1 files changed, 71 insertions, 37 deletions

diff --git a/kernel/livepatch/shadow.c b/kernel/livepatch/shadow.c
index fdac27588d60..83958c814439 100644
--- a/kernel/livepatch/shadow.c
+++ b/kernel/livepatch/shadow.c
@@ -113,8 +113,10 @@ void *klp_shadow_get(void *obj, unsigned long id)
 }
 EXPORT_SYMBOL_GPL(klp_shadow_get);
 
-static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
-                       size_t size, gfp_t gfp_flags, bool warn_on_exist)
+static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id,
+                                       size_t size, gfp_t gfp_flags,
+                                       klp_shadow_ctor_t ctor, void *ctor_data,
+                                       bool warn_on_exist)
 {
         struct klp_shadow *new_shadow;
         void *shadow_data;
@@ -125,18 +127,15 @@ static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
         if (shadow_data)
                 goto exists;
 
-        /* Allocate a new shadow variable for use inside the lock below */
+        /*
+         * Allocate a new shadow variable.  Fill it with zeroes by default.
+         * More complex setting can be done by @ctor function.  But it is
+         * called only when the buffer is really used (under klp_shadow_lock).
+         */
         new_shadow = kzalloc(size + sizeof(*new_shadow), gfp_flags);
         if (!new_shadow)
                 return NULL;
 
-        new_shadow->obj = obj;
-        new_shadow->id = id;
-
-        /* Initialize the shadow variable if data provided */
-        if (data)
-                memcpy(new_shadow->data, data, size);
-
         /* Look for <obj, id> again under the lock */
         spin_lock_irqsave(&klp_shadow_lock, flags);
         shadow_data = klp_shadow_get(obj, id);
@@ -150,6 +149,22 @@ static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
                 goto exists;
         }
 
+        new_shadow->obj = obj;
+        new_shadow->id = id;
+
+        if (ctor) {
+                int err;
+
+                err = ctor(obj, new_shadow->data, ctor_data);
+                if (err) {
+                        spin_unlock_irqrestore(&klp_shadow_lock, flags);
+                        kfree(new_shadow);
+                        pr_err("Failed to construct shadow variable <%p, %lx> (%d)\n",
+                               obj, id, err);
+                        return NULL;
+                }
+        }
+
         /* No <obj, id> found, so attach the newly allocated one */
         hash_add_rcu(klp_shadow_hash, &new_shadow->node,
                      (unsigned long)new_shadow->obj);
@@ -170,26 +185,32 @@ exists:
  * klp_shadow_alloc() - allocate and add a new shadow variable
  * @obj:        pointer to parent object
  * @id:         data identifier
- * @data:       pointer to data to attach to parent
  * @size:       size of attached data
  * @gfp_flags:  GFP mask for allocation
+ * @ctor:       custom constructor to initialize the shadow data (optional)
+ * @ctor_data:  pointer to any data needed by @ctor (optional)
+ *
+ * Allocates @size bytes for new shadow variable data using @gfp_flags.
+ * The data are zeroed by default.  They are further initialized by @ctor
+ * function if it is not NULL.  The new shadow variable is then added
+ * to the global hashtable.
  *
- * Allocates @size bytes for new shadow variable data using @gfp_flags
- * and copies @size bytes from @data into the new shadow variable's own
- * data space.  If @data is NULL, @size bytes are still allocated, but
- * no copy is performed.  The new shadow variable is then added to the
- * global hashtable.
+ * If an existing <obj, id> shadow variable can be found, this routine will
+ * issue a WARN, exit early and return NULL.
  *
- * If an existing <obj, id> shadow variable can be found, this routine
- * will issue a WARN, exit early and return NULL.
+ * This function guarantees that the constructor function is called only when
+ * the variable did not exist before.  The cost is that @ctor is called
+ * in atomic context under a spin lock.
  *
  * Return: the shadow variable data element, NULL on duplicate or
  * failure.
  */
-void *klp_shadow_alloc(void *obj, unsigned long id, void *data,
-                       size_t size, gfp_t gfp_flags)
+void *klp_shadow_alloc(void *obj, unsigned long id,
+                       size_t size, gfp_t gfp_flags,
+                       klp_shadow_ctor_t ctor, void *ctor_data)
 {
-        return __klp_shadow_get_or_alloc(obj, id, data, size, gfp_flags, true);
+        return __klp_shadow_get_or_alloc(obj, id, size, gfp_flags,
+                                         ctor, ctor_data, true);
 }
 EXPORT_SYMBOL_GPL(klp_shadow_alloc);
 
