linux/arch/arm64/lib/strncpy_from_user.S
Catalin Marinas 0aea86a217 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>
2012-09-17 13:42:11 +01:00

51 lines
1.3 KiB
ArmAsm

/*
* Based on arch/arm/lib/strncpy_from_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
/*
* Copy a string from user space to kernel space.
* x0 = dst, x1 = src, x2 = byte length
* returns the number of characters copied (strlen of copied string),
* -EFAULT on exception, or "len" if we fill the whole buffer
*/
ENTRY(__strncpy_from_user)
mov x4, x1
1: subs x2, x2, #1
bmi 2f
USER(9f, ldrb w3, [x1], #1 )
strb w3, [x0], #1
cbnz w3, 1b
sub x1, x1, #1 // take NUL character out of count
2: sub x0, x1, x4
ret
ENDPROC(__strncpy_from_user)
.section .fixup,"ax"
.align 0
9: strb wzr, [x0] // null terminate
mov x0, #-EFAULT
ret
.previous