arch/arm/mm/alignment.c

   1 /*
   2  *  linux/arch/arm/mm/alignment.c
   3  *
   4  *  Copyright (C) 1995  Linus Torvalds
   5  *  Modifications for ARM processor (c) 1995-2001 Russell King
   6  *  Thumb alignment fault fixups (c) 2004 MontaVista Software, Inc.
   7  *  - Adapted from gdb/sim/arm/thumbemu.c -- Thumb instruction emulation.
   8  *    Copyright (C) 1996, Cygnus Software Technologies Ltd.
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  */
  14 #include <linux/compiler.h>
  15 #include <linux/kernel.h>
  16 #include <linux/errno.h>
  17 #include <linux/string.h>
  18 #include <linux/proc_fs.h>
  19 #include <linux/init.h>
  20 #include <linux/sched.h>
  21 #include <linux/uaccess.h>
  22
  23 #include <asm/unaligned.h>
  24
  25 #include "fault.h"
  26
  27 /*
  28  * 32-bit misaligned trap handler (c) 1998 San Mehat (CCC) -July 1998
  29  * /proc/sys/debug/alignment, modified and integrated into
  30  * Linux 2.1 by Russell King
  31  *
  32  * Speed optimisations and better fault handling by Russell King.
  33  *
  34  * *** NOTE ***
  35  * This code is not portable to processors with late data abort handling.
  36  */
  37 #define CODING_BITS(i)  (i & 0x0e000000)
  38
  39 #define LDST_I_BIT(i)   (i & (1 << 26))         /* Immediate constant   */
  40 #define LDST_P_BIT(i)   (i & (1 << 24))         /* Preindex             */
  41 #define LDST_U_BIT(i)   (i & (1 << 23))         /* Add offset           */
  42 #define LDST_W_BIT(i)   (i & (1 << 21))         /* Writeback            */
  43 #define LDST_L_BIT(i)   (i & (1 << 20))         /* Load                 */
  44
  45 #define LDST_P_EQ_U(i)  ((((i) ^ ((i) >> 1)) & (1 << 23)) == 0)
  46
  47 #define LDSTHD_I_BIT(i) (i & (1 << 22))         /* double/half-word immed */
  48 #define LDM_S_BIT(i)    (i & (1 << 22))         /* write CPSR from SPSR */
  49
  50 #define RN_BITS(i)      ((i >> 16) & 15)        /* Rn                   */
  51 #define RD_BITS(i)      ((i >> 12) & 15)        /* Rd                   */
  52 #define RM_BITS(i)      (i & 15)                /* Rm                   */
  53
  54 #define REGMASK_BITS(i) (i & 0xffff)
  55 #define OFFSET_BITS(i)  (i & 0x0fff)
  56
  57 #define IS_SHIFT(i)     (i & 0x0ff0)
  58 #define SHIFT_BITS(i)   ((i >> 7) & 0x1f)
  59 #define SHIFT_TYPE(i)   (i & 0x60)
  60 #define SHIFT_LSL       0x00
  61 #define SHIFT_LSR       0x20
  62 #define SHIFT_ASR       0x40
  63 #define SHIFT_RORRRX    0x60
  64
  65 #define BAD_INSTR       0xdeadc0de
  66
  67 /* Thumb-2 32 bit format per ARMv7 DDI0406A A6.3, either f800h,e800h,f800h */
  68 #define IS_T32(hi16) \
  69         (((hi16) & 0xe000) == 0xe000 && ((hi16) & 0x1800))
  70
  71 static unsigned long ai_user;
  72 static unsigned long ai_sys;
  73 static unsigned long ai_skipped;
  74 static unsigned long ai_half;
  75 static unsigned long ai_word;
  76 static unsigned long ai_dword;
  77 static unsigned long ai_multi;
  78 static int ai_usermode;
  79
  80 #define UM_WARN         (1 << 0)
  81 #define UM_FIXUP        (1 << 1)
  82 #define UM_SIGNAL       (1 << 2)
  83
  84 #ifdef CONFIG_PROC_FS
  85 static const char *usermode_action[] = {
  86         "ignored",
  87         "warn",
  88         "fixup",
  89         "fixup+warn",
  90         "signal",
  91         "signal+warn"
  92 };
  93
  94 static int
  95 proc_alignment_read(char *page, char **start, off_t off, int count, int *eof,
  96                     void *data)
  97 {
  98         char *p = page;
  99         int len;
 100
 101         p += sprintf(p, "User:\t\t%lu\n", ai_user);
 102         p += sprintf(p, "System:\t\t%lu\n", ai_sys);
 103         p += sprintf(p, "Skipped:\t%lu\n", ai_skipped);
 104         p += sprintf(p, "Half:\t\t%lu\n", ai_half);
 105         p += sprintf(p, "Word:\t\t%lu\n", ai_word);
 106         if (cpu_architecture() >= CPU_ARCH_ARMv5TE)
 107                 p += sprintf(p, "DWord:\t\t%lu\n", ai_dword);
 108         p += sprintf(p, "Multi:\t\t%lu\n", ai_multi);
 109         p += sprintf(p, "User faults:\t%i (%s)\n", ai_usermode,
 110                         usermode_action[ai_usermode]);
 111
 112         len = (p - page) - off;
 113         if (len < 0)
 114                 len = 0;
 115
 116         *eof = (len <= count) ? 1 : 0;
 117         *start = page + off;
 118
 119         return len;
 120 }
 121
 122 static int proc_alignment_write(struct file *file, const char __user *buffer,
 123                                 unsigned long count, void *data)
 124 {
 125         char mode;
 126
 127         if (count > 0) {
 128                 if (get_user(mode, buffer))
 129                         return -EFAULT;
 130                 if (mode >= '0' && mode <= '5')
 131                         ai_usermode = mode - '0';
