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authorH. Peter Anvin <hpa@linux.intel.com>2014-06-04 13:16:48 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2014-06-04 13:16:48 -0700
commita9cfccee6604854aebc70215610b9788667f4fec (patch)
treefd5386d1e9c8d43eb1a52da94b57382b7a509ee0 /arch/x86/Makefile
parenta9358bc3531901a15e2f7cd48550c9555fc0288f (diff)
downloadlinux-a9cfccee6604854aebc70215610b9788667f4fec.tar.bz2
x86, build: Change code16gcc.h from a C header to an assembly header
By changing code16gcc.h from a C header to an assembly header and use the -Wa,... option to gcc to force it to be added to the assembly input, we can avoid the problems with gcc reordering code bits on us. If we have -m16, we still use it, of course. Suggested-by: Kevin O'Connor <kevin@koconnor.net> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Link: http://lkml.kernel.org/n/tip-xw8ibgdemucl9fz3i1bymu6w@git.kernel.org
Diffstat (limited to 'arch/x86/Makefile')
-rw-r--r--arch/x86/Makefile9
1 files changed, 3 insertions, 6 deletions
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 602f57e590b5..a98cc9064d8b 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -15,12 +15,9 @@ endif
# that way we can complain to the user if the CPU is insufficient.
#
# The -m16 option is supported by GCC >= 4.9 and clang >= 3.5. For
-# older versions of GCC, we need to play evil and unreliable tricks to
-# attempt to ensure that our asm(".code16gcc") is first in the asm
-# output.
-CODE16GCC_CFLAGS := -m32 -include $(srctree)/arch/x86/boot/code16gcc.h \
- $(call cc-option, -fno-toplevel-reorder,\
- $(call cc-option, -fno-unit-at-a-time))
+# older versions of GCC, include an *assembly* header to make sure that
+# gcc doesn't play any games behind our back.
+CODE16GCC_CFLAGS := -m32 -Wa,$(srctree)/arch/x86/boot/code16gcc.h
M16_CFLAGS := $(call cc-option, -m16, $(CODE16GCC_CFLAGS))
REALMODE_CFLAGS := $(M16_CFLAGS) -g -Os -D__KERNEL__ \