Re: Sharing memory between user and kernel spaces [Re: copy_to/from_user and a bottom half]

From: rkaiser@sysgo.de (rob@rob.devdep.sysgo.de)
Date: Fri May 19 2000 - 03:59:35 EDT

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    In article <3924CD55.5781A269@ueidaq.com>,
            aivchenko@ueidaq.com (Alex Ivchenko) writes:
    > Hi, Andi,
    >
    > My NT driver works as follows:
    >
    > 1. App allocates memory in user space (page-aligned).
    > (BTW, I didn't find the way of doing it on Linux beside to allocate
    > memory with malloc() and then align it to the page boundaries).
    >
    > 2. Inform driver about start address and size.
    >
    > 3. Driver translates user-space address into its virtual address
    > and locks pages into physical memory.
    > Now we have two handles (addresses) (kernel and user) to the same
    > piece of memory.
    >
    > 4. Then one can translate kernel-space virtual address into physical
    > one to supply to scater-gather BM-capable hardware.
    >
    > Is it any way to do this with Linux?
    >

    There is a kernel patch available at ftp://ftp.sysgo.de/pub/Linux
    that adds a facility to do this for the 2.0.x and 2.2.x kernels.

    I understand the 2.3.x kernels have a new facility (kiovec)
    to support this too, albeit in a completely different way.

    Rob

    ----------------------------------------------------------------
    Robert Kaiser email: rkaiser@sysgo.de
    SYSGO RTS GmbH
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