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      1 /*
      2  * Copyright (C) 2016 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 #ifndef LIBMEMUNREACHABLE_SCOPED_SIGNAL_HANDLER_H_
     18 #define LIBMEMUNREACHABLE_SCOPED_SIGNAL_HANDLER_H_
     19 
     20 #include <errno.h>
     21 #include <signal.h>
     22 
     23 #include <functional>
     24 
     25 #include "android-base/macros.h"
     26 
     27 #include "log.h"
     28 
     29 class ScopedSignalHandler {
     30  public:
     31   using Fn = std::function<void(ScopedSignalHandler&, int, siginfo_t*, void*)>;
     32 
     33   explicit ScopedSignalHandler(Allocator<Fn> allocator) : allocator_(allocator), signal_(-1) {}
     34   ~ScopedSignalHandler() {
     35     reset();
     36   }
     37 
     38   template <class F>
     39   void install(int signal, F&& f) {
     40     LOG_ALWAYS_FATAL_IF(signal_ != -1, "ScopedSignalHandler already installed");
     41 
     42     handler_ = SignalFn(std::allocator_arg, allocator_,
     43         [=](int signal, siginfo_t* si, void* uctx) {
     44           f(*this, signal, si, uctx);
     45         });
     46 
     47     struct sigaction act{};
     48     act.sa_sigaction = [](int signal, siginfo_t* si, void* uctx) {
     49       handler_(signal, si, uctx);
     50     };
     51     act.sa_flags = SA_SIGINFO;
     52 
     53     int ret = sigaction(signal, &act, &old_act_);
     54     if (ret < 0) {
     55       LOG_ALWAYS_FATAL("failed to install segfault handler: %s", strerror(errno));
     56     }
     57 
     58     signal_ = signal;
     59   }
     60 
     61   void reset() {
     62     if (signal_ != -1) {
     63       int ret = sigaction(signal_, &old_act_, NULL);
     64       if (ret < 0) {
     65         ALOGE("failed to uninstall segfault handler");
     66       }
     67       handler_ = SignalFn{};
     68       signal_ = -1;
     69     }
     70   }
     71 
     72 
     73  private:
     74   using SignalFn = std::function<void(int, siginfo_t*, void*)>;
     75   DISALLOW_COPY_AND_ASSIGN(ScopedSignalHandler);
     76   Allocator<Fn> allocator_;
     77   int signal_;
     78   struct sigaction old_act_;
     79   // TODO(ccross): to support multiple ScopedSignalHandlers handler_ would need
     80   // to be a static map of signals to handlers, but allocated with Allocator.
     81   static SignalFn handler_;
     82 };
     83 
     84 #endif // LIBMEMUNREACHABLE_SCOPED_SIGNAL_HANDLER_H_
     85