1 /* -*- linux-c -*- --------------------------------------------------------- *
3 * linux/fs/devpts/inode.c
5 * Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
7 * This file is part of the Linux kernel and is made available under
8 * the terms of the GNU General Public License, version 2, or at your
9 * option, any later version, incorporated herein by reference.
11 * ------------------------------------------------------------------------- */
13 #include <linux/module.h>
14 #include <linux/init.h>
16 #include <linux/sched.h>
17 #include <linux/namei.h>
18 #include <linux/slab.h>
19 #include <linux/mount.h>
20 #include <linux/tty.h>
21 #include <linux/mutex.h>
22 #include <linux/magic.h>
23 #include <linux/idr.h>
24 #include <linux/devpts_fs.h>
25 #include <linux/parser.h>
26 #include <linux/fsnotify.h>
27 #include <linux/seq_file.h>
29 #define DEVPTS_DEFAULT_MODE 0600
31 * ptmx is a new node in /dev/pts and will be unused in legacy (single-
32 * instance) mode. To prevent surprises in user space, set permissions of
33 * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
36 #define DEVPTS_DEFAULT_PTMX_MODE 0000
40 * sysctl support for setting limits on the number of Unix98 ptys allocated.
41 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
43 static int pty_limit
= NR_UNIX98_PTY_DEFAULT
;
44 static int pty_reserve
= NR_UNIX98_PTY_RESERVE
;
45 static int pty_limit_min
;
46 static int pty_limit_max
= INT_MAX
;
49 static struct ctl_table pty_table
[] = {
52 .maxlen
= sizeof(int),
55 .proc_handler
= proc_dointvec_minmax
,
56 .extra1
= &pty_limit_min
,
57 .extra2
= &pty_limit_max
,
59 .procname
= "reserve",
60 .maxlen
= sizeof(int),
63 .proc_handler
= proc_dointvec_minmax
,
64 .extra1
= &pty_limit_min
,
65 .extra2
= &pty_limit_max
,
68 .maxlen
= sizeof(int),
71 .proc_handler
= proc_dointvec
,
76 static struct ctl_table pty_kern_table
[] = {
85 static struct ctl_table pty_root_table
[] = {
89 .child
= pty_kern_table
,
94 static DEFINE_MUTEX(allocated_ptys_lock
);
96 static struct vfsmount
*devpts_mnt
;
98 struct pts_mount_opts
{
110 Opt_uid
, Opt_gid
, Opt_mode
, Opt_ptmxmode
, Opt_newinstance
, Opt_max
,
114 static const match_table_t tokens
= {
117 {Opt_mode
, "mode=%o"},
118 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
119 {Opt_ptmxmode
, "ptmxmode=%o"},
120 {Opt_newinstance
, "newinstance"},
127 struct ida allocated_ptys
;
128 struct pts_mount_opts mount_opts
;
129 struct dentry
*ptmx_dentry
;
132 static inline struct pts_fs_info
*DEVPTS_SB(struct super_block
*sb
)
134 return sb
->s_fs_info
;
137 static inline struct super_block
*pts_sb_from_inode(struct inode
*inode
)
139 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
140 if (inode
->i_sb
->s_magic
== DEVPTS_SUPER_MAGIC
)
143 return devpts_mnt
->mnt_sb
;
146 #define PARSE_MOUNT 0
147 #define PARSE_REMOUNT 1
150 * parse_mount_options():
151 * Set @opts to mount options specified in @data. If an option is not
152 * specified in @data, set it to its default value. The exception is
153 * 'newinstance' option which can only be set/cleared on a mount (i.e.
154 * cannot be changed during remount).
156 * Note: @data may be NULL (in which case all options are set to default).
