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authorAndy Lutomirski <luto@kernel.org>2015-07-21 19:27:18 +0300
committerIngo Molnar <mingo@kernel.org>2015-07-22 09:20:29 +0300
commitb2c51106c7581866c37ffc77c5d739f3d4b7cbc9 (patch)
tree228177956681a7e4b1afec070d12f2071dafc740
parentf2a50f8b7da45ff2de93a71393e715a2ab9f3b68 (diff)
downloadlinux-b2c51106c7581866c37ffc77c5d739f3d4b7cbc9.tar.xz
x86/build: Fix detection of GCC -mpreferred-stack-boundary support
As per: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383 GCC only allows -mpreferred-stack-boundary=3 on x86_64 if -mno-sse is set. That means that cc-option will not detect -mpreferred-stack-boundary=3 support, because we test for it before setting -mno-sse. Fix it by reordering the Makefile bits. Compile-tested only. This should help avoid code generation issues such as the one that was worked around in: b96fecbfa8c8 ("x86/fpu: Fix boot crash in the early FPU code") I'm a bit concerned that we could still have problems on older GCC versions given that our asm code does not respect GCC's idea of the ABI-required stack alignment. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jan Kara <jack@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/f5297c192969adfa0d28b84cf8a22d59573db26d.1436126872.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/x86/Makefile13
1 files changed, 10 insertions, 3 deletions
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 118e6debc483..054ff969fcdb 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -39,6 +39,16 @@ ifdef CONFIG_X86_NEED_RELOCS
LDFLAGS_vmlinux := --emit-relocs
endif
+#
+# Prevent GCC from generating any FP code by mistake.
+#
+# This must happen before we try the -mpreferred-stack-boundary, see:
+#
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
+#
+KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
+KBUILD_CFLAGS += $(call cc-option,-mno-avx,)
+
ifeq ($(CONFIG_X86_32),y)
BITS := 32
UTS_MACHINE := i386
@@ -167,9 +177,6 @@ KBUILD_CFLAGS += -pipe
KBUILD_CFLAGS += -Wno-sign-compare
#
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
-# prevent gcc from generating any FP code by mistake
-KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
-KBUILD_CFLAGS += $(call cc-option,-mno-avx,)
KBUILD_CFLAGS += $(mflags-y)
KBUILD_AFLAGS += $(mflags-y)