Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758816AbeAIPTG (ORCPT + 1 other); Tue, 9 Jan 2018 10:19:06 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:35365 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758665AbeAIPTD (ORCPT ); Tue, 9 Jan 2018 10:19:03 -0500 X-Google-Smtp-Source: ACJfBov9iE06djsHk3m9mvhs9L5LG/gvlvDzNj49x6OoTWTjepAdR/WNyiuiKDpRIHSVm/bBk2nE9A== From: Crt Mori To: Jonathan Cameron Cc: Ingo Molnar , Andrew Morton , Kees Cook , Rusty Russell , Ian Abbott , Larry Finger , Niklas Soderlund , Thomas Gleixner , Krzysztof Kozlowski , Masahiro Yamada , linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, Peter Zijlstra , Joe Perches , David Laight , Crt Mori Subject: [PATCH v12 1/3] lib: Add strongly typed 64bit int_sqrt Date: Tue, 9 Jan 2018 16:18:47 +0100 Message-Id: <20180109151847.30258-1-cmo@melexis.com> X-Mailer: git-send-email 2.15.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: There is no option to perform 64bit integer sqrt on 32bit platform. Added stronger typed int_sqrt64 enables the 64bit calculations to be performed on 32bit platforms. Using same algorithm as int_sqrt() with strong typing provides enough precision also on 32bit platforms, but it sacrifices some performance. Signed-off-by: Crt Mori --- include/linux/kernel.h | 9 +++++++++ lib/int_sqrt.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 0ad4c3044cf9..e4a3dc64e650 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -460,6 +460,15 @@ extern int func_ptr_is_kernel_text(void *ptr); unsigned long int_sqrt(unsigned long); +#if BITS_PER_LONG < 64 +u32 int_sqrt64(u64 x); +#else +static inline u32 int_sqrt64(u64 x) +{ + return (u32)int_sqrt(x); +} +#endif + extern void bust_spinlocks(int yes); extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */ extern int panic_timeout; diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c index 1ef4cc344977..737fca54bb02 100644 --- a/lib/int_sqrt.c +++ b/lib/int_sqrt.c @@ -7,6 +7,7 @@ #include #include +#include /** * int_sqrt - rough approximation to sqrt @@ -36,3 +37,34 @@ unsigned long int_sqrt(unsigned long x) return y; } EXPORT_SYMBOL(int_sqrt); + +#if BITS_PER_LONG < 64 +/** + * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input + * is expected. + * @x: 64bit integer of which to calculate the sqrt + */ +u32 int_sqrt64(u64 x) +{ + u64 b, m; + u32 y = 0; + + if (x <= 1) + return x; + + m = 1ULL << (fls64(x) & ~1ULL); + while (m != 0) { + b = y + m; + y >>= 1; + + if (x >= b) { + x -= b; + y += m; + } + m >>= 2; + } + + return y; +} +EXPORT_SYMBOL(int_sqrt64); +#endif -- 2.15.0