kernel/arch/csky/include/asm/bitops.h, branch linux-rolling-stable

csky: Add __attribute_const__ to ffs()-family implementations

2025-09-08T21:58:50Z

While tracking down a problem where constant expressions used by BUILD_BUG_ON() suddenly stopped working[1], we found that an added static initializer was convincing the compiler that it couldn't track the state of the prior statically initialized value. Tracing this down found that ffs() was used in the initializer macro, but since it wasn't marked with __attribute__const__, the compiler had to assume the function might change variable states as a side-effect (which is not true for ffs(), which provides deterministic math results). Add missing __attribute_const__ annotations to C-SKY's implementations of ffs(), __ffs(), fls(), and __fls() functions. These are pure mathematical functions that always return the same result for the same input with no side effects, making them eligible for compiler optimization. Build tested ARCH=csky defconfig with GCC csky-linux 15.1.0. Link: https://github.com/KSPP/linux/issues/364 [1] Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250804164417.1612371-3-kees@kernel.org Signed-off-by: Kees Cook

include: move find.h from asm_generic to linux

2022-01-15T16:47:31Z

find_bit API and bitmap API are closely related, but inclusion paths are different - include/asm-generic and include/linux, correspondingly. In the past it made a lot of troubles due to circular dependencies and/or undefined symbols. Fix this by moving find.h under include/linux. Signed-off-by: Yury Norov Tested-by: Wolfram Sang Acked-by: Geert Uytterhoeven

csky: bitops: Remove duplicate __clear_bit define

2021-10-15T23:20:12Z

Building csky:allmodconfig results in the following build error. In file included from ./include/linux/bitops.h:33, from ./include/linux/log2.h:12, from kernel/bounds.c:13: ./arch/csky/include/asm/bitops.h:77: error: "__clear_bit" redefined Since commit 9248e52fec95 ("locking/atomic: simplify non-atomic wrappers"), __clear_bit is defined in include/asm-generic/bitops/non-atomic.h, and the define in the csky include file is no longer necessary or useful. Remove it. Fixes: 9248e52fec95 ("locking/atomic: simplify non-atomic wrappers") Signed-off-by: Guenter Roeck Signed-off-by: Guo Ren

csky: Fixup compile error

2021-02-27T14:04:14Z

fls: change parameter to unsigned int

2019-01-04T21:13:46Z

When testing in userspace, UBSAN pointed out that shifting into the sign bit is undefined behaviour. It doesn't really make sense to ask for the highest set bit of a negative value, so just turn the argument type into an unsigned int. Some architectures (eg ppc) already had it declared as an unsigned int, so I don't expect too many problems. Link: http://lkml.kernel.org/r/20181105221117.31828-1-willy@infradead.org Signed-off-by: Matthew Wilcox Acked-by: Thomas Gleixner Acked-by: Geert Uytterhoeven Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

csky: Misc headers

2018-10-25T16:54:26Z

This patch adds csky registers' definition, bitops, byteorder, asm-offsets codes. Signed-off-by: Guo Ren Reviewed-by: Arnd Bergmann