github.com/rkt/rkt@v1.30.1-0.20200224141603-171c416fac02/stage0/enter.go (about) 1 // Copyright 2014 The rkt 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 //+build linux 16 17 package stage0 18 19 import ( 20 "errors" 21 "fmt" 22 "os" 23 "path/filepath" 24 "syscall" 25 26 "github.com/appc/spec/schema/types" 27 "github.com/hashicorp/errwrap" 28 ) 29 30 // Enter enters the pod/app by exec()ing the stage1's /enter similar to /init 31 // /enter can expect to have its CWD set to the app root. 32 // appName and command are supplied to /enter on argv followed by any arguments. 33 // stage1Path is the path of the stage1 rootfs 34 func Enter(cdir string, podPID int, appName types.ACName, stage1Path string, cmdline []string) error { 35 if err := os.Chdir(cdir); err != nil { 36 return errwrap.Wrap(errors.New("error changing to dir"), err) 37 } 38 39 ep, err := getStage1Entrypoint(cdir, enterEntrypoint) 40 if err != nil { 41 return errwrap.Wrap(errors.New("error determining 'enter' entrypoint"), err) 42 } 43 44 argv := []string{filepath.Join(stage1Path, ep)} 45 argv = append(argv, fmt.Sprintf("--pid=%d", podPID)) 46 argv = append(argv, fmt.Sprintf("--appname=%s", appName.String())) 47 argv = append(argv, "--") 48 argv = append(argv, cmdline...) 49 if err := syscall.Exec(argv[0], argv, os.Environ()); err != nil { 50 return errwrap.Wrap(errors.New("error execing enter"), err) 51 } 52 53 // never reached 54 return nil 55 }