1 files changed, 60 insertions, 0 deletions

diff --git a/arch/x86/include/asm/div64.h b/arch/x86/include/asm/div64.h
new file mode 100644
index 000000000000..f9530f23f1d6
--- /dev/null
+++ b/arch/x86/include/asm/div64.h
@@ -0,0 +1,60 @@
+#ifndef ASM_X86__DIV64_H
+#define ASM_X86__DIV64_H
+
+#ifdef CONFIG_X86_32
+
+#include <linux/types.h>
+
+/*
+ * do_div() is NOT a C function. It wants to return
+ * two values (the quotient and the remainder), but
+ * since that doesn't work very well in C, what it
+ * does is:
+ *
+ * - modifies the 64-bit dividend _in_place_
+ * - returns the 32-bit remainder
+ *
+ * This ends up being the most efficient "calling
+ * convention" on x86.
+ */
+#define do_div(n, base)                                         \
+({                                                              \
+        unsigned long __upper, __low, __high, __mod, __base;    \
+        __base = (base);                                        \
+        asm("":"=a" (__low), "=d" (__high) : "A" (n));          \
+        __upper = __high;                                       \
+        if (__high) {                                           \
+                __upper = __high % (__base);                    \
+                __high = __high / (__base);                     \
+        }                                                       \
+        asm("divl %2":"=a" (__low), "=d" (__mod)                \
+            : "rm" (__base), "0" (__low), "1" (__upper));       \
+        asm("":"=A" (n) : "a" (__low), "d" (__high));           \
+        __mod;                                                  \
+})
+
+static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
+{
+        union {
+                u64 v64;
+                u32 v32[2];
+        } d = { dividend };
+        u32 upper;
+
+        upper = d.v32[1];
+        d.v32[1] = 0;
+        if (upper >= divisor) {
+                d.v32[1] = upper / divisor;
+                upper %= divisor;
+        }
+        asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) :
+                "rm" (divisor), "0" (d.v32[0]), "1" (upper));
+        return d.v64;
+}
+#define div_u64_rem     div_u64_rem
+
+#else
+# include <asm-generic/div64.h>
+#endif /* CONFIG_X86_32 */
+
+#endif /* ASM_X86__DIV64_H */