microblaze: Futex support

Microblaze v7.20 provides new lwx, swx instructions which bring
possibility to implement lock rutines.

There are some tests in open posix thread LTP part but current
toolchain not support it.
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/include/asm/futex.h

-#include <asm-generic/futex.h>
+#ifndef _ASM_MICROBLAZE_FUTEX_H
+#define _ASM_MICROBLAZE_FUTEX_H
+
+#ifdef __KERNEL__
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <asm/errno.h>
+
+#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
+({									\
+	__asm__ __volatile__ (						\
+			"1:	lwx	%0, %2, r0; "			\
+				insn					\
+			"2:	swx	%1, %2, r0;			\
+				addic	%1, r0, 0;			\
+				bnei	%1, 1b;				\
+			3:						\
+			.section .fixup,\"ax\";				\
+			4:	brid	3b;				\
+				addik	%1, r0, %3;			\
+			.previous;					\
+			.section __ex_table,\"a\";			\
+			.word	1b,4b,2b,4b;				\
+			.previous;"					\
+	: "=&r" (oldval), "=&r" (ret)					\
+	: "b" (uaddr), "i" (-EFAULT), "r" (oparg)			\
+	);								\
+})
+
+static inline int
+futex_atomic_op_inuser(int encoded_op, int __user *uaddr)
+{
+	int op = (encoded_op >> 28) & 7;
+	int cmp = (encoded_op >> 24) & 15;
+	int oparg = (encoded_op << 8) >> 20;
+	int cmparg = (encoded_op << 20) >> 20;
+	int oldval = 0, ret;
+	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
+		oparg = 1 << oparg;
+
+	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+		return -EFAULT;
+
+	pagefault_disable();
+
+	switch (op) {
+	case FUTEX_OP_SET:
+		__futex_atomic_op("or %1,%4,%4;", ret, oldval, uaddr, oparg);
+		break;
+	case FUTEX_OP_ADD:
+		__futex_atomic_op("add %1,%0,%4;", ret, oldval, uaddr, oparg);
+		break;
+	case FUTEX_OP_OR:
+		__futex_atomic_op("or %1,%0,%4;", ret, oldval, uaddr, oparg);
+		break;
+	case FUTEX_OP_ANDN:
+		__futex_atomic_op("and %1,%0,%4;", ret, oldval, uaddr, oparg);
+		break;
+	case FUTEX_OP_XOR:
+		__futex_atomic_op("xor %1,%0,%4;", ret, oldval, uaddr, oparg);
+		break;
+	default:
+		ret = -ENOSYS;
+	}
+
+	pagefault_enable();
+
+	if (!ret) {
+		switch (cmp) {
+		case FUTEX_OP_CMP_EQ:
+			ret = (oldval == cmparg);
+			break;
+		case FUTEX_OP_CMP_NE:
+			ret = (oldval != cmparg);
+			break;
+		case FUTEX_OP_CMP_LT:
+			ret = (oldval < cmparg);
+			break;
+		case FUTEX_OP_CMP_GE:
+			ret = (oldval >= cmparg);
+			break;
+		case FUTEX_OP_CMP_LE:
+			ret = (oldval <= cmparg);
+			break;
+		case FUTEX_OP_CMP_GT:
+			ret = (oldval > cmparg);
+			break;
+		default:
+			ret = -ENOSYS;
+		}
+	}
+	return ret;
+}
+
+static inline int
+futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
+{
+	int prev, cmp;
+
+	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+		return -EFAULT;
+
+	__asm__ __volatile__ ("1:	lwx	%0, %2, r0;		\
+					cmp	%1, %0, %3;		\
+					beqi	%1, 3f;			\
+				2:	swx	%4, %2, r0;		\
+					addic	%1, r0, 0;		\
+					bnei	%1, 1b;			\
+				3:					\
+				.section .fixup,\"ax\";			\
+				4:	brid	3b;			\
+					addik	%0, r0, %5;		\
+				.previous;				\
+				.section __ex_table,\"a\";		\
+				.word	1b,4b,2b,4b;			\
+				.previous;"				\
+		: "=&r" (prev), "=&r"(cmp)				\
+		: "r" (uaddr), "r" (oldval), "r" (newval), "i" (-EFAULT));
+
+	return prev;
+}
+
+#endif /* __KERNEL__ */
+
+#endif