From f9fc8254b23c765750f07ccb26327dec0d3307e8 Mon Sep 17 00:00:00 2001 From: Andrey Smirnov Date: Tue, 7 Aug 2018 14:00:37 -0700 Subject: ARM: Mark SP as being clobbered in arm_setup_stack() 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 Signed-off-by: Sascha Hauer --- 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 97bfdc43f5..c32cdfe5ec 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 */ -- cgit v1.2.3