/* * 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 <asm/semaphore.h> #include "sysfs.h" static int object_depth(struct kobject * kobj) { struct kobject * p = kobj; int depth = 0; do { depth++; } while ((p = p->parent)); return depth; } static int object_path_length(struct kobject * kobj) { struct kobject * p = kobj; int length = 1; do { length += strlen(kobject_name(p)) + 1; p = p->parent; } while (p); return length; } static void fill_object_path(struct kobject * kobj, char * buffer, int length) { struct kobject * p; --length; for (p = kobj; p; p = p->parent) { int cur = strlen(kobject_name(p)); /* back up enough to print this bus id with '/' */ length -= cur; strncpy(buffer + length,kobject_name(p),cur); *(buffer + --length) = '/'; } } static int sysfs_add_link(struct dentry * parent, const char * name, struct kobject * target) { struct sysfs_dirent * parent_sd = parent->d_fsdata; struct sysfs_symlink * sl; int error = 0; error = -ENOMEM; sl = kmalloc(sizeof(*sl), GFP_KERNEL); if (!sl) goto exit1; sl->link_name = kmalloc(strlen(name) + 1, GFP_KERNEL); if (!sl->link_name) goto exit2; strcpy(sl->link_name, name); sl->target_kobj = kobject_get(target); error = sysfs_make_dirent(parent_sd, NULL, sl, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); if (!error) return 0; kobject_put(target); kfree(sl->link_name); exit2: kfree(sl); exit1: return error; } /** * 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 dentry *dentry = NULL; int error = -EEXIST; BUG_ON(!name); if (!kobj) { if (sysfs_mount && sysfs_mount->mnt_sb) dentry = sysfs_mount->mnt_sb->s_root; } else dentry = kobj->dentry; if (!dentry) return -EFAULT; mutex_lock(&dentry->d_inode->i_mutex); if (!sysfs_dirent_exist(dentry->d_fsdata, name)) error = sysfs_add_link(dentry, name, target); mutex_unlock(&dentry->d_inode->i_mutex); 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->dentry,name); } static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target, char *path) { char * s; int depth, size; depth = object_depth(kobj); size = object_path_length(target) + 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, path, size); pr_debug("%s: path = '%s'\n", __FUNCTION__, path); return 0; } static int sysfs_getlink(struct dentry *dentry, char * path) { struct kobject *kobj, *target_kobj; int error = 0; kobj = sysfs_get_kobject(dentry->d_parent); if (!kobj) return -EINVAL; target_kobj = sysfs_get_kobject(dentry); if (!target_kobj) { kobject_put(kobj); return -EINVAL; } down_read(&sysfs_rename_sem); error = sysfs_get_target_path(kobj, target_kobj, path); up_read(&sysfs_rename_sem); kobject_put(kobj); kobject_put(target_kobj); 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);