On Wed, Jul 08, 2015 at 06:14:33PM +0200, Marc Kleine-Budde wrote:
> On 07/08/2015 12:57 PM, Sascha Hauer wrote:
> > This becomes important with gcc-4.9. Without this gcc assumes
> > that accessing NULL pointers traps and everything that happens
> > behind the access is not executed. This recently happened with
> > i.MX53 which has:
> >
> > static int imx53_silicon_revision(void)
> > {
> > void __iomem *rom = MX53_IROM_BASE_ADDR;
> >
> > rev = readl(rom + SI_REV);
> > ...
> > }
> >
> > This resulted in object code in which the last instruction is
> > the readl, the reset of the function is missing because gcc assumes this
> > is never executed.
> >
> > Disable this optimization with -fno-delete-null-pointer-checks since
> > in barebox NULL pointers can indeed be valid.
> >
> > Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> > ---
> > Makefile | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/Makefile b/Makefile
> > index e7db67a..0fe9274 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -301,7 +301,8 @@ CPPFLAGS := -D__KERNEL__ -D__BAREBOX__ $(LINUXINCLUDE) -fno-builtin -ffre
> >
> > CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
> > -Werror-implicit-function-declaration \
> > - -fno-strict-aliasing -fno-common -Os -pipe
> > + -fno-strict-aliasing -fno-common -Os -pipe \
> > + -fno-delete-null-pointer-checks
> The kernel uses:
> $(call cc-option,-fno-delete-null-pointer-checks,)
Changed it to do the same.
Sascha
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