arm64: User access library functions
This patch add support for various user access functions. These
functions use the standard LDR/STR instructions and not the LDRT/STRT
variants in order to allow kernel addresses (after set_fs(KERNEL_DS)).
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/arch/arm64/lib/strnlen_user.S b/arch/arm64/lib/strnlen_user.S
new file mode 100644
index 0000000..7f7b176
--- /dev/null
+++ b/arch/arm64/lib/strnlen_user.S
@@ -0,0 +1,47 @@
+/*
+ * Based on arch/arm/lib/strnlen_user.S
+ *
+ * Copyright (C) 1995-2000 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+#include <asm/errno.h>
+
+ .text
+ .align 5
+
+/* Prototype: unsigned long __strnlen_user(const char *str, long n)
+ * Purpose : get length of a string in user memory
+ * Params : str - address of string in user memory
+ * Returns : length of string *including terminator*
+ * or zero on exception, or n if too long
+ */
+ENTRY(__strnlen_user)
+ mov x2, x0
+1: subs x1, x1, #1
+ b.mi 2f
+USER(9f, ldrb w3, [x0], #1 )
+ cbnz w3, 1b
+2: sub x0, x0, x2
+ ret
+ENDPROC(__strnlen_user)
+
+ .section .fixup,"ax"
+ .align 0
+9: mov x0, #0
+ ret
+ .previous