defining ZRELADDR as PHYS_OFFSET + TEXT_OFFSET

[Uwe Kleine-König]

Hallo George,

On Sun, Jan 31, 2010 at 08:24:25PM -0500, George G. Davis wrote:
> On Thu, Jan 28, 2010 at 12:15:23AM +0000, Russell King - ARM Linux wrote:
> > On Wed, Jan 27, 2010 at 11:12:28AM +0100, Uwe Kleine-König wrote:
> > > Hello,
> > > 
> > > currently all platforms need to define zreladdr-y in
> > > arch/arm/mach-$mach/Makefile.boot and PHYS_OFFSET (in
> > > arch/arm/mach-$mach/include/mach/memory.h).
> > > 
> > > Constraints for these are:
> > > 
> > >  TEXTADDR = PAGE_OFFSET + TEXT_OFFSET
> > >  __virt_to_phys(virt) = virt - PAGE_OFFSET + PHYS_OFFSET (at least for
> > > 	"small" virtual addresses)
> > >  ZRELADDR = __virt_to_phys(TEXTADDR)
> > > 
> > > (The equallity for __virt_to_phys only holds "normaly" according to
> > > http://lists.arm.linux.org.uk/lurker/message/20010723.185051.94ce743c.en.html.
> > > In practice it holds for addresses of the first bank of RAM which is
> > > enough for the purposes of this mail.)
> > > 
> > > So we can deduce ZRELADDR = PHYS_OFFSET + TEXT_OFFSET.
> > > 
> > > Is there something I missed or is it possible to get rid of zreladdr-y
> > > in .../Makefile.boot and define it according to the equation above?
> > 
> > You'd need to find some way to get PHYS_OFFSET out of the C code
> > into the makefile.  With all sorts of stuff going on in various
> > platforms memory.h files, that doesn't look simple.
> 
> How about this?:
> 
> diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
> index 4a590f4..b79050e 100644
> --- a/arch/arm/boot/Makefile
> +++ b/arch/arm/boot/Makefile
> @@ -21,7 +21,7 @@ endif
>  #   ZRELADDR == virt_to_phys(PAGE_OFFSET + TEXT_OFFSET)
>  #   PARAMS_PHYS must be within 4MB of ZRELADDR
>  #   INITRD_PHYS must be in RAM
> -ZRELADDR    := $(zreladdr-y)
> +ZRELADDR    := $(shell printf "0x%08x" $$[`echo PHYS_OFFSET + $(TEXT_OFFSET)  | $(CPP) $(CPP_FLAGS) -D__ASSEMBLY__ -xc -include arch/arm/include/asm/memory.h - | tail -n 1`])
>  PARAMS_PHYS := $(params_phys-y)
>  INITRD_PHYS := $(initrd_phys-y)
hui!  Is this really robust?

> Since params_phys-y is (always?) constant relative to zreladdr-y, it can
> also be calculated in a similar fashion, e.g.
> 
> PARAMS_PHYS := $(shell printf "0x%08x" $$[$(ZRELADDR) - 0x7f00])
This isn't necessarily true I think.  And I'd prefer getting rid of
PARAMS_PHYS.  This is only used for bootp and maybe if the bootloader
doesn't pass r2 properly.

Best regards
Uwe

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