A Question on Physical Memory Access from Applications

eejape at tpu.fi eejape at tpu.fi
Thu Aug 9 15:55:09 EST 2001


Could you make a "short" example of this?


----- Alkuperäinen viesti -----
Lähettäjä: Rabeeh Khoury <rabeeh at galileo.co.il>
Päiväys: Torstai, Elokuu 9, 2001 0:24
Aihe: Re: A Question on Physical Memory Access from Applications

> Hi,
> We had such a problem few months ago ; what we've done is allocating
> contigious physical memory using kmalloc in kernel space.
> From the pointer that you get from kmalloc remove the 4 MSB bits
> (usually 0xc) and pass it (some how) to the user space application.
> The user space application map the address that was passed from the
> kernel, and it will get another virtual contigious memory space.
> Now the memory area that you have in user space is contigious AND the
> physical memory that the page tables points to is contigious
> (because it
> was allocated in kernel space using kmalloc), therfore it is
> enough that
> your ADA applications just refer to the allocated memory using a
> pointerto the virtual memory.
> Regards,
> Rabeeh
> Karaaslan, Utku wrote:
> >I have ported the Linux bootloader/kernel to our home-made boards
> >(Motorola 860) and they have been running well up to now. However,
> >I have a problem: we've got a number of ADA applications which are
> >using direct memory access to certain hardware registers. Under
> >VxWorks, this is not a problem as it lacks kernelspace/userspace
> >separation. Under Linux, I know I can do direct memory access
> (through>/dev/mem), but in this case I want to use the
> applications as they are,
> >with no change to the ADA code. Is there any way to do physical
> memory>access transparently wrt the application? Many thanks in
> advance.

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