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    SubjectRe: [PATCH 0/2] selftests/mlock2: Build warning fixes on Debian/m68k 4.0
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    Hi Eric,

    [CC linux-arch for more architecture-specific breakage]

    On Mon, Nov 9, 2015 at 4:48 PM, Eric B Munson <emunson@akamai.com> wrote:
    > On Mon, 09 Nov 2015, Geert Uytterhoeven wrote:
    >> The following 2 patches are needed to fix build warnings on Debian/m68k
    >> 4.0.
    >>
    >> However, after wiring up the mlock2 syscall, the test fails with:
    >>
    >> # ./mlock2-tests
    >> fread kpageflags: Success
    >> #
    >>
    >> as the fread() call returns 0, not 1.
    >
    > This would fail is the index into the kpageflags file is not being
    > calculated properly. This tests works on x86_64 (I am in the process of
    > testing x86 incase this is a 32bit issue). I am fairly sure that I
    > tested it on x86, but it has been a while.

    Found it: /proc/kpageflags is always empty, as m68k doesn't set up max_pfn.

    After fixing that, the test is working fine.
    Funny how we managed to survive that long without setting it ;-)

    Note that several other architectures also don't set max_pfn. Some may
    be nommu, and are thus not affected, but others probably are:

    hexagon
    mn10300
    nios2
    score

    And a few of the others (e.g. avr32, didn't check all of them) assign to a
    local max_pfn variable instead of the global one, so it won't work on those
    neither.

    >> The original commit description for the test said "Note that the limit
    >> test needs to be run a normal user.". But running it as a non-root user
    >> also fails:
    >
    > The original commit says that the on-fault-limit test needs to be run as
    > a regular user becuase it relies on enforcing memory limits.
    > mlock2-tests has to be run as root to get access to the various files
    > under /proc it needs to verify things are working.

    Ah, I just used "git log -p" on mlock2-tests.c, and didn't notice the commit
    actually added two tests.

    Thanks!

    Gr{oetje,eeting}s,

    Geert

    --
    Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

    In personal conversations with technical people, I call myself a hacker. But
    when I'm talking to journalists I just say "programmer" or something like that.
    -- Linus Torvalds


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