xenocara/xserver/hw/xfree86/os-support/linux/lnx_kmod.c

#ifdef HAVE_XORG_CONFIG_H
#include <xorg-config.h>
#endif

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/wait.h>
#include <signal.h>
#include "xf86_OSlib.h"
#include "xf86.h"

#define MODPROBE_PATH_FILE      "/proc/sys/kernel/modprobe"
#define MAX_PATH                1024

#if 0
/* XFree86 #defines execl to be the xf86execl() function which does
 * a fork AND exec.  We don't want that.  We want the regular,
 * standard execl().
 */
#ifdef execl
#undef execl
#endif
#endif

/*
 * Load a Linux kernel module.
 * This is used by the DRI/DRM to load a DRM kernel module when
 * the X server starts.  It could be used for other purposes in the future.
 * Input:
 *    modName - name of the kernel module (Ex: "tdfx")
 * Return:
 *    0 for failure, 1 for success
 */
int
xf86LoadKernelModule(const char *modName)
{
    char mpPath[MAX_PATH] = "";
    int fd = -1, status, n;
    pid_t pid;

    /* get the path to the modprobe program */
    fd = open(MODPROBE_PATH_FILE, O_RDONLY);
    if (fd >= 0) {
        int count = read(fd, mpPath, MAX_PATH - 1);

        if (count <= 0) {
            mpPath[0] = 0;
        }
        else if (mpPath[count - 1] == '\n') {
            mpPath[count - 1] = 0;      /* replaces \n with \0 */
        }
        close(fd);
        /* if this worked, mpPath will be "/sbin/modprobe" or similar. */
    }

    if (mpPath[0] == 0) {
        /* we failed to get the path from the system, use a default */
        strcpy(mpPath, "/sbin/modprobe");
    }

    /* now fork/exec the modprobe command */
    /*
     * It would be good to capture stdout/stderr so that it can be directed
     * to the log file.  modprobe errors currently are missing from the log
     * file.
     */
    switch (pid = fork()) {
    case 0:                    /* child */
        /* change real/effective user ID to 0/0 as we need to
         * preinstall agpgart module for some DRM modules 
         */
        if (setreuid(0, 0)) {
            xf86Msg(X_WARNING, "LoadKernelModule: "
                    "Setting of real/effective user Id to 0/0 failed");
        }
        setenv("PATH", "/sbin", 1);
        n = execl(mpPath, "modprobe", modName, NULL);
        xf86Msg(X_WARNING, "LoadKernelModule %s\n", strerror(errno));
        exit(EXIT_FAILURE);     /* if we get here the child's exec failed */
        break;
    case -1:                   /* fork failed */
        return 0;
    default:                   /* fork worked */
    {
        /* XXX we loop over waitpid() because it sometimes fails on
         * the first attempt.  Don't know why!
         */
        int count = 0, p;

        do {
            p = waitpid(pid, &status, 0);
        } while (p == -1 && count++ < 4);

        if (p == -1) {
            return 0;
        }

        if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
            return 1;           /* success! */
        }
        else {
            return 0;
        }
    }
    }

    /* never get here */
    return 0;
}