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 <variant/core.h>
  15 #include <linux/errno.h>
  16
  17 /* Load or store instructions that may cause exceptions use the EX macro. */
  18
  19 #define EX(insn,reg1,reg2,offset,handler)       \
  20 9:      insn    reg1, reg2, offset;             \
  21         .section __ex_table, "a";               \
  22         .word   9b, handler;                    \
  23         .previous
  24
  25 /*
  26  * char *__strncpy_user(char *dst, const char *src, size_t len)
  27  */
  28
  29 #ifdef __XTENSA_EB__
  30 # define MASK0 0xff000000
  31 # define MASK1 0x00ff0000
  32 # define MASK2 0x0000ff00
  33 # define MASK3 0x000000ff
  34 #else
  35 # define MASK0 0x000000ff
  36 # define MASK1 0x0000ff00
  37 # define MASK2 0x00ff0000
  38 # define MASK3 0xff000000
  39 #endif
  40
  41 # Register use
  42 #   a0/ return address
  43 #   a1/ stack pointer
  44 #   a2/ return value
  45 #   a3/ src
  46 #   a4/ len
  47 #   a5/ mask0
  48 #   a6/ mask1
  49 #   a7/ mask2
  50 #   a8/ mask3
  51 #   a9/ tmp
  52 #   a10/ tmp
  53 #   a11/ dst
  54 #   a12/ tmp
  55
  56 .text
  57 .align  4
  58 .global __strncpy_user
  59 .type   __strncpy_user,@function
  60 __strncpy_user:
  61         entry   sp, 16          # minimal stack frame
  62         # a2/ dst, a3/ src, a4/ len
  63         mov     a11, a2         # leave dst in return value register
  64         beqz    a4, .Lret       # if len is zero
  65         movi    a5, MASK0       # mask for byte 0
  66         movi    a6, MASK1       # mask for byte 1
  67         movi    a7, MASK2       # mask for byte 2
  68         movi    a8, MASK3       # mask for byte 3
  69         bbsi.l  a3, 0, .Lsrc1mod2 # if only  8-bit aligned
  70         bbsi.l  a3, 1, .Lsrc2mod4 # if only 16-bit aligned
  71 .Lsrcaligned:   # return here when src is word-aligned
  72         srli    a12, a4, 2      # number of loop iterations with 4B per loop
  73         movi    a9, 3
  74         bnone   a11, a9, .Laligned
  75         j       .Ldstunaligned
  76
  77 .Lsrc1mod2:     # src address is odd
  78         EX(l8ui, a9, a3, 0, fixup_l)    # get byte 0
  79         addi    a3, a3, 1               # advance src pointer
  80         EX(s8i, a9, a11, 0, fixup_s)    # store byte 0
  81         beqz    a9, .Lret               # if byte 0 is zero
  82         addi    a11, a11, 1             # advance dst pointer
  83         addi    a4, a4, -1              # decrement len
  84         beqz    a4, .Lret               # if len is zero
  85         bbci.l  a3, 1, .Lsrcaligned     # if src is now word-aligned
  86
  87 .Lsrc2mod4:     # src address is 2 mod 4
  88         EX(l8ui, a9, a3, 0, fixup_l)    # get byte 0
  89         /* 1-cycle interlock */
  90         EX(s8i, a9, a11, 0, fixup_s)    # store byte 0
  91         beqz    a9, .Lret               # if byte 0 is zero
  92         addi    a11, a11, 1             # advance dst pointer
  93         addi    a4, a4, -1              # decrement len
  94         beqz    a4, .Lret               # if len is zero
  95         EX(l8ui, a9, a3, 1, fixup_l)    # get byte 0
  96         addi    a3, a3, 2               # advance src pointer
  97         EX(s8i, a9, a11, 0, fixup_s)    # store byte 0
  98         beqz    a9, .Lret               # if byte 0 is zero
  99         addi    a11, a11, 1             # advance dst pointer
 100         addi    a4, a4, -1              # decrement len
 101         bnez    a4, .Lsrcaligned        # if len is nonzero
 102 .Lret:
 103         sub     a2, a11, a2             # compute strlen
 104         retw
 105
 106 /*
 107  * dst is word-aligned, src is word-aligned
 108  */
 109         .align  4               # 1 mod 4 alignment for LOOPNEZ
 110         .byte   0               # (0 mod 4 alignment for LBEG)
 111 .Laligned:
 112 #if XCHAL_HAVE_LOOPS
 113         loopnez a12, .Loop1done
 114 #else
 115         beqz    a12, .Loop1done
 116         slli    a12, a12, 2
 117         add     a12, a12, a11   # a12 = end of last 4B chunck
