From: Eliav Farber <farbere@amazon•com>
To: <gregkh@linuxfoundation•org>, <stable@vger•kernel.org>,
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Cc: Christoph Hellwig <hch@infradead•org>,
Linus Torvalds <torvalds@linux-foundation•org>
Subject: [PATCH v2 12/27 5.10.y] minmax: relax check to allow comparison between unsigned arguments and signed constants
Date: Fri, 17 Oct 2025 09:05:04 +0000 [thread overview]
Message-ID: <20251017090519.46992-13-farbere@amazon.com> (raw)
In-Reply-To: <20251017090519.46992-1-farbere@amazon.com>
From: David Laight <David.Laight@ACULAB•COM>
[ Upstream commit 867046cc7027703f60a46339ffde91a1970f2901 ]
Allow (for example) min(unsigned_var, 20).
The opposite min(signed_var, 20u) is still errored.
Since a comparison between signed and unsigned never makes the unsigned
value negative it is only necessary to adjust the __types_ok() test.
Link: https://lkml.kernel.org/r/633b64e2f39e46bb8234809c5595b8c7@AcuMS.aculab.com
Signed-off-by: David Laight <david.laight@aculab•com>
Cc: Andy Shevchenko <andriy.shevchenko@linux•intel.com>
Cc: Christoph Hellwig <hch@infradead•org>
Cc: Jason A. Donenfeld <Jason@zx2c4•com>
Cc: Linus Torvalds <torvalds@linux-foundation•org>
Cc: Matthew Wilcox (Oracle) <willy@infradead•org>
Signed-off-by: Andrew Morton <akpm@linux-foundation•org>
Signed-off-by: Eliav Farber <farbere@amazon•com>
---
include/linux/minmax.h | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)
diff --git a/include/linux/minmax.h b/include/linux/minmax.h
index 842c1db62ffe..2ec559284a9f 100644
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -10,13 +10,18 @@
/*
* min()/max()/clamp() macros must accomplish three things:
*
- * - avoid multiple evaluations of the arguments (so side-effects like
+ * - Avoid multiple evaluations of the arguments (so side-effects like
* "x++" happen only once) when non-constant.
- * - 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
+ * - Retain result as a constant expressions when called with only
* constant expressions (to avoid tripping VLA warnings in stack
* allocation usage).
+ * - Perform signed v unsigned type-checking (to generate compile
+ * errors instead of nasty runtime surprises).
+ * - Unsigned char/short are always promoted to signed int and can be
+ * compared against signed or unsigned arguments.
+ * - Unsigned arguments can be compared against non-negative signed constants.
+ * - Comparison of a signed argument against an unsigned constant fails
+ * even if the constant is below __INT_MAX__ and could be cast to int.
*/
#define __typecheck(x, y) \
(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
@@ -26,9 +31,14 @@
__builtin_choose_expr(__is_constexpr(is_signed_type(typeof(x))), \
is_signed_type(typeof(x)), 0)
-#define __types_ok(x, y) \
- (__is_signed(x) == __is_signed(y) || \
- __is_signed((x) + 0) == __is_signed((y) + 0))
+/* True for a non-negative signed int constant */
+#define __is_noneg_int(x) \
+ (__builtin_choose_expr(__is_constexpr(x) && __is_signed(x), x, -1) >= 0)
+
+#define __types_ok(x, y) \
+ (__is_signed(x) == __is_signed(y) || \
+ __is_signed((x) + 0) == __is_signed((y) + 0) || \
+ __is_noneg_int(x) || __is_noneg_int(y))
#define __cmp_op_min <
#define __cmp_op_max >
--
2.47.3