@@ -197,37 +218,51 @@ EXPORT_SYMBOL_GPL(klp_shadow_alloc);
  * klp_shadow_get_or_alloc() - get existing or allocate a new shadow variable
  * @obj:        pointer to parent object
  * @id:         data identifier
- * @data:       pointer to data to attach to parent
  * @size:       size of attached data
  * @gfp_flags:  GFP mask for allocation
+ * @ctor:       custom constructor to initialize the shadow data (optional)
+ * @ctor_data:  pointer to any data needed by @ctor (optional)
  *
  * Returns a pointer to existing shadow data if an <obj, id> shadow
  * variable is already present.  Otherwise, it creates a new shadow
  * variable like klp_shadow_alloc().
  *
- * This function guarantees that only one shadow variable exists with
- * the given @id for the given @obj.  It also guarantees that the shadow
- * variable will be initialized by the given @data only when it did not
- * exist before.
+ * This function guarantees that only one shadow variable exists with the given
+ * @id for the given @obj.  It also guarantees that the constructor function
+ * will be called only when the variable did not exist before.  The cost is
+ * that @ctor is called in atomic context under a spin lock.
  *
  * Return: the shadow variable data element, NULL on failure.
  */
-void *klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
-                               size_t size, gfp_t gfp_flags)
+void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
+                              size_t size, gfp_t gfp_flags,
+                              klp_shadow_ctor_t ctor, void *ctor_data)
 {
-        return __klp_shadow_get_or_alloc(obj, id, data, size, gfp_flags, false);
+        return __klp_shadow_get_or_alloc(obj, id, size, gfp_flags,
+                                         ctor, ctor_data, false);
 }
 EXPORT_SYMBOL_GPL(klp_shadow_get_or_alloc);
 
+static void klp_shadow_free_struct(struct klp_shadow *shadow,
+                                   klp_shadow_dtor_t dtor)
+{
+        hash_del_rcu(&shadow->node);
+        if (dtor)
+                dtor(shadow->obj, shadow->data);
+        kfree_rcu(shadow, rcu_head);
+}
+
 /**
  * klp_shadow_free() - detach and free a <obj, id> shadow variable
  * @obj:        pointer to parent object
  * @id:         data identifier
+ * @dtor:       custom callback that can be used to unregister the variable
+ *              and/or free data that the shadow variable points to (optional)
  *
  * This function releases the memory for this <obj, id> shadow variable
  * instance, callers should stop referencing it accordingly.
  */
-void klp_shadow_free(void *obj, unsigned long id)
+void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor)
 {
         struct klp_shadow *shadow;
         unsigned long flags;
@@ -239,8 +274,7 @@ void klp_shadow_free(void *obj, unsigned long id)
                                (unsigned long)obj) {
 
                 if (klp_shadow_match(shadow, obj, id)) {
-                        hash_del_rcu(&shadow->node);
-                        kfree_rcu(shadow, rcu_head);
+                        klp_shadow_free_struct(shadow, dtor);
                         break;
                 }
         }
@@ -252,11 +286,13 @@ EXPORT_SYMBOL_GPL(klp_shadow_free);
 /**
  * klp_shadow_free_all() - detach and free all <*, id> shadow variables
  * @id:         data identifier
+ * @dtor:       custom callback that can be used to unregister the variable
+ *              and/or free data that the shadow variable points to (optional)
  *
  * This function releases the memory for all <*, id> shadow variable
  * instances, callers should stop referencing them accordingly.
  */
-void klp_shadow_free_all(unsigned long id)
+void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor)
 {
         struct klp_shadow *shadow;
         unsigned long flags;
@@ -266,10 +302,8 @@ void klp_shadow_free_all(unsigned long id)
 
         /* Delete all <*, id> from hash */
         hash_for_each(klp_shadow_hash, i, shadow, node) {
-                if (klp_shadow_match(shadow, shadow->obj, id)) {
-                        hash_del_rcu(&shadow->node);
-                        kfree_rcu(shadow, rcu_head);
-                }
+                if (klp_shadow_match(shadow, shadow->obj, id))
+                        klp_shadow_free_struct(shadow, dtor);
         }
 
         spin_unlock_irqrestore(&klp_shadow_lock, flags);