linux-kernel - [patch core/stackprotector] stackprotector: Fix build when compiler lacks support

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Message-ID: <alpine.DEB.2.02.1312301331520.10482@chino.kir.corp.google.com>
Date:	Mon, 30 Dec 2013 13:37:54 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Ingo Molnar <mingo@...nel.org>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	peterz@...radead.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux@....linux.org.uk, ralf@...ux-mips.org, tglx@...utronix.de,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	arjan@...ux.intel.com, james.hogan@...tec.com,
	Michal Marek <mmarek@...e.cz>, lethal@...ux-sh.org,
	shawn.guo@...aro.org, Kees Cook <keescook@...omium.org>,
	sfr@...b.auug.org.au, linux-kbuild@...r.kernel.org,
	linux-tip-commits@...r.kernel.org
Subject: [patch core/stackprotector] stackprotector: Fix build when compiler
 lacks support

8779657d29c0 ("stackprotector: Introduce CONFIG_CC_STACKPROTECTOR_STRONG") 
causes the build to break when the compiler doesn't support 
-fstack-protector-strong:

	cc1: error: unrecognized command line option ‘-fstack-protector-strong’
	cc1: error: unrecognized command line option ‘-fstack-protector-strong’

with at least gcc 4.6.3.

Instead of breaking the build, just warn of the failure and disable the 
feature.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -603,10 +603,11 @@ ifdef CONFIG_CC_STACKPROTECTOR_REGULAR
 	      -fstack-protector not supported by compiler))
   endif
 else ifdef CONFIG_CC_STACKPROTECTOR_STRONG
-  stackp-flag := -fstack-protector-strong
-  ifeq ($(call cc-option, $(stackp-flag)),)
+  ifeq ($(call cc-option, -fstack-protector-strong),)
     $(warning Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: \
 	      -fstack-protector-strong not supported by compiler)
+  else
+    stackp-flag := -fstack-protector-strong
   endif
 else
   # Force off for distro compilers that enable stack protector by default.