linux-kernel - Re: [PATCH] cross-architecture ELF clean up

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Date:	Tue, 26 Jun 2007 15:29:01 -0400
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Roman Zippel <zippel@...ux-m68k.org>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Arch <linux-arch@...r.kernel.org>,
	Al Viro <viro@....linux.org.uk>
Subject: Re: [PATCH] cross-architecture ELF clean up

Roman Zippel wrote:
>> This patch cleans up the ELF headers and their users.  It does several
>> related things:
>>
>> 1. split linux/elf.h into pieces
>>
>> This splits linux/elf.h into several pieces:
>> 	linux/elf.h		- still the common elf header,
>> 				  functionally unchanged
>> 	linux/elf-const.h	- ELF constants, includable by asm code
>>     
>
> We have the __ASSEMBLY__ define for this, so just for asm code we don't 
> need a separate header.
>   

Hm.  The number of __ASSEMBLY__s end up being pretty large, and it just 
seemed cleaner to put them in separate headers.

>> 	linux/elf-decl.h	- ELF type declarations, without definitions
>> 	linux/elf-defn.h	- ELF type definitions
>>     
>
> What's the point in splitting these two?
>   

Because there are other headers which just need some type 
forward-declarations, and don't need the whole set of ELF types 
defined.  In particular, linux/module.h - which is included all over the 
place in the kernel - needs a couple of ELF types declared, and 
including it all over the place is just a waste.  Also, there were some 
nasty cyclic header dependency problems around linux/elf.h, 
linux/module.h, linux/bug.h and asm/bug.h which ended up leading to some 
awkward hacks; I need to remind myself what the problems were and see if 
this elf cleanup helps (pretty sure it should).

> After this patch <linux/elf.h> seems to be pretty much empty, I'd rather 
> suggest to move the function declarations to elfcore.h and leave the basic 
> elf definitions in elf.h. Many small header files have the disadvantage 
> that it takes longer to find the needed information.
>   
linux/elf.h ends up pulling in a really surprising amount of stuff, 
mostly because it ends up including asm/elf.h.  asm/elf.h, in turn, 
depending on the architecture, pulls in a wide variety of other 
headers.  When I cleaned this up, I found quite a few buggy .c files 
which ended up relying on implicit includes via this chain.

Given that there's been a general push to try and cut down on the number 
of header dependency entanglements, I thought I could contribute while 
solving my own immediate problems.

linux/elfcore.h is specifically related to ELF core files, so the two 
corefile notes-related headers could be moved there.

    J
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