x86, um: ... and asm-x86 move

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

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 00000000000..f9530f23f1d
--- /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 */