[PATCH 5/5] asm-generic: fix build error in fix_to_virt with CONFIG_DEBUG_EXPERIENCE

From: changbin.du@intel.com
To: yamada.masahiro@socionext.com, michal.lkml@markovi.net,
	tglx@linutronix.de, mingo@redhat.com, akpm@linux-foundation.org
Cc: x86@kernel.org, lgirdwood@gmail.com, broonie@kernel.org,
	arnd@arndb.de, linux-kbuild@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	Changbin Du <changbin.du@intel.com>
Subject: [PATCH 5/5] asm-generic: fix build error in fix_to_virt with CONFIG_DEBUG_EXPERIENCE
Date: Tue,  1 May 2018 21:00:14 +0800	[thread overview]
Message-ID: <1525179614-14571-6-git-send-email-changbin.du@intel.com> (raw)
In-Reply-To: <1525179614-14571-1-git-send-email-changbin.du@intel.com>

From: Changbin Du <changbin.du@intel.com>

With '-Og' optimization level, GCC would not optimize a count for a loop
as a constant value. But BUILD_BUG_ON() only accept compile-time constant
values.

arch/arm/mm/mmu.o: In function `fix_to_virt':
/home/changbin/work/linux/./include/asm-generic/fixmap.h:31: undefined reference to `__compiletime_assert_31'
Makefile:1051: recipe for target 'vmlinux' failed
make: *** [vmlinux] Error 1

Signed-off-by: Changbin Du <changbin.du@intel.com>
---
 include/asm-generic/fixmap.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h
index 827e4d3..a6576d4 100644
--- a/include/asm-generic/fixmap.h
+++ b/include/asm-generic/fixmap.h
@@ -28,7 +28,8 @@
  */
 static __always_inline unsigned long fix_to_virt(const unsigned int idx)
 {
-	BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
+	BUILD_BUG_ON(__builtin_constant_p(idx) &&
+		     idx >= __end_of_fixed_addresses);
 	return __fix_to_virt(idx);
 }
 
-- 
2.7.4
