root/arch/xtensa/lib/strncpy_user.S

   1 /*
   2  *  arch/xtensa/lib/strncpy_user.S
   3  *
   4  *  This file is subject to the terms and conditions of the GNU General
   5  *  Public License.  See the file "COPYING" in the main directory of
   6  *  this archive for more details.
   7  *
   8  *  Returns: -EFAULT if exception before terminator, N if the entire
   9  *  buffer filled, else strlen.
  10  *
  11  *  Copyright (C) 2002 Tensilica Inc.
  12  */
  13 
  14 #include <linux/errno.h>
  15 #include <linux/linkage.h>
  16 #include <asm/asmmacro.h>
  17 #include <asm/core.h>
  18 
  19 /*
  20  * char *__strncpy_user(char *dst, const char *src, size_t len)
  21  */
  22 
  23 #ifdef __XTENSA_EB__
  24 # define MASK0 0xff000000
  25 # define MASK1 0x00ff0000
  26 # define MASK2 0x0000ff00
  27 # define MASK3 0x000000ff
  28 #else
  29 # define MASK0 0x000000ff
  30 # define MASK1 0x0000ff00
  31 # define MASK2 0x00ff0000
  32 # define MASK3 0xff000000
  33 #endif
  34 
  35 # Register use
  36 #   a0/ return address
  37 #   a1/ stack pointer
  38 #   a2/ return value
  39 #   a3/ src
  40 #   a4/ len
  41 #   a5/ mask0
  42 #   a6/ mask1
  43 #   a7/ mask2
  44 #   a8/ mask3
  45 #   a9/ tmp
  46 #   a10/ tmp
  47 #   a11/ dst
  48 #   a12/ tmp
  49 
  50 .text
  51 ENTRY(__strncpy_user)
  52 
  53         abi_entry_default
  54         # a2/ dst, a3/ src, a4/ len
  55         mov     a11, a2         # leave dst in return value register
  56         beqz    a4, .Lret       # if len is zero
  57         movi    a5, MASK0       # mask for byte 0
  58         movi    a6, MASK1       # mask for byte 1
  59         movi    a7, MASK2       # mask for byte 2
  60         movi    a8, MASK3       # mask for byte 3
  61         bbsi.l  a3, 0, .Lsrc1mod2 # if only  8-bit aligned
  62         bbsi.l  a3, 1, .Lsrc2mod4 # if only 16-bit aligned
  63 .Lsrcaligned:   # return here when src is word-aligned
  64         srli    a12, a4, 2      # number of loop iterations with 4B per loop
  65         movi    a9, 3
  66         bnone   a11, a9, .Laligned
  67         j       .Ldstunaligned
  68 
  69 .Lsrc1mod2:     # src address is odd
  70 EX(11f) l8ui    a9, a3, 0               # get byte 0
  71         addi    a3, a3, 1               # advance src pointer
  72 EX(10f) s8i     a9, a11, 0              # store byte 0
  73         beqz    a9, .Lret               # if byte 0 is zero
  74         addi    a11, a11, 1             # advance dst pointer
  75         addi    a4, a4, -1              # decrement len
  76         beqz    a4, .Lret               # if len is zero
  77         bbci.l  a3, 1, .Lsrcaligned     # if src is now word-aligned
  78 
  79 .Lsrc2mod4:     # src address is 2 mod 4
  80 EX(11f) l8ui    a9, a3, 0               # get byte 0
  81         /* 1-cycle interlock */
  82 EX(10f) s8i     a9, a11, 0              # store byte 0
  83         beqz    a9, .Lret               # if byte 0 is zero
  84         addi    a11, a11, 1             # advance dst pointer
  85         addi    a4, a4, -1              # decrement len
  86         beqz    a4, .Lret               # if len is zero
  87 EX(11f) l8ui    a9, a3, 1               # get byte 0
  88         addi    a3, a3, 2               # advance src pointer
  89 EX(10f) s8i     a9, a11, 0              # store byte 0
  90         beqz    a9, .Lret               # if byte 0 is zero
  91         addi    a11, a11, 1             # advance dst pointer
  92         addi    a4, a4, -1              # decrement len
  93         bnez    a4, .Lsrcaligned        # if len is nonzero
  94 .Lret:
  95         sub     a2, a11, a2             # compute strlen
  96         abi_ret_default
  97 
  98 /*
  99  * dst is word-aligned, src is word-aligned
 100  */
 101         .align  4               # 1 mod 4 alignment for LOOPNEZ
 102         .byte   0               # (0 mod 4 alignment for LBEG)
 103 .Laligned:
 104 #if XCHAL_HAVE_LOOPS
 105         loopnez a12, .Loop1done
 106 #else
 107         beqz    a12, .Loop1done
 108         slli    a12, a12, 2
