64-bit U-Boot image is a combination of 32-bit U-Boot (SPL) plus 64-bit U-Boot (proper). For the U-Boot proper, it has be compiled to 64-bit object codes. Attempting to use a toolchain to compile 64-bit U-Boot for qemu-x86_64, like kernel.org 4.9 i386-linux-gcc, fails with the following errors:
arch/x86/cpu/intel_common/microcode.c:79:2: error: PIC register clobbered by 'ebx' in 'asm'
The issue is because toolchain is preconfigured to generate code for the 32-bit architecture (i386), and currently '-m64' is missing in the makefile fragment. Using kernel.org 4.9 x86_64-linux-gcc works out of the box, since it is preconfigured to generate 64-bit codes.
When compiling U-Boot SPL, '-m32' is passed to the toolchain, no mater 32-bit (i386-linux-) or 64-bit (x86_64-linux) the toolchain is preconfigured to generate.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
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Changes in v2: - reword the commit message
arch/x86/config.mk | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/config.mk b/arch/x86/config.mk index 043425e..8835dcf 100644 --- a/arch/x86/config.mk +++ b/arch/x86/config.mk @@ -26,7 +26,7 @@ endif ifeq ($(IS_32BIT),y) PLATFORM_CPPFLAGS += -march=i386 -m32 else -PLATFORM_CPPFLAGS += $(if $(CONFIG_SPL_BUILD),,-fpic) -fno-common +PLATFORM_CPPFLAGS += $(if $(CONFIG_SPL_BUILD),,-fpic) -fno-common -m64 endif
PLATFORM_RELFLAGS += -ffunction-sections -fvisibility=hidden