 118 #endif
 119 .Loop1:
 120         EX(l32i, a9, a3, 0, fixup_l)    # get word from src
 121         addi    a3, a3, 4               # advance src pointer
 122         bnone   a9, a5, .Lz0            # if byte 0 is zero
 123         bnone   a9, a6, .Lz1            # if byte 1 is zero
 124         bnone   a9, a7, .Lz2            # if byte 2 is zero
 125         EX(s32i, a9, a11, 0, fixup_s)   # store word to dst
 126         bnone   a9, a8, .Lz3            # if byte 3 is zero
 127         addi    a11, a11, 4             # advance dst pointer
 128 #if !XCHAL_HAVE_LOOPS
 129         blt     a11, a12, .Loop1
 130 #endif
 131
 132 .Loop1done:
 133         bbci.l  a4, 1, .L100
 134         # copy 2 bytes
 135         EX(l16ui, a9, a3, 0, fixup_l)
 136         addi    a3, a3, 2               # advance src pointer
 137 #ifdef __XTENSA_EB__
 138         bnone   a9, a7, .Lz0            # if byte 2 is zero
 139         bnone   a9, a8, .Lz1            # if byte 3 is zero
 140 #else
 141         bnone   a9, a5, .Lz0            # if byte 0 is zero
 142         bnone   a9, a6, .Lz1            # if byte 1 is zero
 143 #endif
 144         EX(s16i, a9, a11, 0, fixup_s)
 145         addi    a11, a11, 2             # advance dst pointer
 146 .L100:
 147         bbci.l  a4, 0, .Lret
 148         EX(l8ui, a9, a3, 0, fixup_l)
 149         /* slot */
 150         EX(s8i, a9, a11, 0, fixup_s)
 151         beqz    a9, .Lret               # if byte is zero
 152         addi    a11, a11, 1-3           # advance dst ptr 1, but also cancel
 153                                         # the effect of adding 3 in .Lz3 code
 154         /* fall thru to .Lz3 and "retw" */
 155
 156 .Lz3:   # byte 3 is zero
 157         addi    a11, a11, 3             # advance dst pointer
 158         sub     a2, a11, a2             # compute strlen
 159         retw
 160 .Lz0:   # byte 0 is zero
 161 #ifdef __XTENSA_EB__
 162         movi    a9, 0
 163 #endif /* __XTENSA_EB__ */
 164         EX(s8i, a9, a11, 0, fixup_s)
 165         sub     a2, a11, a2             # compute strlen
 166         retw
 167 .Lz1:   # byte 1 is zero
 168 #ifdef __XTENSA_EB__
 169         extui   a9, a9, 16, 16
 170 #endif /* __XTENSA_EB__ */
 171         EX(s16i, a9, a11, 0, fixup_s)
 172         addi    a11, a11, 1             # advance dst pointer
 173         sub     a2, a11, a2             # compute strlen
 174         retw
 175 .Lz2:   # byte 2 is zero
 176 #ifdef __XTENSA_EB__
 177         extui   a9, a9, 16, 16
 178 #endif /* __XTENSA_EB__ */
 179         EX(s16i, a9, a11, 0, fixup_s)
 180         movi    a9, 0
 181         EX(s8i, a9, a11, 2, fixup_s)
 182         addi    a11, a11, 2             # advance dst pointer
 183         sub     a2, a11, a2             # compute strlen
 184         retw
 185
 186         .align  4               # 1 mod 4 alignment for LOOPNEZ
 187         .byte   0               # (0 mod 4 alignment for LBEG)
 188 .Ldstunaligned:
 189 /*
 190  * for now just use byte copy loop
 191  */
 192 #if XCHAL_HAVE_LOOPS
 193         loopnez a4, .Lunalignedend
 194 #else
 195         beqz    a4, .Lunalignedend
 196         add     a12, a11, a4            # a12 = ending address
 197 #endif /* XCHAL_HAVE_LOOPS */
 198 .Lnextbyte:
 199         EX(l8ui, a9, a3, 0, fixup_l)
 200         addi    a3, a3, 1
 201         EX(s8i, a9, a11, 0, fixup_s)
 202         beqz    a9, .Lunalignedend
 203         addi    a11, a11, 1
 204 #if !XCHAL_HAVE_LOOPS
 205         blt     a11, a12, .Lnextbyte
 206 #endif
 207
 208 .Lunalignedend:
 209         sub     a2, a11, a2             # compute strlen
 210         retw
 211
 212
 213         .section .fixup, "ax"
 214         .align  4
 215
 216         /* For now, just return -EFAULT.  Future implementations might
 217          * like to clear remaining kernel space, like the fixup
 218          * implementation in memset().  Thus, we differentiate between
 219          * load/store fixups. */
 220
 221 fixup_s:
 222 fixup_l:
 223         movi    a2, -EFAULT
 224         retw
 225