linux-kernel - Re: [PATCH] proc: fix proc-self-map-files selftest for arm

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Date:   Thu, 11 Oct 2018 23:56:01 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Rafael David Tinoco <rafael.tinoco@...aro.org>
Cc:     linux-kselftest@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, gorcunov@...il.com,
        akpm@...ux-foundation.org, shuah@...nel.org
Subject: Re: [PATCH] proc: fix proc-self-map-files selftest for arm

On Thu, Oct 11, 2018 at 03:43:59PM -0300, Rafael David Tinoco wrote:
> MAP_FIXED is important for this test but, unfortunately, lowest virtual
> address for user space mapping on arm is (PAGE_SIZE * 2) and NULL hint
> does not seem to guarantee that when MAP_FIXED is given. This patch sets
> the virtual address that will hold the mapping for the test, fixing the
> issue.
> 
> Link: https://bugs.linaro.org/show_bug.cgi?id=3782
> Signed-off-by: Rafael David Tinoco <rafael.tinoco@...aro.org>
> ---
>  tools/testing/selftests/proc/proc-self-map-files-002.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/proc/proc-self-map-files-002.c b/tools/testing/selftests/proc/proc-self-map-files-002.c
> index 6f1f4a6e1ecb..0a47eaca732a 100644
> --- a/tools/testing/selftests/proc/proc-self-map-files-002.c
> +++ b/tools/testing/selftests/proc/proc-self-map-files-002.c
> @@ -55,7 +55,9 @@ int main(void)
>  	if (fd == -1)
>  		return 1;
>  
> -	p = mmap(NULL, PAGE_SIZE, PROT_NONE, MAP_PRIVATE|MAP_FILE|MAP_FIXED, fd, 0);
> +	p = mmap((void *) (2 * PAGE_SIZE), PAGE_SIZE, PROT_NONE,
> +			MAP_PRIVATE|MAP_FILE|MAP_FIXED, fd, 0);

As the comment in the beginning says this test is specifically for addresss 0.
Maybe it should be ifdeffed with __arm__ then.