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/moduleparam.h>
  15 #include <linux/compiler.h>
  16 #include <linux/kernel.h>
  17 #include <linux/errno.h>
  18 #include <linux/string.h>
  19 #include <linux/proc_fs.h>
  20 #include <linux/seq_file.h>
  21 #include <linux/init.h>
  22 #include <linux/sched.h>
  23 #include <linux/uaccess.h>
  24
  25 #include <asm/cp15.h>
  26 #include <asm/system_info.h>
  27 #include <asm/unaligned.h>
  28
  29 #include "fault.h"
  30
  31 /*
  32  * 32-bit misaligned trap handler (c) 1998 San Mehat (CCC) -July 1998
  33  * /proc/sys/debug/alignment, modified and integrated into
  34  * Linux 2.1 by Russell King
  35  *
  36  * Speed optimisations and better fault handling by Russell King.
  37  *
  38  * *** NOTE ***
  39  * This code is not portable to processors with late data abort handling.
  40  */
  41 #define CODING_BITS(i)  (i & 0x0e000000)
  42
  43 #define LDST_I_BIT(i)   (i & (1 << 26))         /* Immediate constant   */
  44 #define LDST_P_BIT(i)   (i & (1 << 24))         /* Preindex             */
  45 #define LDST_U_BIT(i)   (i & (1 << 23))         /* Add offset           */
  46 #define LDST_W_BIT(i)   (i & (1 << 21))         /* Writeback            */
  47 #define LDST_L_BIT(i)   (i & (1 << 20))         /* Load                 */
  48
  49 #define LDST_P_EQ_U(i)  ((((i) ^ ((i) >> 1)) & (1 << 23)) == 0)
  50
  51 #define LDSTHD_I_BIT(i) (i & (1 << 22))         /* double/half-word immed */
  52 #define LDM_S_BIT(i)    (i & (1 << 22))         /* write CPSR from SPSR */
  53
  54 #define RN_BITS(i)      ((i >> 16) & 15)        /* Rn                   */
  55 #define RD_BITS(i)      ((i >> 12) & 15)        /* Rd                   */
  56 #define RM_BITS(i)      (i & 15)                /* Rm                   */
  57
  58 #define REGMASK_BITS(i) (i & 0xffff)
  59 #define OFFSET_BITS(i)  (i & 0x0fff)
  60
  61 #define IS_SHIFT(i)     (i & 0x0ff0)
  62 #define SHIFT_BITS(i)   ((i >> 7) & 0x1f)
  63 #define SHIFT_TYPE(i)   (i & 0x60)
  64 #define SHIFT_LSL       0x00
  65 #define SHIFT_LSR       0x20
  66 #define SHIFT_ASR       0x40
  67 #define SHIFT_RORRRX    0x60
  68
  69 #define BAD_INSTR       0xdeadc0de
  70
  71 /* Thumb-2 32 bit format per ARMv7 DDI0406A A6.3, either f800h,e800h,f800h */
  72 #define IS_T32(hi16) \
  73         (((hi16) & 0xe000) == 0xe000 && ((hi16) & 0x1800))
  74
  75 static unsigned long ai_user;
  76 static unsigned long ai_sys;
  77 static unsigned long ai_skipped;
  78 static unsigned long ai_half;
  79 static unsigned long ai_word;
  80 static unsigned long ai_dword;
  81 static unsigned long ai_multi;
  82 static int ai_usermode;
  83
  84 core_param(alignment, ai_usermode, int, 0600);
  85
  86 #define UM_WARN         (1 << 0)
  87 #define UM_FIXUP        (1 << 1)
  88 #define UM_SIGNAL       (1 << 2)
  89
  90 /* Return true if and only if the ARMv6 unaligned access model is in use. */
  91 static bool cpu_is_v6_unaligned(void)
  92 {
  93         return cpu_architecture() >= CPU_ARCH_ARMv6 && (cr_alignment & CR_U);
  94 }
  95
  96 static int safe_usermode(int new_usermode, bool warn)
  97 {
  98         /*
  99          * ARMv6 and later CPUs can perform unaligned accesses for
 100          * most single load and store instructions up to word size.
 101          * LDM, STM, LDRD and STRD still need to be handled.
 102          *
 103          * Ignoring the alignment fault is not an option on these
 104          * CPUs since we spin re-faulting the instruction without
 105          * making any progress.
