linux-kernel - Re: [RFC][PATCH 1/3] powerpc: Don't force ENOSYS as error on syscall fail

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Date:	Mon, 9 Feb 2015 10:56:04 +0200
From:	Purcareata Bogdan <b43198@...escale.com>
To:	Bogdan Purcareata <bogdan.purcareata@...escale.com>,
	<benh@...nel.crashing.org>, <paulus@...ba.org>,
	<linuxppc-dev@...ts.ozlabs.org>
CC:	<linux-kernel@...r.kernel.org>, <pmoore@...hat.com>,
	<strosake@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 1/3] powerpc: Don't force ENOSYS as error on syscall
 fail

Obvious mistake on my behalf to send the patch with lines commented out. 
I will fix it in v2.

On 09.02.2015 09:55, Bogdan Purcareata wrote:
> In certain scenarios - e.g. seccomp filtering with ERRNO as default action -
> the system call fails for other reasons than the syscall not being available.
> The seccomp filter can be configured to store a user-defined error code on
> return from a blacklisted syscall.
>
> The RFC is this: are there currently any user-space scenarios where it is
> required that the system call return ENOSYS as error code on failure, no matter
> the circumstances? I don't want to break userspace requirements. I have not
> added code to force this error code in situations different than
> secure_computing failure, in order to keep overhead at a minimum.
>
> Signed-off-by: Bogdan Purcareata <bogdan.purcareata@...escale.com>
> ---
>   arch/powerpc/kernel/entry_32.S | 3 ++-
>   arch/powerpc/kernel/entry_64.S | 2 +-
>   2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index 59848e5..52e48dd 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -425,7 +425,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
>   	b	1b
>   #endif  /* CONFIG_44x */
>
> -66:	li	r3,-ENOSYS
> +66:
> +#	li	r3,-ENOSYS
>   	b	ret_from_syscall
>
>   	.globl	ret_from_fork
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index e6bfe8e..80db02e 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -269,7 +269,7 @@ syscall_dotrace:
>   	b	.Lsyscall_dotrace_cont
>
>   syscall_enosys:
> -	li	r3,-ENOSYS
> +#	li	r3,-ENOSYS
>   	b	syscall_exit
>   	
>   syscall_exit_work:
>
--
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