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Message-Id: <20171220142001.18161-1-cmo@melexis.com> Date: Wed, 20 Dec 2017 15:20:01 +0100 From: Crt Mori <cmo@...exis.com> To: Jonathan Cameron <jic23@...nel.org> Cc: Ingo Molnar <mingo@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, Rusty Russell <rusty@...tcorp.com.au>, Ian Abbott <abbotti@....co.uk>, Larry Finger <Larry.Finger@...inger.net>, Niklas Soderlund <niklas.soderlund+renesas@...natech.se>, Thomas Gleixner <tglx@...utronix.de>, Krzysztof Kozlowski <krzk@...nel.org>, Masahiro Yamada <yamada.masahiro@...ionext.com>, linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>, Joe Perches <joe@...ches.com>, Crt Mori <cmo@...exis.com> Subject: [PATCH v10 1/3] lib: Add strongly typed 64bit int_sqrt 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. Although int_sqrt() is a rough approximation, the same algorithm is used in int_sqrt64() as good enough on 32bit platform. Signed-off-by: Crt Mori <cmo@...exis.com> --- include/linux/kernel.h | 9 +++++++++ lib/int_sqrt.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 40 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..184da54677ec 100644 --- a/lib/int_sqrt.c +++ b/lib/int_sqrt.c @@ -7,6 +7,7 @@ #include <linux/kernel.h> #include <linux/export.h> +#include <linux/bitops.h> /** * int_sqrt - rough approximation to sqrt @@ -36,3 +37,33 @@ 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, 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
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