linux-kernel - Re: section breakage on ppc64 (aka _

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Date:	Thu, 7 Feb 2008 19:54:09 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Chuck Ebbert <cebbert@...hat.com>,
	Jan Beulich <jbeulich@...ell.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: section breakage on ppc64 (aka __devinitconst is broken by design)

On Thu, Feb 07, 2008 at 01:33:50PM -0500, Chuck Ebbert wrote:
> On 02/03/2008 08:08 AM, Al Viro wrote:
> >
> > The reason why it didn't visibly bite us before is that usually __devinit...
> > just expanded to nothing (unless you disable HOTPLUG, which requires
> > EMBEDDED, which wasn't apparently common enough for ppc64 builds).
> >
> > Suggestions?
> 
> This ugly hackset was needed to get 2.6.24 to build with GCC 4.3. It would
> be nice to get a real fix...

I cannot see any other way out of this than to loose all the newly added
consts. We have to different behavior across platforms to find a suitable
solution that is reliable.

[Kept rest of mail as I added Jan - hope he have some ideas to throw in].

	Sam

> 
> 
> --- a/include/linux/moduleparam.h
> +++ b/include/linux/moduleparam.h
> @@ -62,6 +62,15 @@ struct kparam_array
>  	void *elem;
>  };
> 
> +/* On some platforms relocations to global data cannot go into read-only
> +   sections, so 'const' makes no sense and even causes compile failures
> +   with some compilers. */
> +#if defined(CONFIG_ALPHA) || defined(CONFIG_IA64) || defined(CONFIG_PPC64)
> +#define __moduleparam_const
> +#else
> +#define __moduleparam_const const
> +#endif
> +
>  /* This is the fundamental function for registering boot/module
>     parameters.  perm sets the visibility in sysfs: 000 means it's
>     not there, read bits mean it's readable, write bits mean it's
> @@ -71,7 +80,7 @@ struct kparam_array
>  	static int __param_perm_check_##name __attribute__((unused)) =	\
>  	BUILD_BUG_ON_ZERO((perm) < 0 || (perm) > 0777 || ((perm) & 2));	\
>  	static const char __param_str_##name[] = prefix #name;		\
> -	static struct kernel_param const __param_##name			\
> +	static struct kernel_param __moduleparam_const __param_##name	\
>  	__attribute_used__						\
>      __attribute__ ((unused,__section__ ("__param"),aligned(sizeof(void *)))) \
>  	= { __param_str_##name, perm, set, get, { arg } }
> --- linux-2.6.24.noarch.orig/include/linux/module.h
> +++ linux-2.6.24.noarch/include/linux/module.h
> @@ -30,6 +30,15 @@
> 
>  #define MODULE_NAME_LEN (64 - sizeof(unsigned long))
> 
> +/* On some platforms relocations to global data cannot go into read-only
> +   sections, so 'const' makes no sense and even causes compile failures
> +   with some compilers. */
> +#if defined(CONFIG_ALPHA) || defined(CONFIG_IA64) || defined(CONFIG_PPC64)
> +#define __ksym_const
> +#else
> +#define __ksym_const const
> +#endif
> +
>  struct kernel_symbol
>  {
>  	unsigned long value;
> @@ -192,7 +201,7 @@ void *__symbol_get_gpl(const char *symbo
>  	static const char __kstrtab_##sym[]			\
>  	__attribute__((section("__ksymtab_strings")))		\
>  	= MODULE_SYMBOL_PREFIX #sym;                    	\
> -	static const struct kernel_symbol __ksymtab_##sym	\
> +	static __ksym_const struct kernel_symbol __ksymtab_##sym	\
>  	__attribute_used__					\
>  	__attribute__((section("__ksymtab" sec), unused))	\
>  	= { (unsigned long)&sym, __kstrtab_##sym }
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