 132         }
 133         return count;
 134 }
 135
 136 #endif /* CONFIG_PROC_FS */
 137
 138 union offset_union {
 139         unsigned long un;
 140           signed long sn;
 141 };
 142
 143 #define TYPE_ERROR      0
 144 #define TYPE_FAULT      1
 145 #define TYPE_LDST       2
 146 #define TYPE_DONE       3
 147
 148 #ifdef __ARMEB__
 149 #define BE              1
 150 #define FIRST_BYTE_16   "mov    %1, %1, ror #8\n"
 151 #define FIRST_BYTE_32   "mov    %1, %1, ror #24\n"
 152 #define NEXT_BYTE       "ror #24"
 153 #else
 154 #define BE              0
 155 #define FIRST_BYTE_16
 156 #define FIRST_BYTE_32
 157 #define NEXT_BYTE       "lsr #8"
 158 #endif
 159
 160 #define __get8_unaligned_check(ins,val,addr,err)        \
 161         __asm__(                                        \
 162         "1:     "ins"   %1, [%2], #1\n"                 \
 163         "2:\n"                                          \
 164         "       .section .fixup,\"ax\"\n"               \
 165         "       .align  2\n"                            \
 166         "3:     mov     %0, #1\n"                       \
 167         "       b       2b\n"                           \
 168         "       .previous\n"                            \
 169         "       .section __ex_table,\"a\"\n"            \
 170         "       .align  3\n"                            \
 171         "       .long   1b, 3b\n"                       \
 172         "       .previous\n"                            \
 173         : "=r" (err), "=&r" (val), "=r" (addr)          \
 174         : "0" (err), "2" (addr))
 175
 176 #define __get16_unaligned_check(ins,val,addr)                   \
 177         do {                                                    \
 178                 unsigned int err = 0, v, a = addr;              \
 179                 __get8_unaligned_check(ins,v,a,err);            \
 180                 val =  v << ((BE) ? 8 : 0);                     \
 181                 __get8_unaligned_check(ins,v,a,err);            \
 182                 val |= v << ((BE) ? 0 : 8);                     \
 183                 if (err)                                        \
 184                         goto fault;                             \
 185         } while (0)
 186
 187 #define get16_unaligned_check(val,addr) \
 188         __get16_unaligned_check("ldrb",val,addr)
 189
 190 #define get16t_unaligned_check(val,addr) \
 191         __get16_unaligned_check("ldrbt",val,addr)
 192
 193 #define __get32_unaligned_check(ins,val,addr)                   \
 194         do {                                                    \
 195                 unsigned int err = 0, v, a = addr;              \
 196                 __get8_unaligned_check(ins,v,a,err);            \
 197                 val =  v << ((BE) ? 24 :  0);                   \
 198                 __get8_unaligned_check(ins,v,a,err);            \
 199                 val |= v << ((BE) ? 16 :  8);                   \
 200                 __get8_unaligned_check(ins,v,a,err);            \
 201                 val |= v << ((BE) ?  8 : 16);                   \
 202                 __get8_unaligned_check(ins,v,a,err);            \
 203                 val |= v << ((BE) ?  0 : 24);                   \
 204                 if (err)                                        \
 205                         goto fault;                             \
 206         } while (0)
 207
 208 #define get32_unaligned_check(val,addr) \
 209         __get32_unaligned_check("ldrb",val,addr)
 210
 211 #define get32t_unaligned_check(val,addr) \
 212         __get32_unaligned_check("ldrbt",val,addr)
 213
 214 #define __put16_unaligned_check(ins,val,addr)                   \
 215         do {                                                    \
 216                 unsigned int err = 0, v = val, a = addr;        \
 217                 __asm__( FIRST_BYTE_16                          \
 218                 "1:     "ins"   %1, [%2], #1\n"                 \
 219                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 220                 "2:     "ins"   %1, [%2]\n"                     \
 221                 "3:\n"                                          \
 222                 "       .section .fixup,\"ax\"\n"               \
 223                 "       .align  2\n"                            \
 224                 "4:     mov     %0, #1\n"                       \
 225                 "       b       3b\n"                           \
 226                 "       .previous\n"                            \
 227                 "       .section __ex_table,\"a\"\n"            \
 228                 "       .align  3\n"                            \
 229                 "       .long   1b, 4b\n"                       \
