From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AA8BDC3A5A1 for ; Thu, 22 Aug 2019 17:46:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83A4323400 for ; Thu, 22 Aug 2019 17:46:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566495979; bh=G8LchBmt1VAVngPgsDs7T/u2yerKpz+40DXVd0aEkhU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0DqWpXWlQEh5/yWH+GvHjefz5MBn9WR5qj0t1CLmyIYLDToNx68170QejyQqmgUxF UVMxlrJklgJJqVcZ7PUqUFmug+Sv7dd8I5Ftna0pG1628kedenvGTlb/jKrrEbExUx RF4aL406z/+BEMhWb23N0Eozm+ONpI/qoryDCeRo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393077AbfHVRqS (ORCPT ); Thu, 22 Aug 2019 13:46:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:41960 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391674AbfHVRW5 (ORCPT ); Thu, 22 Aug 2019 13:22:57 -0400 Received: from localhost (wsip-184-188-36-2.sd.sd.cox.net [184.188.36.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E3C7523406; Thu, 22 Aug 2019 17:22:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566494576; bh=G8LchBmt1VAVngPgsDs7T/u2yerKpz+40DXVd0aEkhU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fcKURPDmWq7FK8pqSs6ZCxU20iUaTpO2E5j3OyOWXRYqV/1qY2/wS9rMwxUexmXnZ brkbMGZexCdDOZNKDdw56J86vOv2vAajl17UslEDZwdxSW4+kEmpqSqaXTjdgMC/zm +MyvPtjmEwMScbww/NSkfw8FAVyeQi1S8Vc6mzQk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Arnd Bergmann Subject: [PATCH 4.4 67/78] asm-generic: default BUG_ON(x) to if(x)BUG() Date: Thu, 22 Aug 2019 10:19:11 -0700 Message-Id: <20190822171833.970801534@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190822171832.012773482@linuxfoundation.org> References: <20190822171832.012773482@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Arnd Bergmann commit 3c047057d1206ec0f3b88c7809cacba478067a0c upstream. When CONFIG_BUG is disabled, BUG_ON() will only evaluate the condition, but will not actually stop the current thread. GCC warns about a couple of BUG_ON() users where this actually leads to further undefined behavior: include/linux/ceph/osdmap.h: In function 'ceph_can_shift_osds': include/linux/ceph/osdmap.h:54:1: warning: control reaches end of non-void function fs/ext4/inode.c: In function 'ext4_map_blocks': fs/ext4/inode.c:548:5: warning: 'retval' may be used uninitialized in this function drivers/mfd/db8500-prcmu.c: In function 'prcmu_config_clkout': drivers/mfd/db8500-prcmu.c:762:10: warning: 'div_mask' may be used uninitialized in this function drivers/mfd/db8500-prcmu.c:769:13: warning: 'mask' may be used uninitialized in this function drivers/mfd/db8500-prcmu.c:757:7: warning: 'bits' may be used uninitialized in this function drivers/tty/serial/8250/8250_core.c: In function 'univ8250_release_irq': drivers/tty/serial/8250/8250_core.c:252:18: warning: 'i' may be used uninitialized in this function drivers/tty/serial/8250/8250_core.c:235:19: note: 'i' was declared here There is an obvious conflict of interest here: on the one hand, someone who disables CONFIG_BUG() will want the kernel to be as small as possible and doesn't care about printing error messages to a console that nobody looks at. On the other hand, running into a BUG_ON() condition means that something has gone wrong, and we probably want to also stop doing things that might cause data corruption. This patch picks the second choice, and changes the NOP to BUG(), which normally stops the execution of the current thread in some form (endless loop or a trap). This follows the logic we applied in a4b5d580e078 ("bug: Make BUG() always stop the machine"). For ARM multi_v7_defconfig, the size slightly increases: section CONFIG_BUG=y CONFIG_BUG=n CONFIG_BUG=n+patch .text 8320248 | 8180944 | 8207688 .rodata 3633720 | 3567144 | 3570648 __bug_table 32508 | --- | --- __modver 692 | 1584 | 2176 .init.text 558132 | 548300 | 550088 .exit.text 12380 | 12256 | 12380 .data 1016672 | 1016064 | 1016128 Total 14622556 | 14374510 | 14407326 So instead of saving 1.70% of the total image size, we only save 1.48% by turning off CONFIG_BUG, but in return we can ensure that we don't run into cases of uninitialized variable or return code uses when something bad happens. Aside from that, we significantly reduce the number of warnings in randconfig builds, which makes it easier to fix the warnings about other problems. Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman --- include/asm-generic/bug.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/include/asm-generic/bug.h +++ b/include/asm-generic/bug.h @@ -143,7 +143,7 @@ extern void warn_slowpath_null(const cha #endif #ifndef HAVE_ARCH_BUG_ON -#define BUG_ON(condition) do { if (condition) ; } while (0) +#define BUG_ON(condition) do { if (condition) BUG(); } while (0) #endif #ifndef HAVE_ARCH_WARN_ON