arch/arm64/lib/memset.S

   1 /*
   2  * Copyright (C) 2013 ARM Ltd.
   3  * Copyright (C) 2013 Linaro.
   4  *
   5  * This code is based on glibc cortex strings work originally authored by Linaro
   6  * and re-licensed under GPLv2 for the Linux kernel. The original code can
   7  * be found @
   8  *
   9  * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
  10  * files/head:/src/aarch64/
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License version 2 as
  14  * published by the Free Software Foundation.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  23  */
  24
  25 #include <linux/linkage.h>
  26 #include <asm/assembler.h>
  27 #include <asm/cache.h>
  28
  29 /*
  30  * Fill in the buffer with character c (alignment handled by the hardware)
  31  *
  32  * Parameters:
  33  *      x0 - buf
  34  *      x1 - c
  35  *      x2 - n
  36  * Returns:
  37  *      x0 - buf
  38  */
  39
  40 dstin           .req    x0
  41 val             .req    w1
  42 count           .req    x2
  43 tmp1            .req    x3
  44 tmp1w           .req    w3
  45 tmp2            .req    x4
  46 tmp2w           .req    w4
  47 zva_len_x       .req    x5
  48 zva_len         .req    w5
  49 zva_bits_x      .req    x6
  50
  51 A_l             .req    x7
  52 A_lw            .req    w7
  53 dst             .req    x8
  54 tmp3w           .req    w9
  55 tmp3            .req    x9
  56
  57         .weak memset
  58 ENTRY(__memset)
  59 ENTRY(memset)
  60         mov     dst, dstin      /* Preserve return value.  */
  61         and     A_lw, val, #255
  62         orr     A_lw, A_lw, A_lw, lsl #8
  63         orr     A_lw, A_lw, A_lw, lsl #16
  64         orr     A_l, A_l, A_l, lsl #32
  65
  66         cmp     count, #15
  67         b.hi    .Lover16_proc
  68         /*All store maybe are non-aligned..*/
  69         tbz     count, #3, 1f
  70         str     A_l, [dst], #8
  71 1:
  72         tbz     count, #2, 2f
  73         str     A_lw, [dst], #4
  74 2:
  75         tbz     count, #1, 3f
  76         strh    A_lw, [dst], #2
  77 3:
  78         tbz     count, #0, 4f
  79         strb    A_lw, [dst]
  80 4:
  81         ret
  82
  83 .Lover16_proc:
  84         /*Whether  the start address is aligned with 16.*/
  85         neg     tmp2, dst
  86         ands    tmp2, tmp2, #15
  87         b.eq    .Laligned
  88 /*
  89 * The count is not less than 16, we can use stp to store the start 16 bytes,
  90 * then adjust the dst aligned with 16.This process will make the current
  91 * memory address at alignment boundary.
  92 */
  93         stp     A_l, A_l, [dst] /*non-aligned store..*/
  94         /*make the dst aligned..*/
  95         sub     count, count, tmp2
  96         add     dst, dst, tmp2
  97
  98 .Laligned:
  99         cbz     A_l, .Lzero_mem
 100
 101 .Ltail_maybe_long:
 102         cmp     count, #64
 103         b.ge    .Lnot_short
 104 .Ltail63:
 105         ands    tmp1, count, #0x30
 106         b.eq    3f
 107         cmp     tmp1w, #0x20
 108         b.eq    1f
 109         b.lt    2f
 110         stp     A_l, A_l, [dst], #16
 111 1:
 112         stp     A_l, A_l, [dst], #16
 113 2:
 114         stp     A_l, A_l, [dst], #16
 115 /*
 116 * The last store length is less than 16,use stp to write last 16 bytes.
 117 * It will lead some bytes written twice and the access is non-aligned.
