userspace: improve dynamic object allocation

We now have a low-level function z_dynamic_object_create()
which is not a system call and is used for installing
kernel objects that are not supported by k_object_alloc().

Checking for valid object type enumeration values moved
completely to the implementation function.

A few debug messages and comments were improved.

Futexes and sys_mutexes are now properly excluded from
dynamic generation.

Signed-off-by: Andrew Boie <[email protected]>

Author: Andrew Boie

include/kernel.h

@@ -352,6 +352,27 @@ void k_object_access_all_grant(void *object);
 __syscall void *k_object_alloc(enum k_objects otype);
 
 #ifdef CONFIG_DYNAMIC_OBJECTS
+/**
+ * Allocate memory and install as a generic kernel object
+ *
+ * This is a low-level function to allocate some memory, and register that
+ * allocated memory in the kernel object lookup tables with type K_OBJ_ANY.
+ * Initialization state and thread permissions will be cleared. The
+ * returned z_object's data value will be uninitialized.
+ *
+ * Most users will want to use k_object_alloc() instead.
+ *
+ * Memory allocated will be drawn from the calling thread's reasource pool
+ * and may be freed later by passing the actual object pointer (found
+ * in the returned z_object's 'name' member) to k_object_free().
+ *
+ * @param size Size of the allocated object
+ * @return NULL on insufficient memory
+ * @return A pointer to the associated z_object that is installed in the
+ *	kernel object tables
+ */
+struct z_object *z_dynamic_object_create(size_t size);
+
 /**
  * Free a kernel object previously allocated with k_object_alloc()
  *
@@ -370,6 +391,14 @@ static inline void *z_impl_k_object_alloc(enum k_objects otype)
 
 	return NULL;
 }
+
+static inline struct z_object *z_dynamic_object_create(size_t size)
+{
+	ARG_UNUSED(size);
+
+	return NULL;
+}
+
 /**
  * @brief Free an object
  *

kernel/userspace.c

@@ -72,6 +72,9 @@ const char *otype_to_str(enum k_objects otype)
 	/* otype-to-str.h is generated automatically during build by
 	 * gen_kobject_list.py
 	 */
+	case K_OBJ_ANY:
+		ret = "generic";
+		break;
 #include <otype-to-str.h>
 	default:
 		ret = "?";
@@ -252,51 +255,81 @@ static void thread_idx_free(uintptr_t tidx)
 	sys_bitfield_set_bit((mem_addr_t)_thread_idx_map, tidx);
 }
 
-void *z_impl_k_object_alloc(enum k_objects otype)
+struct z_object *z_dynamic_object_create(size_t size)
 {
 	struct dyn_obj *dyn_obj;
-	uintptr_t tidx;
-
-	/* Stacks are not supported, we don't yet have mem pool APIs
-	 * to request memory that is aligned
-	 */
-	__ASSERT(otype > K_OBJ_ANY && otype < K_OBJ_LAST &&
-		 otype != K_OBJ_THREAD_STACK_ELEMENT,
-		 "bad object type requested");
 
-	dyn_obj = z_thread_malloc(sizeof(*dyn_obj) + obj_size_get(otype));
+	dyn_obj = z_thread_malloc(sizeof(*dyn_obj) + size);
 	if (dyn_obj == NULL) {
-		LOG_WRN("could not allocate kernel object");
+		LOG_ERR("could not allocate kernel object, out of memory");
 		return NULL;
 	}
 
-	dyn_obj->kobj.name = (char *)&dyn_obj->data;
-	dyn_obj->kobj.type = otype;
-	dyn_obj->kobj.flags = K_OBJ_FLAG_ALLOC;
+	dyn_obj->kobj.name = &dyn_obj->data;
+	dyn_obj->kobj.type = K_OBJ_ANY;
+	dyn_obj->kobj.flags = 0;
 	(void)memset(dyn_obj->kobj.perms, 0, CONFIG_MAX_THREAD_BYTES);
 
