github.com/MerlinKodo/gvisor@v0.0.0-20231110090155-957f62ecf90e/runsc/cmd/wait.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 cmd
    16  
    17  import (
    18  	"context"
    19  	"encoding/json"
    20  	"os"
    21  
    22  	"github.com/MerlinKodo/gvisor/runsc/cmd/util"
    23  	"github.com/MerlinKodo/gvisor/runsc/config"
    24  	"github.com/MerlinKodo/gvisor/runsc/container"
    25  	"github.com/MerlinKodo/gvisor/runsc/flag"
    26  	"github.com/google/subcommands"
    27  	"golang.org/x/sys/unix"
    28  )
    29  
    30  const (
    31  	unsetPID = -1
    32  )
    33  
    34  // Wait implements subcommands.Command for the "wait" command.
    35  type Wait struct {
    36  	rootPID int
    37  	pid     int
    38  }
    39  
    40  // Name implements subcommands.Command.Name.
    41  func (*Wait) Name() string {
    42  	return "wait"
    43  }
    44  
    45  // Synopsis implements subcommands.Command.Synopsis.
    46  func (*Wait) Synopsis() string {
    47  	return "wait on a process inside a container"
    48  }
    49  
    50  // Usage implements subcommands.Command.Usage.
    51  func (*Wait) Usage() string {
    52  	return `wait [flags] <container id>`
    53  }
    54  
    55  // SetFlags implements subcommands.Command.SetFlags.
    56  func (wt *Wait) SetFlags(f *flag.FlagSet) {
    57  	f.IntVar(&wt.rootPID, "rootpid", unsetPID, "select a PID in the sandbox root PID namespace to wait on instead of the container's root process")
    58  	f.IntVar(&wt.pid, "pid", unsetPID, "select a PID in the container's PID namespace to wait on instead of the container's root process")
    59  }
    60  
    61  // Execute implements subcommands.Command.Execute. It waits for a process in a
    62  // container to exit before returning.
    63  func (wt *Wait) Execute(_ context.Context, f *flag.FlagSet, args ...any) subcommands.ExitStatus {
    64  	if f.NArg() != 1 {
    65  		f.Usage()
    66  		return subcommands.ExitUsageError
    67  	}
    68  	// You can't specify both -pid and -rootpid.
    69  	if wt.rootPID != unsetPID && wt.pid != unsetPID {
    70  		util.Fatalf("only one of -pid and -rootPid can be set")
    71  	}
    72  
    73  	id := f.Arg(0)
    74  	conf := args[0].(*config.Config)
    75  
    76  	c, err := container.Load(conf.RootDir, container.FullID{ContainerID: id}, container.LoadOpts{})
    77  	if err != nil {
    78  		util.Fatalf("loading container: %v", err)
    79  	}
    80  
    81  	var waitStatus unix.WaitStatus
    82  	switch {
    83  	// Wait on the whole container.
    84  	case wt.rootPID == unsetPID && wt.pid == unsetPID:
    85  		ws, err := c.Wait()
    86  		if err != nil {
    87  			util.Fatalf("waiting on container %q: %v", c.ID, err)
    88  		}
    89  		waitStatus = ws
    90  	// Wait on a PID in the root PID namespace.
    91  	case wt.rootPID != unsetPID:
    92  		ws, err := c.WaitRootPID(int32(wt.rootPID))
    93  		if err != nil {
    94  			util.Fatalf("waiting on PID in root PID namespace %d in container %q: %v", wt.rootPID, c.ID, err)
    95  		}
    96  		waitStatus = ws
    97  	// Wait on a PID in the container's PID namespace.
    98  	case wt.pid != unsetPID:
    99  		ws, err := c.WaitPID(int32(wt.pid))
   100  		if err != nil {
   101  			util.Fatalf("waiting on PID %d in container %q: %v", wt.pid, c.ID, err)
   102  		}
   103  		waitStatus = ws
   104  	}
   105  	result := waitResult{
   106  		ID:         id,
   107  		ExitStatus: exitStatus(waitStatus),
   108  	}
   109  	// Write json-encoded wait result directly to stdout.
   110  	if err := json.NewEncoder(os.Stdout).Encode(result); err != nil {
   111  		util.Fatalf("marshaling wait result: %v", err)
   112  	}
   113  	return subcommands.ExitSuccess
   114  }
   115  
   116  type waitResult struct {
   117  	ID         string `json:"id"`
   118  	ExitStatus int    `json:"exitStatus"`
   119  }
   120  
   121  // exitStatus returns the correct exit status for a process based on if it
   122  // was signaled or exited cleanly.
   123  func exitStatus(status unix.WaitStatus) int {
   124  	if status.Signaled() {
   125  		return 128 + int(status.Signal())
   126  	}
   127  	return status.ExitStatus()
   128  }