Date: Mon, 7 Aug 2023 01:00:18 GMT From: "Bjoern A. Zeeb" <bz@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 1dcd1a539275 - main - LinuxKPI: implement get_random_u32_inclusive() Message-ID: <202308070100.37710InY087010@gitrepo.freebsd.org>
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The branch main has been updated by bz: URL: https://cgit.FreeBSD.org/src/commit/?id=1dcd1a539275fe69173bfc4dfc32c963fc7dcdbe commit 1dcd1a539275fe69173bfc4dfc32c963fc7dcdbe Author: Bjoern A. Zeeb <bz@FreeBSD.org> AuthorDate: 2023-05-16 21:03:30 +0000 Commit: Bjoern A. Zeeb <bz@FreeBSD.org> CommitDate: 2023-08-07 00:52:41 +0000 LinuxKPI: implement get_random_u32_inclusive() Implementation of get_random_u32_inclusive(). This is needed by an update for wireless drivers. Sponsored by: The FreeBSD Foundation MFC after: 10 days Differential Revision: https://reviews.freebsd.org/D40121 --- sys/compat/linuxkpi/common/include/linux/random.h | 30 +++++++++++++++++++++-- 1 file changed, 28 insertions(+), 2 deletions(-) diff --git a/sys/compat/linuxkpi/common/include/linux/random.h b/sys/compat/linuxkpi/common/include/linux/random.h index fafb87cae9fe..561953be277a 100644 --- a/sys/compat/linuxkpi/common/include/linux/random.h +++ b/sys/compat/linuxkpi/common/include/linux/random.h @@ -4,6 +4,10 @@ * Copyright (c) 2010 Panasas, Inc. * Copyright (c) 2013-2016 Mellanox Technologies, Ltd. * All rights reserved. + * Copyright 2023 The FreeBSD Foundation + * + * Portions of this software was developed by Björn Zeeb + * under sponsorship from the FreeBSD Foundation. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions @@ -36,8 +40,6 @@ #include <sys/random.h> #include <sys/libkern.h> -#define get_random_u32() get_random_int() - static inline void get_random_bytes(void *buf, int nbytes) { @@ -54,6 +56,30 @@ get_random_int(void) return (val); } +#define get_random_u32() get_random_int() + +/* + * See "Fast Random Integer Generation in an Interval" by Daniel Lemire + * [https://arxiv.org/pdf/1805.10941.pdf] for implementation insights. + */ +static inline uint32_t +get_random_u32_inclusive(uint32_t floor, uint32_t ceil) +{ + uint64_t x; + uint32_t t, v; + + MPASS(ceil >= floor); + + v = get_random_u32(); + t = ceil - floor + 1; + x = (uint64_t)t * v; + while (x < t) + x = (uint64_t)t * get_random_u32(); + v = x >> 32; + + return (floor + v); +} + static inline u_long get_random_long(void) {
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