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[98.38.17.99]) by smtp.googlemail.com with ESMTPSA id 8926c6da1cb9f-5aea7ce584bsm1212138173.27.2025.10.25.14.15.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 25 Oct 2025 14:15:27 -0700 (PDT) From: Jim Cromie To: linux-kernel@vger.kernel.org Cc: akpm@linuxfoundation.org, Jim Cromie , Andy Whitcroft , Joe Perches , Dwaipayan Ray , Lukas Bulwahn Subject: [PATCH 1/3] checkpatch: add --drx option and drx_print() helper Date: Sat, 25 Oct 2025 15:15:16 -0600 Message-ID: <20251025211519.1616439-2-jim.cromie@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251025211519.1616439-1-jim.cromie@gmail.com> References: <20251025211519.1616439-1-jim.cromie@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" checkpatch has ~235 heuristic s/$patt// statements which strip code-snippets that are "OK", leaving the remainder for further heuristics to apply further "cleanups". Many of these have obvious purpose, but surely some are inscrutable. For those cases, add drx_print($reason) helper, which is designed to be called from a s/// or s///g statement (in the 'replacement' side), to "explain" what it is doing. You can use it to instrument the code to "explain" itself, then validate that explanation by experiment and exersize: s/$patt/drx_print("why")/e; s/$patt/drx_print("whys")/ge; To activate the "debug" output, pass --drx or --drx=3Dwhy to enable all (or just matching) cleanup heuristics to validate the "whys". Here it is in action, on a patch which triggered enough noise that I wanted this visibility into what it was doing. $ scripts/checkpatch.pl --strict --drx=3Dbuiltins ../linux.git/pt-1 drx_print: -builtins- >> Matched (`$&`): <__builtin_constant_p(cls> >> Capture 1 (`$1`): <__builtin_constant_p> Signed-off-by: Jim Cromie fixup --- scripts/checkpatch.pl | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index e722dd6fa8ef..2b0275dcc5a4 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -74,6 +74,7 @@ my $allow_c99_comments =3D 1; # Can be overridden by --ig= nore C99_COMMENT_TOLERANC my $git_command =3D'export LANGUAGE=3Den_US.UTF-8; git'; my $tabsize =3D 8; my ${CONFIG_} =3D "CONFIG_"; +my $drx; # enable s/$patt/drx_print("reason")/e; debugging =20 my %maybe_linker_symbol; # for externs in c exceptions, when seen in *vmli= nux.lds.h =20 @@ -169,6 +170,30 @@ my $DO_WHILE_0_ADVICE =3D q{ Enjoy this qualification while we work to improve our heuristics. }; =20 +# call this from s/$patt/drx_print("why")/e - to see whats happening there. +sub drx_print { + my ($why) =3D @_; + return "" unless defined $drx; # --drx or --drx=3D + + # avoid regex test to preserve caller's match, captures + return "" if (defined $drx && $drx ne '' && index($why, $drx) =3D=3D -1); + + # report what was matched and removed + print "drx_print: $why\n"; + print " >> Matched (`\$&`): <$&>\n"; + + # Only print captures if they exist + if (defined $1) { + print " >> Capture 1 (`\$1`): <$1>\n"; + } + if (defined $2) { + print " >> Capture 2 (`\$2`): <$2>\n"; + } + # The subroutine must return the replacement string. For s/$pat// + # statements (our target use), this is an empty string. + return ""; +} + sub uniq { my %seen; return grep { !$seen{$_}++ } @_; @@ -348,6 +373,7 @@ GetOptions( 'no-color' =3D> \$color, #keep old behaviors of -nocolor 'nocolor' =3D> \$color, #keep old behaviors of -nocolor 'kconfig-prefix=3Ds' =3D> \${CONFIG_}, + 'drx:s' =3D> \$drx, 'h|help' =3D> \$help, 'version' =3D> \$help ) or $help =3D 2; --=20 2.51.0 From nobody Sun Feb 8 01:51:54 2026 Received: from mail-il1-f181.google.com (mail-il1-f181.google.com [209.85.166.