add devpts patch

2 files changed, 449 insertions, 0 deletions

diff --git a/devpts.patch b/devpts.patch
new file mode 100644
index 0000000..cca51dc
--- /dev/null
+++ b/devpts.patch
@@ -0,0 +1,447 @@
+Subject: devpts: properly integrate with /dev/ptmx
+
+The following patch is just to clean up the confusion about userspace
+and the unfortunate idea of legacy vs. non-legacy mount options. It is
+nowhere ready to merge, but it should make is pretty clear, that
+userspace should be left alone here, and it's a job for the kernel only.
+
+# ls -l /dev
+crw------- 1 root root     10,   1 Apr  9 14:21 psaux
+lrwxrwxrwx 1 root root           8 Apr  9 14:20 ptmx -> pts/ptmx
+drwxr-xr-x 2 root root           0 Apr  9 14:21 pts
+crw-rw-rw- 1 root root      1,   8 Apr  9 14:21 random
+
+# ls -l /dev/pts
+total 0
+crw--w---- 1 root tty 136, 0 Apr  9 14:22 0
+crw--w---- 1 kay  tty 136, 1 Apr  9 14:22 1
+crw-rw-rw- 1 root tty   5, 2 Apr  9 14:22 ptmx
+
+---
+ drivers/base/devtmpfs.c |   60 ++++++++++++++++++++++++-
+ drivers/tty/Kconfig     |   11 ----
+ drivers/tty/pty.c       |    3 -
+ fs/devpts/inode.c       |  112 +++++++-----------------------------------------
+ include/linux/device.h  |    2 
+ 5 files changed, 76 insertions(+), 112 deletions(-)
+
+--- a/drivers/base/devtmpfs.c
++++ b/drivers/base/devtmpfs.c
+@@ -40,6 +40,7 @@ static struct req {
+ 	struct completion done;
+ 	int err;
+ 	const char *name;
++	const char *target;
+ 	umode_t mode;	/* 0 => delete */
+ 	struct device *dev;
+ } *requests;
+@@ -84,7 +85,7 @@ int devtmpfs_create_node(struct device *
+ 	if (!thread)
+ 		return 0;
+ 
+-	req.mode = 0;
++	memset(&req, 0, sizeof(struct req));
+ 	req.name = device_get_devnode(dev, &req.mode, &tmp);
+ 	if (!req.name)
+ 		return -ENOMEM;
+@@ -113,6 +114,31 @@ int devtmpfs_create_node(struct device *
+ 	return req.err;
+ }
+ 
++int devtmpfs_create_link(const char *name, const char *target)
++{
++	struct req req;
++
++	if (!thread)
++		return 0;
++
++	memset(&req, 0, sizeof(struct req));
++	req.mode = 0666;
++	req.name = name;
++	req.target = target;
++
++	init_completion(&req.done);
++
++	spin_lock(&req_lock);
++	req.next = requests;
++	requests = &req;
++	spin_unlock(&req_lock);
++
++	wake_up_process(thread);
++	wait_for_completion(&req.done);
++
++	return req.err;
++}
++
+ int devtmpfs_delete_node(struct device *dev)
+ {
+ 	const char *tmp = NULL;
+@@ -121,11 +147,11 @@ int devtmpfs_delete_node(struct device *
+ 	if (!thread)
+ 		return 0;
+ 
++	memset(&req, 0, sizeof(struct req));
+ 	req.name = device_get_devnode(dev, NULL, &tmp);
+ 	if (!req.name)
+ 		return -ENOMEM;
+ 
+-	req.mode = 0;
+ 	req.dev = dev;
+ 
+ 	init_completion(&req.done);
+@@ -225,6 +251,28 @@ static int handle_create(const char *nod
+ 	return err;
+ }
+ 
++static int handle_create_link(const char *name, const char *target)
++{
++	struct dentry *dentry;
++	struct path path;
++	int err;
++
++	dentry = kern_path_create(AT_FDCWD, name, &path, 0);
++	if (dentry == ERR_PTR(-ENOENT)) {
++		create_path(name);
++		dentry = kern_path_create(AT_FDCWD, name, &path, 0);
++	}
++	if (IS_ERR(dentry))
