From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-pf1-x444.google.com ([2607:f8b0:4864:20::444]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fn96B-0005PO-C0 for barebox@lists.infradead.org; Tue, 07 Aug 2018 21:01:00 +0000 Received: by mail-pf1-x444.google.com with SMTP id l9-v6so12407pff.9 for ; Tue, 07 Aug 2018 14:00:47 -0700 (PDT) From: Andrey Smirnov Date: Tue, 7 Aug 2018 14:00:37 -0700 Message-Id: <20180807210037.29239-1-andrew.smirnov@gmail.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 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: [PATCH] ARM: Mark SP as being clobbered in arm_setup_stack() To: barebox@lists.infradead.org Cc: Andrey Smirnov 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 --- 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