 106          */
 107         if (cpu_is_v6_unaligned() && !(new_usermode & (UM_FIXUP | UM_SIGNAL))) {
 108                 new_usermode |= UM_FIXUP;
 109
 110                 if (warn)
 111                         printk(KERN_WARNING "alignment: ignoring faults is unsafe on this CPU.  Defaulting to fixup mode.\n");
 112         }
 113
 114         return new_usermode;
 115 }
 116
 117 #ifdef CONFIG_PROC_FS
 118 static const char *usermode_action[] = {
 119         "ignored",
 120         "warn",
 121         "fixup",
 122         "fixup+warn",
 123         "signal",
 124         "signal+warn"
 125 };
 126
 127 static int alignment_proc_show(struct seq_file *m, void *v)
 128 {
 129         seq_printf(m, "User:\t\t%lu\n", ai_user);
 130         seq_printf(m, "System:\t\t%lu\n", ai_sys);
 131         seq_printf(m, "Skipped:\t%lu\n", ai_skipped);
 132         seq_printf(m, "Half:\t\t%lu\n", ai_half);
 133         seq_printf(m, "Word:\t\t%lu\n", ai_word);
 134         if (cpu_architecture() >= CPU_ARCH_ARMv5TE)
 135                 seq_printf(m, "DWord:\t\t%lu\n", ai_dword);
 136         seq_printf(m, "Multi:\t\t%lu\n", ai_multi);
 137         seq_printf(m, "User faults:\t%i (%s)\n", ai_usermode,
 138                         usermode_action[ai_usermode]);
 139
 140         return 0;
 141 }
 142
 143 static int alignment_proc_open(struct inode *inode, struct file *file)
 144 {
 145         return single_open(file, alignment_proc_show, NULL);
 146 }
 147
 148 static ssize_t alignment_proc_write(struct file *file, const char __user *buffer,
 149                                     size_t count, loff_t *pos)
 150 {
 151         char mode;
 152
 153         if (count > 0) {
 154                 if (get_user(mode, buffer))
 155                         return -EFAULT;
 156                 if (mode >= '0' && mode <= '5')
 157                         ai_usermode = safe_usermode(mode - '0', true);
 158         }
 159         return count;
 160 }
 161
 162 static const struct file_operations alignment_proc_fops = {
 163         .open           = alignment_proc_open,
 164         .read           = seq_read,
 165         .llseek         = seq_lseek,
 166         .release        = single_release,
 167         .write          = alignment_proc_write,
 168 };
 169 #endif /* CONFIG_PROC_FS */
 170
 171 union offset_union {
 172         unsigned long un;
 173           signed long sn;
 174 };
 175
 176 #define TYPE_ERROR      0
 177 #define TYPE_FAULT      1
 178 #define TYPE_LDST       2
 179 #define TYPE_DONE       3
 180
 181 #ifdef __ARMEB__
 182 #define BE              1
 183 #define FIRST_BYTE_16   "mov    %1, %1, ror #8\n"
 184 #define FIRST_BYTE_32   "mov    %1, %1, ror #24\n"
 185 #define NEXT_BYTE       "ror #24"
 186 #else
 187 #define BE              0
 188 #define FIRST_BYTE_16
 189 #define FIRST_BYTE_32
 190 #define NEXT_BYTE       "lsr #8"
 191 #endif
 192
 193 #define __get8_unaligned_check(ins,val,addr,err)        \
 194         __asm__(                                        \
 195  ARM(   "1:     "ins"   %1, [%2], #1\n" )               \
 196  THUMB( "1:     "ins"   %1, [%2]\n"     )               \
 197  THUMB( "       add     %2, %2, #1\n"   )               \
 198         "2:\n"                                          \
 199         "       .pushsection .fixup,\"ax\"\n"           \
 200         "       .align  2\n"                            \
 201         "3:     mov     %0, #1\n"                       \
 202         "       b       2b\n"                           \
 203         "       .popsection\n"                          \
 204         "       .pushsection __ex_table,\"a\"\n"        \
 205         "       .align  3\n"                            \
 206         "       .long   1b, 3b\n"                       \
 207         "       .popsection\n"                          \
 208         : "=r" (err), "=&r" (val), "=r" (addr)          \
 209         : "0" (err), "2" (addr))
 210
 211 #define __get16_unaligned_check(ins,val,addr)                   \
 212         do {                                                    \
 213                 unsigned int err = 0, v, a = addr;              \
 214                 __get8_unaligned_check(ins,v,a,err);            \
 215                 val =  v << ((BE) ? 8 : 0);                     \
 216                 __get8_unaligned_check(ins,v,a,err);            \
 217                 val |= v << ((BE) ? 0 : 8);                     \
 218                 if (err)                                        \
 219                         goto fault;                             \
 220         } while (0)
 221
 222 #define get16_unaligned_check(val,addr) \
 223         __get16_unaligned_check("ldrb",val,addr)
 224
 225 #define get16t_unaligned_check(val,addr) \
 226         __get16_unaligned_check("ldrbt",val,addr)
 227
 228 #define __get32_unaligned_check(ins,val,addr)                   \
 229         do {                                                    \
 230                 unsigned int err = 0, v, a = addr;              \