 230                 "       .long   2b, 4b\n"                       \
 231                 "       .previous\n"                            \
 232                 : "=r" (err), "=&r" (v), "=&r" (a)              \
 233                 : "0" (err), "1" (v), "2" (a));                 \
 234                 if (err)                                        \
 235                         goto fault;                             \
 236         } while (0)
 237
 238 #define put16_unaligned_check(val,addr)  \
 239         __put16_unaligned_check("strb",val,addr)
 240
 241 #define put16t_unaligned_check(val,addr) \
 242         __put16_unaligned_check("strbt",val,addr)
 243
 244 #define __put32_unaligned_check(ins,val,addr)                   \
 245         do {                                                    \
 246                 unsigned int err = 0, v = val, a = addr;        \
 247                 __asm__( FIRST_BYTE_32                          \
 248                 "1:     "ins"   %1, [%2], #1\n"                 \
 249                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 250                 "2:     "ins"   %1, [%2], #1\n"                 \
 251                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 252                 "3:     "ins"   %1, [%2], #1\n"                 \
 253                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 254                 "4:     "ins"   %1, [%2]\n"                     \
 255                 "5:\n"                                          \
 256                 "       .section .fixup,\"ax\"\n"               \
 257                 "       .align  2\n"                            \
 258                 "6:     mov     %0, #1\n"                       \
 259                 "       b       5b\n"                           \
 260                 "       .previous\n"                            \
 261                 "       .section __ex_table,\"a\"\n"            \
 262                 "       .align  3\n"                            \
 263                 "       .long   1b, 6b\n"                       \
 264                 "       .long   2b, 6b\n"                       \
 265                 "       .long   3b, 6b\n"                       \
 266                 "       .long   4b, 6b\n"                       \
 267                 "       .previous\n"                            \
 268                 : "=r" (err), "=&r" (v), "=&r" (a)              \
 269                 : "0" (err), "1" (v), "2" (a));                 \
 270                 if (err)                                        \
 271                         goto fault;                             \
 272         } while (0)
 273
 274 #define put32_unaligned_check(val,addr) \
 275         __put32_unaligned_check("strb", val, addr)
 276
 277 #define put32t_unaligned_check(val,addr) \
 278         __put32_unaligned_check("strbt", val, addr)
 279
 280 static void
 281 do_alignment_finish_ldst(unsigned long addr, unsigned long instr, struct pt_regs *regs, union offset_union offset)
 282 {
 283         if (!LDST_U_BIT(instr))
 284                 offset.un = -offset.un;
 285
 286         if (!LDST_P_BIT(instr))
 287                 addr += offset.un;
 288
 289         if (!LDST_P_BIT(instr) || LDST_W_BIT(instr))
 290                 regs->uregs[RN_BITS(instr)] = addr;
 291 }
 292
 293 static int
 294 do_alignment_ldrhstrh(unsigned long addr, unsigned long instr, struct pt_regs *regs)
 295 {
 296         unsigned int rd = RD_BITS(instr);
 297
 298         ai_half += 1;
 299
 300         if (user_mode(regs))
 301                 goto user;
 302
 303         if (LDST_L_BIT(instr)) {
 304                 unsigned long val;
 305                 get16_unaligned_check(val, addr);
 306
 307                 /* signed half-word? */
 308                 if (instr & 0x40)
 309                         val = (signed long)((signed short) val);
 310
 311                 regs->uregs[rd] = val;
 312         } else
 313                 put16_unaligned_check(regs->uregs[rd], addr);
 314
 315         return TYPE_LDST;
 316
 317  user:
 318         if (LDST_L_BIT(instr)) {
 319                 unsigned long val;
 320                 get16t_unaligned_check(val, addr);
 321
 322                 /* signed half-word? */
 323                 if (instr & 0x40)
 324                         val = (signed long)((signed short) val);
 325
 326                 regs->uregs[rd] = val;
 327         } else
 328                 put16t_unaligned_check(regs->uregs[rd], addr);
 329
 330         return TYPE_LDST;
 331
 332  fault:
 333         return TYPE_FAULT;
 334 }
 335
 336 static int
 337 do_alignment_ldrdstrd(unsigned long addr, unsigned long instr,
 338                       struct pt_regs *regs)
 339 {
 340         unsigned int rd = RD_BITS(instr);
 341         unsigned int rd2;
 342         int load;
 343
 344         if ((instr & 0xfe000000) == 0xe8000000) {
 345                 /* ARMv7 Thumb-2 32-bit LDRD/STRD */
 346                 rd2 = (instr >> 8) & 0xf;
 347                 load = !!(LDST_L_BIT(instr));
 348         } else if (((rd & 1) == 1) || (rd == 14))
 349                 goto bad;
 350         else {
 351                 load = ((instr & 0xf0) == 0xd0);
 352                 rd2 = rd + 1;
 353         }
 354
 355         ai_dword += 1;
 356
 357         if (user_mode(regs))
 358                 goto user;
 359
 360         if (load) {
 361                 unsigned long val;
 362                 get32_unaligned_check(val, addr);
 363                 regs->uregs[rd] = val;
 364                 get32_unaligned_check(val, addr + 4);
 365                 regs->uregs[rd2] = val;
 366         } else {
 367                 put32_unaligned_check(regs->uregs[rd], addr);
 368                 put32_unaligned_check(regs->uregs[rd2], addr + 4);
 369         }
 370
 371         return TYPE_LDST;
 372
 373  user:
 374         if (load) {
 375                 unsigned long val;
 376                 get32t_unaligned_check(val, addr);
 377                 regs->uregs[rd] = val;
 378                 get32t_unaligned_check(val, addr + 4);
 379                 regs->uregs[rd2] = val;
 380         } else {
 381                 put32t_unaligned_check(regs->uregs[rd], addr);
 382                 put32t_unaligned_check(regs->uregs[rd2], addr + 4);
 383         }
 384
 385         return TYPE_LDST;
 386  bad:
 387         return TYPE_ERROR;
 388  fault:
 389         return TYPE_FAULT;
 390 }
 391
 392 static int
 393 do_alignment_ldrstr(unsigned long addr, unsigned long instr, struct pt_regs *regs)
 394 {
 395         unsigned int rd = RD_BITS(instr);
 396
 397         ai_word += 1;
 398
 399         if ((!LDST_P_BIT(instr) && LDST_W_BIT(instr)) || user_mode(regs))
 400                 goto trans;
 401
 402         if (LDST_L_BIT(instr)) {
 403                 unsigned int val;
 404                 get32_unaligned_check(val, addr);
 405                 regs->uregs[rd] = val;
 406         } else
 407                 put32_unaligned_check(regs->uregs[rd], addr);
 408         return TYPE_LDST;
 409
 410  trans:
 411         if (LDST_L_BIT(instr)) {
 412                 unsigned int val;
 413                 get32t_unaligned_check(val, addr);
 414                 regs->uregs[rd] = val;
 415         } else
 416                 put32t_unaligned_check(regs->uregs[rd], addr);
 417         return TYPE_LDST;
 418
 419  fault:
 420         return TYPE_FAULT;
 421 }
 422
 423 /*
 424  * LDM/STM alignment handler.
 425  *
 426  * There are 4 variants of this instruction:
 427  *
 428  * B = rn pointer before instruction, A = rn pointer after instruction
 429  *              ------ increasing address ----->
 430  *              |    | r0 | r1 | ... | rx |    |
 431  * PU = 01             B                    A
 432  * PU = 11        B                    A
 433  * PU = 00        A                    B
 434  * PU = 10             A                    B
 435  */
 436 static int
 437 do_alignment_ldmstm(unsigned long addr, unsigned long instr, struct pt_regs *regs)
 438 {
 439         unsigned int rd, rn, correction, nr_regs, regbits;
 440         unsigned long eaddr, newaddr;
 441
 442         if (LDM_S_BIT(instr))
 443                 goto bad;
 444
 445         correction = 4; /* processor implementation defined */
 446         regs->ARM_pc += correction;
 447
 448         ai_multi += 1;
 449
 450         /* count the number of registers in the mask to be transferred */
 451         nr_regs = hweight16(REGMASK_BITS(instr)) * 4;
 452
 453         rn = RN_BITS(instr);
 454         newaddr = eaddr = regs->uregs[rn];
 455
 456         if (!LDST_U_BIT(instr))
 457                 nr_regs = -nr_regs;
 458         newaddr += nr_regs;
 459         if (!LDST_U_BIT(instr))
 460                 eaddr = newaddr;
 461
 462         if (LDST_P_EQ_U(instr)) /* U = P */
 463                 eaddr += 4;
 464
 465         /*
 466          * For alignment faults on the ARM922T/ARM920T the MMU  makes
 467          * the FSR (and hence addr) equal to the updated base address
 468          * of the multiple access rather than the restored value.
 469          * Switch this message off if we've got a ARM92[02], otherwise
 470          * [ls]dm alignment faults are noisy!
 471          */
 472 #if !(defined CONFIG_CPU_ARM922T)  && !(defined CONFIG_CPU_ARM920T)
 473         /*
 474          * This is a "hint" - we already have eaddr worked out by the
 475          * processor for us.
