[U-Boot] [PATCH v4 05/13] Move memcpy(), memset() into new lib/membasic.c

[Graeme Russ]

Hi Mike,

On Wed, Mar 7, 2012 at 3:20 AM, Mike Frysinger <vapier at gentoo.org> wrote:
> On Tuesday 06 March 2012 01:34:24 Simon Glass wrote:
>> On Mon, Mar 5, 2012 at 9:05 PM, Mike Frysinger wrote:
>> > On Monday 20 February 2012 20:32:47 Simon Glass wrote:
>> >> These basic functions are needed by relocation. To avoid bringing in all
>> >> string.c functions (and the resulting code bloat for architectures where
>> >> -ffunction-sections is not used), move these into their own file.
>> >
>> > seems like fixing -f{data,function}-sections would be a more useful goal.
>> >  i don't know why arm doesn't support this today ... it's fairly easy to
>> > do.
>>
>> I did enable it for Tegra at one point with no ill effects except for
>> breaking warmboot, which relied on function ordering. I notice the
>> no-toplevel-reorder flag on x86 but not with ARM. But I assumed there
>> must be some reason it is not used and thought this patch safer, since
>> it is just a minor tweak on a series that has has some review.
>
> if we keep assuming that, then it'll never get fixed, and we'll sit on a steady
> stream of "small safe patches".  plus, fixing this yields general improvements
> in anti-bloat for everyone.
>
> function ordering sounds like something that should be imposed at the linker
> level ... for Blackfin, all i had to care about was the entry point was at the
> start of the .text, although warmbooting is fairly low level magic, and i
> handle that in the SPL-like core.

Can't the entry point be forced to be at the start of the u-boot image by
putting that function in a dedicated section and specifying that section
as the first in the linker script?

This has always bothered me:

#########################################################################
# U-Boot objects....order is important (i.e. start must be first)

OBJS  = $(CPUDIR)/start.o
ifeq ($(CPU),x86)
OBJS += $(CPUDIR)/start16.o
OBJS += $(CPUDIR)/resetvec.o
endif
ifeq ($(CPU),ppc4xx)
OBJS += $(CPUDIR)/resetvec.o
endif
ifeq ($(CPU),mpc85xx)
OBJS += $(CPUDIR)/resetvec.o
endif

I've been meaning to get rid of this for x86 as I believe this can be
adequately handled by putting the code in relevant sections and locating
the sections at the correct location using the linker script.

For x86 there are only two requirements:
 - The first byte of resetvec.o sits 16 bytes from the end of flash
 - The first byte of start.o is the first byte of the core u-boot image
   (there is other cruft above it in the flash like an embedded kernel
    image)

Regards,

Graeme