linux-kernel - Re: [PATCH RFC 1/4] x86/thread_info: add TIF

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Message-ID: <alpine.DEB.2.20.1801081756120.1735@nanos>
Date:   Mon, 8 Jan 2018 17:57:11 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Willy Tarreau <w@....eu>
cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        gnomes@...rguk.ukuu.org.uk, torvalds@...ux-foundation.org
Subject: Re: [PATCH RFC 1/4] x86/thread_info: add TIF_NOPTI to disable PTI
 per task

On Mon, 8 Jan 2018, Willy Tarreau wrote:

> This flag indicates that the task will not use isolated page tables.
> 
> Signed-off-by: Willy Tarreau <w@....eu>
> ---
>  arch/x86/include/asm/thread_info.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
> index 0022333..2f92cf1 100644
> --- a/arch/x86/include/asm/thread_info.h
> +++ b/arch/x86/include/asm/thread_info.h
> @@ -126,6 +126,14 @@ struct thread_info {
>  #define _TIF_X32		(1 << TIF_X32)
>  #define _TIF_FSCHECK		(1 << TIF_FSCHECK)
>  
> +/* The following flags only exist on x86-64. We can't use the shift anymore

Please do not use this horrible comment syle

And what's wrong with (1UL << 32)?

> + * due to C using signed ints by default and asm using unsigned longs.
> + */
> +#ifdef CONFIG_X86_64
> +# define  TIF_NOPTI		32	/* disable PTI for this task */

No tail comments please.

> +# define _TIF_NOPTI		0x0000000100000000
> +#endif
> +

Thanks,

	tglx