linux-kernel - Re: [PATCH] arm64/kernel: minor coding style tweaks

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Date:   Wed, 3 Feb 2021 11:31:38 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Zhiyuan Dai <daizhiyuan@...tium.com.cn>
Cc:     catalin.marinas@....com, will@...nel.org, Dave.Martin@....com,
        broonie@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/kernel: minor coding style tweaks

On Wed, Feb 03, 2021 at 01:19:12PM +0800, Zhiyuan Dai wrote:
> Fixed two coding style issues in kernel/trap.c
> 1. spaces required around that '='

This change makes sense to me as a cleanup.

> 2. Missing a blank line after declarations

We're inconsistent w.r.t. this across the tree, and applying this
everywhere would be very churny, but I think it makes sense to be
consistent locally (e.g. within a function).

Currently call_undef_hook() is inconsistent in this respect, but I think
this patch leaves it inconsistent in a different way. Please see below.

> Signed-off-by: Zhiyuan Dai <daizhiyuan@...tium.com.cn>
> ---
>  arch/arm64/kernel/traps.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 6895ce7..4001a39 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -45,7 +45,7 @@
>  #include <asm/system_misc.h>
>  #include <asm/sysreg.h>
>  
> -static const char *handler[]= {
> +static const char *handler[] = {
>  	"Synchronous Abort",
>  	"IRQ",
>  	"FIQ",
> @@ -318,6 +318,7 @@ static int call_undef_hook(struct pt_regs *regs)
>  	} else if (compat_thumb_mode(regs)) {
>  		/* 16-bit Thumb instruction */
>  		__le16 instr_le;
> +
>  		if (get_user(instr_le, (__le16 __user *)pc))
>  			goto exit;
>  		instr = le16_to_cpu(instr_le);

Immediately above this we have:

|	if (!user_mode(regs)) {
|		__le32 instr_le;
|		if (get_kernel_nofault(instr_le, (__force __le32 *)pc))
|			goto exit;
|		instr = le32_to_cpu(instr_le);

... which we should either change at the same time, or not bother with
this at all.

Thanks,
Mark.

> @@ -332,6 +333,7 @@ static int call_undef_hook(struct pt_regs *regs)
>  	} else {
>  		/* 32-bit ARM instruction */
>  		__le32 instr_le;
> +
>  		if (get_user(instr_le, (__le32 __user *)pc))
>  			goto exit;
>  		instr = le32_to_cpu(instr_le);
> -- 
> 1.8.3.1
>