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Object Cores

Object cores are a kernel debugging tool that can be used to both identify and perform operations on registered objects.

Object Core Concepts 

Each instance of an object embeds an object core field named obj_core. Objects of the same type are linked together via their respective object cores to form a singly linked list. Each object core also links to the their respective object type. Each object type contains a singly linked list linking together all the object cores of that type. Object types are also linked together via a singly linked list. Together, this can allow debugging tools to traverse all the objects in the system.

Object cores have been integrated into following kernel objects:

Developers are free to integrate them if desired into other objects within their projects.

Object Core Statistics Concepts 

A variety of kernel objects allow for the gathering and reporting of statistics. Object cores provide a uniform means to retrieve that information via object core statistics. When enabled, the object type contains a pointer to a statistics descriptor that defines the various operations that have been enabled for interfacing with the object’s statistics. Additionally, the object core contains a pointer to the “raw” statistical information associated with that object. Raw data is the raw, unmanipulated data associated with the statistics. Queried data may be “raw”, but it may also have been manipulated in some way by calculation (such as determining an average).

The following table indicates both what objects have been integrated into the object core statistics as well as the structures used for both “raw” and “queried” data.

Object	Raw Data Type	Query Data Type
struct mem_slab	struct mem_slab_info	struct sys_memory_stats
struct sys_mem_blocks	struct sys_mem_blocks_info	struct sys_memory_stats
struct k_thread	struct k_cycle_stats	struct k_thread_runtime_stats
struct _cpu	struct k_cycle_stats	struct k_thread_runtime_stats
struct z_kernel	struct k_cycle_stats[num CPUs]	struct k_thread_runtime_stats

Implementation 

Defining a New Object Type 

An object type is defined using a global variable of type k_obj_type. It must be initialized before any objects of that type are initialized. The following code shows how a new object type can be initialized for use with object cores and object core statistics.

/* Unique object type ID */

#define K_OBJ_TYPE_MY_NEW_TYPE  K_OBJ_TYPE_ID_GEN("UNIQ")
struct k_obj_type  my_obj_type;

struct my_obj_type_raw_info {
    ...
};

struct my_obj_type_query_stats {
    ...
};

struct my_new_obj {
    ...
    struct k_obj_core obj_core;
    struct my_obj_type_raw_info  info;
};

struct k_obj_core_stats_desc my_obj_type_stats_desc = {
    .raw_size = sizeof(struct my_obj_type_raw_stats),
    .query_size = sizeof(struct my_obj_type_query_stats),
    .raw = my_obj_type_stats_raw,
    .query = my_obj_type_stats_query,
    .reset = my_obj_type_stats_reset,
    .disable = NULL,    /* Stats gathering is always on */
    .enable = NULL,     /* Stats gathering is always on */
};

void my_obj_type_init(void)
{
    z_obj_type_init(&my_obj_type, K_OBJ_TYPE_MY_NEW_TYPE,
                    offsetof(struct my_new_obj, obj_core);
    k_obj_type_stats_init(&my_obj_type, &my_obj_type_stats_desc);
}

Initializing a New Object Core 

Kernel objects that have already been integrated into the object core framework automatically have their object cores initialized when the object is initialized. However, developers that wish to add their own objects into the framework need to both initialize the object core and link it. The following code builds on the example above and initializes the object core.

void my_new_obj_init(struct my_new_obj *new_obj)
{
    ...
    k_obj_core_init(K_OBJ_CORE(new_obj), &my_obj_type);
    k_obj_core_link(K_OBJ_CORE(new_obj));
    k_obj_core_stats_register(K_OBJ_CORE(new_obj), &new_obj->raw_stats,
                              sizeof(struct my_obj_type_raw_info));
}

Walking a List of Object Cores 

Two routines exist for walking the list of object cores linked to an object type. These are k_obj_type_walk_locked() and k_obj_type_walk_unlocked(). The following code builds upon the example above and prints the addresses of all the objects of that new object type.

int walk_op(struct k_obj_core *obj_core, void *data)
{
    uint8_t *ptr;

    ptr = obj_core;
    ptr -= obj_core->type->obj_core_offset;

    printk("%p\n", ptr);

    return 0;
}

void print_object_addresses(void)
{
    struct k_obj_type *obj_type;

    /* Find the object type */

    obj_type = k_obj_type_find(K_OBJ_TYPE_MY_NEW_TYPE);

    /* Walk the list of objects */

    k_obj_type_walk_unlocked(obj_type, walk_op, NULL);
}

Object Core Statistics Querying 

The following code builds on the examples above and shows how an object integrated into the object core statistics framework can both retrieve queried data and reset the stats associated with the object.

struct my_new_obj my_obj;

...

void my_func(void)
{
    struct my_obj_type_query_stats  my_stats;
    int  status;

    my_obj_type_init(&my_obj);

    ...

    status = k_obj_core_stats_query(K_OBJ_CORE(&my_obj),
                                    &my_stats, sizeof(my_stats));
    if (status != 0) {
        /* Failed to get stats */
        ...
    } else {
        k_obj_core_stats_reset(K_OBJ_CORE(&my_obj));
    }

    ...
}

API Reference 

Object Core APIs

Object Core Statistics APIs