Makefile: move stack-protector availability out of Kconfig

Various portions of the kernel, especially per-architecture pieces,
need to know if the compiler is building with the stack protector.
This was done in the arch/Kconfig with 'select', but this doesn't
allow a way to do auto-detected compiler support. In preparation for
creating an on-if-available default, move the logic for the definition of
CONFIG_CC_STACKPROTECTOR into the Makefile.

Link: http://lkml.kernel.org/r/1510076320-69931-3-git-send-email-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 20b1aa928d78..f0f934097f64 100644
--- a/Makefile
+++ b/Makefile
@@ -693,7 +693,7 @@ else
 endif
 endif
 # Find arch-specific stack protector compiler sanity-checking script.
-ifdef CONFIG_CC_STACKPROTECTOR
+ifdef stackp-name
   stackp-path := $(srctree)/scripts/gcc-$(SRCARCH)_$(BITS)-has-stack-protector.sh
   stackp-check := $(wildcard $(stackp-path))
   # If the wildcard test matches a test script, run it to check functionality.
@@ -702,6 +702,10 @@ ifdef CONFIG_CC_STACKPROTECTOR
       stackp-broken := y
     endif
   endif
+  ifndef stackp-broken
+    # If the stack protector is functional, enable code that depends on it.
+    KBUILD_CPPFLAGS += -DCONFIG_CC_STACKPROTECTOR
+  endif
 endif
 KBUILD_CFLAGS += $(stackp-flag)