 476          */
 477         if (addr != eaddr) {
 478                 printk(KERN_ERR "LDMSTM: PC = %08lx, instr = %08lx, "
 479                         "addr = %08lx, eaddr = %08lx\n",
 480                          instruction_pointer(regs), instr, addr, eaddr);
 481                 show_regs(regs);
 482         }
 483 #endif
 484
 485         if (user_mode(regs)) {
 486                 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
 487                      regbits >>= 1, rd += 1)
 488                         if (regbits & 1) {
 489                                 if (LDST_L_BIT(instr)) {
 490                                         unsigned int val;
 491                                         get32t_unaligned_check(val, eaddr);
 492                                         regs->uregs[rd] = val;
 493                                 } else
 494                                         put32t_unaligned_check(regs->uregs[rd], eaddr);
 495                                 eaddr += 4;
 496                         }
 497         } else {
 498                 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
 499                      regbits >>= 1, rd += 1)
 500                         if (regbits & 1) {
 501                                 if (LDST_L_BIT(instr)) {
 502                                         unsigned int val;
 503                                         get32_unaligned_check(val, eaddr);
 504                                         regs->uregs[rd] = val;
 505                                 } else
 506                                         put32_unaligned_check(regs->uregs[rd], eaddr);
 507                                 eaddr += 4;
 508                         }
 509         }
 510
 511         if (LDST_W_BIT(instr))
 512                 regs->uregs[rn] = newaddr;
 513         if (!LDST_L_BIT(instr) || !(REGMASK_BITS(instr) & (1 << 15)))
 514                 regs->ARM_pc -= correction;
 515         return TYPE_DONE;
 516
 517 fault:
 518         regs->ARM_pc -= correction;
 519         return TYPE_FAULT;
 520
 521 bad:
 522         printk(KERN_ERR "Alignment trap: not handling ldm with s-bit set\n");
 523         return TYPE_ERROR;
 524 }
 525
 526 /*
 527  * Convert Thumb ld/st instruction forms to equivalent ARM instructions so
 528  * we can reuse ARM userland alignment fault fixups for Thumb.
 529  *
 530  * This implementation was initially based on the algorithm found in
 531  * gdb/sim/arm/thumbemu.c. It is basically just a code reduction of same
 532  * to convert only Thumb ld/st instruction forms to equivalent ARM forms.
 533  *
 534  * NOTES:
 535  * 1. Comments below refer to ARM ARM DDI0100E Thumb Instruction sections.
 536  * 2. If for some reason we're passed an non-ld/st Thumb instruction to
 537  *    decode, we return 0xdeadc0de. This should never happen under normal
 538  *    circumstances but if it does, we've got other problems to deal with
 539  *    elsewhere and we obviously can't fix those problems here.
 540  */
 541
 542 static unsigned long
 543 thumb2arm(u16 tinstr)
 544 {
 545         u32 L = (tinstr & (1<<11)) >> 11;
 546
 547         switch ((tinstr & 0xf800) >> 11) {
 548         /* 6.5.1 Format 1: */
 549         case 0x6000 >> 11:                              /* 7.1.52 STR(1) */
 550         case 0x6800 >> 11:                              /* 7.1.26 LDR(1) */
 551         case 0x7000 >> 11:                              /* 7.1.55 STRB(1) */
 552         case 0x7800 >> 11:                              /* 7.1.30 LDRB(1) */
 553                 return 0xe5800000 |
 554                         ((tinstr & (1<<12)) << (22-12)) |       /* fixup */
 555                         (L<<20) |                               /* L==1? */
 556                         ((tinstr & (7<<0)) << (12-0)) |         /* Rd */
 557                         ((tinstr & (7<<3)) << (16-3)) |         /* Rn */
 558                         ((tinstr & (31<<6)) >>                  /* immed_5 */
 559                                 (6 - ((tinstr & (1<<12)) ? 0 : 2)));
 560         case 0x8000 >> 11:                              /* 7.1.57 STRH(1) */
 561         case 0x8800 >> 11:                              /* 7.1.32 LDRH(1) */
 562                 return 0xe1c000b0 |
 563                         (L<<20) |                               /* L==1? */
 564                         ((tinstr & (7<<0)) << (12-0)) |         /* Rd */
 565                         ((tinstr & (7<<3)) << (16-3)) |         /* Rn */
 566                         ((tinstr & (7<<6)) >> (6-1)) |   /* immed_5[2:0] */
 567                         ((tinstr & (3<<9)) >> (9-8));    /* immed_5[4:3] */
 568
 569         /* 6.5.1 Format 2: */
 570         case 0x5000 >> 11:
 571         case 0x5800 >> 11:
 572                 {
 573                         static const u32 subset[8] = {
 574                                 0xe7800000,             /* 7.1.53 STR(2) */
 575                                 0xe18000b0,             /* 7.1.58 STRH(2) */
 576                                 0xe7c00000,             /* 7.1.56 STRB(2) */
 577                                 0xe19000d0,             /* 7.1.34 LDRSB */
 578                                 0xe7900000,             /* 7.1.27 LDR(2) */
 579                                 0xe19000b0,             /* 7.1.33 LDRH(2) */
 580                                 0xe7d00000,             /* 7.1.31 LDRB(2) */
 581                                 0xe19000f0              /* 7.1.35 LDRSH */
 582                         };
 583                         return subset[(tinstr & (7<<9)) >> 9] |
 584                             ((tinstr & (7<<0)) << (12-0)) |     /* Rd */
 585                             ((tinstr & (7<<3)) << (16-3)) |     /* Rn */
 586                             ((tinstr & (7<<6)) >> (6-0));       /* Rm */
 587                 }
 588
 589         /* 6.5.1 Format 3: */
 590         case 0x4800 >> 11:                              /* 7.1.28 LDR(3) */
 591                 /* NOTE: This case is not technically possible. We're
 592                  *       loading 32-bit memory data via PC relative
 593                  *       addressing mode. So we can and should eliminate
 594                  *       this case. But I'll leave it here for now.