++		return PTR_ERR(dentry);
++
++	err = vfs_symlink(path.dentry->d_inode, dentry, target);
++	dput(dentry);
++
++	mutex_unlock(&path.dentry->d_inode->i_mutex);
++	path_put(&path);
++	return err;
++}
++
+ static int dev_rmdir(const char *name)
+ {
+ 	struct nameidata nd;
+@@ -378,8 +426,11 @@ int devtmpfs_mount(const char *mntdir)
+ 
+ static DECLARE_COMPLETION(setup_done);
+ 
+-static int handle(const char *name, umode_t mode, struct device *dev)
++static int handle(const char *name, umode_t mode,
++		  struct device *dev, const char *target)
+ {
++	if (target)
++		return handle_create_link(name, target);
+ 	if (mode)
+ 		return handle_create(name, mode, dev);
+ 	else
+@@ -407,7 +458,8 @@ static int devtmpfsd(void *p)
+ 			spin_unlock(&req_lock);
+ 			while (req) {
+ 				struct req *next = req->next;
+-				req->err = handle(req->name, req->mode, req->dev);
++				req->err = handle(req->name, req->mode,
++						  req->dev, req->target);
+ 				complete(&req->done);
+ 				req = next;
+ 			}
+--- a/drivers/tty/Kconfig
++++ b/drivers/tty/Kconfig
+@@ -109,17 +109,6 @@ config UNIX98_PTYS
+ 	  All modern Linux systems use the Unix98 ptys.  Say Y unless
+ 	  you're on an embedded system and want to conserve memory.
+ 
+-config DEVPTS_MULTIPLE_INSTANCES
+-	bool "Support multiple instances of devpts"
+-	depends on UNIX98_PTYS
+-	default n
+-	---help---
+-	  Enable support for multiple instances of devpts filesystem.
+-	  If you want to have isolated PTY namespaces (eg: in containers),
+-	  say Y here.  Otherwise, say N. If enabled, each mount of devpts
+-	  filesystem with the '-o newinstance' option will create an
+-	  independent PTY namespace.
+-
+ config LEGACY_PTYS
+ 	bool "Legacy (BSD) PTY support"
+ 	default y
+--- a/drivers/tty/pty.c
++++ b/drivers/tty/pty.c
+@@ -706,7 +706,7 @@ static void __init unix98_pty_init(void)
+ 	if (tty_register_driver(pts_driver))
+ 		panic("Couldn't register Unix98 pts driver");
+ 
+-	/* Now create the /dev/ptmx special device */
++	/* Hook up the ptmx cdev which lives inside the devpts filesystem */
+ 	tty_default_fops(&ptmx_fops);
+ 	ptmx_fops.open = ptmx_open;
+ 
+@@ -714,7 +714,6 @@ static void __init unix98_pty_init(void)
+ 	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
+ 	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
+ 		panic("Couldn't register /dev/ptmx driver\n");
+-	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
+ }
+ 
+ #else
+--- a/fs/devpts/inode.c
++++ b/fs/devpts/inode.c
+@@ -26,15 +26,9 @@
+ #include <linux/fsnotify.h>
+ #include <linux/seq_file.h>
+ 
+-#define DEVPTS_DEFAULT_MODE 0600
+-/*
+- * ptmx is a new node in /dev/pts and will be unused in legacy (single-
+- * instance) mode. To prevent surprises in user space, set permissions of
+- * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
+- * permissions.
+- */
+-#define DEVPTS_DEFAULT_PTMX_MODE 0000
+-#define PTMX_MINOR	2
++#define DEVPTS_DEFAULT_MODE		0600
++#define DEVPTS_DEFAULT_PTMX_MODE	0666
++#define PTMX_MINOR			2
+ 
+ /*
+  * sysctl support for setting limits on the number of Unix98 ptys allocated.
