From patchwork Tue Apr 7 03:10:38 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 11477419 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9BF5792A for ; Tue, 7 Apr 2020 03:10:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5F31E214AF for ; Tue, 7 Apr 2020 03:10:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q4LJx0dB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F31E214AF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 179268E0082; Mon, 6 Apr 2020 23:10:41 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 1514D8E0062; Mon, 6 Apr 2020 23:10:41 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 08C8D8E0082; Mon, 6 Apr 2020 23:10:41 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id E1BA88E0062 for ; Mon, 6 Apr 2020 23:10:40 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id AAF85A8CF for ; Tue, 7 Apr 2020 03:10:40 +0000 (UTC) X-FDA: 76679581440.18.shoe74_5df070733161 X-Spam-Summary: 2,0,0,bbdc241875e76cfe,d41d8cd98f00b204,akpm@linux-foundation.org,,RULES_HIT:41:355:379:800:960:967:973:988:989:1260:1263:1345:1359:1381:1431:1437:1535:1543:1711:1730:1747:1777:1792:2393:2525:2559:2564:2682:2685:2693:2859:2902:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3167:3355:3865:3866:3867:3868:3870:3871:3872:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4250:4321:5007:6117:6119:6261:6653:6737:7514:7576:7903:7904:8599:9025:9036:9545:10004:10913:11026:11473:11658:11914:12043:12048:12291:12297:12438:12517:12519:12555:12679:12698:12737:12783:12986:13161:13229:13846:14181:14721:14819:14849:21063:21080:21451:21627:21740:21939:21990:30054:30070:30091,0,RBL:198.145.29.99:@linux-foundation.org:.lbl8.mailshell.net-62.2.0.100 64.100.201.201,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:2,LUA_SUMMARY:none X-HE-Tag: shoe74_5df070733161 X-Filterd-Recvd-Size: 5119 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Tue, 7 Apr 2020 03:10:40 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 E389120716; Tue, 7 Apr 2020 03:10:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586229039; bh=HIaba1rSBj0VPkRgG8RzQApmSUX3kIoFFe7U8GvgMa8=; h=Date:From:To:Subject:In-Reply-To:From; b=Q4LJx0dBHXGuJHAb6rxvCyj8LQqc88XSD22JMiBacG19bZ5BA0ncFCfLbIyT3/17K jDpMvt1jzc9uo9NSiKrIlR0kkBpTS0NVvCIsyQfS3W2nYKIae0sM8k88rBUXSPsKBS CFjjUFy5800mvaktVuGEiWSDSPLecoTBl/oVJo7g= Date: Mon, 06 Apr 2020 20:10:38 -0700 From: Andrew Morton To: akpm@linux-foundation.org, bp@alien8.de, geert@linux-m68k.org, haren@us.ibm.com, joe@perches.com, johannes@sipsolutions.net, keescook@chromium.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mingo@redhat.com, mm-commits@vger.kernel.org, rikard.falkeborn@gmail.com, tglx@linutronix.de, torvalds@linux-foundation.org, yamada.masahiro@socionext.com Subject: [patch 124/166] linux/bits.h: add compile time sanity check of GENMASK inputs Message-ID: <20200407031038.8mS1ou6Ll%akpm@linux-foundation.org> In-Reply-To: <20200406200254.a69ebd9e08c4074e41ddebaf@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Rikard Falkeborn Subject: linux/bits.h: add compile time sanity check of GENMASK inputs GENMASK() and GENMASK_ULL() are supposed to be called with the high bit as the first argument and the low bit as the second argument. Mixing them will return a mask with zero bits set. Recent commits show getting this wrong is not uncommon, see e.g. commit aa4c0c9091b0 ("net: stmmac: Fix misuses of GENMASK macro") and commit 9bdd7bb3a844 ("clocksource/drivers/npcm: Fix misuse of GENMASK macro"). To prevent such mistakes from appearing again, add compile time sanity checking to the arguments of GENMASK() and GENMASK_ULL(). If both arguments are known at compile time, and the low bit is higher than the high bit, break the build to detect the mistake immediately. Since GENMASK() is used in declarations, BUILD_BUG_ON_ZERO() must be used instead of BUILD_BUG_ON(). __builtin_constant_p does not evaluate is argument, it only checks if it is a constant or not at compile time, and __builtin_choose_expr does not evaluate the expression that is not chosen. Therefore, GENMASK(x++, 0) does only evaluate x++ once. Commit 95b980d62d52 ("linux/bits.h: make BIT(), GENMASK(), and friends available in assembly") made the macros in linux/bits.h available in assembly. Since BUILD_BUG_OR_ZERO() is not asm compatible, disable the checks if the file is included in an asm file. Due to bugs in GCC versions before 4.9 [0], disable the check if building with a too old GCC compiler. [0]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19449 Link: http://lkml.kernel.org/r/20200308193954.2372399-1-rikard.falkeborn@gmail.com Signed-off-by: Rikard Falkeborn Reviewed-by: Masahiro Yamada Reviewed-by: Kees Cook Cc: Borislav Petkov Cc: Geert Uytterhoeven Cc: Haren Myneni Cc: Joe Perches Cc: Johannes Berg Cc: lkml Cc: Ingo Molnar Cc: Thomas Gleixner Signed-off-by: Andrew Morton --- include/linux/bits.h | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) --- a/include/linux/bits.h~linux-bitsh-add-compile-time-sanity-check-of-genmask-inputs +++ a/include/linux/bits.h @@ -18,12 +18,30 @@ * position @h. For example * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000. */ -#define GENMASK(h, l) \ +#if !defined(__ASSEMBLY__) && \ + (!defined(CONFIG_CC_IS_GCC) || CONFIG_GCC_VERSION >= 49000) +#include +#define GENMASK_INPUT_CHECK(h, l) \ + (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ + __builtin_constant_p((l) > (h)), (l) > (h), 0))) +#else +/* + * BUILD_BUG_ON_ZERO is not available in h files included from asm files, + * disable the input check if that is the case. + */ +#define GENMASK_INPUT_CHECK(h, l) 0 +#endif + +#define __GENMASK(h, l) \ (((~UL(0)) - (UL(1) << (l)) + 1) & \ (~UL(0) >> (BITS_PER_LONG - 1 - (h)))) +#define GENMASK(h, l) \ + (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) -#define GENMASK_ULL(h, l) \ +#define __GENMASK_ULL(h, l) \ (((~ULL(0)) - (ULL(1) << (l)) + 1) & \ (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h)))) +#define GENMASK_ULL(h, l) \ + (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l)) #endif /* __LINUX_BITS_H */