@@ -445,6 +445,39 @@ void sysfs_remove_link_from_group(struct kobject *kobj, const char *group_name,
}
EXPORT_SYMBOL_GPL(sysfs_remove_link_from_group);
+/**
+ * sysfs_add_link_to_sibling_group - add a symlink to a sibling attribute group.
+ * @kobj: The kobject containing the groups.
+ * @link_grp: The name of the group in which to create the symlink.
+ * @link: The name of the symlink to create.
+ * @target_grp: The name of the target group.
+ * @target: The name of the target attribute.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_add_link_to_sibling_group(struct kobject *kobj,
+ const char *link_grp, const char *link,
+ const char *target_grp, const char *target)
+{
+ struct kernfs_node *target_grp_kn __free(kernfs_put),
+ *target_kn __free(kernfs_put) = NULL,
+ *link_grp_kn __free(kernfs_put) = NULL;
+
+ target_grp_kn = kernfs_find_and_get(kobj->sd, target_grp);
+ if (!target_grp_kn)
+ return -ENOENT;
+
+ target_kn = kernfs_find_and_get(target_grp_kn, target);
+ if (!target_kn)
+ return -ENOENT;
+
+ link_grp_kn = kernfs_find_and_get(kobj->sd, link_grp);
+ if (!link_grp_kn)
+ return -ENOENT;
+
+ return PTR_ERR_OR_ZERO(kernfs_create_link(link_grp_kn, link, target_kn));
+}
+
/**
* compat_only_sysfs_link_entry_to_kobj - add a symlink to a kobject pointing
* to a group or an attribute
@@ -407,6 +407,8 @@ struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
void kernfs_get(struct kernfs_node *kn);
void kernfs_put(struct kernfs_node *kn);
+DEFINE_FREE(kernfs_put, struct kernfs_node *, if (_T) kernfs_put(_T))
+
struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
@@ -465,6 +465,9 @@ int sysfs_add_link_to_group(struct kobject *kobj, const char *group_name,
struct kobject *target, const char *link_name);
void sysfs_remove_link_from_group(struct kobject *kobj, const char *group_name,
const char *link_name);
+int sysfs_add_link_to_sibling_group(struct kobject *kobj,
+ const char *link_grp, const char *link,
+ const char *target_grp, const char *target);
int compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
struct kobject *target_kobj,
const char *target_name,
@@ -702,6 +705,13 @@ static inline void sysfs_remove_link_from_group(struct kobject *kobj,
{
}
+static inline int sysfs_add_link_to_sibling_group(struct kobject *kobj,
+ const char *link_grp, const char *link,
+ const char *target_grp, const char *target)
+{
+ return 0;
+}
+
static inline int compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
struct kobject *target_kobj,
const char *target_name,
A subsequent commit has the need to create a symlink from an attribute in a first group to an attribute in a second group. Both groups belong to the same kobject. More specifically, each signature received from an authentication- capable device is going to be represented by a file in the first group and shall be accompanied by a symlink pointing to the certificate slot in the second group which was used to generate the signature (a device may have multiple certificate slots and each is represented by a separate file in the second group): /sys/devices/.../signatures/0_certificate_chain -> .../certificates/slot0 There is already a sysfs_add_link_to_group() helper to add a symlink to a group which points to another kobject, but this isn't what's needed here. So add a new function to add a symlink among sibling groups of the same kobject. The existing sysfs_add_link_to_group() helper goes through a locking dance of acquiring sysfs_symlink_target_lock in order to acquire a reference on the target kobject. That's unnecessary for the present use case as the link itself and its target reside below the same kobject. To simplify error handling in the newly introduced function, add a DEFINE_FREE() clause for kernfs_put(). Signed-off-by: Lukas Wunner <lukas@wunner.de> --- fs/sysfs/group.c | 33 +++++++++++++++++++++++++++++++++ include/linux/kernfs.h | 2 ++ include/linux/sysfs.h | 10 ++++++++++ 3 files changed, 45 insertions(+)