arch/arm64/lib/strncpy_from_user.S

   1 /*
   2  * Based on arch/arm/lib/strncpy_from_user.S
   3  *
   4  * Copyright (C) 1995-2000 Russell King
   5  * Copyright (C) 2012 ARM Ltd.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/linkage.h>
  21 #include <asm/assembler.h>
  22 #include <asm/errno.h>
  23
  24         .text
  25         .align  5
  26
  27 /*
  28  * Copy a string from user space to kernel space.
  29  *  x0 = dst, x1 = src, x2 = byte length
  30  * returns the number of characters copied (strlen of copied string),
  31  *  -EFAULT on exception, or "len" if we fill the whole buffer
  32  */
  33 ENTRY(__strncpy_from_user)
  34         mov     x4, x1
  35 1:      subs    x2, x2, #1
  36         bmi     2f
  37 USER(9f, ldrb   w3, [x1], #1    )
  38         strb    w3, [x0], #1
  39         cbnz    w3, 1b
  40         sub     x1, x1, #1      // take NUL character out of count
  41 2:      sub     x0, x1, x4
  42         ret
  43 ENDPROC(__strncpy_from_user)
  44
  45         .section .fixup,"ax"
  46         .align  0
  47 9:      strb    wzr, [x0]       // null terminate
  48         mov     x0, #-EFAULT
  49         ret
  50         .previous