linux-kernel - Re: [RFC] ptrace: add generic SET

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Message-ID: <20141107140405.GA30156@redhat.com>
Date:	Fri, 7 Nov 2014 15:04:05 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:	roland@...k.frob.com, linux@....linux.org.uk, will.deacon@....com,
	dsaxena@...aro.org, keescook@...omium.org,
	linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] ptrace: add generic SET_SYSCALL request

On 11/07, AKASHI Takahiro wrote:
>
> --- a/arch/arm/kernel/ptrace.c
> +++ b/arch/arm/kernel/ptrace.c
> @@ -853,11 +853,6 @@ long arch_ptrace(struct task_struct *child, long request,
>  				       datap);
>  			break;
>  
> -		case PTRACE_SET_SYSCALL:
> -			task_thread_info(child)->syscall = data;
> -			ret = 0;
> -			break;
> -
>  #ifdef CONFIG_CRUNCH
>  		case PTRACE_GETCRUNCHREGS:
>  			ret = ptrace_getcrunchregs(child, datap);
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 54e7522..d7048fa 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -1001,6 +1001,12 @@ int ptrace_request(struct task_struct *child, long request,
>  		break;
>  	}
>  #endif
> +
> +#ifdef PTRACE_SET_SYSCALL
> +	case PTRACE_SET_SYSCALL:
> +		ret = syscall_set_nr(child, task_pt_regs(child), data);
> +		break;
> +#endif

I too do not understand why it makes sense to move PTRACE_SET_SYSCALL into
the common kernel/ptrace.c.

To me the fact that PTRACE_SET_SYSCALL can be undefined and syscall_set_nr()
is very much arch-dependant (but most probably trivial) means that this code
should live in arch_ptrace().

In any case, I think it doesn't make sense to pass task_pt_regs(child), this
helper can do this itself if it needs struct pt_regs.

Oleg.

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