From nobody Wed Dec 17 17:23:09 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B3A0D1A08A3; Tue, 16 Jul 2024 17:52:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721152338; cv=none; b=Rob1HkZw7LumLyTIQh1Xd/5EDfx0+zuOq7V6NvraA9blpCsIUvr0ZwoM0E0sYiFOmqbu11SaLlpTARvnYJWBK7xiC2+54cNuIyClv+qihvxR/4MGw1wqRdKSY0+byzp1ckReXHF0Hy9EyQ2uC22uSdN6Q4ljp1kDQqRAFa3wDUQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721152338; c=relaxed/simple; bh=G7wLAJvUm7VMiE14Qqoyq66ELgz7AVWyGzvBzNL41RQ=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=cfArmHsL2YTdY4BwOGhJTqRn2z72A3sg1ipocia3KzJcXs4AqDlwmzNFRkq/OpveGL9PLil7saoUVdMiDWQuCpm4RaKgRcXuaZLcPwuRiyjtcgzAGMdpG7KjhFQCEfnFB3r08VnxCGeGLDu5Mvr7b3+ZFvL5NcSIPnUW1qXjJpc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ecX4Aaz/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ecX4Aaz/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6EA67C4AF0D; Tue, 16 Jul 2024 17:52:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1721152338; bh=G7wLAJvUm7VMiE14Qqoyq66ELgz7AVWyGzvBzNL41RQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ecX4Aaz/tPre631RXbuX9gcfRwlnwxZ5ITNV30nvFX90HPj/XszpFxqLi2a5auN84 QXs7tvnrFkN4z3WEASWdASkKIiQRJUln8ZimYg6LQv7b8ds8P8TtJ617zFlU/Y1036 /Pgl+godDfCyDqpRwS006LV0thWO5h8l4EZ1e+U/zYXY/V0e0n1sPH8vjtt510dE71 lh1wCvm7WV4Wr+DVK9iwqQGehlMM4TZfkCIZ9ZkhL7pIdaNoyHt40KfAgxhGK4ajOR CsaKST6gX906h6fIfqrE+RIkBVNqjgfBArix2W1Kzc5b69XMDOtwWPiKciwPq0cbkb +T2TWDkUwpuag== From: SeongJae Park To: stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: David Laight , linux-kernel@vger.kernel.org, David Laight , Andy Shevchenko , Christoph Hellwig , "Jason A . Donenfeld" , Linus Torvalds , Matthew Wilcox , Andrew Morton , SeongJae Park Subject: [PATCH 6.1.y 4/7] minmax: allow min()/max()/clamp() if the arguments have the same signedness. Date: Tue, 16 Jul 2024 10:52:02 -0700 Message-Id: <20240716175205.51280-5-sj@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240716175205.51280-1-sj@kernel.org> References: <20240716175205.51280-1-sj@kernel.org> 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" From: David Laight commit d03eba99f5bf7cbc6e2fdde3b6fa36954ad58e09 upstream. The type-check in min()/max() is there to stop unexpected results if a negative value gets converted to a large unsigned value. However it also rejects 'unsigned int' v 'unsigned long' compares which are common and never problematc. Replace the 'same type' check with a 'same signedness' check. The new test isn't itself a compile time error, so use static_assert() to report the error and give a meaningful error message. Due to the way builtin_choose_expr() works detecting the error in the 'non-constant' side (where static_assert() can be used) also detects errors when the arguments are constant. Link: https://lkml.kernel.org/r/fe7e6c542e094bfca655abcd323c1c98@AcuMS.acul= ab.com Signed-off-by: David Laight Cc: Andy Shevchenko Cc: Christoph Hellwig Cc: Jason A. Donenfeld Cc: Linus Torvalds Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton (cherry picked from commit d03eba99f5bf7cbc6e2fdde3b6fa36954ad58e09) Signed-off-by: SeongJae Park --- include/linux/minmax.h | 60 ++++++++++++++++++++++-------------------- 1 file changed, 32 insertions(+), 28 deletions(-) diff --git a/include/linux/minmax.h b/include/linux/minmax.h index e8e9642809e0..501fab582d68 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -11,9 +11,8 @@ * * - avoid multiple evaluations of the arguments (so side-effects like * "x++" happen only once) when non-constant. - * - perform strict type-checking (to generate warnings instead of - * nasty runtime surprises). See the "unnecessary" pointer comparison - * in __typecheck(). + * - perform signed v unsigned type-checking (to generate compile + * errors instead of nasty runtime surprises). * - retain result as a constant expressions when called with only * constant expressions (to avoid tripping VLA warnings in stack * allocation usage). @@ -21,23 +20,30 @@ #define __typecheck(x, y) \ (!!