From mboxrd@z Thu Jan  1 00:00:00 1970
From: mark.rutland@arm.com (Mark Rutland)
Date: Mon, 13 Jul 2015 15:14:40 +0100
Subject: [PATCH v2 02/10] arm64/debug: Mask off all reserved bits from
 generated ESR values
In-Reply-To: <1436793967-7138-3-git-send-email-Dave.Martin@arm.com>
References: <1436793967-7138-1-git-send-email-Dave.Martin@arm.com>
 <1436793967-7138-3-git-send-email-Dave.Martin@arm.com>
Message-ID: <20150713141440.GC19083@leverpostej>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Mon, Jul 13, 2015 at 02:25:49PM +0100, Dave P Martin wrote:
> There are only 16 comment bits in a BRK instruction, which
> correspond to ESR bits 15:0.  Bits 24:16 of the ESR are RES0,
> and might have weird meanings in the future.
> 
> This code inserts 16 bits of comment in the ESR value instead of
> 20 (almost certainly a typo in the original code).

I'd guess that someone got confused with the instruction encoding where
the immediate lives in bits 20:5, though the mask would be wrong anyway.

> 
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>

Looks sane to me.

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  arch/arm64/include/asm/debug-monitors.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
> index f3d2dbd..ab7d5a8 100644
> --- a/arch/arm64/include/asm/debug-monitors.h
> +++ b/arch/arm64/include/asm/debug-monitors.h
> @@ -45,7 +45,7 @@
>  /*
>   * ESR values expected for dynamic and compile time BRK instruction
>   */
> -#define DBG_ESR_VAL_BRK(x)	(0xf2000000 | ((x) & 0xfffff))
> +#define DBG_ESR_VAL_BRK(x)	(0xf2000000 | ((x) & 0xffff))
>  
>  /*
>   * #imm16 values used for BRK instruction generation
> -- 
> 1.7.10.4
>