diff options
author | David Woodhouse <dwmw2@infradead.org> | 2014-01-29 07:16:47 -0500 |
---|---|---|
committer | H. Peter Anvin <hpa@linux.intel.com> | 2014-01-30 11:05:36 -0500 |
commit | de3accdaec88851874c573031de007283e90b199 (patch) | |
tree | 95dacded75ffe16891ddb7a26aacd7b2ea280621 /arch/x86/Makefile | |
parent | 5fbbc25a99d680feca99a3095f0440f65d4307cc (diff) |
x86, build: Build 16-bit code with -m16 where possible
Both clang 3.5 and GCC 4.9 will support this (as of r199754 and r207196
respectively). Both have been tested to produce booting kernels when the
16-bit code is built with -m16. (Modulo LLVM PR3997, at least.)
[ hpa: folded test for -m16 into M16_CFLAGS ]
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Link: http://lkml.kernel.org/r/1390997807.20153.133.camel@i7.infradead.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/Makefile')
-rw-r--r-- | arch/x86/Makefile | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 9ecbc1c46c74..eeda43abed6e 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile | |||
@@ -13,14 +13,22 @@ endif | |||
13 | 13 | ||
14 | # How to compile the 16-bit code. Note we always compile for -march=i386; | 14 | # How to compile the 16-bit code. Note we always compile for -march=i386; |
15 | # that way we can complain to the user if the CPU is insufficient. | 15 | # that way we can complain to the user if the CPU is insufficient. |
16 | REALMODE_CFLAGS := -m32 -g -Os -D__KERNEL__ -DDISABLE_BRANCH_PROFILING \ | 16 | # |
17 | # The -m16 option is supported by GCC >= 4.9 and clang >= 3.5. For | ||
18 | # older versions of GCC, we need to play evil and unreliable tricks to | ||
19 | # attempt to ensure that our asm(".code16gcc") is first in the asm | ||
20 | # output. | ||
21 | CODE16GCC_CFLAGS := -m32 -include $(srctree)/arch/x86/boot/code16gcc.h \ | ||
22 | $(call cc-option, -fno-toplevel-reorder,\ | ||
23 | $(call cc-option, -fno-unit-at-a-time)) | ||
24 | M16_CFLAGS := $(call cc-option, -m16, $(CODE16GCC_CFLAGS)) | ||
25 | |||
26 | REALMODE_CFLAGS := $(M16_CFLAGS) -g -Os -D__KERNEL__ \ | ||
27 | -DDISABLE_BRANCH_PROFILING \ | ||
17 | -Wall -Wstrict-prototypes -march=i386 -mregparm=3 \ | 28 | -Wall -Wstrict-prototypes -march=i386 -mregparm=3 \ |
18 | -include $(srctree)/arch/x86/boot/code16gcc.h \ | ||
19 | -fno-strict-aliasing -fomit-frame-pointer -fno-pic \ | 29 | -fno-strict-aliasing -fomit-frame-pointer -fno-pic \ |
20 | -mno-mmx -mno-sse \ | 30 | -mno-mmx -mno-sse \ |
21 | $(call cc-option, -ffreestanding) \ | 31 | $(call cc-option, -ffreestanding) \ |
22 | $(call cc-option, -fno-toplevel-reorder,\ | ||
23 | $(call cc-option, -fno-unit-at-a-time)) \ | ||
24 | $(call cc-option, -fno-stack-protector) \ | 32 | $(call cc-option, -fno-stack-protector) \ |
25 | $(call cc-option, -mpreferred-stack-boundary=2) | 33 | $(call cc-option, -mpreferred-stack-boundary=2) |
26 | export REALMODE_CFLAGS | 34 | export REALMODE_CFLAGS |