[U-Boot] [PATCH v2 2/2] x86: Enforce toolchain to generate 64-bit codes for 64-bit U-Boot

[Bin Meng]

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 at gmail.com>

---

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
-- 
2.9.2