Trouble with copyout, memcpy.... Plain-Text version =)

[Leunam Elebek]

Hey list,

I currently code a driver under Current 8.0 for Current 8.0.
But there are some problems with kernel/user-space interaction.

I've the following structure:

struct daq_kitinfo {
        uint32_t ki_maxdata;
        uint32_t ki_flags;
        uint32_t ki_rng_type;
        int      ki_type;
        int      ki_nchan;
        int      ki_len_chanl;
};

The above structure is used in my user-space app:

int main(void) {
        struct daq_kitinfo *info;
        struct daq_kit kit; 
        int fd, size; 
        ...
        ...
        ...
        /* 
         * At this point I'll try to alloc memory. Notice that 
         * the size i dependet from another struct entry.
         */
        size = sizeof(*info) * kit.k_nkits;
        info = malloc(size);
        if (info == NULL)
                exit(ENOMEM);

        /*
         * The next step is to call the drivers ioctl() interface
         * (the reason for that is described below).
         */
        if (ioctl(fd, DAQ_KITINFO, info)) {
                printf("errno: %d\n", errno); 
                 exit(errno);
        }

         printf("[ki_nchan] %d\n", info.ki_nchan);
         ...
         ...
         return (0);
}


and inside the driver (put it simply):


static int
my_ioctl(struct cdev *dev, u_long cmd, caddr_t arg, int flags,
    struct thread *td)
{
        struct daq_kitinfo *info;
        struct daq_kit = dev->si_drv1; 
        int size; 
        ...
        /* Do something useful e.g mutex'ing... */
        ...
        /* The same as in user-space... */
        size = sizeof(*info) * kit.k_nkits;
        info = malloc(sz, M_DAQ, M_NOWAIT | M_ZERO);
        if (info == NULL)
                ....
        /*
         * Here I want to copy struct info from kernel to user-space.
         * If i use memcpy, the result is that the system hangs
         * and I need to reboot the machine. OK, I thought
         * copyout() should be able to do the job for me...
         */
         if (copyout(info, arg, sz))
                 /*
                  * Fuc[k-k] i still come inside this block. I always
                  * get an EFAULT error. 
                  */
}

I really don't know what I should do to let the driver working
properly. The driver should grap some informations/attributes,
and fill up the info structure, so we can copy the filled info struct
to the user's app.

I hope somebody can help me to resolve that problem.

Ah, the corresponding ioctl is:


#define GRP                        'd'
#define DAQ_KITINFO        _IOR(GRP, 3, struct daq_kitinfo)

Thanks for attention and greatz from germany

MG