linux-kernel - Re: [RFC -next] linux/linkage.h: fix symbol prefix handling

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Message-ID: <20130313181538.GA20097@merkur.ravnborg.org>
Date:	Wed, 13 Mar 2013 19:15:38 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	James Hogan <james.hogan@...tec.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Al Viro <viro@...iv.linux.org.uk>,
	Michal Marek <mmarek@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Jean Delvare <khali@...ux-fr.org>,
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
	Mike Frysinger <vapier@...too.org>,
	uclinux-dist-devel@...ckfin.uclinux.org, linux-next@...r.kernel.org
Subject: Re: [RFC -next] linux/linkage.h: fix symbol prefix handling

On Wed, Mar 13, 2013 at 09:21:01AM +0000, James Hogan wrote:
> Hi Sam,
> 
> On 13/03/13 06:31, Sam Ravnborg wrote:
> >>  /* Some toolchains use a `_' prefix for all user symbols. */
> >> -#ifdef CONFIG_SYMBOL_PREFIX
> >> -#define MODULE_SYMBOL_PREFIX CONFIG_SYMBOL_PREFIX
> >> +#ifdef CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX
> >> +#define __VMLINUX_SYMBOL(x) _##x
> >> +#define __VMLINUX_SYMBOL_STR(x) "_" #x
> >> +#define VMLINUX_SYMBOL_PREFIX_STR "_"
> >>  #else
> >> -#define MODULE_SYMBOL_PREFIX ""
> >> +#define __VMLINUX_SYMBOL(x) x
> >> +#define __VMLINUX_SYMBOL_STR(x) #x
> >> +#define VMLINUX_SYMBOL_PREFIX_STR ""
> >>  #endif
> > 
> > We know the prefix is an underscore. No benefits from defining
> > VMLINUX_SYMBOL_PREFIX_STR.
> 
> scripts/modpost.c uses the actual prefix string though:
> 
> >	if (memcmp(symname, MODULE_SYMBOL_PREFIX,
> >		   strlen(MODULE_SYMBOL_PREFIX)) == 0) {
> >		mod->unres =
> >		  alloc_symbol(symname +
> >		               strlen(MODULE_SYMBOL_PREFIX),
> > 		               ELF_ST_BIND(sym->st_info) == STB_WEAK,
> > 		               mod->unres);
> 

Allowing ourself to know this is "_" then we could make the above code look
something like:

	if (have_symbol_prefix_underscore) {
		if (symname[0] == '_') {
			mod->unres =
			...

But I do not feel strong about this part.

It is much more important to clean up so we use the
same definition all over the kernel.

	Sam
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