github.com/MerlinKodo/gvisor@v0.0.0-20231110090155-957f62ecf90e/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/MerlinKodo/gvisor/pkg/abi/linux"
    19  )
    20  
    21  // SignalHandlers holds information about signal actions.
    22  //
    23  // +stateify savable
    24  type SignalHandlers struct {
    25  	// mu protects actions, as well as the signal state of all tasks and thread
    26  	// groups using this SignalHandlers object. (See comment on
    27  	// ThreadGroup.signalHandlers.)
    28  	mu signalHandlersMutex `state:"nosave"`
    29  
    30  	// actions is the action to be taken upon receiving each signal.
    31  	actions map[linux.Signal]linux.SigAction
    32  }
    33  
    34  // NewSignalHandlers returns a new SignalHandlers specifying all default
    35  // actions.
    36  func NewSignalHandlers() *SignalHandlers {
    37  	return &SignalHandlers{
    38  		actions: make(map[linux.Signal]linux.SigAction),
    39  	}
    40  }
    41  
    42  // Fork returns a copy of sh for a new thread group.
    43  func (sh *SignalHandlers) Fork() *SignalHandlers {
    44  	sh2 := NewSignalHandlers()
    45  	sh.mu.Lock()
    46  	defer sh.mu.Unlock()
    47  	for sig, act := range sh.actions {
    48  		sh2.actions[sig] = act
    49  	}
    50  	return sh2
    51  }
    52  
    53  // CopyForExec returns a copy of sh for a thread group that is undergoing an
    54  // execve. (See comments in Task.finishExec.)
    55  func (sh *SignalHandlers) CopyForExec() *SignalHandlers {
    56  	sh2 := NewSignalHandlers()
    57  	sh.mu.Lock()
    58  	defer sh.mu.Unlock()
    59  	for sig, act := range sh.actions {
    60  		if act.Handler == linux.SIG_IGN {
    61  			sh2.actions[sig] = linux.SigAction{
    62  				Handler: linux.SIG_IGN,
    63  			}
    64  		}
    65  	}
    66  	return sh2
    67  }
    68  
    69  // IsIgnored returns true if the signal is ignored.
    70  func (sh *SignalHandlers) IsIgnored(sig linux.Signal) bool {
    71  	sh.mu.Lock()
    72  	defer sh.mu.Unlock()
    73  	sa, ok := sh.actions[sig]
    74  	return ok && sa.Handler == linux.SIG_IGN
    75  }
    76  
    77  // dequeueActionLocked returns the SignalAct that should be used to handle sig.
    78  //
    79  // Preconditions: sh.mu must be locked.
    80  func (sh *SignalHandlers) dequeueAction(sig linux.Signal) linux.SigAction {
    81  	act := sh.actions[sig]
    82  	if act.Flags&linux.SA_RESETHAND != 0 {
    83  		delete(sh.actions, sig)
    84  	}
    85  	return act
    86  }