linux-kernel - Re: [PATCH RESEND v3 09/24] ptrace: cleanup arch

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Date:	Sat, 02 Oct 2010 03:18:28 +0000
From:	"Daniel K." <dk@...no>
To:	Namhyung Kim <namhyung@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Roland McGrath <roland@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	David Howells <dhowells@...hat.com>
Subject: Re: [PATCH RESEND v3 09/24] ptrace: cleanup arch_ptrace() on frv

Namhyung Kim wrote:
> Use new 'regno', 'datap' variables in order to remove duplicated
> expressions and unnecessary castings. Alse remove checking @addr
> less than 0 because addr is now unsigned.
> 
> Signed-off-by: Namhyung Kim <namhyung@...il.com>
> Cc: David Howells <dhowells@...hat.com>
> ---
>  arch/frv/kernel/ptrace.c |   29 +++++++++++++----------------
>  1 files changed, 13 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/frv/kernel/ptrace.c b/arch/frv/kernel/ptrace.c
> index e9dbfad..9d68f7f 100644
> --- a/arch/frv/kernel/ptrace.c
> +++ b/arch/frv/kernel/ptrace.c
> @@ -259,19 +259,21 @@ long arch_ptrace(struct task_struct *child, long request,
>  {
>  	unsigned long tmp;
>  	int ret;
> +	int regno = addr >> 2;
> +	unsigned long __user *datap = (unsigned long __user *) data;
>  
>  	switch (request) {
>  		/* read the word at location addr in the USER area. */
>  	case PTRACE_PEEKUSR: {
>  		tmp = 0;
>  		ret = -EIO;
> -		if ((addr & 3) || addr < 0)
> +		if (addr & 3)
>  			break;
>  
>  		ret = 0;
> -		switch (addr >> 2) {
> +		switch (regno) {
>  		case 0 ... PT__END - 1:
> -			tmp = get_reg(child, addr >> 2);
> +			tmp = get_reg(child, regno);
>  			break;
>  
>  		case PT__END + 0:
> @@ -300,23 +302,18 @@ long arch_ptrace(struct task_struct *child, long request,
>  		}
>  
>  		if (ret == 0)
> -			ret = put_user(tmp, (unsigned long *) data);
> +			ret = put_user(tmp, datap);
>  		break;
>  	}
>  
>  	case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
>  		ret = -EIO;
> -		if ((addr & 3) || addr < 0)
> +		if (addr & 3)
>  			break;
>  
> -		ret = 0;
> -		switch (addr >> 2) {
> +		switch (regno) {
>  		case 0 ... PT__END - 1:
> -			ret = put_reg(child, addr >> 2, data);
> -			break;
> -
> -		default:
> -			ret = -EIO;
> +			ret = put_reg(child, regno, data);
>  			break;
>  		}
>  		break;

With this, you remove the default case, and no longer return -EIO in the
cases of PT__END + n, as in the PTRACE_PEEKUSR section above.

This is a change of behaviour as far as I can tell, and not just a cleanup.


Daniel K.
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