 231                 __get8_unaligned_check(ins,v,a,err);            \
 232                 val =  v << ((BE) ? 24 :  0);                   \
 233                 __get8_unaligned_check(ins,v,a,err);            \
 234                 val |= v << ((BE) ? 16 :  8);                   \
 235                 __get8_unaligned_check(ins,v,a,err);            \
 236                 val |= v << ((BE) ?  8 : 16);                   \
 237                 __get8_unaligned_check(ins,v,a,err);            \
 238                 val |= v << ((BE) ?  0 : 24);                   \
 239                 if (err)                                        \
 240                         goto fault;                             \
 241         } while (0)
 242
 243 #define get32_unaligned_check(val,addr) \
 244         __get32_unaligned_check("ldrb",val,addr)
 245
 246 #define get32t_unaligned_check(val,addr) \
 247         __get32_unaligned_check("ldrbt",val,addr)
 248
 249 #define __put16_unaligned_check(ins,val,addr)                   \
 250         do {                                                    \
 251                 unsigned int err = 0, v = val, a = addr;        \
 252                 __asm__( FIRST_BYTE_16                          \
 253          ARM(   "1:     "ins"   %1, [%2], #1\n" )               \
 254          THUMB( "1:     "ins"   %1, [%2]\n"     )               \
 255          THUMB( "       add     %2, %2, #1\n"   )               \
 256                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 257                 "2:     "ins"   %1, [%2]\n"                     \
 258                 "3:\n"                                          \
 259                 "       .pushsection .fixup,\"ax\"\n"           \
 260                 "       .align  2\n"                            \
 261                 "4:     mov     %0, #1\n"                       \
 262                 "       b       3b\n"                           \
 263                 "       .popsection\n"                          \
 264                 "       .pushsection __ex_table,\"a\"\n"        \
 265                 "       .align  3\n"                            \
 266                 "       .long   1b, 4b\n"                       \
 267                 "       .long   2b, 4b\n"                       \
 268                 "       .popsection\n"                          \
 269                 : "=r" (err), "=&r" (v), "=&r" (a)              \
 270                 : "0" (err), "1" (v), "2" (a));                 \
 271                 if (err)                                        \
 272                         goto fault;                             \
 273         } while (0)
 274
 275 #define put16_unaligned_check(val,addr)  \
 276         __put16_unaligned_check("strb",val,addr)
 277
 278 #define put16t_unaligned_check(val,addr) \
 279         __put16_unaligned_check("strbt",val,addr)
 280
 281 #define __put32_unaligned_check(ins,val,addr)                   \
 282         do {                                                    \
 283                 unsigned int err = 0, v = val, a = addr;        \
 284                 __asm__( FIRST_BYTE_32                          \
 285          ARM(   "1:     "ins"   %1, [%2], #1\n" )               \
 286          THUMB( "1:     "ins"   %1, [%2]\n"     )               \
 287          THUMB( "       add     %2, %2, #1\n"   )               \
 288                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 289          ARM(   "2:     "ins"   %1, [%2], #1\n" )               \
 290          THUMB( "2:     "ins"   %1, [%2]\n"     )               \
 291          THUMB( "       add     %2, %2, #1\n"   )               \
 292                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 293          ARM(   "3:     "ins"   %1, [%2], #1\n" )               \
 294          THUMB( "3:     "ins"   %1, [%2]\n"     )               \
 295          THUMB( "       add     %2, %2, #1\n"   )               \
 296                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 297                 "4:     "ins"   %1, [%2]\n"                     \
 298                 "5:\n"                                          \
 299                 "       .pushsection .fixup,\"ax\"\n"           \
 300                 "       .align  2\n"                            \
 301                 "6:     mov     %0, #1\n"                       \
 302                 "       b       5b\n"                           \
 303                 "       .popsection\n"                          \
 304                 "       .pushsection __ex_table,\"a\"\n"        \
 305                 "       .align  3\n"                            \
 306                 "       .long   1b, 6b\n"                       \
 307                 "       .long   2b, 6b\n"                       \
 308                 "       .long   3b, 6b\n"                       \
 309                 "       .long   4b, 6b\n"                       \
 310                 "       .popsection\n"                          \
 311                 : "=r" (err), "=&r" (v), "=&r" (a)              \
