From: Marc Kleine-Budde <mkl@pengutronix.de>
To: Sascha Hauer <s.hauer@pengutronix.de>,
Barebox List <barebox@lists.infradead.org>
Subject: Re: [PATCH] Build with -fno-delete-null-pointer-checks
Date: Wed, 8 Jul 2015 18:14:33 +0200 [thread overview]
Message-ID: <559D4C69.8080001@pengutronix.de> (raw)
In-Reply-To: <1436353060-22497-1-git-send-email-s.hauer@pengutronix.de>
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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@pengutronix.de>
> ---
> 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,)
> AFLAGS := -D__ASSEMBLY__
>
> LDFLAGS_barebox := -Map barebox.map
>
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Industrial Linux Solutions | Phone: +49-231-2826-924 |
Vertretung West/Dortmund | Fax: +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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next prev parent reply other threads:[~2015-07-08 16:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-08 10:57 Sascha Hauer
2015-07-08 16:14 ` Marc Kleine-Budde [this message]
2015-07-13 7:13 ` Sascha Hauer
2015-07-13 7:19 ` Uwe Kleine-König
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