x86: stackprotector & PARAVIRT fix

on paravirt enabled 64-bit kernels the paravirt ops do function
calls themselves - which is bad with the stackprotector - for
example pda_init() loads 0 into %gs and then does MSR_GS_BASE
write (which modifies gs.base) - but that MSR write is a function
call on paravirt, which with stackprotector tries to read the
stack canary from the PDA ... crashing the bootup.

the solution was suggested by Arjan van de Ven: to exclude paravirt.c
from stackprotector, too many lowlevel functionality is in it. It's
not like we'll have paravirt functions with character arrays on
their stack anyway...

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 5e618c3..8161e5a 100644 (file)
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -14,6 +14,7 @@ nostackp := $(call cc-option, -fno-stack-protector)
 CFLAGS_vsyscall_64.o   := $(PROFILING) -g0 $(nostackp)
 CFLAGS_hpet.o          := $(nostackp)
 CFLAGS_tsc_64.o                := $(nostackp)
+CFLAGS_paravirt.o      := $(nostackp)
 
 obj-y                  := process_$(BITS).o signal_$(BITS).o entry_$(BITS).o
 obj-y                  += traps_$(BITS).o irq_$(BITS).o