With the '-march=core2' fix, it seems that we have some luck that the 64-bit U-Boot boots again. However if we examine the disassembly codes there are still SSE instructions elsewhere which means passing cpu type to GCC is not enough to prevent it from generating these instructions. A simple test case is doing a 'bootefi selftest' from the U-Boot shell and it leads to a reset too.
The 'bootefi selftest' reset is even seen with the image created by the relative older GCC 5.4.0, the one shipped by Ubuntu 16.04.
The reset actually originates from undefined instruction exception caused by these SSE instructions. To keep U-Boot as a bootloader as simple as possible, we don't want to handle such advanced SIMD stuff. To make sure no MMX/SSE instruction sets are generated, tell GCC not to do this. Note AVX is out of the question as CORE2 is old enough to support AVX yet.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
--- Changes in this version: - revise the commit message for the reason of turning off MMX/SSE
arch/x86/config.mk | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/x86/config.mk b/arch/x86/config.mk index 576501e..8151e47 100644 --- a/arch/x86/config.mk +++ b/arch/x86/config.mk @@ -24,6 +24,7 @@ ifeq ($(IS_32BIT),y) PLATFORM_CPPFLAGS += -march=i386 -m32 else PLATFORM_CPPFLAGS += $(if $(CONFIG_SPL_BUILD),,-fpic) -fno-common -march=core2 -m64 +PLATFORM_CPPFLAGS += -mno-mmx -mno-sse endif
PLATFORM_RELFLAGS += -fdata-sections -ffunction-sections -fvisibility=hidden