cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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int_sqrt.c (1179B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Copyright (C) 2013 Davidlohr Bueso <davidlohr.bueso@hp.com>
      4 *
      5 *  Based on the shift-and-subtract algorithm for computing integer
      6 *  square root from Guy L. Steele.
      7 */
      8
      9#include <linux/export.h>
     10#include <linux/bitops.h>
     11#include <linux/limits.h>
     12#include <linux/math.h>
     13
     14/**
     15 * int_sqrt - computes the integer square root
     16 * @x: integer of which to calculate the sqrt
     17 *
     18 * Computes: floor(sqrt(x))
     19 */
     20unsigned long int_sqrt(unsigned long x)
     21{
     22	unsigned long b, m, y = 0;
     23
     24	if (x <= 1)
     25		return x;
     26
     27	m = 1UL << (__fls(x) & ~1UL);
     28	while (m != 0) {
     29		b = y + m;
     30		y >>= 1;
     31
     32		if (x >= b) {
     33			x -= b;
     34			y += m;
     35		}
     36		m >>= 2;
     37	}
     38
     39	return y;
     40}
     41EXPORT_SYMBOL(int_sqrt);
     42
     43#if BITS_PER_LONG < 64
     44/**
     45 * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input
     46 * is expected.
     47 * @x: 64bit integer of which to calculate the sqrt
     48 */
     49u32 int_sqrt64(u64 x)
     50{
     51	u64 b, m, y = 0;
     52
     53	if (x <= ULONG_MAX)
     54		return int_sqrt((unsigned long) x);
     55
     56	m = 1ULL << ((fls64(x) - 1) & ~1ULL);
     57	while (m != 0) {
     58		b = y + m;
     59		y >>= 1;
     60
     61		if (x >= b) {
     62			x -= b;
     63			y += m;
     64		}
     65		m >>= 2;
     66	}
     67
     68	return y;
     69}
     70EXPORT_SYMBOL(int_sqrt64);
     71#endif