 312                 : "0" (err), "1" (v), "2" (a));                 \
 313                 if (err)                                        \
 314                         goto fault;                             \
 315         } while (0)
 316
 317 #define put32_unaligned_check(val,addr) \
 318         __put32_unaligned_check("strb", val, addr)
 319
 320 #define put32t_unaligned_check(val,addr) \
 321         __put32_unaligned_check("strbt", val, addr)
 322
 323 static void
 324 do_alignment_finish_ldst(unsigned long addr, unsigned long instr, struct pt_regs *regs, union offset_union offset)
 325 {
 326         if (!LDST_U_BIT(instr))
 327                 offset.un = -offset.un;
 328
 329         if (!LDST_P_BIT(instr))
 330                 addr += offset.un;
 331
 332         if (!LDST_P_BIT(instr) || LDST_W_BIT(instr))
 333                 regs->uregs[RN_BITS(instr)] = addr;
 334 }
 335
 336 static int
 337 do_alignment_ldrhstrh(unsigned long addr, unsigned long instr, struct pt_regs *regs)
 338 {
 339         unsigned int rd = RD_BITS(instr);
 340
 341         ai_half += 1;
 342
 343         if (user_mode(regs))
 344                 goto user;
 345
 346         if (LDST_L_BIT(instr)) {
 347                 unsigned long val;
 348                 get16_unaligned_check(val, addr);
 349
 350                 /* signed half-word? */
 351                 if (instr & 0x40)
 352                         val = (signed long)((signed short) val);
 353
 354                 regs->uregs[rd] = val;
 355         } else
 356                 put16_unaligned_check(regs->uregs[rd], addr);
 357
 358         return TYPE_LDST;
 359
 360  user:
 361         if (LDST_L_BIT(instr)) {
 362                 unsigned long val;
 363                 get16t_unaligned_check(val, addr);
 364
 365                 /* signed half-word? */
 366                 if (instr & 0x40)
 367                         val = (signed long)((signed short) val);
 368
 369                 regs->uregs[rd] = val;
 370         } else
 371                 put16t_unaligned_check(regs->uregs[rd], addr);
 372
 373         return TYPE_LDST;
 374
 375  fault:
 376         return TYPE_FAULT;
 377 }
 378
 379 static int
 380 do_alignment_ldrdstrd(unsigned long addr, unsigned long instr,
 381                       struct pt_regs *regs)
 382 {
 383         unsigned int rd = RD_BITS(instr);
 384         unsigned int rd2;
 385         int load;
 386
 387         if ((instr & 0xfe000000) == 0xe8000000) {
 388                 /* ARMv7 Thumb-2 32-bit LDRD/STRD */
 389                 rd2 = (instr >> 8) & 0xf;
 390                 load = !!(LDST_L_BIT(instr));
 391         } else if (((rd & 1) == 1) || (rd == 14))
 392                 goto bad;
 393         else {
 394                 load = ((instr & 0xf0) == 0xd0);
 395                 rd2 = rd + 1;
 396         }
 397
 398         ai_dword += 1;
 399
 400         if (user_mode(regs))
 401                 goto user;
 402
 403         if (load) {
 404                 unsigned long val;
 405                 get32_unaligned_check(val, addr);
 406                 regs->uregs[rd] = val;
 407                 get32_unaligned_check(val, addr + 4);
 408                 regs->uregs[rd2] = val;
 409         } else {
 410                 put32_unaligned_check(regs->uregs[rd], addr);
 411                 put32_unaligned_check(regs->uregs[rd2], addr + 4);
 412         }
 413
 414         return TYPE_LDST;
 415
 416  user:
 417         if (load) {
 418                 unsigned long val;
 419                 get32t_unaligned_check(val, addr);
 420                 regs->uregs[rd] = val;
 421                 get32t_unaligned_check(val, addr + 4);
 422                 regs->uregs[rd2] = val;
 423         } else {
 424                 put32t_unaligned_check(regs->uregs[rd], addr);
 425                 put32t_unaligned_check(regs->uregs[rd2], addr + 4);
 426         }
 427
 428         return TYPE_LDST;
 429  bad:
 430         return TYPE_ERROR;
 431  fault:
 432         return TYPE_FAULT;
 433 }
 434
 435 static int
 436 do_alignment_ldrstr(unsigned long addr, unsigned long instr, struct pt_regs *regs)
 437 {
 438         unsigned int rd = RD_BITS(instr);
 439
 440         ai_word += 1;
 441
 442         if ((!LDST_P_BIT(instr) && LDST_W_BIT(instr)) || user_mode(regs))
 443                 goto trans;
 444
 445         if (LDST_L_BIT(instr)) {
 446                 unsigned int val;
 447                 get32_unaligned_check(val, addr);
 448                 regs->uregs[rd] = val;
 449         } else
 450                 put32_unaligned_check(regs->uregs[rd], addr);
 451         return TYPE_LDST;
 452
 453  trans:
 454         if (LDST_L_BIT(instr)) {
 455                 unsigned int val;
 456                 get32t_unaligned_check(val, addr);
 457                 regs->uregs[rd] = val;
 458         } else
 459                 put32t_unaligned_check(regs->uregs[rd], addr);
 460         return TYPE_LDST;
 461
 462  fault:
 463         return TYPE_FAULT;
 464 }
 465
 466 /*
 467  * LDM/STM alignment handler.
