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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC133C433FE for ; Thu, 20 Oct 2022 00:04:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229819AbiJTAEB (ORCPT ); Wed, 19 Oct 2022 20:04:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59212 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230054AbiJTAEB (ORCPT ); Wed, 19 Oct 2022 20:04:01 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF6CA1960A0 for ; Wed, 19 Oct 2022 17:03:57 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B95E1614EF for ; Thu, 20 Oct 2022 00:03:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 177CDC433C1; Thu, 20 Oct 2022 00:03:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1666224236; bh=BwzUOsMA5yzmnhDzcXKOanlkPFXzDZZhVeKtNcMUSI8=; h=Date:To:From:Subject:From; b=cQgACLoG6Od3a8r0NS6qa2kdwAwP6pAIsEymoTaopCSUmtWl83697Z9AlQal4yW0A DLVycjKBS4tgaICQUkU9LRXMPoHdPBPr1QaKOlFoFSn0WhhVKk8bl81kbbkYw1mOW0 DSk5XpUw3+Op7YuWM6QLu68dfTRD5L4hSTrWZLcw= Date: Wed, 19 Oct 2022 17:03:55 -0700 To: mm-commits@vger.kernel.org, torvalds@linux-foundation.org, masahiroy@kernel.org, keescook@chromium.org, gregkh@linuxfoundation.org, andriy.shevchenko@linux.intel.com, Jason@zx2c4.com, akpm@linux-foundation.org From: Andrew Morton Subject: + kbuild-treat-char-as-always-unsigned.patch added to mm-nonmm-unstable branch Message-Id: <20221020000356.177CDC433C1@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: kbuild: treat char as always unsigned has been added to the -mm mm-nonmm-unstable branch. Its filename is kbuild-treat-char-as-always-unsigned.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kbuild-treat-char-as-always-unsigned.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: "Jason A. Donenfeld" Subject: kbuild: treat char as always unsigned Date: Wed, 19 Oct 2022 14:30:34 -0600 Recently, some compile-time checking I added to the clamp_t family of functions triggered a build error when a poorly written driver was compiled on ARM, because the driver assumed that the naked `char` type is signed, but ARM treats it as unsigned, and the C standard says it's architecture-dependent. I doubt this particular driver is the only instance in which unsuspecting authors make assumptions about `char` with no `signed` or `unsigned` specifier. We were lucky enough this time that that driver used `clamp_t(char, negative_value, positive_value)`, so the new checking code found it, and I've sent a patch to fix it, but there are likely other places lurking that won't be so easily unearthed. So let's just eliminate this particular variety of heisensign bugs entirely. Set `-funsigned-char` globally, so that gcc makes the type unsigned on all architectures. This will break things in some places and fix things in others, so this will likely cause a bit of churn while reconciling the type misuse. Link: https://lkml.kernel.org/r/20221019203034.3795710-1-Jason@zx2c4.com Link: https://lore.kernel.org/lkml/202210190108.ESC3pc3D-lkp@intel.com/ Signed-off-by: Jason A. Donenfeld Cc: Masahiro Yamada Cc: Kees Cook Cc: Linus Torvalds Cc: Andy Shevchenko Cc: Greg Kroah-Hartman Signed-off-by: Andrew Morton --- Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/Makefile~kbuild-treat-char-as-always-unsigned +++ a/Makefile @@ -562,7 +562,7 @@ KBUILD_AFLAGS := -D__ASSEMBLY__ -fno-P KBUILD_CFLAGS := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \ -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \ -Werror=implicit-function-declaration -Werror=implicit-int \ - -Werror=return-type -Wno-format-security \ + -Werror=return-type -Wno-format-security -funsigned-char \ -std=gnu11 KBUILD_CPPFLAGS := -D__KERNEL__ KBUILD_RUSTFLAGS := $(rust_common_flags) \ _ Patches currently in -mm which might be from Jason@zx2c4.com are wifi-rt2x00-use-explicitly-signed-type-for-clamping.patch minmax-sanity-check-constant-bounds-when-clamping.patch minmax-clamp-more-efficiently-by-avoiding-extra-comparison.patch kbuild-treat-char-as-always-unsigned.patch