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authorBorislav Petkov <bp@suse.de>2014-02-05 01:55:11 +0100
committerH. Peter Anvin <hpa@zytor.com>2014-02-04 20:00:35 -0800
commitb399fe355b30d0102e7690c99e6f764ddfd32ec3 (patch)
tree78699801f7a010228cb646c25a87af3f267a54e3 /arch/x86/Makefile
parent38dbfb59d1175ef458d006556061adeaa8751b72 (diff)
x86: Disable generation of traditional x87 instructions
We recently had the case where wrongly used floating-constant 'E' caused the generation of traditional x87 instructions in kernel code and wreaking all kinds of havoc. Disable the generation of those too. This will save people a lot of time when trying to debug such issues by erroring out of the build instead of let them manifest themselves in very spectacular and happy-crappy ways at runtime. We're using -mno-fp-ret-in-387 in addition to -mno-80387 (which is == -msoft-float) because, as the gcc manpage says: On machines where a function returns floating-point results in the 80387 register stack, some floating-point opcodes may be emitted even if -msoft-float is used. so we want to turn off *all* non-integer instructions involving any architectural FPU state, unless it is absolutely necessary (and those cases need special handling anyway). Cc: Jiri Kosina <jkosina@suse.cz> Cc: Michael Matz <matz@suse.de> Cc: Michal Hocko <mhocko@suse.cz> Signed-off-by: Borislav Petkov <bp@suse.de> Link: http://lkml.kernel.org/r/1391561711-3023-1-git-send-email-bp@alien8.de Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/Makefile')
-rw-r--r--arch/x86/Makefile4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index eeda43abed6e..a414b1471ffc 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -82,8 +82,8 @@ else
KBUILD_AFLAGS += -m64
KBUILD_CFLAGS += -m64
- # Don't autogenerate MMX or SSE instructions
- KBUILD_CFLAGS += -mno-mmx -mno-sse
+ # Don't autogenerate traditional x87, MMX or SSE instructions
+ KBUILD_CFLAGS += -mno-mmx -mno-sse -mno-80387 -mno-fp-ret-in-387
# Use -mpreferred-stack-boundary=3 if supported.
KBUILD_CFLAGS += $(call cc-option,-mpreferred-stack-boundary=3)