linux-kernel - Re: [PATCH v2 1/7] powerpc: properly negate error in syscall_set_return

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Message-ID: <6558110c-c2cb-4aa3-9472-b3496f71ebb8@csgroup.eu>
Date: Mon, 13 Jan 2025 18:34:44 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: "Dmitry V. Levin" <ldv@...ace.io>, Oleg Nesterov <oleg@...hat.com>,
 Michael Ellerman <mpe@...erman.id.au>
Cc: Eugene Syromyatnikov <evgsyr@...il.com>,
 Mike Frysinger <vapier@...too.org>, Renzo Davoli <renzo@...unibo.it>,
 Davide Berardi <berardi.dav@...il.com>, strace-devel@...ts.strace.io,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Nicholas Piggin <npiggin@...il.com>, Naveen N Rao <naveen@...nel.org>,
 linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] powerpc: properly negate error in
 syscall_set_return_value()

Le 13/01/2025 à 18:10, Dmitry V. Levin a écrit :
> Bring syscall_set_return_value() in sync with syscall_get_error(),
> and let upcoming ptrace/set_syscall_info selftest pass on powerpc.
> 
> This reverts commit 1b1a3702a65c ("powerpc: Don't negate error in
> syscall_set_return_value()").

There is a clear detailed explanation in that commit of why it needs to 
be done.

If you think that commit is wrong you have to explain why with at least 
the same level of details.

> 
> Signed-off-by: Dmitry V. Levin <ldv@...ace.io>
> ---
>   arch/powerpc/include/asm/syscall.h | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
> index 3dd36c5e334a..422d7735ace6 100644
> --- a/arch/powerpc/include/asm/syscall.h
> +++ b/arch/powerpc/include/asm/syscall.h
> @@ -82,7 +82,11 @@ static inline void syscall_set_return_value(struct task_struct *task,
>   		 */
>   		if (error) {
>   			regs->ccr |= 0x10000000L;
> -			regs->gpr[3] = error;
> +			/*
> +			 * In case of an error regs->gpr[3] contains
> +			 * a positive ERRORCODE.
> +			 */
> +			regs->gpr[3] = -error;
>   		} else {
>   			regs->ccr &= ~0x10000000L;
>   			regs->gpr[3] = val;