delete[] allocated_signal_stack;
77 }
78
79 } // namespace art
80