nsfs.rar_SOC

#include <linux/mount.h> #include <linux/file.h> #include <linux/fs.h> #include <linux/proc_ns.h> #include <linux/magic.h> #include <linux/ktime.h> static struct vfsmount *nsfs_mnt; static const struct file_operations ns_file_operations = { .llseek = no_llseek, }; static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) { struct inode *inode = dentry->d_inode; const struct proc_ns_operations *ns_ops = dentry->d_fsdata; return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]", ns_ops->name, inode->i_ino); } static void ns_prune_dentry(struct dentry *dentry) { struct inode *inode = dentry->d_inode; if (inode) { struct ns_common *ns = inode->i_private; atomic_long_set(&ns->stashed, 0); } } const struct dentry_operations ns_dentry_operations = { .d_prune = ns_prune_dentry, .d_delete = always_delete_dentry, .d_dname = ns_dname, }; static void nsfs_evict(struct inode *inode) { struct ns_common *ns = inode->i_private; clear_inode(inode); ns->ops->put(ns); } void *ns_get_path(struct path *path, struct task_struct *task, const struct proc_ns_operations *ns_ops) { struct vfsmount *mnt = mntget(nsfs_mnt); struct qstr qname = { .name = "", }; struct dentry *dentry; struct inode *inode; struct ns_common *ns; unsigned long d; again: ns = ns_ops->get(task); if (!ns) { mntput(mnt); return ERR_PTR(-ENOENT); } rcu_read_lock(); d = atomic_long_read(&ns->stashed); if (!d) goto slow; dentry = (struct dentry *)d; if (!lockref_get_not_dead(&dentry->d_lockref)) goto slow; rcu_read_unlock(); ns_ops->put(ns); got_it: path->mnt = mnt; path->dentry = dentry; return NULL; slow: rcu_read_unlock(); inode = new_inode_pseudo(mnt->mnt_sb); if (!inode) { ns_ops->put(ns); mntput(mnt); return ERR_PTR(-ENOMEM); } inode->i_ino = ns->inum; inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; inode->i_flags |= S_IMMUTABLE; inode->i_mode = S_IFREG | S_IRUGO; inode->i_fop = &ns_file_operations; inode->i_private = ns; dentry = d_alloc_pseudo(mnt->mnt_sb, &qname); if (!dentry) { iput(inode); mntput(mnt); return ERR_PTR(-ENOMEM); } d_instantiate(dentry, inode); dentry->d_fsdata = (void *)ns_ops; d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry); if (d) { d_delete(dentry); /* make sure ->d_prune() does nothing */ dput(dentry); cpu_relax(); goto again; } goto got_it; } int ns_get_name(char *buf, size_t size, struct task_struct *task, const struct proc_ns_operations *ns_ops) { struct ns_common *ns; int res = -ENOENT; ns = ns_ops->get(task); if (ns) { res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum); ns_ops->put(ns); } return res; } struct file *proc_ns_fget(int fd) { struct file *file; file = fget(fd); if (!file) return ERR_PTR(-EBADF); if (file->f_op != &ns_file_operations) goto out_invalid; return file; out_invalid: fput(file); return ERR_PTR(-EINVAL); } static const struct super_operations nsfs_ops = { .statfs = simple_statfs, .evict_inode = nsfs_evict, }; static struct dentry *nsfs_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { return mount_pseudo(fs_type, "nsfs:", &nsfs_ops, &ns_dentry_operations, NSFS_MAGIC); } static struct file_system_type nsfs = { .name = "nsfs", .mount = nsfs_mount, .kill_sb = kill_anon_super, }; void __init nsfs_init(void) { nsfs_mnt = kern_mount(&nsfs); if (IS_ERR(nsfs_mnt)) panic("can't set nsfs up\n"); nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER; }