[U-Boot] [PATCH V4] ARM: prevent misaligned array inits

[Tom Rini]

On Tue, Oct 09, 2012 at 08:42:26PM +0200, Albert ARIBAUD wrote:
> Hi Tom,
> 
> On Tue, 9 Oct 2012 11:34:11 -0700, Tom Rini <trini at ti.com> wrote:
> 
> > On Mon, Oct 08, 2012 at 09:50:18PM +0200, Albert ARIBAUD wrote:
> > 
> > > Under option -munaligned-access, gcc can perform local char
> > > or 16-bit array initializations using misaligned native
> > > accesses which will throw a data abort exception. Fix files
> > > where these array initializations were unneeded, and for
> > > files known to contain such initializations, enforce gcc
> > > option -mno-unaligned-access.
> > > 
> > > Signed-off-by: Albert ARIBAUD <albert.u.boot at aribaud.net>
> > 
> > We unfortunately have a problem here.  This ends up passing
> > -mno-unaligned-access globally, for all platforms.  We need something
> > like the following:
> 
> General remark: I'd strongly suggest not to copy-paste in a list reply
> somtheing that looks suspiciously like a (new) patch. It leads to this
> kind of things: http://patchwork.ozlabs.org/patch/190403/ which may not
> be what you wanted.
> 
> > Ensure that we only pass -mno-unaligned-access to ARMv7 platforms (where
> > we must ensure this flag is passed so no using call-cc-option).
> > 
> > Signed-off-by; Tom Rini <trini at ti.com>
> > 
> > diff --git a/arch/arm/cpu/armv7/config.mk b/arch/arm/cpu/armv7/config.mk
> > index 5407cb6..3c5ca23 100644
> > --- a/arch/arm/cpu/armv7/config.mk
> > +++ b/arch/arm/cpu/armv7/config.mk
> > @@ -34,6 +34,10 @@ PLATFORM_CPPFLAGS += $(PF_CPPFLAGS_ARMV7)
> >  # =========================================================================
> >  PF_RELFLAGS_SLB_AT := $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,))
> >  PLATFORM_RELFLAGS += $(PF_RELFLAGS_SLB_AT)
> > +
> > +# SEE README.arm-unaligned-accesses
> > +PLATFORM_NO_UNALIGNED := -mno-unaligned-access
> 
> I suspect that you meant
> 
> PLATFORM_NO_UNALIGNED := $(call cc-option,-mno-unaligned-access,)

This could lead to silently not applying the flag when we want to apply
the flag.  Just like before, I think we need to force the option, until
such time as we can do $(call
cc-option,-mdont-unalign-strings-for-fun,-mno-unaligned-access).

-- 
Tom
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