1/* 2 * arch/xtensa/lib/usercopy.S 3 * 4 * Copy to/from user space (derived from arch/xtensa/lib/hal/memcopy.S) 5 * 6 * DO NOT COMBINE this function with <arch/xtensa/lib/hal/memcopy.S>. 7 * It needs to remain separate and distinct. The hal files are part 8 * of the Xtensa link-time HAL, and those files may differ per 9 * processor configuration. Patching the kernel for another 10 * processor configuration includes replacing the hal files, and we 11 * could lose the special functionality for accessing user-space 12 * memory during such a patch. We sacrifice a little code space here 13 * in favor to simplify code maintenance. 14 * 15 * This file is subject to the terms and conditions of the GNU General 16 * Public License. See the file "COPYING" in the main directory of 17 * this archive for more details. 18 * 19 * Copyright (C) 2002 Tensilica Inc. 20 */ 21 22 23/* 24 * size_t __xtensa_copy_user (void *dst, const void *src, size_t len); 25 * 26 * The returned value is the number of bytes not copied. Implies zero 27 * is success. 28 * 29 * The general case algorithm is as follows: 30 * If the destination and source are both aligned, 31 * do 16B chunks with a loop, and then finish up with 32 * 8B, 4B, 2B, and 1B copies conditional on the length. 33 * If destination is aligned and source unaligned, 34 * do the same, but use SRC to align the source data. 35 * If destination is unaligned, align it by conditionally 36 * copying 1B and 2B and then retest. 37 * This code tries to use fall-through braches for the common 38 * case of aligned destinations (except for the branches to 39 * the alignment label). 40 * 41 * Register use: 42 * a0/ return address 43 * a1/ stack pointer 44 * a2/ return value 45 * a3/ src 46 * a4/ length 47 * a5/ dst 48 * a6/ tmp 49 * a7/ tmp 50 * a8/ tmp 51 * a9/ tmp 52 * a10/ tmp 53 * a11/ original length 54 */ 55 56#include <variant/core.h> 57 58#ifdef __XTENSA_EB__ 59#define ALIGN(R, W0, W1) src R, W0, W1 60#define SSA8(R) ssa8b R 61#else 62#define ALIGN(R, W0, W1) src R, W1, W0 63#define SSA8(R) ssa8l R 64#endif 65 66/* Load or store instructions that may cause exceptions use the EX macro. */ 67 68#define EX(insn,reg1,reg2,offset,handler) \ 699: insn reg1, reg2, offset; \ 70 .section __ex_table, "a"; \ 71 .word 9b, handler; \ 72 .previous 73 74 75 .text 76 .align 4 77 .global __xtensa_copy_user 78 .type __xtensa_copy_user,@function 79__xtensa_copy_user: 80 entry sp, 16 # minimal stack frame 81 # a2/ dst, a3/ src, a4/ len 82 mov a5, a2 # copy dst so that a2 is return value 83 mov a11, a4 # preserve original len for error case 84.Lcommon: 85 bbsi.l a2, 0, .Ldst1mod2 # if dst is 1 mod 2 86 bbsi.l a2, 1, .Ldst2mod4 # if dst is 2 mod 4 87.Ldstaligned: # return here from .Ldstunaligned when dst is aligned 88 srli a7, a4, 4 # number of loop iterations with 16B 89 # per iteration 90 movi a8, 3 # if source is also aligned, 91 bnone a3, a8, .Laligned # then use word copy 92 SSA8( a3) # set shift amount from byte offset 93 bnez a4, .Lsrcunaligned 94 movi a2, 0 # return