linux-kernel - [PATCH v2 1/3] Makefile: Move stack-protector compiler breakage test earlier

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Date:   Tue,  7 Nov 2017 09:38:38 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Arnd Bergmann <arnd@...db.de>, linux-kbuild@...r.kernel.org,
        Josh Triplett <josh@...htriplett.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Laura Abbott <labbott@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/3] Makefile: Move stack-protector compiler breakage test earlier

In order to make stack-protector failures warn instead of unconditionally
breaking the build, this moves the compiler output sanity-check earlier,
and sets a flag for later testing. Future patches can choose to warn or
fail, depending on the flag value.

Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: linux-kbuild@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 Makefile | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index cf007a31d575..caa3f7e6f524 100644
--- a/Makefile
+++ b/Makefile
@@ -692,6 +692,12 @@ endif
 ifdef CONFIG_CC_STACKPROTECTOR
   stackp-path := $(srctree)/scripts/gcc-$(SRCARCH)_$(BITS)-has-stack-protector.sh
   stackp-check := $(wildcard $(stackp-path))
+  # If the wildcard test matches a test script, run it to check functionality.
+  ifdef stackp-check
+    ifneq ($(shell $(CONFIG_SHELL) $(stackp-check) $(CC) $(KBUILD_CPPFLAGS) $(biarch)),y)
+      stackp-broken := y
+    endif
+  endif
 endif
 KBUILD_CFLAGS += $(stackp-flag)
 
@@ -1087,11 +1093,9 @@ ifdef stackp-name
   endif
 endif
 # Make sure compiler does not have buggy stack-protector support.
-ifdef stackp-check
-  ifneq ($(shell $(CONFIG_SHELL) $(stackp-check) $(CC) $(KBUILD_CPPFLAGS) $(biarch)),y)
+ifdef stackp-broken
 	@echo Cannot use CONFIG_CC_STACKPROTECTOR_$(stackp-name): \
                   $(stackp-flag) available but compiler is broken >&2 && exit 1
-  endif
 endif
 	@:
 
-- 
2.7.4