gistfile1.c

// Test to understand what https://gist.github.com/2517475 is actually doing.

#include <stdio.h>

#define __AC(X,Y)       (X##Y)
#define _AC(X,Y)        __AC(X,Y)
#define BITS_PER_BYTE   8
#define PAGE_SHIFT      12
#define PAGE_SIZE       (_AC(1,UL) << PAGE_SHIFT)
#define __user
#define EINVAL          22      /* Invalid argument */

// extracted from <linux-kernel>/mm/mempolicy.c
static int get_nodes(const unsigned long __user *nmask,
                     unsigned long maxnode)
{
    --maxnode;
    if (maxnode == 0 || !nmask)
        return 0;
    if (maxnode > PAGE_SIZE*BITS_PER_BYTE)
        return -EINVAL;
}

int
main(int argc, char *argv[])
{
    unsigned long null_nodemask=0, maxnode=0;
    printf("get_nodes(NULL,0) = %d\n", get_nodes(NULL,maxnode));
    printf("get_nodes(&null_nodemask,0) = %d\n", get_nodes(&null_nodemask,maxnode));
    return 0;
}