 595                  */
 596                 return 0xe59f0000 |
 597                     ((tinstr & (7<<8)) << (12-8)) |             /* Rd */
 598                     ((tinstr & 255) << (2-0));                  /* immed_8 */
 599
 600         /* 6.5.1 Format 4: */
 601         case 0x9000 >> 11:                              /* 7.1.54 STR(3) */
 602         case 0x9800 >> 11:                              /* 7.1.29 LDR(4) */
 603                 return 0xe58d0000 |
 604                         (L<<20) |                               /* L==1? */
 605                         ((tinstr & (7<<8)) << (12-8)) |         /* Rd */
 606                         ((tinstr & 255) << 2);                  /* immed_8 */
 607
 608         /* 6.6.1 Format 1: */
 609         case 0xc000 >> 11:                              /* 7.1.51 STMIA */
 610         case 0xc800 >> 11:                              /* 7.1.25 LDMIA */
 611                 {
 612                         u32 Rn = (tinstr & (7<<8)) >> 8;
 613                         u32 W = ((L<<Rn) & (tinstr&255)) ? 0 : 1<<21;
 614
 615                         return 0xe8800000 | W | (L<<20) | (Rn<<16) |
 616                                 (tinstr&255);
 617                 }
 618
 619         /* 6.6.1 Format 2: */
 620         case 0xb000 >> 11:                              /* 7.1.48 PUSH */
 621         case 0xb800 >> 11:                              /* 7.1.47 POP */
 622                 if ((tinstr & (3 << 9)) == 0x0400) {
 623                         static const u32 subset[4] = {
 624                                 0xe92d0000,     /* STMDB sp!,{registers} */
 625                                 0xe92d4000,     /* STMDB sp!,{registers,lr} */
 626                                 0xe8bd0000,     /* LDMIA sp!,{registers} */
 627                                 0xe8bd8000      /* LDMIA sp!,{registers,pc} */
 628                         };
 629                         return subset[(L<<1) | ((tinstr & (1<<8)) >> 8)] |
 630                             (tinstr & 255);             /* register_list */
 631                 }
 632                 /* Else fall through for illegal instruction case */
 633
 634         default:
 635                 return BAD_INSTR;
 636         }
 637 }
 638
 639 /*
 640  * Convert Thumb-2 32 bit LDM, STM, LDRD, STRD to equivalent instruction
 641  * handlable by ARM alignment handler, also find the corresponding handler,
 642  * so that we can reuse ARM userland alignment fault fixups for Thumb.
 643  *
 644  * @pinstr: original Thumb-2 instruction; returns new handlable instruction
 645  * @regs: register context.
 646  * @poffset: return offset from faulted addr for later writeback
 647  *
 648  * NOTES:
 649  * 1. Comments below refer to ARMv7 DDI0406A Thumb Instruction sections.
