linux-kernel - Re: [PATCH RFC 1/5] scripts: Add sortextable to sort the kernel's exception table.

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Date:	Mon, 21 Nov 2011 13:50:56 -0500
From:	Mike Frysinger <vapier@...too.org>
To:	David Daney <ddaney.cavm@...il.com>
Cc:	linux-mips@...ux-mips.org, ralf@...ux-mips.org,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-embedded@...r.kernel.org, x86@...nel.org,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH RFC 1/5] scripts: Add sortextable to sort the kernel's exception table.

On Monday 21 November 2011 13:25:36 David Daney wrote:
> On 11/20/2011 03:22 PM, Mike Frysinger wrote:
> > On Friday 18 November 2011 14:37:44 David Daney wrote:
> >> +	switch (w2(ehdr->e_machine)) {
> >> +	default:
> >> +		fprintf(stderr, "unrecognized e_machine %d %s\n",
> >> +			w2(ehdr->e_machine), fname);
> >> +		fail_file();
> >> +		break;
> >> +	case EM_386:
> >> +	case EM_MIPS:
> >> +	case EM_X86_64:
> >> +		break;
> >> +	}  /* end switch */
> > 
> > unlike recordmcount, this file doesn't do anything arch specific.  so
> > let's just delete this and be done.
> 
> Not really true at this point.  We don't know the size or layout of the
> architecture specific exception table entries, likewise for
> CONFIG_ARCH_HAS_SORT_EXTABLE, we don't even know how to do the comparison.

all of your code that i could see is based on "is it 32bit or is it 64bit".  
there is no code that says "if it's x86, we need to do XXX".

when i look in the kernel, we have common code behind ARCH_HAS_SORT_EXTABLE.  
so you could easily do the same thing:

scripts/sortextable.c:
	#ifdef ARCH_HAS_SORT_EXTABLE
		switch (w2(ehdr->e_machine)) {
		default:
			fprintf(stderr, "unrecognized e_machine %d %s\n",
				w2(ehdr->e_machine), fname);
			... return a unique exit code like 77 ...
			break;
		/* add arch sorting info here */
		}  /* end switch */
	#endif

kernel/extable.c:
	#if defined(ARCH_HAS_SORT_EXTABLE) && !defined(ARCH_HAS_SORTED_EXTABLE)
	void __init sort_main_extable(void)
	{
		sort_extable(__start___ex_table, __stop___ex_table);
	}
	#endif

this way all the people not doing unique stuff work out of the box.  only the 
people who are doing funky stuff need to extend things.
-mike

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