 109         add     a12, a12, a11   # a12 = end of last 4B chunck
 110 #endif
 111 .Loop1:
 112 EX(11f) l32i    a9, a3, 0               # get word from src
 113         addi    a3, a3, 4               # advance src pointer
 114         bnone   a9, a5, .Lz0            # if byte 0 is zero
 115         bnone   a9, a6, .Lz1            # if byte 1 is zero
 116         bnone   a9, a7, .Lz2            # if byte 2 is zero
 117 EX(10f) s32i    a9, a11, 0              # store word to dst
 118         bnone   a9, a8, .Lz3            # if byte 3 is zero
 119         addi    a11, a11, 4             # advance dst pointer
 120 #if !XCHAL_HAVE_LOOPS
 121         blt     a11, a12, .Loop1
 122 #endif
 123 
 124 .Loop1done:
 125         bbci.l  a4, 1, .L100
 126         # copy 2 bytes
 127 EX(11f) l16ui   a9, a3, 0
 128         addi    a3, a3, 2               # advance src pointer
 129 #ifdef __XTENSA_EB__
 130         bnone   a9, a7, .Lz0            # if byte 2 is zero
 131         bnone   a9, a8, .Lz1            # if byte 3 is zero
 132 #else
 133         bnone   a9, a5, .Lz0            # if byte 0 is zero
 134         bnone   a9, a6, .Lz1            # if byte 1 is zero
 135 #endif
 136 EX(10f) s16i    a9, a11, 0
 137         addi    a11, a11, 2             # advance dst pointer
 138 .L100:
 139         bbci.l  a4, 0, .Lret
 140 EX(11f) l8ui    a9, a3, 0
 141         /* slot */
 142 EX(10f) s8i     a9, a11, 0
 143         beqz    a9, .Lret               # if byte is zero
 144         addi    a11, a11, 1-3           # advance dst ptr 1, but also cancel
 145                                         # the effect of adding 3 in .Lz3 code
 146         /* fall thru to .Lz3 and "retw" */
 147 
 148 .Lz3:   # byte 3 is zero
 149         addi    a11, a11, 3             # advance dst pointer
 150         sub     a2, a11, a2             # compute strlen
 151         abi_ret_default
 152 .Lz0:   # byte 0 is zero
 153 #ifdef __XTENSA_EB__
 154         movi    a9, 0
 155 #endif /* __XTENSA_EB__ */
 156 EX(10f) s8i     a9, a11, 0
 157         sub     a2, a11, a2             # compute strlen
 158         abi_ret_default
 159 .Lz1:   # byte 1 is zero
 160 #ifdef __XTENSA_EB__
 161         extui   a9, a9, 16, 16
 162 #endif /* __XTENSA_EB__ */
 163 EX(10f) s16i    a9, a11, 0
 164         addi    a11, a11, 1             # advance dst pointer
 165         sub     a2, a11, a2             # compute strlen
 166         abi_ret_default
 167 .Lz2:   # byte 2 is zero
 168 #ifdef __XTENSA_EB__
 169         extui   a9, a9, 16, 16
 170 #endif /* __XTENSA_EB__ */
 171 EX(10f) s16i    a9, a11, 0
 172         movi    a9, 0
 173 EX(10f) s8i     a9, a11, 2
 174         addi    a11, a11, 2             # advance dst pointer
 175         sub     a2, a11, a2             # compute strlen
 176         abi_ret_default
 177 
 178         .align  4               # 1 mod 4 alignment for LOOPNEZ
 179         .byte   0               # (0 mod 4 alignment for LBEG)
 180 .Ldstunaligned:
 181 /*
 182  * for now just use byte copy loop
 183  */
 184 #if XCHAL_HAVE_LOOPS
 185         loopnez a4, .Lunalignedend
 186 #else
 187         beqz    a4, .Lunalignedend
 188         add     a12, a11, a4            # a12 = ending address
 189 #endif /* XCHAL_HAVE_LOOPS */
 190 .Lnextbyte:
 191 EX(11f) l8ui    a9, a3, 0
 192         addi    a3, a3, 1
 193 EX(10f) s8i     a9, a11, 0
 194         beqz    a9, .Lunalignedend
 195         addi    a11, a11, 1
 196 #if !XCHAL_HAVE_LOOPS
 197         blt     a11, a12, .Lnextbyte
 198 #endif
 199 
 200 .Lunalignedend:
 201         sub     a2, a11, a2             # compute strlen
 202         abi_ret_default
 203 
 204 ENDPROC(__strncpy_user)
 205 
 206         .section .fixup, "ax"
 207         .align  4
 208 
 209         /* For now, just return -EFAULT.  Future implementations might
 210          * like to clear remaining kernel space, like the fixup
 211          * implementation in memset().  Thus, we differentiate between
 212          * load/store fixups. */
 213 
 214 10:
 215 11:
 216         movi    a2, -EFAULT
 217         abi_ret_default