Shared memory в модуле ядра linux

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
 
#define SHMSZ     27
 
main()
{
    char c;
    int shmid;
    key_t key;
    char *shm, *s;
 
    /*
     * We'll name our shared memory segment
     * "5678".
     */
    key = 5678;
 
    /*
     * Create the segment.
     */
    if ((shmid = shmget(key, SHMSZ, IPC_CREAT | 0666)) < 0) {
        perror("shmget");
        exit(1);
    }
 
    /*
     * Now we attach the segment to our data space.
     */
    if ((shm = shmat(shmid, NULL, 0)) == (char *) -1) {
        perror("shmat");
        exit(1);
    }
 
    /*
     * Now put some things into the memory for the
     * other process to read.
     */
    s = shm;
 
    for (c = 'h'; c <= 'z'; c++)
        *s++ = c;
    *s = NULL;
 
    /*
     * Finally, we wait until the other process 
     * changes the first character of our memory
     * to '*', indicating that it has read what 
     * we put there.
     */
    while (*shm != '*')
        sleep(1);
 
    exit(0);
}

/*
 * shm-client - client program to demonstrate shared memory.
 */
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
 
#define SHMSZ     27
 
main()
{
    int shmid;
    key_t key;
    char *shm, *s;
 
    /*
     * We need to get the segment named
     * "5678", created by the server.
     */
    key = 5678;
 
    /*
     * Locate the segment.
     */
    if ((shmid = shmget(key, SHMSZ, 0666)) < 0) {
        perror("shmget");
        exit(1);
    }
 
    /*
     * Now we attach the segment to our data space.
     */
    if ((shm = shmat(shmid, NULL, 0)) == (char *) -1) {
        perror("shmat");
        exit(1);
    }
 
    /*
     * Now read what the server put in the memory.
     */
    for (s = shm; *s != NULL; s++)
        putchar(*s);
    putchar('\n');
 
    /*
     * Finally, change the first character of the 
     * segment to '*', indicating we have read 
     * the segment.
     */
    *shm = '*';
 
    exit(0);
}