Re: Question: attribute 'naked'

Re: Question: attribute 'naked'

[Sam Ravnborg]

cc: linux-sparse
On Tue, Aug 04, 2009 at 11:15:11PM +0100, Russell King - ARM Linux wrote:
> On Tue, Aug 04, 2009 at 06:03:22PM -0400, H Hartley Sweeten wrote:
> > When compiling the kernel with sparse, in arch/arm/mm/copypage-v4wb.c
> > I get the following error:
> > 
> > arch/arm/mm/copypage-v4wb.c:25:13: error: attribute 'naked': unknown attribute 
> 
> Sparse doesn't understand the naked attribute.  GCC does.
> 
> > /*
> >  * it doesn't make sense on ARM (currently the only user of __naked) to trace
> >  * naked functions because then mcount is called without stack and frame pointer
> >  * being set up and there is no chance to restore the lr register to the value
> >  * before mcount was called.
> >  */
> > #define __naked				__attribute__((naked)) notrace
> > 
> > Is this macro actually correct?  The compiler I am using is:
> 
> Yes - naked instructions can't be traced, because they tend to have
> entry/exit sequences which mcount won't understand.
> 
> -------------------------------------------------------------------
> List admin: http://lists.arm.linux.org.uk/mailman/listinfo/linux-arm-kernel
> FAQ:        http://www.arm.linux.org.uk/mailinglists/faq.php
> Etiquette:  http://www.arm.linux.org.uk/mailinglists/etiquette.php
> 

Re: Question: attribute 'naked'

[Uwe Kleine-König]

Hello,

On Wed, Aug 05, 2009 at 08:19:36AM +0200, Sam Ravnborg wrote:
> cc: linux-sparse
> On Tue, Aug 04, 2009 at 11:15:11PM +0100, Russell King - ARM Linux wrote:
> > On Tue, Aug 04, 2009 at 06:03:22PM -0400, H Hartley Sweeten wrote:
> > > When compiling the kernel with sparse, in arch/arm/mm/copypage-v4wb.c
> > > I get the following error:
> > > 
> > > arch/arm/mm/copypage-v4wb.c:25:13: error: attribute 'naked': unknown attribute 
> > 
> > Sparse doesn't understand the naked attribute.  GCC does.
> > 
> > > /*
> > >  * it doesn't make sense on ARM (currently the only user of __naked) to trace
> > >  * naked functions because then mcount is called without stack and frame pointer
> > >  * being set up and there is no chance to restore the lr register to the value
> > >  * before mcount was called.
> > >  */
> > > #define __naked				__attribute__((naked)) notrace
> > > 
> > > Is this macro actually correct?  The compiler I am using is:
Quoting gcc documentation:

     Use [naked] on the ARM, AVR, IP2K and SPU ports to indicate
     that the specified function does not need prologue/epilogue
     sequences generated by the compiler.  It is up to the programmer
     to provide these sequences.

This is typically used for functions that only consist of a single asm
statement.

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |
--
To unsubscribe from this list: send the line "unsubscribe linux-sparse" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html