 118 */
 119 3:
 120         ands    count, count, #15
 121         cbz     count, 4f
 122         add     dst, dst, count
 123         stp     A_l, A_l, [dst, #-16]   /* Repeat some/all of last store. */
 124 4:
 125         ret
 126
 127         /*
 128         * Critical loop. Start at a new cache line boundary. Assuming
 129         * 64 bytes per line, this ensures the entire loop is in one line.
 130         */
 131         .p2align        L1_CACHE_SHIFT
 132 .Lnot_short:
 133         sub     dst, dst, #16/* Pre-bias.  */
 134         sub     count, count, #64
 135 1:
 136         stp     A_l, A_l, [dst, #16]
 137         stp     A_l, A_l, [dst, #32]
 138         stp     A_l, A_l, [dst, #48]
 139         stp     A_l, A_l, [dst, #64]!
 140         subs    count, count, #64
 141         b.ge    1b
 142         tst     count, #0x3f
 143         add     dst, dst, #16
 144         b.ne    .Ltail63
 145 .Lexitfunc:
 146         ret
 147
 148         /*
 149         * For zeroing memory, check to see if we can use the ZVA feature to
 150         * zero entire 'cache' lines.
 151         */
 152 .Lzero_mem:
 153         cmp     count, #63
 154         b.le    .Ltail63
 155         /*
 156         * For zeroing small amounts of memory, it's not worth setting up
 157         * the line-clear code.
 158         */
 159         cmp     count, #128
 160         b.lt    .Lnot_short /*count is at least  128 bytes*/
 161
 162         mrs     tmp1, dczid_el0
 163         tbnz    tmp1, #4, .Lnot_short
 164         mov     tmp3w, #4
 165         and     zva_len, tmp1w, #15     /* Safety: other bits reserved.  */
 166         lsl     zva_len, tmp3w, zva_len
 167
 168         ands    tmp3w, zva_len, #63
 169         /*
 170         * ensure the zva_len is not less than 64.
 171         * It is not meaningful to use ZVA if the block size is less than 64.
 172         */
 173         b.ne    .Lnot_short
 174 .Lzero_by_line:
 175         /*
 176         * Compute how far we need to go to become suitably aligned. We're
 177         * already at quad-word alignment.
 178         */
 179         cmp     count, zva_len_x
 180         b.lt    .Lnot_short             /* Not enough to reach alignment.  */
 181         sub     zva_bits_x, zva_len_x, #1
 182         neg     tmp2, dst
 183         ands    tmp2, tmp2, zva_bits_x
 184         b.eq    2f                      /* Already aligned.  */
 185         /* Not aligned, check that there's enough to copy after alignment.*/
 186         sub     tmp1, count, tmp2
 187         /*
 188         * grantee the remain length to be ZVA is bigger than 64,
 189         * avoid to make the 2f's process over mem range.*/
 190         cmp     tmp1, #64
 191         ccmp    tmp1, zva_len_x, #8, ge /* NZCV=0b1000 */
 192         b.lt    .Lnot_short
 193         /*
 194         * We know that there's at least 64 bytes to zero and that it's safe
 195         * to overrun by 64 bytes.
 196         */
 197         mov     count, tmp1
 198 1:
 199         stp     A_l, A_l, [dst]
 200         stp     A_l, A_l, [dst, #16]
 201         stp     A_l, A_l, [dst, #32]
 202         subs    tmp2, tmp2, #64
 203         stp     A_l, A_l, [dst, #48]
 204         add     dst, dst, #64
 205         b.ge    1b
 206         /* We've overrun a bit, so adjust dst downwards.*/
 207         add     dst, dst, tmp2
 208 2:
 209         sub     count, count, zva_len_x
 210 3:
 211         dc      zva, dst
 212         add     dst, dst, zva_len_x
 213         subs    count, count, zva_len_x
 214         b.ge    3b
 215         ands    count, count, zva_bits_x
 216         b.ne    .Ltail_maybe_long
 217         ret
 218 ENDPIPROC(memset)
 219 ENDPROC(__memset)