linux-kernel - Re: [PATCH 18/18] x86/traps: Use a new on_thread

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Message-ID: <20171101103101.oc7ljqml3xikte6y@pd.tnic>
Date:   Wed, 1 Nov 2017 11:31:01 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 18/18] x86/traps: Use a new on_thread_stack() helper to
 clean up an assertion

On Thu, Oct 26, 2017 at 01:26:50AM -0700, Andy Lutomirski wrote:
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> ---
>  arch/x86/include/asm/processor.h | 6 ++++++
>  arch/x86/kernel/traps.c          | 3 +--
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 562c575d8bc3..26fc33231cbd 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -541,6 +541,12 @@ static inline unsigned long current_top_of_stack(void)
>  #endif
>  }
>  
> +static inline bool on_thread_stack(void)
> +{
> +	return (unsigned long)(current_top_of_stack() -
> +			       current_stack_pointer) < THREAD_SIZE;
> +}
> +
>  #ifdef CONFIG_PARAVIRT
>  #include <asm/paravirt.h>
>  #else
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index 67db4f43309e..42a9c4458f5d 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -141,8 +141,7 @@ void ist_begin_non_atomic(struct pt_regs *regs)
>  	 * will catch asm bugs and any attempt to use ist_preempt_enable
>  	 * from double_fault.
>  	 */
> -	BUG_ON((unsigned long)(current_top_of_stack() -
> -			       current_stack_pointer) >= THREAD_SIZE);
> +	BUG_ON(!on_thread_stack());
>  
>  	preempt_enable_no_resched();
>  }
> -- 

Having a commit message is always better. Other than that:

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--