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authorDavid Woodhouse <dwmw2@infradead.org>2014-01-29 07:16:47 -0500
committerH. Peter Anvin <hpa@linux.intel.com>2014-01-30 11:05:36 -0500
commitde3accdaec88851874c573031de007283e90b199 (patch)
tree95dacded75ffe16891ddb7a26aacd7b2ea280621 /arch/x86/Makefile
parent5fbbc25a99d680feca99a3095f0440f65d4307cc (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/Makefile16
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.
16REALMODE_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.
21CODE16GCC_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))
24M16_CFLAGS := $(call cc-option, -m16, $(CODE16GCC_CFLAGS))
25
26REALMODE_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)
26export REALMODE_CFLAGS 34export REALMODE_CFLAGS