-	/* Need to grab a new thread index for k_thread */
-	if (otype == K_OBJ_THREAD) {
+	k_spinlock_key_t key = k_spin_lock(&lists_lock);
+
+	rb_insert(&obj_rb_tree, &dyn_obj->node);
+	sys_dlist_append(&obj_list, &dyn_obj->obj_list);
+	k_spin_unlock(&lists_lock, key);
+
+	return &dyn_obj->kobj;
+}
+
+void *z_impl_k_object_alloc(enum k_objects otype)
+{
+	struct z_object *zo;
+	uintptr_t tidx;
+
+	if (otype <= K_OBJ_ANY || otype >= K_OBJ_LAST) {
+		LOG_ERR("bad object type %d requested", otype);
+		return NULL;
+	}
+
+	switch (otype) {
+	case K_OBJ_THREAD:
 		if (!thread_idx_alloc(&tidx)) {
-			k_free(dyn_obj);
+			LOG_ERR("out of free thread indexes");
 			return NULL;
 		}
+		break;
+	/* The following are currently not allowed at all */
+	case K_OBJ_FUTEX:			/* Lives in user memory */
+	case K_OBJ_SYS_MUTEX:			/* Lives in user memory */
+	case K_OBJ_THREAD_STACK_ELEMENT:	/* No aligned allocator */
+	case K_OBJ_NET_SOCKET:			/* Indeterminate size */
+		LOG_ERR("forbidden object type '%s' requested",
+			otype_to_str(otype));
+		return NULL;
+	default:
+		/* Remainder within bounds are permitted */
+		break;
+	}
 
-		dyn_obj->kobj.data.thread_id = tidx;
+	zo = z_dynamic_object_create(obj_size_get(otype));
+	if (zo == NULL) {
+		return NULL;
+	}
+	zo->type = otype;
+
+	if (otype == K_OBJ_THREAD) {
+		zo->data.thread_id = tidx;
 	}
 
 	/* The allocating thread implicitly gets permission on kernel objects
 	 * that it allocates
 	 */
-	z_thread_perms_set(&dyn_obj->kobj, _current);
+	z_thread_perms_set(zo, _current);
 
-	k_spinlock_key_t key = k_spin_lock(&lists_lock);
-
-	rb_insert(&obj_rb_tree, &dyn_obj->node);
-	sys_dlist_append(&obj_list, &dyn_obj->obj_list);
-	k_spin_unlock(&lists_lock, key);
+	/* Activates reference counting logic for automatic disposal when
+	 * all permissions have been revoked
+	 */
+	zo->flags |= K_OBJ_FLAG_ALLOC;
 
-	return dyn_obj->kobj.name;
+	return zo->name;
 }
 
 void k_object_free(void *obj)
@@ -508,6 +541,12 @@ void z_dump_object_error(int retval, void *obj, struct z_object *ko,
 	switch (retval) {
 	case -EBADF:
 		LOG_ERR("%p is not a valid %s", obj, otype_to_str(otype));
+		if (ko == NULL) {
+			LOG_ERR("address is not a known kernel object");
+		} else {
+			LOG_ERR("address is actually a %s",
+				otype_to_str(ko->type));
+		}
 		break;
 	case -EPERM:
 		dump_permission_error(ko);

kernel/userspace_handler.c

@@ -62,10 +62,6 @@ static inline void z_vrfy_k_object_release(void *object)
 
 static inline void *z_vrfy_k_object_alloc(enum k_objects otype)
 {
-	Z_OOPS(Z_SYSCALL_VERIFY_MSG(otype > K_OBJ_ANY && otype < K_OBJ_LAST &&
-				    otype != K_OBJ_THREAD_STACK_ELEMENT,
-				    "bad object type %d requested", otype));
-
 	return z_impl_k_object_alloc(otype);
 }
 #include <syscalls/k_object_alloc_mrsh.c>

scripts/gen_kobject_list.py

@@ -79,7 +79,8 @@
 #    the object to be located in user-accessible memory.
 #
 #  - The third items is a boolean indicating whether this item can be
-#    dynamically allocated with k_object_alloc()
+#    dynamically allocated with k_object_alloc(). Keep this in sync with
+#    the switch statement in z_impl_k_object_alloc().
 #
 # Key names in all caps do not correspond to a specific data type but instead
 # indicate that objects of its type are of a family of compatible data