Mmap kernel <-> userspace

dasalam · 08-07-2011, 02:14 PM

Hello, all. I have kernel module that using mmap to communicte with usepscae program. Full code of this module paste.org.ru/?ii68m5. Compiliting ok, but when i try to read data drom userspace program(full code of userspace program paste.org.ru/?drk1vp) i get error "invalid address"

Code:

...
struct page *mmap_nopage(struct vm_area_struct *vma, unsigned long address, int *type)
{
    struct page *page;
    struct mmap_info *info;
    /* is the address valid? */
    if (address > vma->vm_end) {
        printk("invalid address\n");
        return NULL;
    }

Please, help me to fix this mistake. Or if you have working mmap please sent it to me. Thank you

nini09 · 08-08-2011, 02:48 PM

In the book, http://lwn.net/Kernel/LDD3/, it has good example of mmap.

dasalam · 08-08-2011, 02:57 PM

Quote:

Originally Posted by nini09

In the book, http://lwn.net/Kernel/LDD3/, it has good example of mmap.

Thanks, i tryed this example yesterday. And replace my func nopage with nopage function from LDD 3, but it didn't work too. I can't understand how to share information with mmap from kernel to user space. Can you explain me this point?

PS. I wrote working module using chrdev. Module code paste.org.ru/?d6jt5k. User space code paste.org.ru/?vtb1ki (/dev/simple char device created with "mknod /dev/simple c 241 0"). I understand how to read and write info from userspace, but i dont khow how do it from kernel space. Can anybody explain me?