#include <sys/syscall.h>
#include <stdio.h>
#include <errno.h>

/* The _syscall0 macro, defined in the unistd.h you put in /usr/include/asm,
 * creates the wrapper function you need to invoke your system call.
 * The "jondich" here needs to be whatever name you used after "sys_"
 * when you modified entry.S (e.g. I added the line ".long sys_jondich"
 * to entry.S).
 */

_syscall0(int,jondich)


int main()
{
    printf( "Hello from main\n" );

    /* Here, I'm invoking the wrapper function created above
     * via the _syscall0 macro. */

    int result = jondich();


    /* If an error occurs, result will be -1, and the global
     * variable errno will get set to an appropriate value.
     * Then perror consults errno to determine what error
     * message to print.  One common error message is something
     * like "function not implemented."  That message will occur,
     * for example, if you neglected to do "make install" after
     * building your new kernel, or if you booted up into the 
     * default kernel rather than your new one. */

    if( result == -1 )
        perror( "Trouble in paradise" );

    return 0;
}