The patch titled
Subject: linux/bits.h: make BIT(), GENMASK(), and friends available in assembly
has been added to the -mm tree. Its filename is
linux-bitsh-make-bit-genmask-and-friends-available-in-assembly.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/linux-bitsh-make-bit-genmask-and-friends-available-in-assembly.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/linux-bitsh-make-bit-genmask-and-friends-available-in-assembly.patch
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From: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Subject: linux/bits.h: make BIT(), GENMASK(), and friends available in assembly
BIT(), GENMASK(), etc. are useful to define register bits of hardware.
However, low-level code is often written in assembly, where they are
not available due to the hard-coded 1UL, 0UL.
In fact, in-kernel headers such as arch/arm64/include/asm/sysreg.h
use _BITUL() instead of BIT() so that the register bit macros are
available in assembly.
Using macros in include/uapi/linux/const.h have two reasons:
[1] For use in uapi headers
We should use underscore-prefixed variants for user-space.
[2] For use in assembly code
Since _BITUL() uses UL(1) instead of 1UL, it can be used as an
alternative of BIT().
For [2], it is pretty easy to change BIT() etc. for use in assembly.
This allows to replace _BUTUL() in kernel-space headers with BIT().
Link: http://lkml.kernel.org/r/20190609153941.17249-1-yamada.masahiro@xxxxxxxxxxxxx
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/bits.h | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
--- a/include/linux/bits.h~linux-bitsh-make-bit-genmask-and-friends-available-in-assembly
+++ a/include/linux/bits.h
@@ -1,13 +1,15 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_BITS_H
#define __LINUX_BITS_H
+
+#include <linux/const.h>
#include <asm/bitsperlong.h>
-#define BIT(nr) (1UL << (nr))
-#define BIT_ULL(nr) (1ULL << (nr))
-#define BIT_MASK(nr) (1UL << ((nr) % BITS_PER_LONG))
+#define BIT(nr) (UL(1) << (nr))
+#define BIT_ULL(nr) (ULL(1) << (nr))
+#define BIT_MASK(nr) (UL(1) << ((nr) % BITS_PER_LONG))
#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
-#define BIT_ULL_MASK(nr) (1ULL << ((nr) % BITS_PER_LONG_LONG))
+#define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG))
#define BIT_ULL_WORD(nr) ((nr) / BITS_PER_LONG_LONG)
#define BITS_PER_BYTE 8
@@ -17,10 +19,11 @@
* GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
*/
#define GENMASK(h, l) \
- (((~0UL) - (1UL << (l)) + 1) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
+ (((~UL(0)) - (UL(1) << (l)) + 1) & \
+ (~UL(0) >> (BITS_PER_LONG - 1 - (h))))
#define GENMASK_ULL(h, l) \
- (((~0ULL) - (1ULL << (l)) + 1) & \
- (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
+ (((~ULL(0)) - (ULL(1) << (l)) + 1) & \
+ (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))
#endif /* __LINUX_BITS_H */
_
Patches currently in -mm which might be from yamada.masahiro@xxxxxxxxxxxxx are
linux-bitsh-make-bit-genmask-and-friends-available-in-assembly.patch
arch-replace-_bitul-in-kernel-space-headers-with-bit.patch