next prev parent reply other threads:[~2025-10-17 9:09 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-17 9:04 [PATCH v2 00/27 5.10.y] Backport minmax.h updates from v6.17-rc7 Eliav Farber
2025-10-17 9:04 ` [PATCH v2 01/27 5.10.y] overflow, tracing: Define the is_signed_type() macro once Eliav Farber
2025-10-17 11:59 ` Greg KH
2025-10-17 12:16 ` Farber, Eliav
2025-10-17 13:21 ` Greg KH
2025-10-17 9:04 ` [PATCH v2 02/27 5.10.y] btrfs: remove duplicated in_range() macro Eliav Farber
2025-10-17 9:04 ` [PATCH v2 03/27 5.10.y] minmax: sanity check constant bounds when clamping Eliav Farber
2025-10-17 9:04 ` [PATCH v2 04/27 5.10.y] minmax: clamp more efficiently by avoiding extra comparison Eliav Farber
2025-10-17 9:04 ` [PATCH v2 05/27 5.10.y] minmax: add in_range() macro Eliav Farber
2025-10-17 9:04 ` [PATCH v2 06/27 5.10.y] minmax: Introduce {min,max}_array() Eliav Farber
2025-10-17 9:04 ` [PATCH v2 07/27 5.10.y] minmax: deduplicate __unconst_integer_typeof() Eliav Farber
2025-10-17 9:05 ` [PATCH v2 08/27 5.10.y] minmax: fix header inclusions Eliav Farber
2025-10-17 9:05 ` [PATCH v2 09/27 5.10.y] minmax: allow min()/max()/clamp() if the arguments have the same signedness Eliav Farber
2025-10-17 9:05 ` [PATCH v2 10/27 5.10.y] minmax: fix indentation of __cmp_once() and __clamp_once() Eliav Farber
2025-10-17 9:05 ` [PATCH v2 11/27 5.10.y] minmax: allow comparisons of 'int' against 'unsigned char/short' Eliav Farber
2025-10-17 9:05 ` Eliav Farber [this message]
2025-10-17 9:05 ` [PATCH v2 13/27 5.10.y] minmax: avoid overly complicated constant expressions in VM code Eliav Farber
2025-10-17 9:05 ` [PATCH v2 14/27 5.10.y] minmax: add a few more MIN_T/MAX_T users Eliav Farber
2025-10-17 9:05 ` [PATCH v2 15/27 5.10.y] minmax: simplify and clarify min_t()/max_t() implementation Eliav Farber
2025-10-17 9:05 ` [PATCH v2 16/27 5.10.y] minmax: make generic MIN() and MAX() macros available everywhere Eliav Farber
2025-10-17 9:05 ` [PATCH v2 17/27 5.10.y] minmax: don't use max() in situations that want a C constant expression Eliav Farber
2025-10-17 9:05 ` [PATCH v2 18/27 5.10.y] minmax: simplify min()/max()/clamp() implementation Eliav Farber
2025-10-17 9:05 ` [PATCH v2 19/27 5.10.y] minmax: improve macro expansion and type checking Eliav Farber
2025-10-17 9:05 ` [PATCH v2 20/27 5.10.y] minmax: fix up min3() and max3() too Eliav Farber
2025-10-17 9:05 ` [PATCH v2 21/27 5.10.y] minmax.h: add whitespace around operators and after commas Eliav Farber
2025-10-17 9:05 ` [PATCH v2 22/27 5.10.y] minmax.h: update some comments Eliav Farber
2025-10-17 9:05 ` [PATCH v2 23/27 5.10.y] minmax.h: reduce the #define expansion of min(), max() and clamp() Eliav Farber
2025-10-17 9:05 ` [PATCH v2 24/27 5.10.y] minmax.h: use BUILD_BUG_ON_MSG() for the lo < hi test in clamp() Eliav Farber
2025-10-17 9:05 ` [PATCH v2 25/27 5.10.y] minmax.h: move all the clamp() definitions after the min/max() ones Eliav Farber
2025-10-17 9:05 ` [PATCH v2 26/27 5.10.y] minmax.h: simplify the variants of clamp() Eliav Farber
2025-10-17 9:05 ` [PATCH v2 27/27 5.10.y] minmax.h: remove some #defines that are only expanded once Eliav Farber
2025-10-17 15:03 ` [PATCH v2 00/27 5.10.y] Backport minmax.h updates from v6.17-rc7 Greg KH
2025-10-17 16:09 ` Nathan Chancellor
2025-10-19 12:38 ` Greg KH
2025-10-18 20:07 ` Farber, Eliav
2025-10-19 12:37 ` Greg KH
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