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![Andy Shevchenko](/assets/img/avatar_default.png)
kernel.h is being used as a dump for all kinds of stuff for a long time. Here is the attempt to start cleaning it up by splitting out mathematical helpers. At the same time convert users in header and lib folder to use new header. Though for time being include new header back to kernel.h to avoid twisted indirected includes for existing users. [sfr@canb.auug.org.au: fix powerpc build] Link: https://lkml.kernel.org/r/20201029150809.13059608@canb.auug.org.au Link: https://lkml.kernel.org/r/20201028173212.41768-1-andriy.shevchenko@linux.intel.com Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Trond Myklebust <trond.myklebust@hammerspace.com> Cc: Jeff Layton <jlayton@kernel.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
235 lines
5.1 KiB
C
235 lines
5.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
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*
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* Based on former do_div() implementation from asm-parisc/div64.h:
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* Copyright (C) 1999 Hewlett-Packard Co
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* Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
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*
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*
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* Generic C version of 64bit/32bit division and modulo, with
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* 64bit result and 32bit remainder.
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*
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* The fast case for (n>>32 == 0) is handled inline by do_div().
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*
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* Code generated for this function might be very inefficient
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* for some CPUs. __div64_32() can be overridden by linking arch-specific
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* assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S
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* or by defining a preprocessor macro in arch/include/asm/div64.h.
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*/
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#include <linux/bitops.h>
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#include <linux/export.h>
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#include <linux/math.h>
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#include <linux/math64.h>
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#include <linux/log2.h>
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/* Not needed on 64bit architectures */
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#if BITS_PER_LONG == 32
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#ifndef __div64_32
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uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
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{
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uint64_t rem = *n;
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uint64_t b = base;
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uint64_t res, d = 1;
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uint32_t high = rem >> 32;
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/* Reduce the thing a bit first */
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res = 0;
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if (high >= base) {
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high /= base;
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res = (uint64_t) high << 32;
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rem -= (uint64_t) (high*base) << 32;
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}
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while ((int64_t)b > 0 && b < rem) {
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b = b+b;
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d = d+d;
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}
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do {
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if (rem >= b) {
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rem -= b;
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res += d;
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}
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b >>= 1;
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d >>= 1;
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} while (d);
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*n = res;
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return rem;
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}
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EXPORT_SYMBOL(__div64_32);
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#endif
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/**
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* div_s64_rem - signed 64bit divide with 64bit divisor and remainder
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* @dividend: 64bit dividend
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* @divisor: 64bit divisor
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* @remainder: 64bit remainder
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*/
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#ifndef div_s64_rem
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s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
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{
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u64 quotient;
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if (dividend < 0) {
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quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
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*remainder = -*remainder;
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if (divisor > 0)
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quotient = -quotient;
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} else {
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quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
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if (divisor < 0)
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quotient = -quotient;
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}
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return quotient;
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}
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EXPORT_SYMBOL(div_s64_rem);
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#endif
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/**
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* div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
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* @dividend: 64bit dividend
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* @divisor: 64bit divisor
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* @remainder: 64bit remainder
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*
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* This implementation is a comparable to algorithm used by div64_u64.
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* But this operation, which includes math for calculating the remainder,
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* is kept distinct to avoid slowing down the div64_u64 operation on 32bit
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* systems.
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*/
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#ifndef div64_u64_rem
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u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
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{
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u32 high = divisor >> 32;
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u64 quot;
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if (high == 0) {
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u32 rem32;
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quot = div_u64_rem(dividend, divisor, &rem32);
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*remainder = rem32;
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} else {
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int n = fls(high);
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quot = div_u64(dividend >> n, divisor >> n);
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if (quot != 0)
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quot--;
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*remainder = dividend - quot * divisor;
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if (*remainder >= divisor) {
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quot++;
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*remainder -= divisor;
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}
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}
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return quot;
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}
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EXPORT_SYMBOL(div64_u64_rem);
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#endif
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/**
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* div64_u64 - unsigned 64bit divide with 64bit divisor
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* @dividend: 64bit dividend
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* @divisor: 64bit divisor
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*
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* This implementation is a modified version of the algorithm proposed
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* by the book 'Hacker's Delight'. The original source and full proof
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* can be found here and is available for use without restriction.
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*
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* 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
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*/
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#ifndef div64_u64
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u64 div64_u64(u64 dividend, u64 divisor)
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{
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u32 high = divisor >> 32;
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u64 quot;
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if (high == 0) {
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quot = div_u64(dividend, divisor);
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} else {
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int n = fls(high);
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quot = div_u64(dividend >> n, divisor >> n);
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if (quot != 0)
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quot--;
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if ((dividend - quot * divisor) >= divisor)
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quot++;
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}
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return quot;
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}
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EXPORT_SYMBOL(div64_u64);
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#endif
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/**
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* div64_s64 - signed 64bit divide with 64bit divisor
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* @dividend: 64bit dividend
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* @divisor: 64bit divisor
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*/
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#ifndef div64_s64
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s64 div64_s64(s64 dividend, s64 divisor)
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{
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s64 quot, t;
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quot = div64_u64(abs(dividend), abs(divisor));
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t = (dividend ^ divisor) >> 63;
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return (quot ^ t) - t;
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}
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EXPORT_SYMBOL(div64_s64);
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#endif
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#endif /* BITS_PER_LONG == 32 */
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/*
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* Iterative div/mod for use when dividend is not expected to be much
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* bigger than divisor.
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*/
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u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
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{
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return __iter_div_u64_rem(dividend, divisor, remainder);
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}
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EXPORT_SYMBOL(iter_div_u64_rem);
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#ifndef mul_u64_u64_div_u64
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u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c)
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{
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u64 res = 0, div, rem;
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int shift;
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/* can a * b overflow ? */
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if (ilog2(a) + ilog2(b) > 62) {
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/*
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* (b * a) / c is equal to
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*
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* (b / c) * a +
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* (b % c) * a / c
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*
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* if nothing overflows. Can the 1st multiplication
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* overflow? Yes, but we do not care: this can only
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* happen if the end result can't fit in u64 anyway.
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*
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* So the code below does
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*
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* res = (b / c) * a;
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* b = b % c;
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*/
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div = div64_u64_rem(b, c, &rem);
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res = div * a;
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b = rem;
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shift = ilog2(a) + ilog2(b) - 62;
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if (shift > 0) {
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/* drop precision */
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b >>= shift;
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c >>= shift;
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if (!c)
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return res;
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}
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}
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return res + div64_u64(a * b, c);
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}
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#endif
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