linux-kernel - [PATCH] uapi: bitops: use UAPI-safe variant of BITS_PER

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Message-Id: <20250630-uapi-genmask-v1-1-eb0ad956a83e@linutronix.de>
Date: Mon, 30 Jun 2025 15:02:18 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Arnaldo Carvalho de Melo <acme@...hat.com>, 
 Vincent Mailhol <mailhol.vincent@...adoo.fr>, 
 Yury Norov <yury.norov@...il.com>, 
 Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH] uapi: bitops: use UAPI-safe variant of BITS_PER_LONG again
 (2)

BITS_PER_LONG does not exist in UAPI headers, so can't be used by the UAPI
__GENMASK(). Instead __BITS_PER_LONG needs to be used.

When __GENMASK() was introduced in commit 3c7a8e190bc5 ("uapi: introduce uapi-friendly macros for GENMASK"),
the code was fine. A broken revert in 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"")
introduced the incorrect usage of BITS_PER_LONG.
That was fixed in commit 11fcf368506d ("uapi: bitops: use UAPI-safe variant of BITS_PER_LONG again").
But a broken sync of the kernel headers with the tools/ headers in
commit fc92099902fb ("tools headers: Synchronize linux/bits.h with the kernel sources")
undid the fix.

Reapply the fix and while at it also fix the tools header.

Fixes: fc92099902fb ("tools headers: Synchronize linux/bits.h with the kernel sources")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
 include/uapi/linux/bits.h       | 4 ++--
 tools/include/uapi/linux/bits.h | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/bits.h b/include/uapi/linux/bits.h
index 682b406e10679dc8baa188830ab0811e7e3e13e3..a04afef9efca42f062e142fcb33f5d267512b1e5 100644
--- a/include/uapi/linux/bits.h
+++ b/include/uapi/linux/bits.h
@@ -4,9 +4,9 @@
 #ifndef _UAPI_LINUX_BITS_H
 #define _UAPI_LINUX_BITS_H
 
-#define __GENMASK(h, l) (((~_UL(0)) << (l)) & (~_UL(0) >> (BITS_PER_LONG - 1 - (h))))
+#define __GENMASK(h, l) (((~_UL(0)) << (l)) & (~_UL(0) >> (__BITS_PER_LONG - 1 - (h))))
 
-#define __GENMASK_ULL(h, l) (((~_ULL(0)) << (l)) & (~_ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))
+#define __GENMASK_ULL(h, l) (((~_ULL(0)) << (l)) & (~_ULL(0) >> (__BITS_PER_LONG_LONG - 1 - (h))))
 
 #define __GENMASK_U128(h, l) \
 	((_BIT128((h)) << 1) - (_BIT128(l)))
diff --git a/tools/include/uapi/linux/bits.h b/tools/include/uapi/linux/bits.h
index 682b406e10679dc8baa188830ab0811e7e3e13e3..a04afef9efca42f062e142fcb33f5d267512b1e5 100644
--- a/tools/include/uapi/linux/bits.h
+++ b/tools/include/uapi/linux/bits.h
@@ -4,9 +4,9 @@
 #ifndef _UAPI_LINUX_BITS_H
 #define _UAPI_LINUX_BITS_H
 
-#define __GENMASK(h, l) (((~_UL(0)) << (l)) & (~_UL(0) >> (BITS_PER_LONG - 1 - (h))))
+#define __GENMASK(h, l) (((~_UL(0)) << (l)) & (~_UL(0) >> (__BITS_PER_LONG - 1 - (h))))
 
-#define __GENMASK_ULL(h, l) (((~_ULL(0)) << (l)) & (~_ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))
+#define __GENMASK_ULL(h, l) (((~_ULL(0)) << (l)) & (~_ULL(0) >> (__BITS_PER_LONG_LONG - 1 - (h))))
 
 #define __GENMASK_U128(h, l) \
 	((_BIT128((h)) << 1) - (_BIT128(l)))

---
base-commit: d0b3b7b22dfa1f4b515fd3a295b3fd958f9e81af
change-id: 20250630-uapi-genmask-d36e3ffc5691

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@...utronix.de>