Memory management question

[Rodrigo Fernandez-Vizarra Bonet <rodrigofv@jazzfree.com>]

Hi,

I'm developing a linux module and I'm having some trouble with the
memory management in Linux.

Basically, what I want to do is to reserve some physical pages from the
kernel when I install the module (insmod module.o), and when a process
requests them (with mmap), I want to map that pages in the process
virtual memory area.

That's what I'm doing now.
1.- In the kernel I get some physical pages with get_free_page or with
__get_free_page.
2.- I create a device entry en /dev/ called pmm with
module_register_chrdev() with my own version of mmap.
3.- This mmap function uses the function remap_page_range() to map one
of the physical pages into the calling process virtual memory. Of course
the calling process must explicitly call mmap on the new device created
before.
4.- In the kernel space I store some information in that pages.
5.- In the user space process I mmap the device and read from it, but I
can not get the information that I stored there :-(


It's not working, and I can't understand why. When the process makes an
mmap on the device it doesn't complain, but the resulting mapping is not
correct, because I can't access the information that is contained in the
physical page.

If any of you can help me It would be apreciated,

thank you very much in advantage.

Best regards,
Rodrigo

-- 
Rodrigo Fernandez-Vizarra Bonet
    e-mail: rodrigofv@jazzfree.com

You still can avoid the GATES of hell, USE LINUX !!!
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