Question

I’m extending a FreeBSD module, and I need to be able to call 2 system call functions that I wrote (using KLD). I know that the system call functions themselves are working fine, since I have a separate test program for them that calls them and returns the correct values just fine.

However, when I tried plugging in the appropriate parts of that test program into the real program, I get

vnode.c: In function 'getSyscall':
vnode.c:1014: warning: implicit declaration of function 'modfind'
vnode.c:1022: warning: implicit declaration of function 'modstat'
*** Error code 1

I have all of the includes of the (working) test program in the real thing, so I don’t understand why it can’t find the modfind and modstat functions.

#include <stdio.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/module.h>
#include <unistd.h>
#include <errno.h>
#include <sys/param.h>

// Lots of other unrelated functions here


/*
 *
 * returns a syscall number or -1 for error
 */
int getSyscall
(char *str)
{
    struct module_stat stat;
    int modid;
    int syscallnum;

    modid = modfind(str);
    if (modid == -1)
    {
        perror("modfind: ");
        return -1;
    }

    stat.version = sizeof(stat);
    if (modstat(modid, &stat) == -1)
    {
        perror("modstat: ");
        return -1;
    }

    syscallnum = stat.data.intval;

    return syscallnum;
}

Answer 1

Be sure to

#include <sys/module.h>

(after sys/param.h). modfind(2) manual page says so.

(Why is this question tagged with “linux” beats me…)