success for len==0 95 retw 96 97/* 98 * Destination is unaligned 99 */ 100 101.Ldst1mod2: # dst is only byte aligned 102 bltui a4, 7, .Lbytecopy # do short copies byte by byte 103 104 # copy 1 byte 105 EX(l8ui, a6, a3, 0, l_fixup) 106 addi a3, a3, 1 107 EX(s8i, a6, a5, 0, s_fixup) 108 addi a5, a5, 1 109 addi a4, a4, -1 110 bbci.l a5, 1, .Ldstaligned # if dst is now aligned, then 111 # return to main algorithm 112.Ldst2mod4: # dst 16-bit aligned 113 # copy 2 bytes 114 bltui a4, 6, .Lbytecopy # do short copies byte by byte 115 EX(l8ui, a6, a3, 0, l_fixup) 116 EX(l8ui, a7, a3, 1, l_fixup) 117 addi a3, a3, 2 118 EX(s8i, a6, a5, 0, s_fixup) 119 EX(s8i, a7, a5, 1, s_fixup) 120 addi a5, a5, 2 121 addi a4, a4, -2 122 j .Ldstaligned # dst is now aligned, return to main algorithm 123 124/* 125 * Byte by byte copy 126 */ 127 .align 4 128 .byte 0 # 1 mod 4 alignment for LOOPNEZ 129 # (0 mod 4 alignment for LBEG) 130.Lbytecopy: 131#if XCHAL_HAVE_LOOPS 132 loopnez a4, .Lbytecopydone 133#else /* !XCHAL_HAVE_LOOPS */ 134 beqz a4, .Lbytecopydone 135 add a7, a3, a4 # a7 = end address for source 136#endif /* !XCHAL_HAVE_LOOPS */ 137.Lnextbyte: 138 EX(l8ui, a6, a3, 0, l_fixup) 139 addi a3, a3, 1 140 EX(s8i, a6, a5, 0, s_fixup) 141 addi a5, a5, 1 142#if !XCHAL_HAVE_LOOPS 143 blt a3, a7, .Lnextbyte 144#endif /* !XCHAL_HAVE_LOOPS */ 145.Lbytecopydone: 146 movi a2, 0 # return success for len bytes copied 147 retw 148 149/* 150 * Destination and source are word-aligned. 151 */ 152 # copy 16 bytes per iteration for word-aligned dst and word-aligned src 153 .align 4 # 1 mod 4 alignment for LOOPNEZ 154 .byte 0 # (0 mod 4 alignment for LBEG) 155.Laligned: 156#if XCHAL_HAVE_LOOPS 157 loopnez a7, .Loop1done 158#else /* !XCHAL_HAVE_LOOPS */ 159 beqz a7, .Loop1done 160 slli a8, a7, 4 161 add a8, a8, a3 # a8 = end of last 16B source chunk 162#endif /* !XCHAL_HAVE_LOOPS */ 163.Loop1: 164 EX(l32i, a6, a3, 0, l_fixup) 165 EX(l32i, a7, a3, 4, l_fixup) 166 EX(s32i, a6, a5, 0, s_fixup) 167 EX(l32i, a6, a3, 8, l_fixup) 168 EX(s32i, a7, a5, 4, s_fixup) 169 EX(l32i, a7, a3, 12, l_fixup) 170 EX(s32i, a6, a5, 8, s_fixup) 171 addi a3, a3, 16 172 EX(s32i, a7, a5, 12, s_fixup) 173 addi a5, a5, 16 174#if !XCHAL_HAVE_LOOPS 175 blt a3, a8, .Loop1 176#endif /* !XCHAL_HAVE_LOOPS */ 177.Loop1done: 178 bbci.l a4, 3, .L2 179 # copy 8 bytes 180 EX(l32i, a6, a3, 0, l_fixup) 181 EX(l32i, a7, a3, 4, l_fixup) 182 addi a3, a3, 8 183 EX(s32i, a6, a5, 0, s_fixup) 184 EX(s32i, a7, a5, 4, s_fixup) 185 addi a5, a5, 8 186.L2: 187 bbci.l a4, 2, .L3 188 # copy 4 bytes 189 EX(l32i, a6, a3, 0, l_fixup) 190 addi a3, a3, 4 191 EX(s32i, a6, a5, 0, s_fixup) 192 addi a5, a5, 4 193.L3: 194 bbci.l a4, 1, .L4 195 # copy 2 bytes 196 EX(l16ui, a6, a3, 0, l_fixup) 197 addi a3, a3, 2 198 EX(s16i, a6, a5, 0, s_fixup) 199 addi a5, a5, 2 200.L4: 201 bbci.l a4, 0, .L5 202 # copy 1 byte 203 EX(l8ui, a6, a3, 0, l_fixup) 204 EX(s8i, a6, a5, 0, s_fixup) 205.L5: 206 movi a2, 0 # return success for len bytes copied 207 retw 208 209/* 210 * Destination is aligned, Source