linux-kernel - Re: [PATCH 07/13] jump label v8: sort jump table at build-time

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Message-ID: <20100520213216.GB14957@Krystal>
Date:	Thu, 20 May 2010 17:32:16 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Jason Baron <jbaron@...hat.com>
Cc:	David Miller <davem@...emloft.net>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, hpa@...or.com, tglx@...utronix.de,
	rostedt@...dmis.org, andi@...stfloor.org, roland@...hat.com,
	rth@...hat.com, mhiramat@...hat.com, fweisbec@...il.com,
	avi@...hat.com, vgoyal@...hat.com
Subject: Re: [PATCH 07/13] jump label v8: sort jump table at build-time

* Jason Baron (jbaron@...hat.com) wrote:
> On Wed, May 19, 2010 at 03:36:34PM -0700, David Miller wrote:
> > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > > index 2092361..fe6f8be 100644
> > > --- a/scripts/mod/modpost.c
> > > +++ b/scripts/mod/modpost.c
> > > @@ -17,6 +17,8 @@
> > >  #include "modpost.h"
> > >  #include "../../include/generated/autoconf.h"
> > >  #include "../../include/linux/license.h"
> > > +#include <linux/types.h>
> > > +#include "jump_entry.h"
> > >  
> > 
> > This breaks the build on non-jump_label-supporting architectures
> > because only they will have the jump_entry.h header file.
> > 
> > I'm really getting tired trying to test your changes and every single
> > time as I go through doing very basic build testing I always hit one
> > patch that assumes jump label support exists, or assumes some x86'ism.
> 
> sorry about that. I mis-tested it. anyways here's the interdiff to this
> patch to fix. btw, how do the sparc bits look?
> 
> thanks,
> 
> -Jason
> 
> 
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index fe6f8be..cc87012 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -18,7 +18,9 @@
>  #include "../../include/generated/autoconf.h"
>  #include "../../include/linux/license.h"
>  #include <linux/types.h>
> -#include "jump_entry.h"

includes with "" is a bit unexpected in kernel code. Any reason for this ?
Is jump_entry.h shipped in scripts/mod/ ?

> +#ifdef CONFIG_HAVE_ARCH_JUMP_LABEL

ifdefs everywhere cripples the code and make it unreadable. You might
want to try to find another way to deal with the problem. E.g.

create linux/jump_entry.h
which contains 

#ifdef CONFIG_HAVE_ARCH_JUMP_LABEL
#include <asm/jump_entry.h>
#else

define some empty static inlines, and use them in the .c files.

e.g. 

static inline void sort_jump_label_table(struct elf_info *info, Elf_Ehdr *hdr)
{
}

#endif

> + #include "jump_entry.h"
> +#endif
>  
>  /* Some toolchains use a `_' prefix for all user symbols. */
>  #ifdef CONFIG_SYMBOL_PREFIX
> @@ -377,6 +379,8 @@ void release_file(void *file, unsigned long size)
>  	munmap(file, size);
>  }
>  
> +#ifdef CONFIG_HAVE_ARCH_JUMP_LABEL
> +
>  static void swap_jump_label_entries(struct jump_entry *previous, struct jump_entry *next)
>  {
>  	struct jump_entry tmp;
> @@ -421,6 +425,8 @@ static void sort_jump_label_table(struct elf_info *info, Elf_Ehdr *hdr)
>  	} while (swapped == 1);
>  }
>  
> +#endif
> +
>  static int parse_elf(struct elf_info *info, const char *filename)
>  {
>  	unsigned int i;
> @@ -539,8 +545,10 @@ static int parse_elf(struct elf_info *info, const char *filename)
>  		sym->st_size  = TO_NATIVE(sym->st_size);
>  	}
>  
> +#ifdef CONFIG_HAVE_ARCH_JUMP_LABEL
>  	if (enable_jump_label)
>  		sort_jump_label_table(info, hdr);
> +#endif

And remove this ifdef.

Thanks,

Mathieu

>  
>  	return 1;
>  }

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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