linux-kernel - Re: [PATCH] x86/signal: Cleanup get_nr_restart

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Date:	Fri, 18 Dec 2015 22:34:50 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Dmitry V. Levin" <ldv@...linux.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andy Lutomirski <luto@...nel.org>
Cc:	Elvira Khabirova <lineprinter0@...il.com>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/signal: Cleanup get_nr_restart_syscall

On 12/18/15 15:37, Dmitry V. Levin wrote:
> Check for TS_COMPAT instead of TIF_IA32 to distinguish ia32 tasks
> from 64-bit tasks.
> Check for __X32_SYSCALL_BIT only if CONFIG_X86_X32_ABI is defined.
>
> Signed-off-by: Dmitry V. Levin <ldv@...linux.org>
> Cc: Elvira Khabirova <lineprinter0@...il.com>
> Cc: Andy Lutomirski <luto@...capital.net>
> ---
>   arch/x86/kernel/signal.c | 13 ++++++++-----
>   1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
> index cb6282c..ff7dedc 100644
> --- a/arch/x86/kernel/signal.c
> +++ b/arch/x86/kernel/signal.c
> @@ -692,12 +692,15 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
>
>   static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
>   {
> -#if defined(CONFIG_X86_32) || !defined(CONFIG_X86_64)
> +#ifdef CONFIG_X86_64
> +	if (is_ia32_task())
> +		return __NR_ia32_restart_syscall;
> +# ifdef CONFIG_X86_X32_ABI
> +	if (regs->orig_ax & __X32_SYSCALL_BIT)
> +		return __NR_restart_syscall | __X32_SYSCALL_BIT;
> +# endif
> +#endif
>   	return __NR_restart_syscall;
> -#else /* !CONFIG_X86_32 && CONFIG_X86_64 */
> -	return test_thread_flag(TIF_IA32) ? __NR_ia32_restart_syscall :
> -		__NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
> -#endif /* CONFIG_X86_32 || !CONFIG_X86_64 */
>   }
>
>   /*
>

I bet you actually made the code slower.

	-hpa

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