(sizeof((typeof(x) *)1 =3D=3D (typeof(y) *)1))) =20 -#define __no_side_effects(x, y) \ - (__is_constexpr(x) && __is_constexpr(y)) +/* is_signed_type() isn't a constexpr for pointer types */ +#define __is_signed(x) \ + __builtin_choose_expr(__is_constexpr(is_signed_type(typeof(x))), \ + is_signed_type(typeof(x)), 0) =20 -#define __safe_cmp(x, y) \ - (__typecheck(x, y) && __no_side_effects(x, y)) +#define __types_ok(x, y) \ + (__is_signed(x) =3D=3D __is_signed(y)) =20 -#define __cmp(x, y, op) ((x) op (y) ? (x) : (y)) +#define __cmp_op_min < +#define __cmp_op_max > =20 -#define __cmp_once(x, y, unique_x, unique_y, op) ({ \ +#define __cmp(op, x, y) ((x) __cmp_op_##op (y) ? (x) : (y)) + +#define __cmp_once(op, x, y, unique_x, unique_y) ({ \ typeof(x) unique_x =3D (x); \ typeof(y) unique_y =3D (y); \ - __cmp(unique_x, unique_y, op); }) + static_assert(__types_ok(x, y), \ + #op "(" #x ", " #y ") signedness error, fix types or consider u" #op "(= ) before " #op "_t()"); \ + __cmp(op, unique_x, unique_y); }) =20 -#define __careful_cmp(x, y, op) \ - __builtin_choose_expr(__safe_cmp(x, y), \ - __cmp(x, y, op), \ - __cmp_once(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y), op)) +#define __careful_cmp(op, x, y) \ + __builtin_choose_expr(__is_constexpr((x) - (y)), \ + __cmp(op, x, y), \ + __cmp_once(op, x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y))) =20 #define __clamp(val, lo, hi) \ ((val) >=3D (hi) ? (hi) : ((val) <=3D (lo) ? (lo) : (val))) @@ -46,17 +52,15 @@ typeof(val) unique_val =3D (val); \ typeof(lo) unique_lo =3D (lo); \ typeof(hi) unique_hi =3D (hi); \ + static_assert(__builtin_choose_expr(__is_constexpr((lo) > (hi)), \ + (lo) <=3D (hi), true), \ + "clamp() low limit " #lo " greater than high limit " #hi); \ + static_assert(__types_ok(val, lo), "clamp() 'lo' signedness error"); \ + static_assert(__types_ok(val, hi), "clamp() 'hi' signedness error"); \ __clamp(unique_val, unique_lo, unique_hi); }) =20 -#define __clamp_input_check(lo, hi) \ - (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ - __is_constexpr((lo) > (hi)), (lo) > (hi), false))) - #define __careful_clamp(val, lo, hi) ({ \ - __clamp_input_check(lo, hi) + \ - __builtin_choose_expr(__typecheck(val, lo) && __typecheck(val, hi) && \ - __typecheck(hi, lo) && __is_constexpr(val) && \ - __is_constexpr(lo) && __is_constexpr(hi), \ + __builtin_choose_expr(__is_constexpr((val) - (lo) + (hi)), \ __clamp(val, lo, hi), \ __clamp_once(val, lo, hi, __UNIQUE_ID(__val), \ __UNIQUE_ID(__lo), __UNIQUE_ID(__hi))); }) @@ -66,14 +70,14 @@ * @x: first value * @y: second value */ -#define min(x, y) __careful_cmp(x, y, <) +#define min(x, y) __careful_cmp(min, x, y) =20 /** * max - return maximum of two values of the same or compatible types * @x: first value * @y: second value */ -#define max(x, y) __careful_cmp(x, y, >) +#define max(x, y) __careful_cmp(max, x, y) =20 /** * umin - return minimum of two non-negative values @@ -82,7 +86,7 @@ * @y: second value */ #define umin(x, y) \ - __careful_cmp((x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull, <) + __careful_cmp(min, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull) =20 /** * umax - return maximum of two non-negative values @@ -90,7 +94,7 @@ * @y: second value */ #define umax(x, y) \ - __careful_cmp((x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull, >) + __careful_cmp(max, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull) =20 /** * min3 - return minimum of three values @@ -142,7 +146,7 @@ * @x: first value * @y: second value */ -#define min_t(type, x, y) __careful_cmp((type)(x), (type)(y), <) +#define min_t(type, x, y) __careful_cmp(min, (type)(x), (type)(y)) =20 /** * max_t - return maximum of two values, using the specified type @@ -150,7 +154,7 @@ * @x: first value * @y: second value */ -#define max_t(type, x, y) __careful_cmp((type)(x), (type)(y), >) +#define max_t(type, x, y) __careful_cmp(max, (type)(x), (type)(y)) =20 /** * clamp_t - return a value clamped to a given range using a given type --=20 2.39.2