Makefile: Disable stack protector due to gcc problems

Depending on how it was built, gcc will use the canary from a global
(works for us) or from the TLS (doesn't work for us and accesses
random stuff instead).

Fixing that would be tricky. There are talks of adding a gcc option
to force use of globals, but in the meantime, disable the stack
protector

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[stewart@linux.vnet.ibm.com: add -fno-stack-protector]
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

(cherry picked from commit fe6f1f9)
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

Makefile.main

@@ -78,12 +78,18 @@ ifeq ($(SKIBOOT_GCOV),1)
 CFLAGS += -fprofile-arcs -ftest-coverage -DSKIBOOT_GCOV=1
 endif
 
+# Stack protector disabled for now. gcc tends to use the TLS to
+# access the canary (depending on how gcc was built), and this won't
+# work for us.
+#
 ifeq ($(STACK_CHECK),1)
-CFLAGS += -fstack-protector-all -pg
+#CFLAGS += -fstack-protector-all -pg
+CFLAGS += -fno-stack-protector -pg
 CPPFLAGS += -DSTACK_CHECK_ENABLED
 else
-CFLAGS += -fstack-protector
-CFLAGS += $(call try-cflag,$(CC),-fstack-protector-strong)
+CFLAGS += -fno-stack-protector
+#CFLAGS += -fstack-protector
+#CFLAGS += $(call try-cflag,$(CC),-fstack-protector-strong)
 endif
 
 CFLAGS += $(call try-cflag,$(CC),-Wjump-misses-init) \