 468  *
 469  * There are 4 variants of this instruction:
 470  *
 471  * B = rn pointer before instruction, A = rn pointer after instruction
 472  *              ------ increasing address ----->
 473  *              |    | r0 | r1 | ... | rx |    |
 474  * PU = 01             B                    A
 475  * PU = 11        B                    A
 476  * PU = 00        A                    B
 477  * PU = 10             A                    B
 478  */
 479 static int
 480 do_alignment_ldmstm(unsigned long addr, unsigned long instr, struct pt_regs *regs)
 481 {
 482         unsigned int rd, rn, correction, nr_regs, regbits;
 483         unsigned long eaddr, newaddr;
 484
 485         if (LDM_S_BIT(instr))
 486                 goto bad;
 487
 488         correction = 4; /* processor implementation defined */
 489         regs->ARM_pc += correction;
 490
 491         ai_multi += 1;
 492
 493         /* count the number of registers in the mask to be transferred */
 494         nr_regs = hweight16(REGMASK_BITS(instr)) * 4;
 495
 496         rn = RN_BITS(instr);
 497         newaddr = eaddr = regs->uregs[rn];
 498
 499         if (!LDST_U_BIT(instr))
 500                 nr_regs = -nr_regs;
 501         newaddr += nr_regs;
 502         if (!LDST_U_BIT(instr))
 503                 eaddr = newaddr;
 504
 505         if (LDST_P_EQ_U(instr)) /* U = P */
 506                 eaddr += 4;
 507
 508         /*
 509          * For alignment faults on the ARM922T/ARM920T the MMU  makes
 510          * the FSR (and hence addr) equal to the updated base address
 511          * of the multiple access rather than the restored value.
 512          * Switch this message off if we've got a ARM92[02], otherwise
 513          * [ls]dm alignment faults are noisy!
 514          */
 515 #if !(defined CONFIG_CPU_ARM922T)  && !(defined CONFIG_CPU_ARM920T)
 516         /*
 517          * This is a "hint" - we already have eaddr worked out by the
 518          * processor for us.
 519          */
 520         if (addr != eaddr) {
 521                 printk(KERN_ERR "LDMSTM: PC = %08lx, instr = %08lx, "
 522                         "addr = %08lx, eaddr = %08lx\n",
 523                          instruction_pointer(regs), instr, addr, eaddr);
 524                 show_regs(regs);
 525         }
 526 #endif
 527
 528         if (user_mode(regs)) {
 529                 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
 530                      regbits >>= 1, rd += 1)
 531                         if (regbits & 1) {
 532                                 if (LDST_L_BIT(instr)) {
 533                                         unsigned int val;
 534                                         get32t_unaligned_check(val, eaddr);
 535                                         regs->uregs[rd] = val;
 536                                 } else
 537                                         put32t_unaligned_check(regs->uregs[rd], eaddr);
 538                                 eaddr += 4;
 539                         }
 540         } else {
 541                 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
 542                      regbits >>= 1, rd += 1)
 543                         if (regbits & 1) {
 544                                 if (LDST_L_BIT(instr)) {
 545                                         unsigned int val;
 546                                         get32_unaligned_check(val, eaddr);
 547                                         regs->uregs[rd] = val;
 548                                 } else
 549                                         put32_unaligned_check(regs->uregs[rd], eaddr);
 550                                 eaddr += 4;
 551                         }
 552         }
 553
 554         if (LDST_W_BIT(instr))
 555                 regs->uregs[rn] = newaddr;
 556         if (!LDST_L_BIT(instr) || !(REGMASK_BITS(instr) & (1 << 15)))
 557                 regs->ARM_pc -= correction;
 558         return TYPE_DONE;
 559
 560 fault:
 561         regs->ARM_pc -= correction;
 562         return TYPE_FAULT;
 563
 564 bad:
 565         printk(KERN_ERR "Alignment trap: not handling ldm with s-bit set\n");
 566         return TYPE_ERROR;
 567 }
 568
 569 /*
 570  * Convert Thumb ld/st instruction forms to equivalent ARM instructions so
 571  * we can reuse ARM userland alignment fault fixups for Thumb.
 572  *
 573  * This implementation was initially based on the algorithm found in
 574  * gdb/sim/arm/thumbemu.c. It is basically just a code reduction of same
 575  * to convert only Thumb ld/st instruction forms to equivalent ARM forms.
 576  *
 577  * NOTES:
 578  * 1. Comments below refer to ARM ARM DDI0100E Thumb Instruction sections.
 579  * 2. If for some reason we're passed an non-ld/st Thumb instruction to
 580  *    decode, we return 0xdeadc0de. This should never happen under normal
 581  *    circumstances but if it does, we've got other problems to deal with
 582  *    elsewhere and we obviously can't fix those problems here.
