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// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package kernel
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sync"
)
// SignalHandlers holds information about signal actions.
//
// +stateify savable
type SignalHandlers struct {
// mu protects actions, as well as the signal state of all tasks and thread
// groups using this SignalHandlers object. (See comment on
// ThreadGroup.signalHandlers.)
mu sync.Mutex `state:"nosave"`
// actions is the action to be taken upon receiving each signal.
actions map[linux.Signal]linux.SigAction
}
// NewSignalHandlers returns a new SignalHandlers specifying all default
// actions.
func NewSignalHandlers() *SignalHandlers {
return &SignalHandlers{
actions: make(map[linux.Signal]linux.SigAction),
}
}
// Fork returns a copy of sh for a new thread group.
func (sh *SignalHandlers) Fork() *SignalHandlers {
sh2 := NewSignalHandlers()
sh.mu.Lock()
defer sh.mu.Unlock()
for sig, act := range sh.actions {
sh2.actions[sig] = act
}
return sh2
}
// CopyForExec returns a copy of sh for a thread group that is undergoing an
// execve. (See comments in Task.finishExec.)
func (sh *SignalHandlers) CopyForExec() *SignalHandlers {
sh2 := NewSignalHandlers()
sh.mu.Lock()
defer sh.mu.Unlock()
for sig, act := range sh.actions {
if act.Handler == linux.SIG_IGN {
sh2.actions[sig] = linux.SigAction{
Handler: linux.SIG_IGN,
}
}
}
return sh2
}
// IsIgnored returns true if the signal is ignored.
func (sh *SignalHandlers) IsIgnored(sig linux.Signal) bool {
sh.mu.Lock()
defer sh.mu.Unlock()
sa, ok := sh.actions[sig]
return ok && sa.Handler == linux.SIG_IGN
}
// dequeueActionLocked returns the SignalAct that should be used to handle sig.
//
// Preconditions: sh.mu must be locked.
func (sh *SignalHandlers) dequeueAction(sig linux.Signal) linux.SigAction {
act := sh.actions[sig]
if act.Flags&linux.SA_RESETHAND != 0 {
delete(sh.actions, sig)
}
return act
}
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