linux-kernel - Re: [PATCH 16/16] percpu: make accessors check for percpu pointer in sparse

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Date:	Wed, 14 Oct 2009 10:41:58 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Tejun Heo <tj@...nel.org>
cc:	linux-kernel@...r.kernel.org, rusty@...tcorp.com.au,
	mingo@...hat.com, tglx@...utronix.de, akpm@...ux-foundation.org,
	rostedt@...dmis.org, hpa@...or.com, cebbert@...hat.com,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 16/16] percpu: make accessors check for percpu pointer
 in sparse

On Wed, 14 Oct 2009, Tejun Heo wrote:

>  #ifndef SHIFT_PERCPU_PTR
>  /* Weird cast keeps both GCC and sparse happy. */
> -#define SHIFT_PERCPU_PTR(__p, __offset)				\
> -	RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))
> +#define SHIFT_PERCPU_PTR(__p, __offset)	({				\
> +	__verify_pcpu_ptr((__p));					\
> +	RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset)); \
> +})

If you have the verification in SHIFT_PER_CPU_PTR then why do you need it
elsewhere?

>  #define __pcpu_size_call_return(stem, variable)				\
>  ({	typeof(variable) pscr_ret__;					\
> +	__verify_pcpu_ptr(&(variable));					\
>  	switch(sizeof(variable)) {					\
>  	case 1: pscr_ret__ = stem##1(variable);break;			\
>  	case 2: pscr_ret__ = stem##2(variable);break;			\
> @@ -250,6 +251,7 @@ extern void __bad_size_call_parameter(void);
>
>  #define __pcpu_size_call(stem, variable, ...)				\
>  do {									\
> +	__verify_pcpu_ptr(&(variable));					\
>  	switch(sizeof(variable)) {					\
>  		case 1: stem##1(variable, __VA_ARGS__);break;		\
>  		case 2: stem##2(variable, __VA_ARGS__);break;		\

Would it not be better to put the verification in the arch code? The
percpu_to/from_op may have multiple callsites (at least they have now). If
you put it in there then all other stuff is covered.


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