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

From: Sam Ravnborg <[email-masked]>
Date: Wed, 13 Mar 2013 19:15:38 +0100

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