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0ABF221FBA for ; Sat, 25 Oct 2025 21:15:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.181 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761426932; cv=none; b=VyxZm0AO/2P5shTCqZS/lzcjshSLj0a6s94afo84hoKPYux8idwDZG/jQDP5wVr6/WZsSr4YsaZPbWj4Fu9srUaBUYUHP152w/aXFPEgUGl1GqKIzL6t7eDsze6+3hZBtIuU2Dfe4KpA6LYuTdn352+bh4HStwXMnVFoZIyuFFU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761426932; c=relaxed/simple; bh=sSEUhz+mbc7CNC+cT2dc2OhAbsKC27gwDz5MBlN/oAc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uGxXOrn06p1yj/FqeQuO1lYyLlVA1tS/j4DjP6Idgvq5Vi/8h02om/+imzUsvVp9fDVhpvU41363N8ChsesqwOcEKzFSNLmL21bqbDIM6EfIurtjsJal8uYyX2SUuPKScApui6pAu/zs0zzfeCQIAvZoyuoVzRbboUcHSbPaIgw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=AeeePxaG; arc=none smtp.client-ip=209.85.166.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="AeeePxaG" Received: by mail-il1-f181.google.com with SMTP id e9e14a558f8ab-430e1f19a1aso17284095ab.1 for ; Sat, 25 Oct 2025 14:15:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1761426929; x=1762031729; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=+Fkyib152otQl2jwWzh+5qLwAlw0aGs/wM5SDuJ8W9g=; b=AeeePxaGAW7jzOicBjMIuXlB622gbNNVT9vhhrHF8HUsrS4aJrx+QFZXXitIYiJUnV BD0YyCflAdE5gHD0ucth3gkm5zqO5jEO6r9wkOqlvpGndBcmzp/+Xid1aqZbexYtXbAY UyD/N9uYHIaA1Y6Yi6wb7nHTq44uGhEf3JEZrR1Vw7iF3QSifyjvkPHwsF7j0xiFS18q UucHdissJXB3Qhe0ZH07iBQrBiSy9jZjmXRS1zy78N4jq2zR5wUzuDtS+XFa2+iGhnIk jJTss5vNft+tCpDIN4BqWznUWR03ETZJ9qETNMYnAdSzY3K2X4lye6meuveD2h76sMwo 2wYg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761426929; x=1762031729; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=+Fkyib152otQl2jwWzh+5qLwAlw0aGs/wM5SDuJ8W9g=; b=jFKcb8r1DGgihn9Uo31/wqNrOMh5flH1mspckl+TXe/6cSx2ByP3quQaV0d6qp2qo6 KdwpIIN4y4BpGmCyr5mUoR4cFyWnm28msd/azTlg0evOuw8kMKlxiw4n3qclJW2WLWHA 6ruNXZWoowqojkfz7O00NiexbPt5OmNokH8ANtnOo3MYNaxKGA0kggdxKzUnWSunp1kl Y2p0uvAlhG3JbcvnAH7tnRapm7xVL7dHgh5HiA0O6iwHyBBK7+Uofh28sEL5tHKrtU7b bdjEc90BkZQ4Uklg4gCbqYe/m6wbfeydFqHJAmeBEpQZ+kDdqsI00xSOoE8HXZBDUxU+ 9aDQ== X-Gm-Message-State: AOJu0Yxu0p8aioMQBmEz15GCDhtAig79lGrLcQRkjbj8E7ZWO2KIq3hd ksP9DeR+/9pqtEe/f2CYLop3X8+Im/RcEsgZYHXIMnX+VmS2JkpL/ciC3gLy3Q== X-Gm-Gg: ASbGncu9vUpSP6TAH90V6W5kK0jN2RmI3GyQX2MeAO5RYULX2vbF6oxFEyQUNCNZeD7 dLIn8+ysKVSiYlQrCTv8BkvYk2v4s7B3vSJR+dcn0fi/fhsAbzF72To0+tKuQH9o9JB2VKTrrnf djfMACJJAYXMugnQfPI16U6gcLZsKsTapZD050liRp8Ldn2TNx/Cvtrumwlp5O0gHJ2hOfQT1GU sQwFYwquKwMdoN4KdzvMHG4Goey70OePUzyFf2MMmKrCdgEmFTgbhUoWQbogMI2gUOC5eJAQRhc LelE4cYiWxYVQ8pazJyHZiiP2Zwn7pwmGUeasKCWDJYy97W03l9jxGRWmTbKRaDzqRC2kY4q7tJ VMax7xMf1gGrr2kXJSRJuxbtwOlMfgI1apceTUB8ousI0aRzYOdSIAJxnuhxPc6Z2mtjAGpSmy7 wRasyeRo4IIHtrUkR2PBbzVMjxtwDrM0e7/tXnyWeA/FZIbCw6VWGaEG8L X-Google-Smtp-Source: AGHT+IFHODqIKZ4NVlQBiQsVgEpqNd0nlVARyGeIx/pSPW5vQYdVUvNRQe0KjOwMpN0ZebpJ3f2kvA== X-Received: by 2002:a05:6e02:378e:b0:430:db6d:30f8 with SMTP id e9e14a558f8ab-431eb5fff30mr104251015ab.4.1761426929513; Sat, 25 Oct 2025 14:15:29 -0700 (PDT) Received: from godzilla.raven-morpho.ts.net (c-98-38-17-99.hsd1.co.comcast.net. [98.38.17.99]) by smtp.googlemail.com with ESMTPSA id 8926c6da1cb9f-5aea7ce584bsm1212138173.27.2025.10.25.14.15.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 25 Oct 2025 14:15:28 -0700 (PDT) From: Jim Cromie To: linux-kernel@vger.kernel.org Cc: akpm@linuxfoundation.org, Jim Cromie , Andy Whitcroft , Joe Perches , Dwaipayan Ray , Lukas Bulwahn Subject: [PATCH 2/3] checkpatch: recognize __chkp_no_side_effects(_var) hint macro Date: Sat, 25 Oct 2025 15:15:17 -0600 Message-ID: <20251025211519.1616439-3-jim.cromie@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251025211519.1616439-1-jim.cromie@gmail.com> References: <20251025211519.1616439-1-jim.cromie@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Teach checkpatch --strict to allow an author to suppress specific var-reuse complaints: CHECK: Macro argument reuse '_var' - possible side-effects? Consider: #define module_param_named(name, value, type, perm) \ + __chkp_no_side_effects(name, value) \ param_check_##type(name, &(value)); \ module_param_cb(name, ¶m_ops_##type, &value, perm); \ __MODULE_PARM_TYPE(name, #type) Without the +line, this kind of multi-statement