linux-kernel - Re: [PATCH V2] arm64/hw_breakpoint: Directly use ESR_ELx

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Message-ID: <ZeBjoq2bzi57EBsU@FVFF77S0Q05N>
Date: Thu, 29 Feb 2024 10:59:46 +0000
From: Mark Rutland <mark.rutland@....com>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
	Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH V2] arm64/hw_breakpoint: Directly use ESR_ELx_WNR for an
 watchpoint exception

On Thu, Feb 29, 2024 at 02:04:31PM +0530, Anshuman Khandual wrote:
> Let's use existing ISS encoding for an watchpoint exception i.e ESR_ELx_WNR
> This represents an instruction's either writing to or reading from a memory
> location during an watchpoint exception. While here this drops non-standard
> macro AARCH64_ESR_ACCESS_MASK.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Reviewed-by: Mark Brown <broonie@...nel.org>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>

This looks like a sensible cleanup, so:

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

Mark.

> ---
> This applies on v6.8-rc5
> 
> Changes in V2:
> 
> - Dropped new ISS encoding details ESR_ELx_WnR and ESR_ELx_WnR_SHIFT
> - Directly used existing ESR_ELx_WNR per Catalin
> - Updated the commit message as required
> 
> Changes in V1:
> 
> https://lore.kernel.org/all/20240223094615.3977323-1-anshuman.khandual@arm.com/ 
> 
>  arch/arm64/include/asm/hw_breakpoint.h | 1 -
>  arch/arm64/kernel/hw_breakpoint.c      | 3 ++-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/hw_breakpoint.h b/arch/arm64/include/asm/hw_breakpoint.h
> index 84055329cd8b..bd81cf17744a 100644
> --- a/arch/arm64/include/asm/hw_breakpoint.h
> +++ b/arch/arm64/include/asm/hw_breakpoint.h
> @@ -59,7 +59,6 @@ static inline void decode_ctrl_reg(u32 reg,
>  /* Watchpoints */
>  #define ARM_BREAKPOINT_LOAD	1
>  #define ARM_BREAKPOINT_STORE	2
> -#define AARCH64_ESR_ACCESS_MASK	(1 << 6)
>  
>  /* Lengths */
>  #define ARM_BREAKPOINT_LEN_1	0x1
> diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
> index 35225632d70a..2f5755192c2b 100644
> --- a/arch/arm64/kernel/hw_breakpoint.c
> +++ b/arch/arm64/kernel/hw_breakpoint.c
> @@ -21,6 +21,7 @@
>  
>  #include <asm/current.h>
>  #include <asm/debug-monitors.h>
> +#include <asm/esr.h>
>  #include <asm/hw_breakpoint.h>
>  #include <asm/traps.h>
>  #include <asm/cputype.h>
> @@ -779,7 +780,7 @@ static int watchpoint_handler(unsigned long addr, unsigned long esr,
>  		 * Check that the access type matches.
>  		 * 0 => load, otherwise => store
>  		 */
> -		access = (esr & AARCH64_ESR_ACCESS_MASK) ? HW_BREAKPOINT_W :
> +		access = (esr & ESR_ELx_WNR) ? HW_BREAKPOINT_W :
>  			 HW_BREAKPOINT_R;
>  		if (!(access & hw_breakpoint_type(wp)))
>  			continue;
> -- 
> 2.25.1
>