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    SubjectRe: [RFC] frandom - fast random generator module
    Eli Billauer wrote:
    > I suppose you're asking why having a /dev/frandom device at all. Why not
    > let everyone write their own little random generator (based upon
    > well-known C functions) whenever random data is needed.
    >
    > There are plenty of handy things in the kernel, that could be done in
    > userspace. /dev/zero is my favourite example, but I'm sure there are
    > other cases where things were put in the kernel simply because people
    > found them handy. Which is a good reason, if you ask me.
    >
    > Besides, it's quite easy to do something wrong with random numbers. By
    > having a good source of random data, I suppose we can spare a lot of
    > people the headache of getting their own user-space application right
    > for the one-off thing they want to do.

    This is completely bogus logic. I can use this (incorrect) argument to
    similar push for applications doing bsearch(3) or qsort(3) via a system
    call.

    When the _implementation_ requires that a piece of code be in-kernel
    (for performance or security, usually), it is.

    In this case, there is no such requirement. More below.


    > But it's really a matter of taste. That's why I bring up the subject here.


    Processors are trending towards putting RNG on the CPU. VIA won't be
    the last, I predict. When generating random bits is a single
    instruction, "xstore", userspace applications _should_ be directly using
    this. It should not be in-kernel. And similarly, if there is no
    requirement that the kernel's entropy pool is used, the userspace
    application _should_ be where the implementation lives.

    So, given that trend and also given the existing /dev/[u]random, I
    disagree completely: /dev/frandom is the perfect example of something
    that should _not_ be in the kernel. If you want /dev/urandom faster,
    then solve _that_ problem. Don't try to solve a /dev/urandom problem by
    creating something totally new.

    Jeff


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