| /* |
| * symlink.c - operations for sysfs symlinks. |
| */ |
| |
| #include <linux/fs.h> |
| #include <linux/mount.h> |
| #include <linux/module.h> |
| #include <linux/kobject.h> |
| #include <linux/namei.h> |
| #include <linux/mutex.h> |
| |
| #include "sysfs.h" |
| |
| static int object_depth(struct sysfs_dirent *sd) |
| { |
| int depth = 0; |
| |
| for (; sd->s_parent; sd = sd->s_parent) |
| depth++; |
| |
| return depth; |
| } |
| |
| static int object_path_length(struct sysfs_dirent * sd) |
| { |
| int length = 1; |
| |
| for (; sd->s_parent; sd = sd->s_parent) |
| length += strlen(sd->s_name) + 1; |
| |
| return length; |
| } |
| |
| static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length) |
| { |
| --length; |
| for (; sd->s_parent; sd = sd->s_parent) { |
| int cur = strlen(sd->s_name); |
| |
| /* back up enough to print this bus id with '/' */ |
| length -= cur; |
| strncpy(buffer + length, sd->s_name, cur); |
| *(buffer + --length) = '/'; |
| } |
| } |
| |
| /** |
| * sysfs_create_link - create symlink between two objects. |
| * @kobj: object whose directory we're creating the link in. |
| * @target: object we're pointing to. |
| * @name: name of the symlink. |
| */ |
| int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name) |
| { |
| struct sysfs_dirent *parent_sd = NULL; |
| struct sysfs_dirent *target_sd = NULL; |
| struct sysfs_dirent *sd = NULL; |
| struct sysfs_addrm_cxt acxt; |
| int error; |
| |
| BUG_ON(!name); |
| |
| if (!kobj) { |
| if (sysfs_mount && sysfs_mount->mnt_sb) |
| parent_sd = sysfs_mount->mnt_sb->s_root->d_fsdata; |
| } else |
| parent_sd = kobj->sd; |
| |
| error = -EFAULT; |
| if (!parent_sd) |
| goto out_put; |
| |
| /* target->sd can go away beneath us but is protected with |
| * sysfs_assoc_lock. Fetch target_sd from it. |
| */ |
| spin_lock(&sysfs_assoc_lock); |
| if (target->sd) |
| target_sd = sysfs_get(target->sd); |
| spin_unlock(&sysfs_assoc_lock); |
| |
| error = -ENOENT; |
| if (!target_sd) |
| goto out_put; |
| |
| error = -ENOMEM; |
| sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); |
| if (!sd) |
| goto out_put; |
| |
| sd->s_elem.symlink.target_sd = target_sd; |
| target_sd = NULL; /* reference is now owned by the symlink */ |
| |
| sysfs_addrm_start(&acxt, parent_sd); |
| |
| if (!sysfs_find_dirent(parent_sd, name)) |
| sysfs_add_one(&acxt, sd); |
| |
| if (!sysfs_addrm_finish(&acxt)) { |
| error = -EEXIST; |
| goto out_put; |
| } |
| |
| return 0; |
| |
| out_put: |
| sysfs_put(target_sd); |
| sysfs_put(sd); |
| return error; |
| } |
| |
| |
| /** |
| * sysfs_remove_link - remove symlink in object's directory. |
| * @kobj: object we're acting for. |
| * @name: name of the symlink to remove. |
| */ |
| |
| void sysfs_remove_link(struct kobject * kobj, const char * name) |
| { |
| sysfs_hash_and_remove(kobj->sd, name); |
| } |
| |
| static int sysfs_get_target_path(struct sysfs_dirent * parent_sd, |
| struct sysfs_dirent * target_sd, char *path) |
| { |
| char * s; |
| int depth, size; |
| |
| depth = object_depth(parent_sd); |
| size = object_path_length(target_sd) + depth * 3 - 1; |
| if (size > PATH_MAX) |
| return -ENAMETOOLONG; |
| |
| pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size); |
| |
| for (s = path; depth--; s += 3) |
| strcpy(s,"../"); |
| |
| fill_object_path(target_sd, path, size); |
| pr_debug("%s: path = '%s'\n", __FUNCTION__, path); |
| |
| return 0; |
| } |
| |
| static int sysfs_getlink(struct dentry *dentry, char * path) |
| { |
| struct sysfs_dirent *sd = dentry->d_fsdata; |
| struct sysfs_dirent *parent_sd = sd->s_parent; |
| struct sysfs_dirent *target_sd = sd->s_elem.symlink.target_sd; |
| int error; |
| |
| mutex_lock(&sysfs_mutex); |
| error = sysfs_get_target_path(parent_sd, target_sd, path); |
| mutex_unlock(&sysfs_mutex); |
| |
| return error; |
| } |
| |
| static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
| { |
| int error = -ENOMEM; |
| unsigned long page = get_zeroed_page(GFP_KERNEL); |
| if (page) |
| error = sysfs_getlink(dentry, (char *) page); |
| nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); |
| return NULL; |
| } |
| |
| static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
| { |
| char *page = nd_get_link(nd); |
| if (!IS_ERR(page)) |
| free_page((unsigned long)page); |
| } |
| |
| const struct inode_operations sysfs_symlink_inode_operations = { |
| .readlink = generic_readlink, |
| .follow_link = sysfs_follow_link, |
| .put_link = sysfs_put_link, |
| }; |
| |
| |
| EXPORT_SYMBOL_GPL(sysfs_create_link); |
| EXPORT_SYMBOL_GPL(sysfs_remove_link); |