From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fnIzI-00019E-KK for barebox@lists.infradead.org; Wed, 08 Aug 2018 07:34:34 +0000 Date: Wed, 8 Aug 2018 09:34:20 +0200 From: Sascha Hauer Message-ID: <20180808073420.mhfjffjsasyw4mei@pengutronix.de> References: <20180807210037.29239-1-andrew.smirnov@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20180807210037.29239-1-andrew.smirnov@gmail.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH] ARM: Mark SP as being clobbered in arm_setup_stack() To: Andrey Smirnov Cc: barebox@lists.infradead.org On Tue, Aug 07, 2018 at 02:00:37PM -0700, Andrey Smirnov wrote: > Not sure why it was working before, but with recent update of AArch64 > GCC to 8.1.1 on my Fedora 28 machine, compiling barebox_arm_entry() > yields the following assembly: > > 0000000000002aac : > 2aac: a9bd7bfd stp x29, x30, [sp, #-48]! > 2ab0: d1404023 sub x3, x1, #0x10, lsl #12 > 2ab4: d1004063 sub x3, x3, #0x10 > 2ab8: 910003fd mov x29, sp > 2abc: 8b000063 add x3, x3, x0 > 2ac0: a90153f3 stp x19, x20, [sp, #16] > 2ac4: aa0003f3 mov x19, x0 > 2ac8: aa0103f4 mov x20, x1 > 2acc: f90017e2 str x2, [sp, #40] <-- storing 'boarddata' on old stack > 2ad0: 9100007f mov sp, x3 <-- setting up new stack > 2ad4: 97ffffdd bl 2a48 > 2ad8: f94017e2 ldr x2, [sp, #40] <--- sadness > 2adc: aa1403e1 mov x1, x20 > 2ae0: aa1303e0 mov x0, x19 > 2ae4: 940000a1 bl 2d68 > > Which result in AArch64 image (i.MX8MQ) not being bootable. With SP > marked as clobbered, the above assembly changes to the following: > > 0000000000002aac : > 2aac: a9bd7bfd stp x29, x30, [sp, #-48]! > 2ab0: d1404023 sub x3, x1, #0x10, lsl #12 > 2ab4: d1004063 sub x3, x3, #0x10 > 2ab8: 910003fd mov x29, sp > 2abc: a90153f3 stp x19, x20, [sp, #16] > 2ac0: 8b000063 add x3, x3, x0 > 2ac4: aa0003f3 mov x19, x0 > 2ac8: aa0103f4 mov x20, x1 > 2acc: f90017a2 str x2, [x29, #40] > 2ad0: 9100007f mov sp, x3 > 2ad4: 97ffffdd bl 2a48 > 2ad8: f94017a2 ldr x2, [x29, #40] > 2adc: aa1403e1 mov x1, x20 > 2ae0: aa1303e0 mov x0, x19 > 2ae4: 940000a1 bl 2d68 > > now x29 is used to access stored x2 which avoids the problem and > allows the system to boot correctly. > > The change is a no-op on AArch32. > > Signed-off-by: Andrey Smirnov Applied, thanks Sascha > --- > arch/arm/include/asm/common.h | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/include/asm/common.h b/arch/arm/include/asm/common.h > index 97bfdc43f..c32cdfe5e 100644 > --- a/arch/arm/include/asm/common.h > +++ b/arch/arm/include/asm/common.h > @@ -48,7 +48,10 @@ static inline unsigned long get_sp(void) > > static inline void arm_setup_stack(unsigned long top) > { > - __asm__ __volatile__("mov sp, %0" : : "r"(top)); > + __asm__ __volatile__("mov sp, %0" > + : > + : "r"(top) > + : "sp"); > } > > #endif /* __ASM_ARM_COMMON_H */ > -- > 2.17.1 > > > _______________________________________________ > barebox mailing list > barebox@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/barebox > -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox