1 files changed, 192 insertions, 0 deletions

diff --git a/lib/math/div64.c b/lib/math/div64.c
new file mode 100644
index 000000000000..368ca7fd0d82
--- /dev/null
+++ b/lib/math/div64.c
@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
+ *
+ * Based on former do_div() implementation from asm-parisc/div64.h:
+ *      Copyright (C) 1999 Hewlett-Packard Co
+ *      Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
+ *
+ *
+ * Generic C version of 64bit/32bit division and modulo, with
+ * 64bit result and 32bit remainder.
+ *
+ * The fast case for (n>>32 == 0) is handled inline by do_div().
+ *
+ * Code generated for this function might be very inefficient
+ * for some CPUs. __div64_32() can be overridden by linking arch-specific
+ * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S
+ * or by defining a preprocessor macro in arch/include/asm/div64.h.
+ */
+
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/math64.h>
+
+/* Not needed on 64bit architectures */
+#if BITS_PER_LONG == 32
+
+#ifndef __div64_32
+uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
+{
+        uint64_t rem = *n;
+        uint64_t b = base;
+        uint64_t res, d = 1;
+        uint32_t high = rem >> 32;
+
+        /* Reduce the thing a bit first */
+        res = 0;
+        if (high >= base) {
+                high /= base;
+                res = (uint64_t) high << 32;
+                rem -= (uint64_t) (high*base) << 32;
+        }
+
+        while ((int64_t)b > 0 && b < rem) {
+                b = b+b;
+                d = d+d;
+        }
+
+        do {
+                if (rem >= b) {
+                        rem -= b;
+                        res += d;
+                }
+                b >>= 1;
+                d >>= 1;
+        } while (d);
+
+        *n = res;
+        return rem;
+}
+EXPORT_SYMBOL(__div64_32);
+#endif
+
+/**
+ * div_s64_rem - signed 64bit divide with 64bit divisor and remainder
+ * @dividend:   64bit dividend
+ * @divisor:    64bit divisor
+ * @remainder:  64bit remainder
+ */
+#ifndef div_s64_rem
+s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
+{
+        u64 quotient;
+
+        if (dividend < 0) {
+                quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
+                *remainder = -*remainder;
+                if (divisor > 0)
+                        quotient = -quotient;
+        } else {
+                quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
+                if (divisor < 0)
+                        quotient = -quotient;
+        }
+        return quotient;
+}
+EXPORT_SYMBOL(div_s64_rem);
+#endif
+
+/**
+ * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
+ * @dividend:   64bit dividend
+ * @divisor:    64bit divisor
+ * @remainder:  64bit remainder
+ *
+ * This implementation is a comparable to algorithm used by div64_u64.
+ * But this operation, which includes math for calculating the remainder,
+ * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
+ * systems.
+ */
+#ifndef div64_u64_rem
+u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
+{
+        u32 high = divisor >> 32;
+        u64 quot;
+
+        if (high == 0) {
+                u32 rem32;
+                quot = div_u64_rem(dividend, divisor, &rem32);
+                *remainder = rem32;
+        } else {
+                int n = fls(high);
+                quot = div_u64(dividend >> n, divisor >> n);
+
+                if (quot != 0)
+                        quot--;
+
+                *remainder = dividend - quot * divisor;
+                if (*remainder >= divisor) {
+                        quot++;
+                        *remainder -= divisor;
+                }
+        }
+
+        return quot;
+}
+EXPORT_SYMBOL(div64_u64_rem);
+#endif
+
+/**
+ * div64_u64 - unsigned 64bit divide with 64bit divisor
+ * @dividend:   64bit dividend
+ * @divisor:    64bit divisor
+ *
+ * This implementation is a modified version of the algorithm proposed
+ * by the book 'Hacker's Delight'.  The original source and full proof
+ * can be found here and is available for use without restriction.
+ *
+ * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
+ */
+#ifndef div64_u64
+u64 div64_u64(u64 dividend, u64 divisor)
+{
+        u32 high = divisor >> 32;
+        u64 quot;
+
+        if (high == 0) {
+                quot = div_u64(dividend, divisor);
+        } else {
+                int n = fls(high);
+                quot = div_u64(dividend >> n, divisor >> n);
+
+                if (quot != 0)
+                        quot--;
+                if ((dividend - quot * divisor) >= divisor)
+                        quot++;
+        }
+
+        return quot;
+}
+EXPORT_SYMBOL(div64_u64);
+#endif
+
+/**
+ * div64_s64 - signed 64bit divide with 64bit divisor
+ * @dividend:   64bit dividend
+ * @divisor:    64bit divisor
+ */
+#ifndef div64_s64
+s64 div64_s64(s64 dividend, s64 divisor)
+{
+        s64 quot, t;
+
+        quot = div64_u64(abs(dividend), abs(divisor));
+        t = (dividend ^ divisor) >> 63;
+
+        return (quot ^ t) - t;
+}
+EXPORT_SYMBOL(div64_s64);
+#endif
+
+#endif /* BITS_PER_LONG == 32 */
+
+/*
+ * Iterative div/mod for use when dividend is not expected to be much
+ * bigger than divisor.
+ */
+u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
+{
+        return __iter_div_u64_rem(dividend, divisor, remainder);
+}
+EXPORT_SYMBOL(iter_div_u64_rem);