linux-kernel - [PATCH 02/15 6.6.y] minmax: simplify and clarify min_t()/max

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20250922103241.16213-3-farbere@amazon.com>
Date: Mon, 22 Sep 2025 10:32:28 +0000
From: Eliav Farber <farbere@...zon.com>
To: <richard@....at>, <anton.ivanov@...bridgegreys.com>,
	<johannes@...solutions.net>, <dave.hansen@...ux.intel.com>,
	<luto@...nel.org>, <peterz@...radead.org>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <x86@...nel.org>, <hpa@...or.com>,
	<tony.luck@...el.com>, <qiuxu.zhuo@...el.com>, <james.morse@....com>,
	<mchehab@...nel.org>, <rric@...nel.org>, <harry.wentland@....com>,
	<sunpeng.li@....com>, <Rodrigo.Siqueira@....com>,
	<alexander.deucher@....com>, <christian.koenig@....com>,
	<Xinhui.Pan@....com>, <airlied@...il.com>, <daniel@...ll.ch>,
	<evan.quan@....com>, <maarten.lankhorst@...ux.intel.com>,
	<mripard@...nel.org>, <tzimmermann@...e.de>, <jdelvare@...e.com>,
	<linux@...ck-us.net>, <linus.walleij@...aro.org>,
	<dmitry.torokhov@...il.com>, <wens@...e.org>, <jernej.skrabec@...il.com>,
	<samuel@...lland.org>, <agk@...hat.com>, <snitzer@...nel.org>,
	<dm-devel@...ts.linux.dev>, <mailhol.vincent@...adoo.fr>,
	<wg@...ndegger.com>, <mkl@...gutronix.de>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<alexandre.torgue@...s.st.com>, <joabreu@...opsys.com>,
	<mcoquelin.stm32@...il.com>, <krzysztof.kozlowski@...aro.org>,
	<malattia@...ux.it>, <hdegoede@...hat.com>, <ilpo.jarvinen@...ux.intel.com>,
	<markgross@...nel.org>, <artur.paszkiewicz@...el.com>, <jejb@...ux.ibm.com>,
	<martin.petersen@...cle.com>, <sakari.ailus@...ux.intel.com>,
	<gregkh@...uxfoundation.org>, <clm@...com>, <josef@...icpanda.com>,
	<dsterba@...e.com>, <luc.vanoostenryck@...il.com>, <rostedt@...dmis.org>,
	<mhiramat@...nel.org>, <pmladek@...e.com>,
	<andriy.shevchenko@...ux.intel.com>, <linux@...musvillemoes.dk>,
	<senozhatsky@...omium.org>, <minchan@...nel.org>,
	<akpm@...ux-foundation.org>, <dsahern@...nel.org>, <shuah@...nel.org>,
	<keescook@...omium.org>, <wad@...omium.org>, <farbere@...zon.com>,
	<David.Laight@...LAB.COM>, <arnd@...nel.org>, <linux-um@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-edac@...r.kernel.org>,
	<amd-gfx@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
	<linux-hwmon@...r.kernel.org>, <linux-input@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-sunxi@...ts.linux.dev>,
	<linux-media@...r.kernel.org>, <linux-can@...r.kernel.org>,
	<netdev@...r.kernel.org>, <linux-stm32@...md-mailman.stormreply.com>,
	<platform-driver-x86@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
	<linux-staging@...ts.linux.dev>, <linux-btrfs@...r.kernel.org>,
	<linux-sparse@...r.kernel.org>, <linux-trace-kernel@...r.kernel.org>,
	<linux-mm@...ck.org>, <linux-kselftest@...r.kernel.org>,
	<bpf@...r.kernel.org>, <stable@...r.kernel.org>
CC: Linus Torvalds <torvalds@...ux-foundation.org>, David Laight
	<David.Laight@...lab.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Subject: [PATCH 02/15 6.6.y] minmax: simplify and clarify min_t()/max_t() implementation

From: Linus Torvalds <torvalds@...ux-foundation.org>

[ Upstream commit 017fa3e89187848fd056af757769c9e66ac3e93d ]

This simplifies the min_t() and max_t() macros by no longer making them
work in the context of a C constant expression.

That means that you can no longer use them for static initializers or
for array sizes in type definitions, but there were only a couple of
such uses, and all of them were converted (famous last words) to use
MIN_T/MAX_T instead.

Cc: David Laight <David.Laight@...lab.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Eliav Farber <farbere@...zon.com>
---
 include/linux/minmax.h | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/include/linux/minmax.h b/include/linux/minmax.h
index a7ef65f78933..9c2848abc804 100644
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -45,17 +45,20 @@
 
 #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 = (x);			\
-	typeof(y) unique_y = (y);			\
+#define __cmp_once_unique(op, type, x, y, ux, uy) \
+	({ type ux = (x); type uy = (y); __cmp(op, ux, uy); })
+
+#define __cmp_once(op, type, x, y) \
+	__cmp_once_unique(op, type, x, y, __UNIQUE_ID(x_), __UNIQUE_ID(y_))
+
+#define __careful_cmp_once(op, x, y) ({			\
 	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); })
+	__cmp_once(op, __auto_type, x, y); })
 
 #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)))
+		__cmp(op, x, y), __careful_cmp_once(op, x, y))
 
 #define __clamp(val, lo, hi)	\
 	((val) >= (hi) ? (hi) : ((val) <= (lo) ? (lo) : (val)))
@@ -158,7 +161,7 @@
  * @x: first value
  * @y: second value
  */
-#define min_t(type, x, y)	__careful_cmp(min, (type)(x), (type)(y))
+#define min_t(type, x, y) __cmp_once(min, type, x, y)
 
 /**
  * max_t - return maximum of two values, using the specified type
@@ -166,7 +169,7 @@
  * @x: first value
  * @y: second value
  */
-#define max_t(type, x, y)	__careful_cmp(max, (type)(x), (type)(y))
+#define max_t(type, x, y) __cmp_once(max, type, x, y)
 
 /*
  * Do not check the array parameter using __must_be_array().
-- 
2.47.3