is unaligned 211 */ 212 213 .align 4 214 .byte 0 # 1 mod 4 alignement for LOOPNEZ 215 # (0 mod 4 alignment for LBEG) 216.Lsrcunaligned: 217 # copy 16 bytes per iteration for word-aligned dst and unaligned src 218 and a10, a3, a8 # save unalignment offset for below 219 sub a3, a3, a10 # align a3 (to avoid sim warnings only; not needed for hardware) 220 EX(l32i, a6, a3, 0, l_fixup) # load first word 221#if XCHAL_HAVE_LOOPS 222 loopnez a7, .Loop2done 223#else /* !XCHAL_HAVE_LOOPS */ 224 beqz a7, .Loop2done 225 slli a12, a7, 4 226 add a12, a12, a3 # a12 = end of last 16B source chunk 227#endif /* !XCHAL_HAVE_LOOPS */ 228.Loop2: 229 EX(l32i, a7, a3, 4, l_fixup) 230 EX(l32i, a8, a3, 8, l_fixup) 231 ALIGN( a6, a6, a7) 232 EX(s32i, a6, a5, 0, s_fixup) 233 EX(l32i, a9, a3, 12, l_fixup) 234 ALIGN( a7, a7, a8) 235 EX(s32i, a7, a5, 4, s_fixup) 236 EX(l32i, a6, a3, 16, l_fixup) 237 ALIGN( a8, a8, a9) 238 EX(s32i, a8, a5, 8, s_fixup) 239 addi a3, a3, 16 240 ALIGN( a9, a9, a6) 241 EX(s32i, a9, a5, 12, s_fixup) 242 addi a5, a5, 16 243#if !XCHAL_HAVE_LOOPS 244 blt a3, a12, .Loop2 245#endif /* !XCHAL_HAVE_LOOPS */ 246.Loop2done: 247 bbci.l a4, 3, .L12 248 # copy 8 bytes 249 EX(l32i, a7, a3, 4, l_fixup) 250 EX(l32i, a8, a3, 8, l_fixup) 251 ALIGN( a6, a6, a7) 252 EX(s32i, a6, a5, 0, s_fixup) 253 addi a3, a3, 8 254 ALIGN( a7, a7, a8) 255 EX(s32i, a7, a5, 4, s_fixup) 256 addi a5, a5, 8 257 mov a6, a8 258.L12: 259 bbci.l a4, 2, .L13 260 # copy 4 bytes 261 EX(l32i, a7, a3, 4, l_fixup) 262 addi a3, a3, 4 263 ALIGN( a6, a6, a7) 264 EX(s32i, a6, a5, 0, s_fixup) 265 addi a5, a5, 4 266 mov a6, a7 267.L13: 268 add a3, a3, a10 # readjust a3 with correct misalignment 269 bbci.l a4, 1, .L14 270 # copy 2 bytes 271 EX(l8ui, a6, a3, 0, l_fixup) 272 EX(l8ui, a7, a3, 1, l_fixup) 273 addi a3, a3, 2 274 EX(s8i, a6, a5, 0, s_fixup) 275 EX(s8i, a7, a5, 1, s_fixup) 276 addi a5, a5, 2 277.L14: 278 bbci.l a4, 0, .L15 279 # copy 1 byte 280 EX(l8ui, a6, a3, 0, l_fixup) 281 EX(s8i, a6, a5, 0, s_fixup) 282.L15: 283 movi a2, 0 # return success for len bytes copied 284 retw 285 286 287 .section .fixup, "ax" 288 .align 4 289 290/* a2 = original dst; a5 = current dst; a11= original len 291 * bytes_copied = a5 - a2 292 * retval = bytes_not_copied = original len - bytes_copied 293 * retval = a11 - (a5 - a2) 294 * 295 * Clearing the remaining pieces of kernel memory plugs security 296 * holes. This functionality is the equivalent of the *_zeroing 297 * functions that some architectures provide. 298 */ 299 300.Lmemset: 301 .word memset 302 303s_fixup: 304 sub a2, a5, a2 /* a2 <-- bytes copied */ 305 sub a2, a11, a2 /* a2 <-- bytes not copied */ 306 retw 307 308l_fixup: 309 sub a2, a5, a2 /* a2 <-- bytes copied */ 310 sub a2, a11, a2 /* a2 <-- bytes not copied == return value */ 311 312 /* void *memset(void *s, int c, size_t n); */ 313 mov a6, a5 /* s */ 314 movi a7, 0 /* c */ 315 mov a8, a2 /* n */ 316 l32r a4, .Lmemset 317 callx4 a4 318 /* Ignore memset return value in a6. */ 319 /* a2 still contains bytes not copied. */ 320 retw 321