From: Martin Kepplinger <martink@xxxxxxxxx> This patch has been added to the stable tree. If you have any objections, please let us know. =============== [ Upstream commit 48e203e21b29cd4b2c58403fe8bca68e2e854895 ] Months back, this was discussed, see https://lkml.org/lkml/2015/1/18/289 The result was the 64-bit version being "likely fine", "valuable" and "correct". The discussion fell asleep but since there are possible users, let's add it. Signed-off-by: Martin Kepplinger <martin.kepplinger@xxxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: George Spelvin <linux@xxxxxxxxxxx> Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> Cc: Maxime Coquelin <maxime.coquelin@xxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: Yury Norov <yury.norov@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> --- include/linux/bitops.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 297f5bda4fdf..858020682ac8 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -171,6 +171,17 @@ static inline __s32 sign_extend32(__u32 value, int index) return (__s32)(value << shift) >> shift; } +/** + * sign_extend64 - sign extend a 64-bit value using specified bit as sign-bit + * @value: value to sign extend + * @index: 0 based bit index (0<=index<64) to sign bit + */ +static inline __s64 sign_extend64(__u64 value, int index) +{ + __u8 shift = 63 - index; + return (__s64)(value << shift) >> shift; +} + static inline unsigned fls_long(unsigned long l) { if (sizeof(l) == 4) -- 2.11.0