 583  */
 584
 585 static unsigned long
 586 thumb2arm(u16 tinstr)
 587 {
 588         u32 L = (tinstr & (1<<11)) >> 11;
 589
 590         switch ((tinstr & 0xf800) >> 11) {
 591         /* 6.5.1 Format 1: */
 592         case 0x6000 >> 11:                              /* 7.1.52 STR(1) */
 593         case 0x6800 >> 11:                              /* 7.1.26 LDR(1) */
 594         case 0x7000 >> 11:                              /* 7.1.55 STRB(1) */
 595         case 0x7800 >> 11:                              /* 7.1.30 LDRB(1) */
 596                 return 0xe5800000 |
 597                         ((tinstr & (1<<12)) << (22-12)) |       /* fixup */
 598                         (L<<20) |                               /* L==1? */
 599                         ((tinstr & (7<<0)) << (12-0)) |         /* Rd */
 600                         ((tinstr & (7<<3)) << (16-3)) |         /* Rn */
 601                         ((tinstr & (31<<6)) >>                  /* immed_5 */
 602                                 (6 - ((tinstr & (1<<12)) ? 0 : 2)));
 603         case 0x8000 >> 11:                              /* 7.1.57 STRH(1) */
 604         case 0x8800 >> 11:                              /* 7.1.32 LDRH(1) */
 605                 return 0xe1c000b0 |
 606                         (L<<20) |                               /* L==1? */
 607                         ((tinstr & (7<<0)) << (12-0)) |         /* Rd */
 608                         ((tinstr & (7<<3)) << (16-3)) |         /* Rn */
 609                         ((tinstr & (7<<6)) >> (6-1)) |   /* immed_5[2:0] */
 610                         ((tinstr & (3<<9)) >> (9-8));    /* immed_5[4:3] */
 611
 612         /* 6.5.1 Format 2: */
 613         case 0x5000 >> 11:
 614         case 0x5800 >> 11:
 615                 {
 616                         static const u32 subset[8] = {
 617                                 0xe7800000,             /* 7.1.53 STR(2) */
 618                                 0xe18000b0,             /* 7.1.58 STRH(2) */
 619                                 0xe7c00000,             /* 7.1.56 STRB(2) */
 620                                 0xe19000d0,             /* 7.1.34 LDRSB */
 621                                 0xe7900000,             /* 7.1.27 LDR(2) */
 622                                 0xe19000b0,             /* 7.1.33 LDRH(2) */
 623                                 0xe7d00000,             /* 7.1.31 LDRB(2) */
 624                                 0xe19000f0              /* 7.1.35 LDRSH */
 625                         };
 626                         return subset[(tinstr & (7<<9)) >> 9] |
 627                             ((tinstr & (7<<0)) << (12-0)) |     /* Rd */
 628                             ((tinstr & (7<<3)) << (16-3)) |     /* Rn */
 629                             ((tinstr & (7<<6)) >> (6-0));       /* Rm */
 630                 }
 631
 632         /* 6.5.1 Format 3: */
 633         case 0x4800 >> 11:                              /* 7.1.28 LDR(3) */
 634                 /* NOTE: This case is not technically possible. We're
 635                  *       loading 32-bit memory data via PC relative
 636                  *       addressing mode. So we can and should eliminate
 637                  *       this case. But I'll leave it here for now.
 638                  */
 639                 return 0xe59f0000 |
 640                     ((tinstr & (7<<8)) << (12-8)) |             /* Rd */
 641                     ((tinstr & 255) << (2-0));                  /* immed_8 */
 642
 643         /* 6.5.1 Format 4: */
 644         case 0x9000 >> 11:                              /* 7.1.54 STR(3) */
 645         case 0x9800 >> 11:                              /* 7.1.29 LDR(4) */
 646                 return 0xe58d0000 |
 647                         (L<<20) |                               /* L==1? */
 648                         ((tinstr & (7<<8)) << (12-8)) |         /* Rd */
 649                         ((tinstr & 255) << 2);                  /* immed_8 */
 650
 651         /* 6.6.1 Format 1: */
 652         case 0xc000 >> 11:                              /* 7.1.51 STMIA */
 653         case 0xc800 >> 11:                              /* 7.1.25 LDMIA */
 654                 {
 655                         u32 Rn = (tinstr & (7<<8)) >> 8;
 656                         u32 W = ((L<<Rn) & (tinstr&255)) ? 0 : 1<<21;
 657
 658                         return 0xe8800000 | W | (L<<20) | (Rn<<16) |
 659                                 (tinstr&255);
 660                 }
 661
 662         /* 6.6.1 Format 2: */
 663         case 0xb000 >> 11:                              /* 7.1.48 PUSH */
 664         case 0xb800 >> 11:                              /* 7.1.47 POP */
 665                 if ((tinstr & (3 << 9)) == 0x0400) {
 666                         static const u32 subset[4] = {
 667                                 0xe92d0000,     /* STMDB sp!,{registers} */
 668                                 0xe92d4000,     /* STMDB sp!,{registers,lr} */
 669                                 0xe8bd0000,     /* LDMIA sp!,{registers} */
 670                                 0xe8bd8000      /* LDMIA sp!,{registers,pc} */
 671                         };
 672                         return subset[(L<<1) | ((tinstr & (1<<8)) >> 8)] |
 673                             (tinstr & 255);             /* register_list */
 674                 }
 675                 /* Else fall through for illegal instruction case */
 676
 677         default:
 678                 return BAD_INSTR;
 679         }
 680 }
 681
 682 /*
 683  * Convert Thumb-2 32 bit LDM, STM, LDRD, STRD to equivalent instruction
 684  * handlable by ARM alignment handler, also find the corresponding handler,
 685  * so that we can reuse ARM userland alignment fault fixups for Thumb.
