arch/mips/lib/strnlen_user.S

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (c) 1996, 1998, 1999, 2004 by Ralf Baechle
   7  * Copyright (c) 1999 Silicon Graphics, Inc.
   8  */
   9 #include <asm/asm.h>
  10 #include <asm/asm-offsets.h>
  11 #include <asm/regdef.h>
  12
  13 #define EX(insn,reg,addr,handler)                       \
  14 9:      insn    reg, addr;                              \
  15         .section __ex_table,"a";                        \
  16         PTR     9b, handler;                            \
  17         .previous
  18
  19 /*
  20  * Return the size of a string including the ending NUL character up to a
  21  * maximum of a1 or 0 in case of error.
  22  *
  23  * Note: for performance reasons we deliberately accept that a user may
  24  *       make strlen_user and strnlen_user access the first few KSEG0
  25  *       bytes.  There's nothing secret there.  On 64-bit accessing beyond
  26  *       the maximum is a tad hairier ...
  27  */
  28 LEAF(__strnlen_user_asm)
  29         LONG_L          v0, TI_ADDR_LIMIT($28)  # pointer ok?
  30         and             v0, a0
  31         bnez            v0, .Lfault
  32
  33 FEXPORT(__strnlen_user_nocheck_asm)
  34         move            v0, a0
  35         PTR_ADDU        a1, a0                  # stop pointer
  36 1:      beq             v0, a1, 1f              # limit reached?
  37         EX(lb, t0, (v0), .Lfault)
  38         PTR_ADDU        v0, 1
  39         bnez            t0, 1b
  40 1:      PTR_SUBU        v0, a0
  41         jr              ra
  42         END(__strnlen_user_asm)
  43
  44 .Lfault:
  45         move            v0, zero
  46         jr              ra