github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/kernel/context.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/context"
    19  )
    20  
    21  // contextID is the kernel package's type for context.Context.Value keys.
    22  type contextID int
    23  
    24  const (
    25  	// CtxCanTrace is a Context.Value key for a function with the same
    26  	// signature and semantics as kernel.Task.CanTrace.
    27  	CtxCanTrace contextID = iota
    28  
    29  	// CtxKernel is a Context.Value key for a Kernel.
    30  	CtxKernel
    31  
    32  	// CtxPIDNamespace is a Context.Value key for a PIDNamespace.
    33  	CtxPIDNamespace
    34  
    35  	// CtxTask is a Context.Value key for a Task.
    36  	CtxTask
    37  
    38  	// CtxUTSNamespace is a Context.Value key for a UTSNamespace.
    39  	CtxUTSNamespace
    40  
    41  	// CtxIPCNamespace is a Context.Value key for a IPCNamespace.
    42  	CtxIPCNamespace
    43  )
    44  
    45  // ContextCanTrace returns true if ctx is permitted to trace t, in the same sense
    46  // as kernel.Task.CanTrace.
    47  func ContextCanTrace(ctx context.Context, t *Task, attach bool) bool {
    48  	if v := ctx.Value(CtxCanTrace); v != nil {
    49  		return v.(func(*Task, bool) bool)(t, attach)
    50  	}
    51  	return false
    52  }
    53  
    54  // KernelFromContext returns the Kernel in which ctx is executing, or nil if
    55  // there is no such Kernel.
    56  func KernelFromContext(ctx context.Context) *Kernel {
    57  	if v := ctx.Value(CtxKernel); v != nil {
    58  		return v.(*Kernel)
    59  	}
    60  	return nil
    61  }
    62  
    63  // PIDNamespaceFromContext returns the PID namespace in which ctx is executing,
    64  // or nil if there is no such PID namespace.
    65  func PIDNamespaceFromContext(ctx context.Context) *PIDNamespace {
    66  	if v := ctx.Value(CtxPIDNamespace); v != nil {
    67  		return v.(*PIDNamespace)
    68  	}
    69  	return nil
    70  }
    71  
    72  // UTSNamespaceFromContext returns the UTS namespace in which ctx is executing,
    73  // or nil if there is no such UTS namespace.
    74  func UTSNamespaceFromContext(ctx context.Context) *UTSNamespace {
    75  	if v := ctx.Value(CtxUTSNamespace); v != nil {
    76  		return v.(*UTSNamespace)
    77  	}
    78  	return nil
    79  }
    80  
    81  // IPCNamespaceFromContext returns the IPC namespace in which ctx is executing,
    82  // or nil if there is no such IPC namespace. It takes a reference on the
    83  // namespace.
    84  func IPCNamespaceFromContext(ctx context.Context) *IPCNamespace {
    85  	if v := ctx.Value(CtxIPCNamespace); v != nil {
    86  		return v.(*IPCNamespace)
    87  	}
    88  	return nil
    89  }
    90  
    91  // TaskFromContext returns the Task associated with ctx, or nil if there is no
    92  // such Task.
    93  func TaskFromContext(ctx context.Context) *Task {
    94  	if v := ctx.Value(CtxTask); v != nil {
    95  		return v.(*Task)
    96  	}
    97  	return nil
    98  }