linux-kernel - Re: [RFC PATCH 1/6] kernel: call constructors

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Message-ID: <482045FF.8070109@de.ibm.com>
Date:	Tue, 06 May 2008 13:50:23 +0200
From:	Peter Oberparleiter <peter.oberparleiter@...ibm.com>
To:	Sam Ravnborg <sam@...nborg.org>
CC:	ltp-list@...ts.sourceforge.net,
	Andrew Morton <akpm@...ux-foundation.org>,
	ltp-coverage@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/6] kernel: call constructors

Sam Ravnborg wrote:
> On Mon, May 05, 2008 at 05:24:04PM +0200, Peter Oberparleiter wrote:
>> From: Peter Oberparleiter <peter.oberparleiter@...ibm.com>
>> +#define CONSTRUCTORS							\
>> +		__CTOR_LIST__ = .;					\
>> +		*(.ctors)						\
>> +		__CTOR_END__ = .;					\
>> +		__DTOR_LIST__ = .;					\
>> +		*(.dtors)						\
>> +		__DTOR_END__ = .;
> 
> You shall use:  VMLINUX_SYMBOL() here.

Ok, will do.

> And why those SHOUTING names?
> All other linker symbols are lowercase.

Here's the background for that: currently, almost all
arch/*/vmlinux.lds.S scripts contain reference to a CONSTRUCTORS
sections which is (as of yet) empty. The info pages for ld contain
a description of the contents of this section (section 3.6.6 Output
Section Keywords), including the following sample linker script:

                __CTOR_LIST__ = .;
                LONG((__CTOR_END__ - __CTOR_LIST__) / 4 - 2)
                *(.ctors)
                LONG(0)
                __CTOR_END__ = .;
                __DTOR_LIST__ = .;
                LONG((__DTOR_END__ - __DTOR_LIST__) / 4 - 2)
                *(.dtors)
                LONG(0)
                __DTOR_END__ = .;

Apparently this sample script is buggy (namely the divide by 4 bit on
64 bit systems) so I changed it into the version found in the patch.
This is somewhat of a trade-off between the information which
should be present in a CONSTRUCTORS section according to the info
page and what really is needed to implement constructor support.

I guess changing the names would be an option if required, as well
as dropping the (unused) destructor bit of the linker script.
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