LinkedList in Kernel Example

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/slab.h>

struct  object_list {
        int     id;
        struct list_head list;
};

LIST_HEAD(obj_context);

static int __init
my_init(void)
{
        struct object_list *obj;
        obj = kmalloc(sizeof(struct object_list), GFP_KERNEL);
        obj->id = 5;

        list_add(&obj->list, &obj_context);

        return (0);
}

static void __exit
my_fini(void)
{
        struct  list_head *pos, *q;

        list_for_each_safe(pos, q, &obj_context) {
                struct object_list *obj = NULL;
                obj = list_entry(pos, struct object_list, list);
                list_del(pos);
                kfree(obj);
        }
        return;
}

module_init(my_init);
module_exit(my_fini);

MODULE_DESCRIPTION("Sample Code");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Krishna Mohan");


I was an working on porting driver in user space and didn't want to write my own implementation. I copied the code from the kernel and tried in userspace and as expected it worked fine. I'm doing the same for other function which i will keep posting on my blog.
#include <stdio.h>
#include <stdlib.h>

#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)

struct list_head {
        struct list_head *next, *prev;
};

struct nvme_ns {
        struct list_head list;
        int num;
};

static inline void INIT_LIST_HEAD(struct list_head *list)
{
        list->next = list;
        list->prev = list;
}

static inline void __list_add(struct list_head *_new,
                              struct list_head *prev,
                              struct list_head *next)
{
        next->prev = _new;
        _new->next = next;
        _new->prev = prev;
        prev->next = _new;
}


static inline void list_add_tail(struct list_head *_new, struct list_head *head)
{
        __list_add(_new, head->prev, head);
}

#define container_of(ptr, type, member) ({                      \
        const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
        (type *)( (char *)__mptr - offsetof(type, member) ); })

#define list_entry(ptr, type, member)   \
        container_of(ptr, type, member)

#define list_for_each_entry(pos, head, member)                          \
        for (pos = list_entry((head)->next, typeof(*pos), member);      \
                &pos->member != (head);                                 \
                pos = list_entry(pos->member.next, typeof(*pos), member))

#define list_for_each_entry_safe(pos, n, head, member)                  \
        for (pos = list_entry((head)->next, typeof(*pos), member),      \
                n = list_entry(pos->member.next, typeof(*pos), member); \
                &pos->member != (head);                                 \
                pos = n, n = list_entry(n->member.next, typeof(*n), member))


static inline void __list_del(struct list_head *prev, struct list_head *next)
{
        next->prev = prev;
        prev->next = next;
}

#define LIST_POISON1    ((void *) 0x00100100)
#define LIST_POISON2    ((void *) 0x00200200)

static inline void list_del(struct list_head *entry)
{
        __list_del(entry->prev, entry->next);
        entry->next = (struct list_head *) LIST_POISON1;
        entry->prev = (struct list_head *) LIST_POISON2;
}


int
main()
{
        struct list_head name;
        struct  nvme_ns *ns, *next;

        INIT_LIST_HEAD(&name);

        ns = malloc(sizeof(struct nvme_ns));
        printf("alloc %p\n", ns);
        ns->num = 1;

        list_add_tail(&ns->list, &name);

        ns = malloc(sizeof(struct nvme_ns));
        printf("alloc %p\n", ns);
        ns->num = 2;
        list_add_tail(&ns->list, &name);

        list_for_each_entry(ns, &name, list)
                printf("num is %d\n", ns->num);

        list_for_each_entry_safe(ns, next, &name, list) {
                list_del(&ns->list);
                printf("free %p\n", ns);
                free(ns);
        }
        return (0);
}