RE: how to use the function copyout()

From: Felix-KM (Felix-KM_at_yandex.ru)
Date: 07/25/05

  • Next message: Giorgos Keramidas: "Re: how to use the function copyout()" 
    Date: Mon, 25 Jul 2005 18:14:05 +0400 (MSD)
To: NKoch@demig.de

    >> #define IOCTL_GET_B _IOWR("F", 127, 0x4)
    >
    >I think the third parameter to _IOWR should directly specify a type,
    >e.g. _IOWR("F", 127, int) or _IOWR("F", 127, struct MyStruct).
    >
    >>
    >> ---- driver ----
    >>
    >> struct my_softc {
    >> ...
    >> short unsigned int B;
    >> };
    >>
    >> ...
    >>
    >> static int
    >> my_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag,
    >> struct thread *td)
    >> {
    >> struct my_softc *my_sc;
    >> int unit, error;
    >> unit = minor(dev);
    >> my_sc = (struct my_softc *)devclass_get_softc(my_devclass, unit);
    >> if (my_sc == NULL)
    >> return (ENXIO);
    >> switch(cmd)
    >> {
    >> ...
    >> case IOCTL_GET_B:
    >> error = copyout(&my_sc->B, data, sizeof(my_sc->B));
    >> switch (error)
    >> {
    >> case 0:
    >> printf(" IOCTL_GET_B: %d\n", my_sc->B);
    >> break;
    >> case EFAULT:
    >> printf("EFAULT\n");
    >> break;
    >> case EIO:
    >> printf("EIO\n");
    >> break;
    >> case ENOMEM:
    >> printf("ENOMEM\n");
    >> break;
    >> case ENOSPC:
    >> printf("ENOSPC\n");
    >> break;
    >> }
    >> break;
    >> default:
    >> break;
    >> }
    >> return 0;
    >> }
    >>
    >> ---user program ----------------------
    >>
    >> ...
    >>
    >> short unsigned int Data[32768];
    >>
    >> int
    >> main(int argc, char *argv[])
    >> { ...
    >>
    >> if (ioctl(fd0, IOCTL_GET_B, Data) == -1)
    >> err(1, "IOCTL_GET_B");
    >>
    >> ...
    >> }
    >>
    >> -------
    >>
    >> Here I get EFAULT.
    >>
    >> What have I done wrong? How can I do it correctly?
    >
    >The caddr_t data in your ioctl is already mapped into kernel
    >memory. Look into the source of other device drivers. You'll
    >find a lot of *(int *) data = ...
    >So your copyout() has to fail because it tries to address
    >memory which is not a part of your application's
    >memory.
    >>From errno(2): EFAULT: Bad address...
    >
    >I have no idea if it is possible for ioctls to have mapped more
    >than a few 100 bytes for data exchange.
    >You should use read and uiomove() instead.

    So if I get it right, it's impossible in FreeBSD to gain access to 64KB of user's program memory with ioctl?

    My situation is this - I have a device driver for Linux. My task is port it as it is (1:1) into FreeBSD.

    In the Linux driver Ioctl is realized with the macroses _put_user _get_user all over it. As I understand in FreeBSD their analogues are functions described in store(9), copy(9) and fetch(9).

    So the problem is that in my user program an array short unsigned int Data[32768] is defined. I need to gain access to the array(to each element of it) from device driver with Ioctl handler.

    Is it possible to do? If yes, then how it can be done?

    >
    >Norbert
    >_______________________________________________
    >freebsd-hackers@freebsd.org mailing list
    >http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
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    -- 
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