do_mmap problem

[Amit A Purohit <apurohit@ic.sunysb.edu>]

Hi,
	I am trying to write a module that allocates memory in kernel (
kmalloc ) and maps it to the user space using do_mmap_pgoff. I have
attached the code for the same. When I load the module and run ioctl
from the user program it is giving error "Unable to handle kernel pageing
request". Any help is appreciated.

static int cosy_mmap_handler( struct file *file, struct vm_area_struct 
*vma )
{
           unsigned long physical;

           physical = vma->vm_pgoff << PAGE_SHIFT;
           physical = __pa(physical);

           if (remap_page_range(vma->vm_start, physical, vma->vm_end -
vma->vm_s
           return -1;

           vma->vm_file = NULL;
           return 0;
}

int io_ioctl (struct inode *inode, struct file *file, unsigned int cmd,
unsigned long user_ptr)
{
        int i;
        unsigned long pAddr,uAddr = 0;
        struct file_operations fops;
        struct file pseudofile;
        unsigned long bsize = 4096;
        int *tmp;

        pAddr = (unsigned long) kmalloc( bsize + 2*PAGE_SIZE, GFP_KERNEL
);
        printk("\nThe kmallocked address =  %ld",pAddr);
        pAddr = (unsigned long)(((unsigned long)pAddr + PAGE_SIZE -1) &
PAGE_MASK);
        printk("\nPage aligned address = %ld",pAddr);
        for (uAddr = pAddr; uAddr<pAddr+bsize; uAddr += PAGE_SIZE) {
                mem_map_reserve(virt_to_page(uAddr));
        }

        tmp = (int *)pAddr;
        for(i=0; i<bsize/(sizeof(int)); i++)
                tmp[i] = i;
        fops.mmap = cosy_mmap_handler;
        pseudofile.f_op = &fops;
        pseudofile.f_mode = 0x3;

        uAddr = do_mmap_pgoff( &pseudofile, 0, bsize, PROT_READ |
PROT_WRITE, MAP_PRIVATE, pAddr);

        printk("\n do_mmaped address is  = %ld",uAddr);

        tmp = (int *)pAddr;
        for(i=0; i<bsize/(sizeof(int)); i++)
                tmp[i] = 9;

        return uAddr;
}

--Amit


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