diff options
Diffstat (limited to 'include/linux/random.h')
| -rw-r--r-- | include/linux/random.h | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/include/linux/random.h b/include/linux/random.h index 3203d13c..9b2bb59a 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -9,7 +9,9 @@ #include <unistd.h> #include <sys/syscall.h> #include <linux/bug.h> +#include <linux/kernel.h> #include <linux/log2.h> +#include <linux/math64.h> #ifdef SYS_getrandom static inline int getrandom(void *buf, size_t buflen, unsigned int flags) @@ -67,4 +69,19 @@ static inline u32 get_random_u32_below(u32 ceil) } } +static inline u64 get_random_u64_below(u64 ceil) +{ + if (ceil <= 1) + return 0; + if (ceil <= U32_MAX) + return get_random_u32_below(ceil); + + for (;;) { + u64 rand = get_random_u64(); + u64 mult = ceil * rand; + if (likely(mult >= -ceil % ceil)) + return mul_u64_u64_shr(ceil, rand, 64); + } +} + #endif /* _LINUX_RANDOM_H */ |