linux-kernel - Re: [REVIEW][PATCH 15/20] signal/x86: Don't compute pkey in __do_page

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Date:   Tue, 18 Sep 2018 22:46:50 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
cc:     LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [REVIEW][PATCH 15/20] signal/x86: Don't compute pkey in
 __do_page_fault

On Tue, 18 Sep 2018, Eric W. Biederman wrote:

> There are no more users of the computed pkey value in __do_page_fault
> so stop computing the value.
> 
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

> ---
>  arch/x86/mm/fault.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 7ba00519fa5d..f82106578364 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1215,7 +1215,6 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
>  	struct mm_struct *mm;
>  	vm_fault_t fault, major = 0;
>  	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
> -	u32 pkey;
>  
>  	tsk = current;
>  	mm = tsk->mm;
> @@ -1387,10 +1386,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
>  	 * (potentially after handling any pending signal during the return to
>  	 * userland). The return to userland is identified whenever
>  	 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
> -	 * Thus we have to be careful about not touching vma after handling the
> -	 * fault, so we read the pkey beforehand.
>  	 */
> -	pkey = vma_pkey(vma);
>  	fault = handle_mm_fault(vma, address, flags);
>  	major |= fault & VM_FAULT_MAJOR;
>  
> -- 
> 2.17.1
> 
>