linux-kernel - Re: [PATCH v4 10/12] arm64: BTI: Reset BTYPE when skipping emulated instructions

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Date:   Tue, 14 Jan 2020 17:36:28 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Will Deacon <will@...nel.org>, Paul Elliott <paul.elliott@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Amit Kachhap <amit.kachhap@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Marc Zyngier <maz@...nel.org>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        "H.J. Lu" <hjl.tools@...il.com>, Andrew Jones <drjones@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>,
        Richard Henderson <richard.henderson@...aro.org>,
        Kristina Martšenko <kristina.martsenko@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Florian Weimer <fweimer@...hat.com>,
        Sudakshina Das <sudi.das@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, Dave Martin <Dave.Martin@....com>
Subject: Re: [PATCH v4 10/12] arm64: BTI: Reset BTYPE when skipping emulated
 instructions

On Wed, Dec 11, 2019 at 03:42:04PM +0000, Mark Brown wrote:
> From: Dave Martin <Dave.Martin@....com>
> 
> Since normal execution of any non-branch instruction resets the
> PSTATE BTYPE field to 0, so do the same thing when emulating a
> trapped instruction.
> 
> Branches don't trap directly, so we should never need to assign a
> non-zero value to BTYPE here.
> 
> Signed-off-by: Dave Martin <Dave.Martin@....com>
> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
>  arch/arm64/kernel/traps.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index bf79d8024fbe..9fc05ae500e6 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -332,6 +332,8 @@ void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size)
>  
>  	if (regs->pstate & PSR_MODE32_BIT)

Same comment as on a previous patch, compat_user_mode() could be used.

Other than this:

Reviewed-by: Catalin Marinas <catalin.marinas@....com>