 686  *
 687  * @pinstr: original Thumb-2 instruction; returns new handlable instruction
 688  * @regs: register context.
 689  * @poffset: return offset from faulted addr for later writeback
 690  *
 691  * NOTES:
 692  * 1. Comments below refer to ARMv7 DDI0406A Thumb Instruction sections.
 693  * 2. Register name Rt from ARMv7 is same as Rd from ARMv6 (Rd is Rt)
 694  */
 695 static void *
 696 do_alignment_t32_to_handler(unsigned long *pinstr, struct pt_regs *regs,
 697                             union offset_union *poffset)
 698 {
 699         unsigned long instr = *pinstr;
 700         u16 tinst1 = (instr >> 16) & 0xffff;
 701         u16 tinst2 = instr & 0xffff;
 702
 703         switch (tinst1 & 0xffe0) {
 704         /* A6.3.5 Load/Store multiple */
 705         case 0xe880:            /* STM/STMIA/STMEA,LDM/LDMIA, PUSH/POP T2 */
 706         case 0xe8a0:            /* ...above writeback version */
 707         case 0xe900:            /* STMDB/STMFD, LDMDB/LDMEA */
 708         case 0xe920:            /* ...above writeback version */
 709                 /* no need offset decision since handler calculates it */
 710                 return do_alignment_ldmstm;
 711
 712         case 0xf840:            /* POP/PUSH T3 (single register) */
 713                 if (RN_BITS(instr) == 13 && (tinst2 & 0x09ff) == 0x0904) {
 714                         u32 L = !!(LDST_L_BIT(instr));
 715                         const u32 subset[2] = {
 716                                 0xe92d0000,     /* STMDB sp!,{registers} */
 717                                 0xe8bd0000,     /* LDMIA sp!,{registers} */
 718                         };
 719                         *pinstr = subset[L] | (1<<RD_BITS(instr));
 720                         return do_alignment_ldmstm;
 721                 }
 722                 /* Else fall through for illegal instruction case */
 723                 break;
 724
 725         /* A6.3.6 Load/store double, STRD/LDRD(immed, lit, reg) */
 726         case 0xe860:
 727         case 0xe960:
 728         case 0xe8e0:
 729         case 0xe9e0:
 730                 poffset->un = (tinst2 & 0xff) << 2;
 731         case 0xe940:
 732         case 0xe9c0:
 733                 return do_alignment_ldrdstrd;
 734
 735         /*
 736          * No need to handle load/store instructions up to word size
 737          * since ARMv6 and later CPUs can perform unaligned accesses.
 738          */
 739         default:
 740                 break;
 741         }
 742         return NULL;
 743 }
 744
 745 static int
 746 do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 747 {
 748         union offset_union offset;
 749         unsigned long instr = 0, instrptr;
 750         int (*handler)(unsigned long addr, unsigned long instr, struct pt_regs *regs);
 751         unsigned int type;
 752         mm_segment_t fs;
 753         unsigned int fault;
 754         u16 tinstr = 0;
 755         int isize = 4;
 756         int thumb2_32b = 0;
 757
 758         if (interrupts_enabled(regs))
 759                 local_irq_enable();
 760
 761         instrptr = instruction_pointer(regs);
 762
 763         fs = get_fs();
 764         set_fs(KERNEL_DS);
 765         if (thumb_mode(regs)) {
 766                 fault = __get_user(tinstr, (u16 *)(instrptr & ~1));
 767                 if (!fault) {
 768                         if (cpu_architecture() >= CPU_ARCH_ARMv7 &&
 769                             IS_T32(tinstr)) {
 770                                 /* Thumb-2 32-bit */
 771                                 u16 tinst2 = 0;
 772                                 fault = __get_user(tinst2, (u16 *)(instrptr+2));
 773                                 instr = (tinstr << 16) | tinst2;
 774                                 thumb2_32b = 1;
 775                         } else {
 776                                 isize = 2;
 777                                 instr = thumb2arm(tinstr);
 778                         }
 779                 }
 780         } else
 781                 fault = __get_user(instr, (u32 *)instrptr);
 782         set_fs(fs);
 783
 784         if (fault) {
 785                 type = TYPE_FAULT;
 786                 goto bad_or_fault;
 787         }
 788
 789         if (user_mode(regs))
 790                 goto user;
 791
 792         ai_sys += 1;
 793
 794  fixup:
 795
 796         regs->ARM_pc += isize;
 797
 798         switch (CODING_BITS(instr)) {
 799         case 0x00000000:        /* 3.13.4 load/store instruction extensions */
 800                 if (LDSTHD_I_BIT(instr))
 801                         offset.un = (instr & 0xf00) >> 4 | (instr & 15);
 802                 else
 803                         offset.un = regs->uregs[RM_BITS(instr)];
 804