158 static int parse_mount_options(char *data
, int op
, struct pts_mount_opts
*opts
)
166 opts
->mode
= DEVPTS_DEFAULT_MODE
;
167 opts
->ptmxmode
= DEVPTS_DEFAULT_PTMX_MODE
;
168 opts
->max
= NR_UNIX98_PTY_MAX
;
170 /* newinstance makes sense only on initial mount */
171 if (op
== PARSE_MOUNT
)
172 opts
->newinstance
= 0;
174 while ((p
= strsep(&data
, ",")) != NULL
) {
175 substring_t args
[MAX_OPT_ARGS
];
182 token
= match_token(p
, tokens
, args
);
185 if (match_int(&args
[0], &option
))
191 if (match_int(&args
[0], &option
))
197 if (match_octal(&args
[0], &option
))
199 opts
->mode
= option
& S_IALLUGO
;
201 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
203 if (match_octal(&args
[0], &option
))
205 opts
->ptmxmode
= option
& S_IALLUGO
;
207 case Opt_newinstance
:
208 /* newinstance makes sense only on initial mount */
209 if (op
== PARSE_MOUNT
)
210 opts
->newinstance
= 1;
213 if (match_int(&args
[0], &option
) ||
214 option
< 0 || option
> NR_UNIX98_PTY_MAX
)
220 printk(KERN_ERR
"devpts: called with bogus options\n");
228 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
229 static int mknod_ptmx(struct super_block
*sb
)
233 struct dentry
*dentry
;
235 struct dentry
*root
= sb
->s_root
;
236 struct pts_fs_info
*fsi
= DEVPTS_SB(sb
);
237 struct pts_mount_opts
*opts
= &fsi
->mount_opts
;
239 mutex_lock(&root
->d_inode
->i_mutex
);
241 /* If we have already created ptmx node, return */
242 if (fsi
->ptmx_dentry
) {
247 dentry
= d_alloc_name(root
, "ptmx");
249 printk(KERN_NOTICE
"Unable to alloc dentry for ptmx node\n");
254 * Create a new 'ptmx' node in this mount of devpts.
256 inode
= new_inode(sb
);
258 printk(KERN_ERR
"Unable to alloc inode for ptmx node\n");
264 inode
->i_mtime
= inode
->i_atime
= inode
->i_ctime
= CURRENT_TIME
;
266 mode
= S_IFCHR
|opts
->ptmxmode
;
267 init_special_inode(inode
, mode
, MKDEV(TTYAUX_MAJOR
, 2));
269 d_add(dentry
, inode
);
271 fsi
->ptmx_dentry
= dentry
;
274 mutex_unlock(&root
->d_inode
->i_mutex
);
278 static void update_ptmx_mode(struct pts_fs_info
*fsi
)
281 if (fsi
->ptmx_dentry
) {
282 inode
= fsi
->ptmx_dentry
->d_inode
;
283 inode
->i_mode
= S_IFCHR
|fsi
->mount_opts
.ptmxmode
;
287 static inline void update_ptmx_mode(struct pts_fs_info
*fsi
)
293 static int devpts_remount(struct super_block
*sb
, int *flags
, char *data
)
296 struct pts_fs_info
*fsi
= DEVPTS_SB(sb
);
297 struct pts_mount_opts
*opts
= &fsi
->mount_opts
;
299 err
= parse_mount_options(data
, PARSE_REMOUNT
, opts
);
302 * parse_mount_options() restores options to default values
303 * before parsing and may have changed ptmxmode. So, update the
304 * mode in the inode too. Bogus options don't fail the remount,
305 * so do this even on error return.
307 update_ptmx_mode(fsi
);
312 static int devpts_show_options(struct seq_file
*seq
, struct dentry
*root
)
314 struct pts_fs_info
*fsi
= DEVPTS_SB(root
->d_sb
);
315 struct pts_mount_opts
*opts
= &fsi
->mount_opts
;
318 seq_printf(seq
, ",uid=%u", opts
->uid
);
320 seq_printf(seq
, ",gid=%u", opts
->gid
);
321 seq_printf(seq
, ",mode=%03o", opts
->mode
);
322 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
323 seq_printf(seq
, ",ptmxmode=%03o", opts
->ptmxmode
);
324 if (opts
->max
< NR_UNIX98_PTY_MAX
)
325 seq_printf(seq
, ",max=%d", opts
->max
);
331 static const struct super_operations devpts_sops
= {
332 .statfs
= simple_statfs
,
333 .remount_fs
= devpts_remount
,
334 .show_options
= devpts_show_options
,
337 static void *new_pts_fs_info(void)
339 struct pts_fs_info
*fsi
;
341 fsi
= kzalloc(sizeof(struct pts_fs_info
), GFP_KERNEL
);
345 ida_init(&fsi
->allocated_ptys
);
346 fsi
->mount_opts
.mode
= DEVPTS_DEFAULT_MODE
;
347 fsi
->mount_opts
.ptmxmode
= DEVPTS_DEFAULT_PTMX_MODE
;
353 devpts_fill_super(struct super_block
*s
, void *data
, int silent
)
357 s
->s_blocksize
= 1024;
358 s
->s_blocksize_bits
= 10;
359 s
->s_magic
= DEVPTS_SUPER_MAGIC
;
360 s
->s_op
= &devpts_sops
;
363 s
->s_fs_info
= new_pts_fs_info();
367 inode
= new_inode(s
);
371 inode
->i_mtime
= inode
->i_atime
= inode
->i_ctime
= CURRENT_TIME
;
372 inode
->i_mode
= S_IFDIR
| S_IRUGO
| S_IXUGO
| S_IWUSR
;
373 inode
->i_op
= &simple_dir_inode_operations
;
374 inode
->i_fop
= &simple_dir_operations
;
377 s
->s_root
= d_make_root(inode
);
381 printk(KERN_ERR
"devpts: get root dentry failed\n");
387 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
388 static int compare_init_pts_sb(struct super_block
*s
, void *p
)
391 return devpts_mnt
->mnt_sb
== s
;
398 * If the '-o newinstance' mount option was specified, mount a new
399 * (private) instance of devpts. PTYs created in this instance are
400 * independent of the PTYs in other devpts instances.