+@@ -102,24 +96,19 @@ struct pts_mount_opts {
+ 	gid_t   gid;
+ 	umode_t mode;
+ 	umode_t ptmxmode;
+-	int newinstance;
+ 	int max;
+ };
+ 
+ enum {
+-	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,  Opt_max,
+-	Opt_err
++	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_max, Opt_err
+ };
+ 
+ static const match_table_t tokens = {
+ 	{Opt_uid, "uid=%u"},
+ 	{Opt_gid, "gid=%u"},
+ 	{Opt_mode, "mode=%o"},
+-#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ 	{Opt_ptmxmode, "ptmxmode=%o"},
+-	{Opt_newinstance, "newinstance"},
+ 	{Opt_max, "max=%d"},
+-#endif
+ 	{Opt_err, NULL}
+ };
+ 
+@@ -136,10 +125,8 @@ static inline struct pts_fs_info *DEVPTS
+ 
+ static inline struct super_block *pts_sb_from_inode(struct inode *inode)
+ {
+-#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ 	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
+ 		return inode->i_sb;
+-#endif
+ 	return devpts_mnt->mnt_sb;
+ }
+ 
+@@ -149,9 +136,7 @@ static inline struct super_block *pts_sb
+ /*
+  * parse_mount_options():
+  * 	Set @opts to mount options specified in @data. If an option is not
+- * 	specified in @data, set it to its default value. The exception is
+- * 	'newinstance' option which can only be set/cleared on a mount (i.e.
+- * 	cannot be changed during remount).
++ * 	specified in @data, set it to its default value.\
+  *
+  * Note: @data may be NULL (in which case all options are set to default).
+  */
+@@ -167,10 +152,6 @@ static int parse_mount_options(char *dat
+ 	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
+ 	opts->max     = NR_UNIX98_PTY_MAX;
+ 
+-	/* newinstance makes sense only on initial mount */
+-	if (op == PARSE_MOUNT)
+-		opts->newinstance = 0;
+-
+ 	while ((p = strsep(&data, ",")) != NULL) {
+ 		substring_t args[MAX_OPT_ARGS];
+ 		int token;
+@@ -198,24 +179,17 @@ static int parse_mount_options(char *dat
+ 				return -EINVAL;
+ 			opts->mode = option & S_IALLUGO;
+ 			break;
+-#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ 		case Opt_ptmxmode:
+ 			if (match_octal(&args[0], &option))
+ 				return -EINVAL;
+ 			opts->ptmxmode = option & S_IALLUGO;
+ 			break;
+-		case Opt_newinstance:
+-			/* newinstance makes sense only on initial mount */
+-			if (op == PARSE_MOUNT)
+-				opts->newinstance = 1;
+-			break;
+ 		case Opt_max:
+ 			if (match_int(&args[0], &option) ||
+ 			    option < 0 || option > NR_UNIX98_PTY_MAX)
+ 				return -EINVAL;
+ 			opts->max = option;
+ 			break;
+-#endif
+ 		default:
+ 			printk(KERN_ERR "devpts: called with bogus options\n");
+ 			return -EINVAL;
+@@ -225,7 +199,6 @@ static int parse_mount_options(char *dat
+ 	return 0;
+ }
+ 
+-#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ static int mknod_ptmx(struct super_block *sb)
+ {
+ 	int mode;
+@@ -260,6 +233,8 @@ static int mknod_ptmx(struct super_block
+ 		goto out;
+ 	}
+ 
++	if (opts->setgid)
++		inode->i_gid = opts->gid;
+ 	inode->i_ino = 2;
+ 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
+ 
+@@ -283,12 +258,6 @@ static void update_ptmx_mode(struct pts_
+ 		inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
+ 	}
+ }
+-#else
+-static inline void update_ptmx_mode(struct pts_fs_info *fsi)
+-{
+-       return;
+-}
+-#endif
+ 
+ static int devpts_remount(struct super_block *sb, int *flags, char *data)
+ {
+@@ -319,11 +288,9 @@ static int devpts_show_options(struct se
+ 	if (opts->setgid)
+ 		seq_printf(seq, ",gid=%u", opts->gid);
+ 	seq_printf(seq, ",mode=%03o", opts->mode);
+-#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+ 	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
+ 	if (opts->max < NR_UNIX98_PTY_MAX)
+ 		seq_printf(seq, ",max=%d", opts->max);
+-#endif
+ 
+ 	return 0;
+ }
+@@ -384,43 +351,8 @@ fail:
+ 	return -ENOMEM;
+ }
+ 
+-#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+-static int compare_init_pts_sb(struct super_block *s, void *p)
+-{
+-	if (devpts_mnt)
+-		return devpts_mnt->mnt_sb == s;
+-	return 0;
+-}
+-
+-/*
+- * devpts_mount()
+- *
+- *     If the '-o newinstance' mount option was specified, mount a new
+- *     (private) instance of devpts.  PTYs created in this instance are
+- *     independent of the PTYs in other devpts instances.
