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Commit 5d707e9c authored by Tejun Heo's avatar Tejun Heo Committed by Ingo Molnar
Browse files

stackprotector: update make rules 



Impact: no default -fno-stack-protector if stackp is enabled, cleanup

Stackprotector make rules had the following problems.

* cc support test and warning are scattered across makefile and
  kernel/panic.c.

* -fno-stack-protector was always added regardless of configuration.

Update such that cc support test and warning are contained in makefile
and -fno-stack-protector is added iff stackp is turned off.  While at
it, prepare for 32bit support.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 76397f72

Makefile

+2 −1
Original line number Diff line number Diff line
@@ -532,8 +532,9 @@ KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN}) 
endif



# Force gcc to behave correct even for buggy distributions

# Arch Makefiles may override this setting

ifndef CONFIG_CC_STACKPROTECTOR

KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)

endif



ifdef CONFIG_FRAME_POINTER

KBUILD_CFLAGS	+= -fno-omit-frame-pointer -fno-optimize-sibling-calls

arch/x86/Makefile

+10 −7
Original line number Diff line number Diff line
@@ -70,14 +70,17 @@ else 
        # this works around some issues with generating unwind tables in older gccs

        # newer gccs do it by default

        KBUILD_CFLAGS += -maccumulate-outgoing-args

endif



        stackp := $(CONFIG_SHELL) $(srctree)/scripts/gcc-x86_64-has-stack-protector.sh

        stackp-$(CONFIG_CC_STACKPROTECTOR) := $(shell $(stackp) \

                "$(CC)" "-fstack-protector -DGCC_HAS_SP" )

        stackp-$(CONFIG_CC_STACKPROTECTOR_ALL) += $(shell $(stackp) \

                "$(CC)" -fstack-protector-all )



ifdef CONFIG_CC_STACKPROTECTOR

	cc_has_sp := $(srctree)/scripts/gcc-x86_$(BITS)-has-stack-protector.sh

        ifeq ($(shell $(CONFIG_SHELL) $(cc_has_sp) $(CC)),y)

                stackp-y := -fstack-protector

                stackp-$(CONFIG_CC_STACKPROTECTOR_ALL) += -fstack-protector-all

                KBUILD_CFLAGS += $(stackp-y)

        else

                $(warning stack protector enabled but no compiler support)

        endif

endif



# Stackpointer is addressed different for 32 bit and 64 bit x86

kernel/panic.c

+0 −4
Original line number Diff line number Diff line
@@ -359,10 +359,6 @@ EXPORT_SYMBOL(warn_slowpath); 


#ifdef CONFIG_CC_STACKPROTECTOR



#ifndef GCC_HAS_SP

#warning You have selected the CONFIG_CC_STACKPROTECTOR option, but the gcc used does not support this.

#endif



/*

 * Called when gcc's -fstack-protector feature is used, and

 * gcc detects corruption of the on-stack canary value

scripts/gcc-x86_64-has-stack-protector.sh

+3 −1
Original line number Diff line number Diff line
@@ -2,5 +2,7 @@ 


echo "int foo(void) { char X[200]; return 3; }" | $1 -S -xc -c -O0 -mcmodel=kernel -fstack-protector - -o - 2> /dev/null | grep -q "%gs"

if [ "$?" -eq "0" ] ; then

	echo $2

	echo y

else

	echo n

fi