stackprotector: turn not having the right gcc into a #warning

If the user selects the stack-protector config option, but does not have
a gcc that has the right bits enabled (for example because it isn't build
with a glibc that supports TLS, as is common for cross-compilers, but also
because it may be too old), then the runtime test fails right now.

This patch adds a warning message for this scenario. This warning accomplishes
two goals
1) the user is informed that the security option he selective isn't available
2) the user is suggested to turn of the CONFIG option that won't work for him,
   and would make the runtime test fail 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/Makefile b/arch/x86/Makefile
index 3cff3c894cf3c0cd80161d1f61a959cbb80f7106..c3e0eeeb1dd2a5096b114593cfe4e0540ecd050d 100644 (file)
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -73,7 +73,7 @@ else
 
         stackp := $(CONFIG_SHELL) $(srctree)/scripts/gcc-x86_64-has-stack-protector.sh
         stackp-$(CONFIG_CC_STACKPROTECTOR) := $(shell $(stackp) \
-                "$(CC)" -fstack-protector )
+                "$(CC)" "-fstack-protector -DGCC_HAS_SP" )
         stackp-$(CONFIG_CC_STACKPROTECTOR_ALL) += $(shell $(stackp) \
                 "$(CC)" -fstack-protector-all )
 

diff --git a/kernel/panic.c b/kernel/panic.c
index 866be9b72e4fcd154b94a6c59b39b94970653aa9..6729e3f4ebcb65d28b08f30c174f44f3a9734f67 100644 (file)
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -325,6 +325,9 @@ EXPORT_SYMBOL(warn_on_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
 static unsigned long __stack_check_testing;
 /*
  * Self test function for the stack-protector feature.