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 "thread.h" 18 19 #include <signal.h> 20 21 #include "base/logging.h" // For VLOG. 22 #include "base/utils.h" 23 24 namespace art { 25 26 void Thread::SetNativePriority(int) { 27 // Do nothing. 28 } 29 30 int Thread::GetNativePriority() { 31 return kNormThreadPriority; 32 } 33 34 static void SigAltStack(stack_t* new_stack, stack_t* old_stack) { 35 if (sigaltstack(new_stack, old_stack) == -1) { 36 PLOG(FATAL) << "sigaltstack failed"; 37 } 38 } 39 40 // The default SIGSTKSZ on linux is 8K. If we do any logging in a signal 41 // handler or do a stack unwind, this is too small. We allocate 32K 42 // instead of the minimum signal stack size. 43 // TODO: We shouldn't do logging (with locks) in signal handlers. 44 static constexpr int kHostAltSigStackSize = 45 32 * KB < MINSIGSTKSZ ? MINSIGSTKSZ : 32 * KB; 46 47 void Thread::SetUpAlternateSignalStack() { 48 // Create and set an alternate signal stack. 49 #ifdef ART_TARGET_ANDROID 50 LOG(FATAL) << "Invalid use of alternate signal stack on Android"; 51 #endif 52 stack_t ss; 53 ss.ss_sp = new uint8_t[kHostAltSigStackSize]; 54 ss.ss_size = kHostAltSigStackSize; 55 ss.ss_flags = 0; 56 CHECK(ss.ss_sp != nullptr); 57 SigAltStack(&ss, nullptr); 58 59 // Double-check that it worked. 60 ss.ss_sp = nullptr; 61 SigAltStack(nullptr, &ss); 62 VLOG(threads) << "Alternate signal stack is " << PrettySize(ss.ss_size) << " at " << ss.ss_sp; 63 } 64 65 void Thread::TearDownAlternateSignalStack() { 66 // Get the pointer so we can free the memory. 67 stack_t ss; 68 SigAltStack(nullptr, &ss); 69 uint8_t* allocated_signal_stack = reinterpret_cast<uint8_t*>(ss.ss_sp); 70 71 // Tell the kernel to stop using it. 72 ss.ss_sp = nullptr; 73 ss.ss_flags = SS_DISABLE; 74 ss.ss_size = kHostAltSigStackSize; // Avoid ENOMEM failure with Mac OS' buggy libc. 75 SigAltStack(&ss, nullptr); 76 77 // Free it. 78 delete[] allocated_signal_stack; 79 } 80 81 } // namespace art 82
