linux-kernel - Re: [RESEND][mmotm][PATCH v2, 0/5] elf coredump: Add extended numbering support

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Message-Id: <20100112.170503.112616928.d.hatayama@jp.fujitsu.com>
Date:	Tue, 12 Jan 2010 17:05:03 +0900 (JST)
From:	Daisuke HATAYAMA <d.hatayama@...fujitsu.com>
To:	akpm@...ux-foundation.org
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	mhiramat@...hat.com, xiyou.wangcong@...il.com, andi@...stfloor.org,
	jdike@...toit.com, tony.luck@...el.com
Subject: Re: [RESEND][mmotm][PATCH v2, 0/5] elf coredump: Add extended
 numbering support

From: Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RESEND][mmotm][PATCH v2, 0/5] elf coredump: Add extended numbering support
Date: Mon, 11 Jan 2010 19:24:18 -0800

> On Tue, 12 Jan 2010 12:12:32 +0900 (JST) Daisuke HATAYAMA <d.hatayama@...fujitsu.com> wrote:
> 
> > From: Andrew Morton <akpm@...ux-foundation.org>
> > Subject: Re: [RESEND][mmotm][PATCH v2, 0/5] elf coredump: Add extended numbering support
> > Date: Thu, 7 Jan 2010 16:29:28 -0800
> > 
> > > On Mon, 04 Jan 2010 10:06:07 +0900 (JST)
> > > Daisuke HATAYAMA <d.hatayama@...fujitsu.com> wrote:
> > > 
> > > > The current ELF dumper can produce broken corefiles if program headers
> > > > exceed 65535. In particular, the program in 64-bit environment often
> > > > demands more than 65535 mmaps. If you google max_map_count, then you
> > > > can find many users facing this problem.
> > > > 
> > > > Solaris has already dealt with this issue, and other OSes have also
> > > > adopted the same method as in Solaris. Currently, Sun's document and
> > > > AMD 64 ABI include the description for the extension, where they call
> > > > the extension Extended Numbering. See Reference for further information.
> > > > 
> > > > I believe that linux kernel should adopt the same way as they did, so
> > > > I've written this patch.
> > > > 
> > > > I am also preparing for patches of GDB and binutils.
> > > 
> > > That's a beautifully presented patchset.  Thanks for doing all that
> > > work - it helps.
> > > 
> > > UML maintenance appears to have ceased in recent times, so if we wish
> > > to have these changes runtime tested (we should) then I think it would
> > > be best if you could find someone to do that please.
> > > 
> > > And no akpm code-review would be complete without: dump_seek() is
> > > waaaay to large to be inlined.  Is there some common .c file to where
> > > we could move it?
> > > 
> > 
> > I am sorry for very late reply.
> > 
> > * Patch Test for UML-i386
> > 
> > I tested on UML-i386 for the stable release of that time, precisely
> > 2.6.32, since even building process for UML-i386 failed for mainline
> > and mmotm trees, as you've expected.
> > 
> > I don't know internal UML implementation at all, so I need to find
> > someone if runtime test for mmotm tree is absolutely necessary.
> 
> OK, thanks.
> 
> > * modification for dump_seek()
> > 
> > I couldn't find any right .c file at which dump_seek() be placed. We
> > need to create a new .c file into which we put auxiliary functions to
> > generate/manipulate coredumps.
> 
> Sure, that sounds appropriate.
> 
> > There is another problem regarding name space. The name dump_seek() is
> > too short.  If we move dump_seek() to some .c file, we need to rename
> > it according to the corresponding object file format, such as
> > elf_core_dump_seek() or aout_dump_seek(); or coredump_dump_seek(), as
> > currently dump_seek() is shared among dumping processes in multiple
> > object formats.
> 
> I don't understand.  Your current inlined dump_seek() looks like it
> will work OK for all dump formats when uninlined?
> 

My concern is possibility of dump_seek()'s very short and general
naming wasting public name space and colliding other global names.  My
idea is, for example, to rename it coredump_dump_seek().

Please ignore remaining part of the previous explanation. As you
mention, current dump_seek() implementation is no problem. When it
will be needed is one of implementations of some object file format
will fork.
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