powerpc: put the gpr sabe/restore functions in their own section

This allows the linker to know that calls to them do not need to switch
TOC and stop errors like the following when linking large configurations:

powerpc64-linux-ld: drivers/built-in.o: In function `.gpiochip_is_requested':
(.text+0x4): sibling call optimization to `_savegpr0_29' does not allow automatic multiple TOCs; recompile with -mminimal-toc or -fno-optimize-sibling-calls, or make `_savegpr0_29' extern

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
 arch/powerpc/lib/crtsavres.S |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

On Fri, 2012-07-06 at 17:09 +1000, Stephen Rothwell wrote:
> This allows the linker to know that calls to them do not need to switch
> TOC and stop errors like the following when linking large configurations:

>  arch/powerpc/lib/crtsavres.S |    5 ++++-

You didn't make any change to the linker script? How does this section
get in there? I don't see a .text* anywhere?

> diff --git a/arch/powerpc/lib/crtsavres.S b/arch/powerpc/lib/crtsavres.S
> index 1c893f0..b2c68ce 100644
> --- a/arch/powerpc/lib/crtsavres.S
> +++ b/arch/powerpc/lib/crtsavres.S
> @@ -41,12 +41,13 @@
>  #include <asm/ppc_asm.h>
>  
>  	.file	"crtsavres.S"
> -	.section ".text"
>  
>  #ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
>  
>  #ifndef CONFIG_PPC64
>  
> +	.section ".text"
> +
>  /* Routines for saving integer registers, called by the compiler.  */
>  /* Called with r11 pointing to the stack header word of the caller of the */
>  /* function, just beyond the end of the integer save area.  */
> @@ -232,6 +233,8 @@ _GLOBAL(_rest32gpr_31_x)
>  
>  #else /* CONFIG_PPC64 */
>  
> +	.section ".text.save.restore","ax",@progbits
> +
>  .globl	_savegpr0_14
>  _savegpr0_14:
>  	std	r14,-144(r1)

Any reason to not put the 32-bit versions in the same section? AFAICS
nothing in that file uses the TOC. 

cheers

Hi Michael,

On Sat, 07 Jul 2012 16:55:21 +1000 Michael Ellerman <michael@ellerman.id.au> wrote:
>
> On Fri, 2012-07-06 at 17:09 +1000, Stephen Rothwell wrote:
> > This allows the linker to know that calls to them do not need to switch
> > TOC and stop errors like the following when linking large configurations:
> 
> >  arch/powerpc/lib/crtsavres.S |    5 ++++-
> 
> You didn't make any change to the linker script? How does this section
> get in there? I don't see a .text* anywhere?

Yeah.  ld just seems to figure it out (I note that we also have sections
called .text.unlikely and .text.startup).

> > diff --git a/arch/powerpc/lib/crtsavres.S b/arch/powerpc/lib/crtsavres.S
> > index 1c893f0..b2c68ce 100644
> > --- a/arch/powerpc/lib/crtsavres.S
> > +++ b/arch/powerpc/lib/crtsavres.S
> > @@ -41,12 +41,13 @@
> >  #include <asm/ppc_asm.h>
> >  
> >  	.file	"crtsavres.S"
> > -	.section ".text"
> >  
> >  #ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
> >  
> >  #ifndef CONFIG_PPC64
> >  
> > +	.section ".text"
> > +
> >  /* Routines for saving integer registers, called by the compiler.  */
> >  /* Called with r11 pointing to the stack header word of the caller of the */
> >  /* function, just beyond the end of the integer save area.  */
> > @@ -232,6 +233,8 @@ _GLOBAL(_rest32gpr_31_x)
> >  
> >  #else /* CONFIG_PPC64 */
> >  
> > +	.section ".text.save.restore","ax",@progbits
> > +
> >  .globl	_savegpr0_14
> >  _savegpr0_14:
> >  	std	r14,-144(r1)
> 
> Any reason to not put the 32-bit versions in the same section? AFAICS
> nothing in that file uses the TOC. 

32 bit does not use a toc (apparently).  And I figured to make the
minimal change to the output.