 650  * 2. Register name Rt from ARMv7 is same as Rd from ARMv6 (Rd is Rt)
 651  */
 652 static void *
 653 do_alignment_t32_to_handler(unsigned long *pinstr, struct pt_regs *regs,
 654                             union offset_union *poffset)
 655 {
 656         unsigned long instr = *pinstr;
 657         u16 tinst1 = (instr >> 16) & 0xffff;
 658         u16 tinst2 = instr & 0xffff;
 659         poffset->un = 0;
 660
 661         switch (tinst1 & 0xffe0) {
 662         /* A6.3.5 Load/Store multiple */
 663         case 0xe880:            /* STM/STMIA/STMEA,LDM/LDMIA, PUSH/POP T2 */
 664         case 0xe8a0:            /* ...above writeback version */
 665         case 0xe900:            /* STMDB/STMFD, LDMDB/LDMEA */
 666         case 0xe920:            /* ...above writeback version */
 667                 /* no need offset decision since handler calculates it */
 668                 return do_alignment_ldmstm;
 669
 670         case 0xf840:            /* POP/PUSH T3 (single register) */
 671                 if (RN_BITS(instr) == 13 && (tinst2 & 0x09ff) == 0x0904) {
 672                         u32 L = !!(LDST_L_BIT(instr));
 673                         const u32 subset[2] = {
 674                                 0xe92d0000,     /* STMDB sp!,{registers} */
 675                                 0xe8bd0000,     /* LDMIA sp!,{registers} */
 676                         };
 677                         *pinstr = subset[L] | (1<<RD_BITS(instr));
 678                         return do_alignment_ldmstm;
 679                 }
 680                 /* Else fall through for illegal instruction case */
 681                 break;
 682
 683         /* A6.3.6 Load/store double, STRD/LDRD(immed, lit, reg) */
 684         case 0xe860:
 685         case 0xe960:
 686         case 0xe8e0:
 687         case 0xe9e0:
 688                 poffset->un = (tinst2 & 0xff) << 2;
 689         case 0xe940:
 690         case 0xe9c0:
 691                 return do_alignment_ldrdstrd;
 692
 693         /*
 694          * No need to handle load/store instructions up to word size
 695          * since ARMv6 and later CPUs can perform unaligned accesses.
 696          */
 697         default:
 698                 break;
 699         }
 700         return NULL;
 701 }
 702
 703 static int
 704 do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 705 {
 706         union offset_union offset;
 707         unsigned long instr = 0, instrptr;
 708         int (*handler)(unsigned long addr, unsigned long instr, struct pt_regs *regs);
 709         unsigned int type;
 710         mm_segment_t fs;
 711         unsigned int fault;
 712         u16 tinstr = 0;
 713         int isize = 4;
 714         int thumb2_32b = 0;
 715
 716         instrptr = instruction_pointer(regs);
 717
 718         fs = get_fs();
 719         set_fs(KERNEL_DS);
 720         if (thumb_mode(regs)) {
 721                 fault = __get_user(tinstr, (u16 *)(instrptr & ~1));
 722                 if (!fault) {
 723                         if (cpu_architecture() >= CPU_ARCH_ARMv7 &&
 724                             IS_T32(tinstr)) {
 725                                 /* Thumb-2 32-bit */
 726                                 u16 tinst2 = 0;
 727                                 fault = __get_user(tinst2, (u16 *)(instrptr+2));
 728                                 instr = (tinstr << 16) | tinst2;
 729                                 thumb2_32b = 1;
 730                         } else {
 731                                 isize = 2;
 732                                 instr = thumb2arm(tinstr);
 733                         }
 734                 }
 735         } else
 736                 fault = __get_user(instr, (u32 *)instrptr);
 737         set_fs(fs);
 738
 739         if (fault) {
 740                 type = TYPE_FAULT;
 741                 goto bad_or_fault;
 742         }
 743
 744         if (user_mode(regs))
 745                 goto user;
 746
 747         ai_sys += 1;
 748
 749  fixup:
 750
 751         regs->ARM_pc += isize;
 752
 753         switch (CODING_BITS(instr)) {
 754         case 0x00000000:        /* 3.13.4 load/store instruction extensions */
 755                 if (LDSTHD_I_BIT(instr))
 756                         offset.un = (instr & 0xf00) >> 4 | (instr & 15);
 757                 else
 758                         offset.un = regs->uregs[RM_BITS(instr)];
 759
 760                 if ((instr & 0x000000f0) == 0x000000b0 || /* LDRH, STRH */
 761                     (instr & 0x001000f0) == 0x001000f0)   /* LDRSH */
 762                         handler = do_alignment_ldrhstrh;
 763                 else if ((instr & 0x001000f0) == 0x000000d0 || /* LDRD */
 764                          (instr & 0x001000f0) == 0x000000f0)   /* STRD */
 765                         handler = do_alignment_ldrdstrd;
 766                 else if ((instr & 0x01f00ff0) == 0x01000090) /* SWP */
 767                         goto swp;
 768                 else
 769                         goto bad;
 770                 break;
 771
 772         case 0x04000000:        /* ldr or str immediate */
 773                 offset.un = OFFSET_BITS(instr);
 774                 handler = do_alignment_ldrstr;
 775                 break;
 776
 777         case 0x06000000:        /* ldr or str register */
 778                 offset.un = regs->uregs[RM_BITS(instr)];
