通过/proc访问内核


#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>

/* Defines the license for this LKM */
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Fortune Cookie Kernel Module");
MODULE_AUTHOR("Dengke Qiu");

#define MAX_COOKIE_LENGTH PAGE_SIZE

static struct proc_dir_entry* proc_entry;
static char *cookie_pot;
static int cookie_index;
static int next_fortune;

ssize_t fortune_write(struct file* filp, const char __user *buff,
        unsigned long len, void* data)
{
    int space_available = (MAX_COOKIE_LENGTH - cookie_index) + 1;

    if(len > space_available){
        printk(KERN_INFO "fortune: cookie pot is full!\n");
        return -ENOSPC;
    }

    if(copy_from_user(&cookie_pot[cookie_index], buff, len)){
        return -EFAULT;
    }

    cookie_index += len;
    cookie_pot[cookie_index-1] = 0;

    return len;
}

int fortune_read(char* page, char **start, off_t off, int count,
            int *eof, void *data)
{
    int len;

    if(off > 0){
        *eof = 1;
        return 0;
    }

    if( next_fortune >= cookie_index) next_fortune = 0;

    len = sprintf(page, "%s\n", &cookie_pot[next_fortune]);
    next_fortune += len;

    return len;
}

int init_fortune_module(void)
{
    int rv = 0;
    
    cookie_pot = (char*) vmalloc(MAX_COOKIE_LENGTH);
    if(!cookie_pot){
        rv = -ENOMEM;
    }
    else
    {
        memset(cookie_pot, 0, MAX_COOKIE_LENGTH);

        proc_entry = create_proc_entry("fortune", 0644, NULL);
        if(proc_entry == NULL){
            rv = -ENOMEM;
            vfree(cookie_pot);
            printk(KERN_INFO "fortune: Couldn't create proc entry.\n");
        }else{
            cookie_index = 0;
            next_fortune = 0;

            proc_entry->read_proc = fortune_read;
            proc_entry->write_proc = fortune_write;
            proc_entry->owner = THIS_MODULE;
            printk(KERN_INFO "fortune: Module loaded.\n");
        }
    }
    
    return rv;
}

void cleanup_forune_module(void)
{
    remove_proc_entry("fortune", &proc_root);
    vfree(cookie_pot);
    printk(KERN_INFO "fortune. Module is now unloaded.\n");

    return;
}

module_init(init_fortune_module);
module_exit(cleanup_forune_module);