Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753298AbZIJX6b (ORCPT ); Thu, 10 Sep 2009 19:58:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753017AbZIJX62 (ORCPT ); Thu, 10 Sep 2009 19:58:28 -0400 Received: from mail3.caviumnetworks.com ([12.108.191.235]:16142 "EHLO mail3.caviumnetworks.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752599AbZIJX5n (ORCPT ); Thu, 10 Sep 2009 19:57:43 -0400 From: David Daney To: torvalds@linux-foundation.org, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, David Daney , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, ralf@linux-mips.org, linux-mips@linux-mips.org, Martin Schwidefsky , Heiko Carstens , linux390@de.ibm.com, linux-s390@vger.kernel.org, David Howells , Koichi Yasutake , linux-am33-list@redhat.com, Kyle McMartin , Helge Deller , linux-parisc@vger.kernel.org, Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@ozlabs.org, Richard Henderson , Ivan Kokshaysky , linux-alpha@vger.kernel.org, Haavard Skinnemoen , Mike Frysinger , uclinux-dist-devel@blackfin.uclinux.org Subject: [PATCH 01/10] Add support for GCC-4.5's __builtin_unreachable() to compiler.h Date: Thu, 10 Sep 2009 16:56:42 -0700 Message-Id: <1252627011-2933-1-git-send-email-ddaney@caviumnetworks.com> X-Mailer: git-send-email 1.6.0.6 In-Reply-To: <4AA991C1.1050800@caviumnetworks.com> References: <4AA991C1.1050800@caviumnetworks.com> X-OriginalArrivalTime: 10 Sep 2009 23:57:04.0797 (UTC) FILETIME=[65BC24D0:01CA3272] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3040 Lines: 87 Starting with version 4.5, GCC has a new built-in function __builtin_unreachable() that can be used in places like the kernel's BUG() where inline assembly is used to transfer control flow. This eliminated the need for an endless loop in these places. The patch adds a new macro 'unreachable()' that will expand to either __builtin_unreachable() or an endless loop depending on the compiler version. Signed-off-by: David Daney CC: Thomas Gleixner CC: Ingo Molnar CC: "H. Peter Anvin" CC: x86@kernel.org CC: ralf@linux-mips.org CC: linux-mips@linux-mips.org CC: Martin Schwidefsky CC: Heiko Carstens CC: linux390@de.ibm.com CC: linux-s390@vger.kernel.org CC: David Howells CC: Koichi Yasutake CC: linux-am33-list@redhat.com CC: Kyle McMartin CC: Helge Deller CC: linux-parisc@vger.kernel.org CC: Benjamin Herrenschmidt CC: Paul Mackerras CC: linuxppc-dev@ozlabs.org CC: Richard Henderson CC: Ivan Kokshaysky CC: linux-alpha@vger.kernel.org CC: Haavard Skinnemoen CC: Mike Frysinger CC: uclinux-dist-devel@blackfin.uclinux.org --- include/linux/compiler-gcc4.h | 14 ++++++++++++++ include/linux/compiler.h | 5 +++++ 2 files changed, 19 insertions(+), 0 deletions(-) diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h index 450fa59..ab3af40 100644 --- a/include/linux/compiler-gcc4.h +++ b/include/linux/compiler-gcc4.h @@ -36,4 +36,18 @@ the kernel context */ #define __cold __attribute__((__cold__)) + +#if __GNUC_MINOR__ >= 5 +/* + * Mark a position in code as unreachable. This can be used to + * suppress control flow warnings after asm blocks that transfer + * control elsewhere. + * + * Early snapshots of gcc 4.5 don't support this and we can't detect + * this in the preprocessor, but we can live with this because they're + * unreleased. Really, we need to have autoconf for the kernel. + */ +#define unreachable() __builtin_unreachable() +#endif + #endif diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 04fb513..7efd73f 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -144,6 +144,11 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); # define barrier() __memory_barrier() #endif +/* Unreachable code */ +#ifndef unreachable +# define unreachable() do { for (;;) ; } while (0) +#endif + #ifndef RELOC_HIDE # define RELOC_HIDE(ptr, off) \ ({ unsigned long __ptr; \ -- 1.6.2.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/