402 * If the '-o newinstance' option was not specified, mount/remount the
403 * initial kernel mount of devpts. This type of mount gives the
404 * legacy, single-instance semantics.
406 * The 'newinstance' option is needed to support multiple namespace
407 * semantics in devpts while preserving backward compatibility of the
408 * current 'single-namespace' semantics. i.e all mounts of devpts
409 * without the 'newinstance' mount option should bind to the initial
410 * kernel mount, like mount_single().
412 * Mounts with 'newinstance' option create a new, private namespace.
416 * For single-mount semantics, devpts cannot use mount_single(),
417 * because mount_single()/sget() find and use the super-block from
418 * the most recent mount of devpts. But that recent mount may be a
419 * 'newinstance' mount and mount_single() would pick the newinstance
420 * super-block instead of the initial super-block.
422 static struct dentry
*devpts_mount(struct file_system_type
*fs_type
,
423 int flags
, const char *dev_name
, void *data
)
426 struct pts_mount_opts opts
;
427 struct super_block
*s
;
429 error
= parse_mount_options(data
, PARSE_MOUNT
, &opts
);
431 return ERR_PTR(error
);
433 if (opts
.newinstance
)
434 s
= sget(fs_type
, NULL
, set_anon_super
, NULL
);
436 s
= sget(fs_type
, compare_init_pts_sb
, set_anon_super
, NULL
);
443 error
= devpts_fill_super(s
, data
, flags
& MS_SILENT
? 1 : 0);
446 s
->s_flags
|= MS_ACTIVE
;
449 memcpy(&(DEVPTS_SB(s
))->mount_opts
, &opts
, sizeof(opts
));
451 error
= mknod_ptmx(s
);
455 return dget(s
->s_root
);
458 deactivate_locked_super(s
);
459 return ERR_PTR(error
);
464 * This supports only the legacy single-instance semantics (no
465 * multiple-instance semantics)
467 static struct dentry
*devpts_mount(struct file_system_type
*fs_type
, int flags
,
468 const char *dev_name
, void *data
)
470 return mount_single(fs_type
, flags
, data
, devpts_fill_super
);
474 static void devpts_kill_sb(struct super_block
*sb
)
476 struct pts_fs_info
*fsi
= DEVPTS_SB(sb
);
479 kill_litter_super(sb
);
482 static struct file_system_type devpts_fs_type
= {
484 .mount
= devpts_mount
,
485 .kill_sb
= devpts_kill_sb
,
489 * The normal naming convention is simply /dev/pts/<number>; this conforms
490 * to the System V naming convention
493 int devpts_new_index(struct inode
*ptmx_inode
)
495 struct super_block
*sb
= pts_sb_from_inode(ptmx_inode
);
496 struct pts_fs_info
*fsi
= DEVPTS_SB(sb
);
501 if (!ida_pre_get(&fsi
->allocated_ptys
, GFP_KERNEL
))
504 mutex_lock(&allocated_ptys_lock
);
505 if (pty_count
>= pty_limit
-
506 (fsi
->mount_opts
.newinstance
? pty_reserve
: 0)) {
507 mutex_unlock(&allocated_ptys_lock
);
511 ida_ret
= ida_get_new(&fsi
->allocated_ptys
, &index
);
513 mutex_unlock(&allocated_ptys_lock
);
514 if (ida_ret
== -EAGAIN
)
519 if (index
>= fsi
->mount_opts
.max
) {
520 ida_remove(&fsi
->allocated_ptys
, index
);
521 mutex_unlock(&allocated_ptys_lock
);
525 mutex_unlock(&allocated_ptys_lock
