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    SubjectRe: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user()
    On Mon, Oct 7, 2019 at 9:09 PM Linus Torvalds
    <torvalds@linux-foundation.org> wrote:
    >
    > Try the attached patch, and then count the number of "rorx"
    > instructions in the kernel. Hint: not many. On my personal config,
    > this triggers 15 times in the whole kernel build (not counting
    > modules).

    .. and four of them are in perf_callchain_user(), and are due to those
    "__copy_from_user_nmi()" with either 4-byte or 8-byte copies.

    It might as well just use __get_user() instead.

    The point being that the silly code in the header files is just
    pointless. We shouldn't do it.

    Linus

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