[PATCH] Add the -fstack-protector option to the CFLAGS

Add a feature check that checks that the gcc compiler has stack-protector
support and has the bugfix for PR28281 to make this work in kernel mode.
The easiest solution I could find was to have a shell script in scripts/
to do the detection; if needed we can make this fancier in the future
without making the makefile too complex.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
CC: Andi Kleen <ak@suse.de>
CC: Sam Ravnborg <sam@ravnborg.org>

2 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86_64/Makefile b/arch/x86_64/Makefile
index d6472ddf5f6e..2b8d07c70106 100644
--- a/arch/x86_64/Makefile
+++ b/arch/x86_64/Makefile
@@ -58,6 +58,9 @@ cflags-y += $(call cc-option,-mno-sse -mno-mmx -mno-sse2 -mno-3dnow,)
 cflags-y += $(call as-instr,.cfi_startproc\n.cfi_endproc,-DCONFIG_AS_CFI=1,)
 AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_endproc,-DCONFIG_AS_CFI=1,)
 
+cflags-$(CONFIG_CC_STACKPROTECTOR) += $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) -fstack-protector )
+cflags-$(CONFIG_CC_STACKPROTECTOR_ALL) += $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) -fstack-protector-all )
+
 CFLAGS += $(cflags-y)
 CFLAGS_KERNEL += $(cflags-kernel-y)
 AFLAGS += -m64
diff --git a/scripts/gcc-x86_64-has-stack-protector.sh b/scripts/gcc-x86_64-has-stack-protector.sh
new file mode 100644
index 000000000000..325c0a1b03b6
--- /dev/null
+++ b/scripts/gcc-x86_64-has-stack-protector.sh
@@ -0,0 +1,6 @@
+#!/bin/sh
+
+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
+fi