+- *
+- *     If the '-o newinstance' option was not specified, mount/remount the
+- *     initial kernel mount of devpts.  This type of mount gives the
+- *     legacy, single-instance semantics.
+- *
+- *     The 'newinstance' option is needed to support multiple namespace
+- *     semantics in devpts while preserving backward compatibility of the
+- *     current 'single-namespace' semantics. i.e all mounts of devpts
+- *     without the 'newinstance' mount option should bind to the initial
+- *     kernel mount, like mount_single().
+- *
+- *     Mounts with 'newinstance' option create a new, private namespace.
+- *
+- *     NOTE:
+- *
+- *     For single-mount semantics, devpts cannot use mount_single(),
+- *     because mount_single()/sget() find and use the super-block from
+- *     the most recent mount of devpts. But that recent mount may be a
+- *     'newinstance' mount and mount_single() would pick the newinstance
+- *     super-block instead of the initial super-block.
+- */
+ static struct dentry *devpts_mount(struct file_system_type *fs_type,
+-	int flags, const char *dev_name, void *data)
++				   int flags, const char *dev_name, void *data)
+ {
+ 	int error;
+ 	struct pts_mount_opts opts;
+@@ -430,10 +362,7 @@ static struct dentry *devpts_mount(struc
+ 	if (error)
+ 		return ERR_PTR(error);
+ 
+-	if (opts.newinstance)
+-		s = sget(fs_type, NULL, set_anon_super, NULL);
+-	else
+-		s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
++	s = sget(fs_type, NULL, set_anon_super, NULL);
+ 
+ 	if (IS_ERR(s))
+ 		return ERR_CAST(s);
+@@ -459,18 +388,6 @@ out_undo_sget:
+ 	return ERR_PTR(error);
+ }
+ 
+-#else
+-/*
+- * This supports only the legacy single-instance semantics (no
+- * multiple-instance semantics)
+- */
+-static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
+-		const char *dev_name, void *data)
+-{
+-	return mount_single(fs_type, flags, data, devpts_fill_super);
+-}
+-#endif
+-
+ static void devpts_kill_sb(struct super_block *sb)
+ {
+ 	struct pts_fs_info *fsi = DEVPTS_SB(sb);
+@@ -502,8 +419,7 @@ retry:
+ 		return -ENOMEM;
+ 
+ 	mutex_lock(&allocated_ptys_lock);
+-	if (pty_count >= pty_limit -
+-			(fsi->mount_opts.newinstance ? pty_reserve : 0)) {
++	if (pty_count >= pty_limit - pty_reserve) {
+ 		mutex_unlock(&allocated_ptys_lock);
+ 		return -ENOSPC;
+ 	}
+@@ -629,9 +545,15 @@ void devpts_pty_kill(struct tty_struct *
+ 
+ static int __init init_devpts_fs(void)
+ {
+-	int err = register_filesystem(&devpts_fs_type);
++	int err;
+ 	struct ctl_table_header *table;
+ 
++	err = devtmpfs_create_link("ptmx", "pts/ptmx");
++	if (err)
++		return err;
++
++	err = register_filesystem(&devpts_fs_type);
++
+ 	if (!err) {
+ 		table = register_sysctl_table(pty_root_table);
+ 		devpts_mnt = kern_mount(&devpts_fs_type);
+--- a/include/linux/device.h
++++ b/include/linux/device.h
+@@ -858,10 +858,12 @@ extern void put_device(struct device *de
+ extern void wait_for_device_probe(void);
+ 
+ #ifdef CONFIG_DEVTMPFS
++extern int devtmpfs_create_link(const char *name, const char *target);
+ extern int devtmpfs_create_node(struct device *dev);
+ extern int devtmpfs_delete_node(struct device *dev);
+ extern int devtmpfs_mount(const char *mntdir);
+ #else
++static int devtmpfs_create_link(const char *name, const char *target) { return 0; }
+ static inline int devtmpfs_create_node(struct device *dev) { return 0; }
+ static inline int devtmpfs_delete_node(struct device *dev) { return 0; }
+ static inline int devtmpfs_mount(const char *mountpoint) { return 0; }
diff --git a/series b/series
index b235040..87acb1a 100644
--- a/series
+++ b/series
@@ -2,3 +2,5 @@ printk-records.patch
 printk-devkmsg.patch
 printk-dev_printk.patch
 kern-cont.patch
+devpts.patch
+