linux-kernel - [PATCH 2/2] ARC: provide optimal __get_user

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Date:	Tue, 20 Nov 2012 20:08:17 +0530
From:	<Vineet.Gupta1@...opsys.com>
To:	<arnd@...db.de>
CC:	<linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: [PATCH 2/2] ARC: provide optimal __get_user_fn()

From: Vineet Gupta <vgupta@...opsys.com>

Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
 arch/arc/include/asm/uaccess.h |   51 ++++++++++++++++++++++++++++++++++++++++
 1 files changed, 51 insertions(+), 0 deletions(-)

diff --git a/arch/arc/include/asm/uaccess.h b/arch/arc/include/asm/uaccess.h
index 503c98d..d9cbae4 100644
--- a/arch/arc/include/asm/uaccess.h
+++ b/arch/arc/include/asm/uaccess.h
@@ -35,6 +35,57 @@
 #define __access_ok(addr, sz)	(unlikely(__kernel_ok) || \
 				 likely(__user_ok((addr), (sz))))
 
+/*********** Single byte/s-word/word copies ******************/
+
+#define __get_user_fn(sz, u, k)					\
+({								\
+	long __ret = 0;	/* success by default */	\
+	switch (sz) {						\
+	case 1: __arc_get_user_one(*(k), u, "ldb", __ret); break;	\
+	case 2: __arc_get_user_one(*(k), u, "ldw", __ret); break;	\
+	case 4: __arc_get_user_one(*(k), u, "ld", __ret);  break;	\
+	case 8: __arc_get_user_one_64(*(k), u, __ret);     break;	\
+	}							\
+	__ret;							\
+})
+
+#define __arc_get_user_one(dst, src, op, ret)	\
+	__asm__ __volatile__(                   \
+	"1:	"op"    %1,[%2]\n"		\
+	"2:	;nop\n"				\
+	"	.section .fixup, \"ax\"\n"	\
+	"	.align 4\n"			\
+	"3:	mov %0, %3\n"			\
+	"	j   2b\n"			\
+	"	.previous\n"			\
+	"	.section __ex_table, \"a\"\n"	\
+	"	.align 4\n"			\
+	"	.word 1b,3b\n"			\
+	"	.previous\n"			\
+						\
+	: "+r" (ret), "=r" (dst)		\
+	: "r" (src), "i" (-EFAULT))
+
+#define __arc_get_user_one_64(dst, src, ret)	\
+	__asm__ __volatile__(                   \
+	"1:	ld   %1,[%2]\n"			\
+	"4:	ld  %R1,[%2, 4]\n"		\
+	"2:	;nop\n"				\
+	"	.section .fixup, \"ax\"\n"	\
+	"	.align 4\n"			\
+	"3:	mov %0, %3\n"			\
+	"	j   2b\n"			\
+	"	.previous\n"			\
+	"	.section __ex_table, \"a\"\n"	\
+	"	.align 4\n"			\
+	"	.word 1b,3b\n"			\
+	"	.word 4b,3b\n"			\
+	"	.previous\n"			\
+						\
+	: "+r" (ret), "=r" (dst)		\
+	: "r" (src), "i" (-EFAULT))
+
+
 static inline unsigned long
 __arc_copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-- 
1.7.4.1

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