);
529 void devpts_kill_index(struct inode
*ptmx_inode
, int idx
)
531 struct super_block
*sb
= pts_sb_from_inode(ptmx_inode
);
532 struct pts_fs_info
*fsi
= DEVPTS_SB(sb
);
534 mutex_lock(&allocated_ptys_lock
);
535 ida_remove(&fsi
->allocated_ptys
, idx
);
537 mutex_unlock(&allocated_ptys_lock
);
540 int devpts_pty_new(struct inode
*ptmx_inode
, struct tty_struct
*tty
)
542 /* tty layer puts index from devpts_new_index() in here */
543 int number
= tty
->index
;
544 struct tty_driver
*driver
= tty
->driver
;
545 dev_t device
= MKDEV(driver
->major
, driver
->minor_start
+number
);
546 struct dentry
*dentry
;
547 struct super_block
*sb
= pts_sb_from_inode(ptmx_inode
);
548 struct inode
*inode
= new_inode(sb
);
549 struct dentry
*root
= sb
->s_root
;
550 struct pts_fs_info
*fsi
= DEVPTS_SB(sb
);
551 struct pts_mount_opts
*opts
= &fsi
->mount_opts
;
555 /* We're supposed to be given the slave end of a pty */
556 BUG_ON(driver
->type
!= TTY_DRIVER_TYPE_PTY
);
557 BUG_ON(driver
->subtype
!= PTY_TYPE_SLAVE
);
562 inode
->i_ino
= number
+ 3;
563 inode
->i_uid
= opts
->setuid
? opts
->uid
: current_fsuid();
564 inode
->i_gid
= opts
->setgid
? opts
->gid
: current_fsgid();
565 inode
->i_mtime
= inode
->i_atime
= inode
->i_ctime
= CURRENT_TIME
;
566 init_special_inode(inode
, S_IFCHR
|opts
->mode
, device
);
567 inode
->i_private
= tty
;
568 tty
->driver_data
= inode
;
570 sprintf(s
, "%d", number
);
572 mutex_lock(&root
->d_inode
->i_mutex
);
574 dentry
= d_alloc_name(root
, s
);
576 d_add(dentry
, inode
);
577 fsnotify_create(root
->d_inode
, dentry
);
583 mutex_unlock(&root
->d_inode
->i_mutex
);
588 struct tty_struct
*devpts_get_tty(struct inode
*pts_inode
, int number
)
590 struct dentry
*dentry
;
591 struct tty_struct
*tty
;
593 BUG_ON(pts_inode
->i_rdev
== MKDEV(TTYAUX_MAJOR
, PTMX_MINOR
));
595 /* Ensure dentry has not been deleted by devpts_pty_kill() */
596 dentry
= d_find_alias(pts_inode
);
601 if (pts_inode
->i_sb
->s_magic
== DEVPTS_SUPER_MAGIC
)
602 tty
= (struct tty_struct
*)pts_inode
->i_private
;
609 void devpts_pty_kill(struct tty_struct
*tty
)
611 struct inode
*inode
= tty
->driver_data
;
612 struct super_block
*sb
= pts_sb_from_inode(inode
);
613 struct dentry
*root
= sb
->s_root
;
614 struct dentry
*dentry
;
616 BUG_ON(inode
->i_rdev
== MKDEV(TTYAUX_MAJOR
, PTMX_MINOR
));
618 mutex_lock(&root
->d_inode
->i_mutex
);
620 dentry
= d_find_alias(inode
);
624 dput(dentry
); /* d_alloc_name() in devpts_pty_new() */
625 dput(dentry
); /* d_find_alias above */
627 mutex_unlock(&root
->d_inode
->i_mutex
);
630 static int __init
init_devpts_fs(void)
632 int err
= register_filesystem(&devpts_fs_type
);
633 struct ctl_table_header
*table
;
636 table
= register_sysctl_table(pty_root_table
);
637 devpts_mnt
= kern_mount(&devpts_fs_type
);
638 if (IS_ERR(devpts_mnt
)) {
639 err
= PTR_ERR(devpts_mnt
);
640 unregister_filesystem(&devpts_fs_type
);
641 unregister_sysctl_table(table
);
646 module_init(init_devpts_fs
)