linux-kernel - Re: [PATCH] powerpc/process: Enhance readability for trap types.

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Date:   Sun, 28 Mar 2021 17:21:58 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Xiongwei Song <sxwjean@...com>, mpe@...erman.id.au,
        benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
        ravi.bangoria@...ux.ibm.com, mikey@...ling.org,
        aneesh.kumar@...ux.ibm.com, haren@...ux.ibm.com
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Xiongwei Song <sxwjean@...il.com>
Subject: Re: [PATCH] powerpc/process: Enhance readability for trap types.



Le 28/03/2021 à 16:35, Xiongwei Song a écrit :
> From: Xiongwei Song <sxwjean@...il.com>
> 
> Define macros to enhance the code readability on ppc trap types.

Good idea

> 
> Signed-off-by: Xiongwei Song <sxwjean@...il.com>
> ---
>   arch/powerpc/kernel/process.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 3231c2df9e26..3bbd3cf353a7 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1451,6 +1451,10 @@ static void print_msr_bits(unsigned long val)
>   #define LAST_VOLATILE	12
>   #endif
>   
> +#define TRAP_MC  0x200 /* Machine Check */

I think usually we use MCE, so TRAP_MCE would be better

> +#define TRAP_DSI 0x300 /* DSI exception */
> +#define TRAP_AM  0x600 /* Alignment exception */

Don't know what AM means. TRAP_ALIGN would be more explicit.

> +

The defines should go in a header file, for instance asm/ptrace.h in order to be re-used in other files.

You should do more. You can find other places to improve with:

git grep "trap ==" arch/powerpc/
git grep "TRAP(regs) ==" arch/powerpc/

>   static void __show_regs(struct pt_regs *regs)
>   {
>   	int i, trap;
> @@ -1465,7 +1469,7 @@ static void __show_regs(struct pt_regs *regs)
>   	trap = TRAP(regs);
>   	if (!trap_is_syscall(regs) && cpu_has_feature(CPU_FTR_CFAR))
>   		pr_cont("CFAR: "REG" ", regs->orig_gpr3);
> -	if (trap == 0x200 || trap == 0x300 || trap == 0x600) {
> +	if (trap == TRAP_MC || trap == TRAP_DSI || trap == TRAP_AM) {
>   		if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE))
>   			pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->dsisr);
>   		else
>