linux-kernel - Re: [PATCH 3/5] parisc: use new macros for .data.init

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Message-ID: <20090502221006.GA4309@uranus.ravnborg.org>
Date:	Sun, 3 May 2009 00:10:06 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Helge Deller <deller@....de>
Cc:	Tim Abbott <tabbott@....EDU>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Anders Kaseorg <andersk@....edu>,
	Waseem Daher <wdaher@....edu>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Jeff Arnold <jbarnold@....edu>,
	Kyle McMartin <kyle@...artin.ca>, linux-parisc@...r.kernel.org
Subject: Re: [PATCH 3/5] parisc: use new macros for .data.init_task.

On Sat, May 02, 2009 at 07:13:37AM +0200, Helge Deller wrote:
> Tim Abbott wrote:
> > .data.init_task should not need a separate output section; this change
> > moves it into the .data section.
> > 
> > Signed-off-by: Tim Abbott <tabbott@....edu>
> > Cc: Kyle McMartin <kyle@...artin.ca>
> > Cc: Helge Deller <deller@....de>
> > Cc: linux-parisc@...r.kernel.org
> 
> 
> I think this patch is wrong, although it is theoretically correct.
> 
> IIRC, gcc on hppa is not able to provide an alignment >= 8k, which is
> why we have done the 16k alignment inside the linker script.
> So, I think this change will prevent the parisc kernel to boot up.
> Needs testing.

The patch does not do much...

> 
> Helge
> 
> > ---
> >  arch/parisc/kernel/init_task.c   |    2 +-
> >  arch/parisc/kernel/vmlinux.lds.S |   10 ++--------
> >  2 files changed, 3 insertions(+), 9 deletions(-)
> > 
> > diff --git a/arch/parisc/kernel/init_task.c b/arch/parisc/kernel/init_task.c
> > index 1e25a45..8ee17ea 100644
> > --- a/arch/parisc/kernel/init_task.c
> > +++ b/arch/parisc/kernel/init_task.c
> > @@ -48,7 +48,7 @@ EXPORT_SYMBOL(init_mm);
> >   * "init_task" linker map entry..
> >   */
> >  union thread_union init_thread_union
> > -	__attribute__((aligned(128))) __attribute__((__section__(".data.init_task"))) =
> > +	__attribute__((aligned(128))) __init_task_data =
> >  		{ INIT_THREAD_INFO(init_task) };
This is a simple replacement with a nicer way to say "this belongs to
the .data.init_task section - no functional difference.


> >  
> >  #if PT_NLEVELS == 3
> > diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S
> > index b5936c9..c8a528d 100644
> > --- a/arch/parisc/kernel/vmlinux.lds.S
> > +++ b/arch/parisc/kernel/vmlinux.lds.S
> > @@ -103,6 +103,8 @@ SECTIONS
> >  	. = ALIGN(L1_CACHE_BYTES);
> >  	/* Data */
> >  	.data : {
> > +		/* assembler code expects init_task to be 16k aligned */
> > +		INIT_TASK_DATA(16384)
> >  		NOSAVE_DATA
> >  		CACHELINE_ALIGNED_DATA(L1_CACHE_BYTES)
> >  		DATA_DATA
> > @@ -133,14 +135,6 @@ SECTIONS
> >  	}
> >  	__bss_stop = .;
> >  
> > -
> > -	/* assembler code expects init_task to be 16k aligned */
> > -	. = ALIGN(16384);
> > -	/* init_task */
> > -	.data.init_task : {
> > -		*(.data.init_task)
> > -	}
> > -
This part moves away from a specific output section to including this in the
.data output section - with the _same_ alignmnet.
So the only issue here is that we move init_task before NOSAVE_DATA etc.

I do not see why you think this changes alignmnet?

	Sam
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