github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/kernel/signal_handlers.go (about)

     1  // Copyright 2018 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package kernel
    16  
    17  import (
    18  	"github.com/SagerNet/gvisor/pkg/abi/linux"
    19  	"github.com/SagerNet/gvisor/pkg/sync"
    20  )
    21  
    22  // SignalHandlers holds information about signal actions.
    23  //
    24  // +stateify savable
    25  type SignalHandlers struct {
    26  	// mu protects actions, as well as the signal state of all tasks and thread
    27  	// groups using this SignalHandlers object. (See comment on
    28  	// ThreadGroup.signalHandlers.)
    29  	mu sync.Mutex `state:"nosave"`
    30  
    31  	// actions is the action to be taken upon receiving each signal.
    32  	actions map[linux.Signal]linux.SigAction
    33  }
    34  
    35  // NewSignalHandlers returns a new SignalHandlers specifying all default
    36  // actions.
    37  func NewSignalHandlers() *SignalHandlers {
    38  	return &SignalHandlers{
    39  		actions: make(map[linux.Signal]linux.SigAction),
    40  	}
    41  }
    42  
    43  // Fork returns a copy of sh for a new thread group.
    44  func (sh *SignalHandlers) Fork() *SignalHandlers {
    45  	sh2 := NewSignalHandlers()
    46  	sh.mu.Lock()
    47  	defer sh.mu.Unlock()
    48  	for sig, act := range sh.actions {
    49  		sh2.actions[sig] = act
    50  	}
    51  	return sh2
    52  }
    53  
    54  // CopyForExec returns a copy of sh for a thread group that is undergoing an
    55  // execve. (See comments in Task.finishExec.)
    56  func (sh *SignalHandlers) CopyForExec() *SignalHandlers {
    57  	sh2 := NewSignalHandlers()
    58  	sh.mu.Lock()
    59  	defer sh.mu.Unlock()
    60  	for sig, act := range sh.actions {
    61  		if act.Handler == linux.SIG_IGN {
    62  			sh2.actions[sig] = linux.SigAction{
    63  				Handler: linux.SIG_IGN,
    64  			}
    65  		}
    66  	}
    67  	return sh2
    68  }
    69  
    70  // IsIgnored returns true if the signal is ignored.
    71  func (sh *SignalHandlers) IsIgnored(sig linux.Signal) bool {
    72  	sh.mu.Lock()
    73  	defer sh.mu.Unlock()
    74  	sa, ok := sh.actions[sig]
    75  	return ok && sa.Handler == linux.SIG_IGN
    76  }
    77  
    78  // dequeueActionLocked returns the SignalAct that should be used to handle sig.
    79  //
    80  // Preconditions: sh.mu must be locked.
    81  func (sh *SignalHandlers) dequeueAction(sig linux.Signal) linux.SigAction {
    82  	act := sh.actions[sig]
    83  	if act.Flags&linux.SA_RESETHAND != 0 {
    84  		delete(sh.actions, sig)
    85  	}
    86  	return act
    87  }