lib: Add strongly typed 64bit int_sqrt

PATCH Superseded Crt Mori 1 participant 1 message Dec 6, 2017

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Crt Mori

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2017-12-06 09:56 UTC #0 lore raw

PATCH v3 3/3 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 <[email protected]>

---
 include/linux/kernel.h |  1 +
 lib/int_sqrt.c         | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

include/linux/kernel.h +1 -0

index 0ad4c3044cf9..09f53063f2c9 100644
@@ -459,6 +459,7 @@ extern int kernel_text_address(unsigned long addr);
 extern int func_ptr_is_kernel_text(void *ptr);
 
 unsigned long int_sqrt(unsigned long);
+u64 int_sqrt64(u64 x);
 
 extern void bust_spinlocks(int yes);
 extern int oops_in_progress;		/* If set, an oops, panic(), BUG() or die() is in progress */

lib/int_sqrt.c +26 -0

index 1ef4cc344977..de5836448ea3 100644
@@ -36,3 +36,29 @@ unsigned long int_sqrt(unsigned long x)
 	return y;
 }
 EXPORT_SYMBOL(int_sqrt);
+
+/**
+ * int_sqrt64 - strongly typed int_sqrt function
+ * @x: 64bit integer of which to calculate the sqrt
+ */
+u64 int_sqrt64(u64 x)
+{
+	u64 b, m, y = 0;
+
+	if (x <= 1)
+		return x;
+
+	m = 1ULL << (64 - 2);
+	while (m != 0) {
+		b = y + m;
+		y >>= 1;
+
+		if (x >= b) {
+			x -= b;
+			y += m;
+		}
+		m >>= 2;
+	}
+	return y;
+}
+EXPORT_SYMBOL(int_sqrt64);

Signature · 1 line

2.15.0