 779
 780                 if (IS_SHIFT(instr)) {
 781                         unsigned int shiftval = SHIFT_BITS(instr);
 782
 783                         switch(SHIFT_TYPE(instr)) {
 784                         case SHIFT_LSL:
 785                                 offset.un <<= shiftval;
 786                                 break;
 787
 788                         case SHIFT_LSR:
 789                                 offset.un >>= shiftval;
 790                                 break;
 791
 792                         case SHIFT_ASR:
 793                                 offset.sn >>= shiftval;
 794                                 break;
 795
 796                         case SHIFT_RORRRX:
 797                                 if (shiftval == 0) {
 798                                         offset.un >>= 1;
 799                                         if (regs->ARM_cpsr & PSR_C_BIT)
 800                                                 offset.un |= 1 << 31;
 801                                 } else
 802                                         offset.un = offset.un >> shiftval |
 803                                                           offset.un << (32 - shiftval);
 804                                 break;
 805                         }
 806                 }
 807                 handler = do_alignment_ldrstr;
 808                 break;
 809
 810         case 0x08000000:        /* ldm or stm, or thumb-2 32bit instruction */
 811                 if (thumb2_32b)
 812                         handler = do_alignment_t32_to_handler(&instr, regs, &offset);
 813                 else
 814                         handler = do_alignment_ldmstm;
 815                 break;
 816
 817         default:
 818                 goto bad;
 819         }
 820
 821         if (!handler)
 822                 goto bad;
 823         type = handler(addr, instr, regs);
 824
 825         if (type == TYPE_ERROR || type == TYPE_FAULT) {
 826                 regs->ARM_pc -= isize;
 827                 goto bad_or_fault;
 828         }
 829
 830         if (type == TYPE_LDST)
 831                 do_alignment_finish_ldst(addr, instr, regs, offset);
 832
 833         return 0;
 834
 835  bad_or_fault:
 836         if (type == TYPE_ERROR)
 837                 goto bad;
 838         /*
 839          * We got a fault - fix it up, or die.
 840          */
 841         do_bad_area(addr, fsr, regs);
 842         return 0;
 843
 844  swp:
 845         printk(KERN_ERR "Alignment trap: not handling swp instruction\n");
 846
 847  bad:
 848         /*
 849          * Oops, we didn't handle the instruction.
 850          */
 851         printk(KERN_ERR "Alignment trap: not handling instruction "
 852                 "%0*lx at [<%08lx>]\n",
 853                 isize << 1,
 854                 isize == 2 ? tinstr : instr, instrptr);
 855         ai_skipped += 1;
 856         return 1;
 857
 858  user:
 859         ai_user += 1;
 860
 861         if (ai_usermode & UM_WARN)
 862                 printk("Alignment trap: %s (%d) PC=0x%08lx Instr=0x%0*lx "
 863                        "Address=0x%08lx FSR 0x%03x\n", current->comm,
 864                         task_pid_nr(current), instrptr,
 865                         isize << 1,
 866                         isize == 2 ? tinstr : instr,
 867                         addr, fsr);
 868
 869         if (ai_usermode & UM_FIXUP)
 870                 goto fixup;
 871
 872         if (ai_usermode & UM_SIGNAL)
 873                 force_sig(SIGBUS, current);
 874         else
 875                 set_cr(cr_no_alignment);
 876
 877         return 0;
 878 }
 879
 880 /*
 881  * This needs to be done after sysctl_init, otherwise sys/ will be
 882  * overwritten.  Actually, this shouldn't be in sys/ at all since
 883  * it isn't a sysctl, and it doesn't contain sysctl information.
 884  * We now locate it in /proc/cpu/alignment instead.
 885  */
 886 static int __init alignment_init(void)
 887 {
 888 #ifdef CONFIG_PROC_FS
 889         struct proc_dir_entry *res;
 890
 891         res = proc_mkdir("cpu", NULL);
 892         if (!res)
 893                 return -ENOMEM;
 894
 895         res = create_proc_entry("alignment", S_IWUSR | S_IRUGO, res);
 896         if (!res)
 897                 return -ENOMEM;
 898
 899         res->read_proc = proc_alignment_read;
 900         res->write_proc = proc_alignment_write;
 901 #endif
 902
 903         /*
 904          * ARMv6 and later CPUs can perform unaligned accesses for
 905          * most single load and store instructions up to word size.
 906          * LDM, STM, LDRD and STRD still need to be handled.
 907          *
 908          * Ignoring the alignment fault is not an option on these
 909          * CPUs since we spin re-faulting the instruction without
 910          * making any progress.
 911          */
 912         if (cpu_architecture() >= CPU_ARCH_ARMv6 && (cr_alignment & CR_U)) {
 913                 cr_alignment &= ~CR_A;
 914                 cr_no_alignment &= ~CR_A;
 915                 set_cr(cr_alignment);
 916                 ai_usermode = UM_FIXUP;
 917         }
 918
 919         hook_fault_code(1, do_alignment, SIGILL, "alignment exception");
 920         hook_fault_code(3, do_alignment, SIGILL, "alignment exception");
 921
 922         return 0;
 923 }
 924
 925 fs_initcall(alignment_init);