kernel/livepatch/shadow.c

3  * shadow.c - Shadow Variables
13  * The shadow variable API provides a simple relationship between an
15  * caller to provide any mutual exclusion required of the shadow data.
17  * Once a shadow variable is attached to its parent object via the
19  * call to klp_shadow_get() may then return the shadow variable's data
20  * pointer.  Callers of klp_shadow_*alloc() should prepare shadow data
23  * The klp_shadow_*alloc() API calls may allocate memory for new shadow
42  * the shadow variables it references.
47  * struct klp_shadow - shadow variable structure
63  * klp_shadow_match() - verify a shadow variable matches given <obj, id>
64  * @shadow:	shadow variable to match
68  * Return: true if the shadow variable matches.
70 static inline bool klp_shadow_match(struct klp_shadow *shadow, void *obj,
73 	return shadow->obj == obj && shadow->id == id;
77  * klp_shadow_get() - retrieve a shadow variable data pointer
81  * Return: the shadow variable data element, NULL on failure.
85 	struct klp_shadow *shadow;
89 	hash_for_each_possible_rcu(klp_shadow_hash, shadow, node,
92 		if (klp_shadow_match(shadow, obj, id)) {
94 			return shadow->data;
113 	/* Check if the shadow variable already exists */
119 	 * Allocate a new shadow variable.  Fill it with zeroes by default.
150 			pr_err("Failed to construct shadow variable <%p, %lx> (%d)\n",
165 		WARN(1, "Duplicate shadow variable <%p, %lx>\n", obj, id);
173  * klp_shadow_alloc() - allocate and add a new shadow variable
178  * @ctor:	custom constructor to initialize the shadow data (optional)
181  * Allocates @size bytes for new shadow variable data using @gfp_flags.
183  * function if it is not NULL.  The new shadow variable is then added
186  * If an existing <obj, id> shadow variable can be found, this routine will
193  * Return: the shadow variable data element, NULL on duplicate or
206  * klp_shadow_get_or_alloc() - get existing or allocate a new shadow variable
211  * @ctor:	custom constructor to initialize the shadow data (optional)
214  * Returns a pointer to existing shadow data if an <obj, id> shadow
215  * variable is already present.  Otherwise, it creates a new shadow
218  * This function guarantees that only one shadow variable exists with the given
223  * Return: the shadow variable data element, NULL on failure.
234 static void klp_shadow_free_struct(struct klp_shadow *shadow,
237 	hash_del_rcu(&shadow->node);
239 		dtor(shadow->obj, shadow->data);
240 	kfree_rcu(shadow, rcu_head);
244  * klp_shadow_free() - detach and free a <obj, id> shadow variable
248  *		and/or free data that the shadow variable points to (optional)
250  * This function releases the memory for this <obj, id> shadow variable
255 	struct klp_shadow *shadow;
261 	hash_for_each_possible(klp_shadow_hash, shadow, node,
264 		if (klp_shadow_match(shadow, obj, id)) {
265 			klp_shadow_free_struct(shadow, dtor);
275  * klp_shadow_free_all() - detach and free all <_, id> shadow variables
278  *		and/or free data that the shadow variable points to (optional)
280  * This function releases the memory for all <_, id> shadow variable
285 	struct klp_shadow *shadow;
292 	hash_for_each(klp_shadow_hash, i, shadow, node) {
293 		if (klp_shadow_match(shadow, shadow->obj, id))
294 			klp_shadow_free_struct(shadow, dtor);