1 files changed, 120 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
new file mode 100644
index 000000000..bc06691d2
--- /dev/null
+++ b/arch/arm64/include/asm/futex.h
@@ -0,0 +1,120 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ */
+#ifndef __ASM_FUTEX_H
+#define __ASM_FUTEX_H
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+
+#include <asm/errno.h>
+
+#define FUTEX_MAX_LOOPS	128 /* What's the largest number you can think of? */
+
+#define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg)		\
+do {									\
+	unsigned int loops = FUTEX_MAX_LOOPS;				\
+									\
+	uaccess_enable_privileged();					\
+	asm volatile(							\
+"	prfm	pstl1strm, %2\n"					\
+"1:	ldxr	%w1, %2\n"						\
+	insn "\n"							\
+"2:	stlxr	%w0, %w3, %2\n"						\
+"	cbz	%w0, 3f\n"						\
+"	sub	%w4, %w4, %w0\n"					\
+"	cbnz	%w4, 1b\n"						\
+"	mov	%w0, %w6\n"						\
+"3:\n"									\
+"	dmb	ish\n"							\
+	_ASM_EXTABLE_UACCESS_ERR(1b, 3b, %w0)				\
+	_ASM_EXTABLE_UACCESS_ERR(2b, 3b, %w0)				\
+	: "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp),	\
+	  "+r" (loops)							\
+	: "r" (oparg), "Ir" (-EAGAIN)					\
+	: "memory");							\
+	uaccess_disable_privileged();					\
+} while (0)
+
+static inline int
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *_uaddr)
+{
+	int oldval = 0, ret, tmp;
+	u32 __user *uaddr = __uaccess_mask_ptr(_uaddr);
+
+	if (!access_ok(_uaddr, sizeof(u32)))
+		return -EFAULT;
+
+	switch (op) {
+	case FUTEX_OP_SET:
+		__futex_atomic_op("mov	%w3, %w5",
+				  ret, oldval, uaddr, tmp, oparg);
+		break;
+	case FUTEX_OP_ADD:
+		__futex_atomic_op("add	%w3, %w1, %w5",
+				  ret, oldval, uaddr, tmp, oparg);
+		break;
+	case FUTEX_OP_OR:
+		__futex_atomic_op("orr	%w3, %w1, %w5",
+				  ret, oldval, uaddr, tmp, oparg);
+		break;
+	case FUTEX_OP_ANDN:
+		__futex_atomic_op("and	%w3, %w1, %w5",
+				  ret, oldval, uaddr, tmp, ~oparg);
+		break;
+	case FUTEX_OP_XOR:
+		__futex_atomic_op("eor	%w3, %w1, %w5",
+				  ret, oldval, uaddr, tmp, oparg);
+		break;
+	default:
+		ret = -ENOSYS;
+	}
+
+	if (!ret)
+		*oval = oldval;
+
+	return ret;
+}
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *_uaddr,
+			      u32 oldval, u32 newval)
+{
+	int ret = 0;
+	unsigned int loops = FUTEX_MAX_LOOPS;
+	u32 val, tmp;
+	u32 __user *uaddr;
+
+	if (!access_ok(_uaddr, sizeof(u32)))
+		return -EFAULT;
+
+	uaddr = __uaccess_mask_ptr(_uaddr);
+	uaccess_enable_privileged();
+	asm volatile("// futex_atomic_cmpxchg_inatomic\n"
+"	prfm	pstl1strm, %2\n"
+"1:	ldxr	%w1, %2\n"
+"	sub	%w3, %w1, %w5\n"
+"	cbnz	%w3, 4f\n"
+"2:	stlxr	%w3, %w6, %2\n"
+"	cbz	%w3, 3f\n"
+"	sub	%w4, %w4, %w3\n"
+"	cbnz	%w4, 1b\n"
+"	mov	%w0, %w7\n"
+"3:\n"
+"	dmb	ish\n"
+"4:\n"
+	_ASM_EXTABLE_UACCESS_ERR(1b, 4b, %w0)
+	_ASM_EXTABLE_UACCESS_ERR(2b, 4b, %w0)
+	: "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp), "+r" (loops)
+	: "r" (oldval), "r" (newval), "Ir" (-EAGAIN)
+	: "memory");
+	uaccess_disable_privileged();
+
+	if (!ret)
+		*uval = val;
+
+	return ret;
+}
+
+#endif /* __ASM_FUTEX_H */