macro-defn would cause checkpatch to carp about name and value being reused. Note that it wouldn't complain about type, even though type is expanded 3 times, because checkpatch knew to strip # and ## constructs on an arg before counting its uses. module_param_named is actually a named $exception, amongst a ~dozen others, so it wouldn't draw the complaint (I said kind of above), but this approach doesn't require further checkpatch tweaks, is specific to the _vars named, and is author initiated, not a carte-blanche exception on the macro-name. IIRC, trybot kicks of a CI pipeline that calls checkpatch --strict, this hint could help reduce CI-noise going forward. Signed-off-by: Jim Cromie --- scripts/checkpatch.pl | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 2b0275dcc5a4..bc807c20fcde 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -6070,11 +6070,24 @@ sub process { next if ($arg =3D~ /\.\.\./); next if ($arg =3D~ /^type$/i); my $tmp_stmt =3D $define_stmt; - $tmp_stmt =3D~ s/\b(__must_be_array|offsetof|sizeof|sizeof_field|__str= ingify|typeof|__typeof__|__builtin\w+|typecheck\s*\(\s*$Type\s*,|\#+)\s*\(*= \s*$arg\s*\)*\b//g; - $tmp_stmt =3D~ s/\#+\s*$arg\b//g; - $tmp_stmt =3D~ s/\b$arg\s*\#\#//g; + + $tmp_stmt =3D~ s/\#+\s*$arg\b/drx_print("strip '#|## arg catenations")= /ge; + $tmp_stmt =3D~ s/\b$arg\s*\#\#/drx_print("strip 'arg ##' catenations")= ;/ge; + + $tmp_stmt =3D~ s{ + \b(__must_be_array|offsetof|sizeof|sizeof_field|__stringify| + typeof|__typeof__|__builtin\w+|typecheck + \s*\(\s*$Type\s*,|\#+)\s*\(*\s*$arg\s*\)*\b } + { + drx_print("-builtins-"); + }xge; + + my $no_side_effect_vars =3D ""; + if ($tmp_stmt =3D~ s/__chkp_no_side_effects\((.+)\)//) { + $no_side_effect_vars =3D $1; + } my $use_cnt =3D () =3D $tmp_stmt =3D~ /\b$arg\b/g; - if ($use_cnt > 1) { + if ($use_cnt > 1 and $no_side_effect_vars !~ m/\b$arg\b/) { CHK("MACRO_ARG_REUSE", "Macro argument reuse '$arg' - possible side-effects?\n" . 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[98.38.17.99]) by smtp.googlemail.com with ESMTPSA id 8926c6da1cb9f-5aea7ce584bsm1212138173.27.2025.10.25.14.15.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 25 Oct 2025 14:15:30 -0700 (PDT) From: Jim Cromie To: linux-kernel@vger.kernel.org Cc: akpm@linuxfoundation.org, Jim Cromie , Luc Van Oostenryck , linux-sparse@vger.kernel.org (open list:SPARSE CHECKER) Subject: [PATCH 3/3] compiler.h: add __chkp_no_side_effects() empty hint/assertion macro Date: Sat, 25 Oct 2025 15:15:18 -0600 Message-ID: <20251025211519.1616439-4-jim.cromie@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251025211519.1616439-1-jim.cromie@gmail.com> References: <20251025211519.1616439-1-jim.cromie@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" cpp has no intrinsic protection against macro arg side-effects, so to compensate, checkpatch is paranoid: CHECK: Macro argument reuse '_var' - possible side-effects? Allow an author to suppress these warnings on _var by adding '__chkp_no_side_effects(_var)' to the body of macros which trigger that warning. This may reduce blowouts in CI pipelines. Signed-off-by: Jim Cromie --- include/linux/compiler.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 64ff73c533e5..96f6bfbd4088 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -379,6 +379,18 @@ static inline void *offset_to_ptr(const int *off) */ #define prevent_tail_call_optimization() mb() =20 +/* + * tell checkpatch --strict that you know the named args (a subset of + * the containing macro's args) are safe for multiple expansions. + * + * Prefer ({ typeof ..}) or do{}while(0) when they work. They would + * not work on module_param_named(name, value, type, perm), or on a + * locally useful "for_simplicity()" macro. + * + * NB: use at top of macro body, omit trailing semicolon. + */ +#define __chkp_no_side_effects(...) /* checkpatch "annotation" helper */ + #include =20 #endif /* __LINUX_COMPILER_H */ --=20 2.51.0