linux-kernel - Re: [PATCH 15/15] arch: add pkey and rseq syscall numbers everywhere

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Message-Id: <20190110203638.GB3676@osiris>
Date:   Thu, 10 Jan 2019 21:36:38 +0100
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     y2038@...ts.linaro.org, linux-api@...r.kernel.org,
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Subject: Re: [PATCH 15/15] arch: add pkey and rseq syscall numbers everywhere

On Thu, Jan 10, 2019 at 05:24:35PM +0100, Arnd Bergmann wrote:
> Most architectures define system call numbers for the rseq and pkey system
> calls, even when they don't support the features, and perhaps never will.
> 
> Only a few architectures are missing these, so just define them anyway
> for consistency. If we decide to add them later to one of these, the
> system call numbers won't get out of sync then.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> diff --git a/arch/s390/include/asm/unistd.h b/arch/s390/include/asm/unistd.h
> index a1fbf15d53aa..ed08f114ee91 100644
> --- a/arch/s390/include/asm/unistd.h
> +++ b/arch/s390/include/asm/unistd.h
> @@ -11,9 +11,6 @@
>  #include <asm/unistd_nr.h>
> 
>  #define __IGNORE_time
> -#define __IGNORE_pkey_mprotect
> -#define __IGNORE_pkey_alloc
> -#define __IGNORE_pkey_free
> 
>  #define __ARCH_WANT_NEW_STAT
>  #define __ARCH_WANT_OLD_READDIR
> diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
> index 428cf512a757..f84ea364a302 100644
> --- a/arch/s390/kernel/syscalls/syscall.tbl
> +++ b/arch/s390/kernel/syscalls/syscall.tbl
> @@ -391,6 +391,9 @@
>  381  common	kexec_file_load		sys_kexec_file_load		compat_sys_kexec_file_load
>  382  common	io_pgetevents		sys_io_pgetevents		compat_sys_io_pgetevents
>  383  common	rseq			sys_rseq			compat_sys_rseq
> +384  common	pkey_alloc		sys_pkey_alloc			sys_pkey_alloc
> +385  common	pkey_free		sys_pkey_free			sys_pkey_free
> +386  common	pkey_mprotect		sys_pkey_mprotect		sys_pkey_mprotect

Since you only need/want the system call numbers, could you please
change these lines to:

> +384  common	pkey_alloc		-				-
> +385  common	pkey_free		-				-
> +386  common	pkey_mprotect		-				-

Otherwise it _looks_ like we would need compat wrappers here as well,
even though all of them would just jump to sys_ni_syscall() in this
case. Making this explicit seems to better.