go-sandbox/forkexec/fork_util.go

110 lines
2.5 KiB
Go

package forkexec
import (
"syscall"
"github.com/criyle/go-sandbox/types/mount"
)
// prepareExec prepares execve parameters
func prepareExec(Args, Env []string) (*byte, []*byte, []*byte, error) {
// make exec args0
argv0, err := syscall.BytePtrFromString(Args[0])
if err != nil {
return nil, nil, nil, err
}
// make exec args
argv, err := syscall.SlicePtrFromStrings(Args)
if err != nil {
return nil, nil, nil, err
}
// make env
envv, err := syscall.SlicePtrFromStrings(Env)
if err != nil {
return nil, nil, nil, err
}
return argv0, argv, envv, nil
}
// prepareFds prapares fd array
func prepareFds(files []uintptr) ([]int, int) {
fd := make([]int, len(files))
nextfd := len(files)
for i, ufd := range files {
if nextfd < int(ufd) {
nextfd = int(ufd)
}
fd[i] = int(ufd)
}
nextfd++
return fd, nextfd
}
// syscallStringFromString prepares *byte if string is not empty, other wise nil
func syscallStringFromString(str string) (*byte, error) {
if str != "" {
return syscall.BytePtrFromString(str)
}
return nil, nil
}
// preparePivotRoot prepares pivot root parameters
func preparePivotRoot(r string) (*byte, *byte, error) {
if r == "" {
return nil, nil, nil
}
root, err := syscall.BytePtrFromString(r)
if err != nil {
return nil, nil, err
}
oldRoot, err := syscall.BytePtrFromString(OldRoot)
if err != nil {
return nil, nil, err
}
return root, oldRoot, nil
}
// prepareMounts prepare mkdir and mount syscall params
func prepareMounts(ms []*mount.Mount) ([]*mount.SyscallParams, [][]*byte, error) {
params, err := mount.ToSyscalls(ms)
if err != nil {
return nil, nil, err
}
// evaluate paths that need to be created
pathsToCreate := make([][]*byte, 0, len(ms))
for _, m := range ms {
prefix := pathPrefix(m.Target)
paths, err := arrayPtrFromStrings(prefix)
if err != nil {
return nil, nil, err
}
pathsToCreate = append(pathsToCreate, paths)
}
return params, pathsToCreate, nil
}
// pathPrefix get all components from path
func pathPrefix(path string) []string {
ret := make([]string, 0)
for i := 1; i < len(path); i++ {
if path[i] == '/' {
ret = append(ret, path[:i])
}
}
ret = append(ret, path)
return ret
}
// arrayPtrFromStrings convers srings to c style strings
func arrayPtrFromStrings(strs []string) ([]*byte, error) {
bytes := make([]*byte, 0, len(strs))
for _, s := range strs {
b, err := syscall.BytePtrFromString(s)
if err != nil {
return nil, err
}
bytes = append(bytes, b)
}
return bytes, nil
}