1//go:build linux
2//+build linux
3
4package pty
5
6import (
7	"os"
8	"strconv"
9	"syscall"
10	"unsafe"
11)
12
13func open() (pty, tty *os.File, err error) {
14	p, err := os.OpenFile("/dev/ptmx", os.O_RDWR, 0)
15	if err != nil {
16		return nil, nil, err
17	}
18	// In case of error after this point, make sure we close the ptmx fd.
19	defer func() {
20		if err != nil {
21			_ = p.Close() // Best effort.
22		}
23	}()
24
25	sname, err := ptsname(p)
26	if err != nil {
27		return nil, nil, err
28	}
29
30	if err := unlockpt(p); err != nil {
31		return nil, nil, err
32	}
33
34	t, err := os.OpenFile(sname, os.O_RDWR|syscall.O_NOCTTY, 0) //nolint:gosec // Expected Open from a variable.
35	if err != nil {
36		return nil, nil, err
37	}
38	return p, t, nil
39}
40
41func ptsname(f *os.File) (string, error) {
42	var n _C_uint
43	err := ioctl(f.Fd(), syscall.TIOCGPTN, uintptr(unsafe.Pointer(&n))) //nolint:gosec // Expected unsafe pointer for Syscall call.
44	if err != nil {
45		return "", err
46	}
47	return "/dev/pts/" + strconv.Itoa(int(n)), nil
48}
49
50func unlockpt(f *os.File) error {
51	var u _C_int
52	// use TIOCSPTLCK with a pointer to zero to clear the lock
53	return ioctl(f.Fd(), syscall.TIOCSPTLCK, uintptr(unsafe.Pointer(&u))) //nolint:gosec // Expected unsafe pointer for Syscall call.
54}
55