linux-kernel - Re: [PATCH 2/2] selftests/userfaultfd: improve syscall number definition

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Date:	Tue, 22 Sep 2015 07:49:13 -0600
From:	Shuah Khan <shuahkh@....samsung.com>
To:	Andre Przywara <andre.przywara@....com>,
	Andrea Arcangeli <aarcange@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
	Pavel Emelyanov <xemul@...allels.com>,
	Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH 2/2] selftests/userfaultfd: improve syscall number
 definition

On 09/22/2015 04:45 AM, Andre Przywara wrote:
> At the moment the userfaultfd test program only supports x86 and an
> architecture called "powewrpc" ;-)
> Fix that typo and add the syscall numbers for other architectures as
> well.
> Also as in an ideal world a syscall number should come from the system
> header file <asm/unistd.h>, include that header and guard the explicit
> syscall number section below to avoid redefinitions.
> 
> Signed-off-by: Andre Przywara <andre.przywara@....com>
> ---
>  tools/testing/selftests/vm/userfaultfd.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index 2c7cca6..63be27f 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -65,16 +65,27 @@
>  #include <sys/ioctl.h>
>  #include <pthread.h>
>  #include "../../../../include/uapi/linux/userfaultfd.h"
> +#include <asm/unistd.h>
>  
> +/* ideally the above user header provides that number, but ... */
> +#ifndef __NR_userfaultfd
>  #ifdef __x86_64__
>  #define __NR_userfaultfd 323
>  #elif defined(__i386__)
>  #define __NR_userfaultfd 374
> -#elif defined(__powewrpc__)
> +#elif defined(__powerpc__)
>  #define __NR_userfaultfd 364
> +#elif defined(__ia64__)
> +#define __NR_userfaultfd 1343
> +#elif defined(__arm__)
> +#define __NR_userfaultfd 388
> +#elif defined(__aarch64__)
> +/* this is from the generic syscall table, used also on other architectures */
> +#define __NR_userfaultfd 283
>  #else
>  #error "missing __NR_userfaultfd definition"
>  #endif
> +#endif /* !__NR_userfaultfd */
>  
>  static unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;
>  
> 

This is not okay. User-space shouldn't be (re)defining/duplicating
syscall numbers. I can't take this patch.

thanks,
-- Shuah

-- 
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
shuahkh@....samsung.com | (970) 217-8978
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