 805                 if ((instr & 0x000000f0) == 0x000000b0 || /* LDRH, STRH */
 806                     (instr & 0x001000f0) == 0x001000f0)   /* LDRSH */
 807                         handler = do_alignment_ldrhstrh;
 808                 else if ((instr & 0x001000f0) == 0x000000d0 || /* LDRD */
 809                          (instr & 0x001000f0) == 0x000000f0)   /* STRD */
 810                         handler = do_alignment_ldrdstrd;
 811                 else if ((instr & 0x01f00ff0) == 0x01000090) /* SWP */
 812                         goto swp;
 813                 else
 814                         goto bad;
 815                 break;
 816
 817         case 0x04000000:        /* ldr or str immediate */
 818                 offset.un = OFFSET_BITS(instr);
 819                 handler = do_alignment_ldrstr;
 820                 break;
 821
 822         case 0x06000000:        /* ldr or str register */
 823                 offset.un = regs->uregs[RM_BITS(instr)];
 824
 825                 if (IS_SHIFT(instr)) {
 826                         unsigned int shiftval = SHIFT_BITS(instr);
 827
 828                         switch(SHIFT_TYPE(instr)) {
 829                         case SHIFT_LSL:
 830                                 offset.un <<= shiftval;
 831                                 break;
 832
 833                         case SHIFT_LSR:
 834                                 offset.un >>= shiftval;
 835                                 break;
 836
 837                         case SHIFT_ASR:
 838                                 offset.sn >>= shiftval;
 839                                 break;
 840
 841                         case SHIFT_RORRRX:
 842                                 if (shiftval == 0) {
 843                                         offset.un >>= 1;
 844                                         if (regs->ARM_cpsr & PSR_C_BIT)
 845                                                 offset.un |= 1 << 31;
 846                                 } else
 847                                         offset.un = offset.un >> shiftval |
 848                                                           offset.un << (32 - shiftval);
 849                                 break;
 850                         }
 851                 }
 852                 handler = do_alignment_ldrstr;
 853                 break;
 854
 855         case 0x08000000:        /* ldm or stm, or thumb-2 32bit instruction */
 856                 if (thumb2_32b) {
 857                         offset.un = 0;
 858                         handler = do_alignment_t32_to_handler(&instr, regs, &offset);
 859                 } else
 860                         handler = do_alignment_ldmstm;
 861                 break;
 862
 863         default:
 864                 goto bad;
 865         }
 866
 867         if (!handler)
 868                 goto bad;
 869         type = handler(addr, instr, regs);
 870
 871         if (type == TYPE_ERROR || type == TYPE_FAULT) {
 872                 regs->ARM_pc -= isize;
 873                 goto bad_or_fault;
 874         }
 875
 876         if (type == TYPE_LDST)
 877                 do_alignment_finish_ldst(addr, instr, regs, offset);
 878
 879         return 0;
 880
 881  bad_or_fault:
 882         if (type == TYPE_ERROR)
 883                 goto bad;
 884         /*
 885          * We got a fault - fix it up, or die.
 886          */
 887         do_bad_area(addr, fsr, regs);
 888         return 0;
 889
 890  swp:
 891         printk(KERN_ERR "Alignment trap: not handling swp instruction\n");
 892
 893  bad:
 894         /*
 895          * Oops, we didn't handle the instruction.
 896          */
 897         printk(KERN_ERR "Alignment trap: not handling instruction "
 898                 "%0*lx at [<%08lx>]\n",
 899                 isize << 1,
 900                 isize == 2 ? tinstr : instr, instrptr);
 901         ai_skipped += 1;
 902         return 1;
 903
 904  user:
 905         ai_user += 1;
 906
 907         if (ai_usermode & UM_WARN)
 908                 printk("Alignment trap: %s (%d) PC=0x%08lx Instr=0x%0*lx "
 909                        "Address=0x%08lx FSR 0x%03x\n", current->comm,
 910                         task_pid_nr(current), instrptr,
 911                         isize << 1,
 912                         isize == 2 ? tinstr : instr,
 913                         addr, fsr);
 914
 915         if (ai_usermode & UM_FIXUP)
 916                 goto fixup;
 917
 918         if (ai_usermode & UM_SIGNAL) {
 919                 siginfo_t si;
 920
 921                 si.si_signo = SIGBUS;
 922                 si.si_errno = 0;
 923                 si.si_code = BUS_ADRALN;
 924                 si.si_addr = (void __user *)addr;
 925
 926                 force_sig_info(si.si_signo, &si, current);
 927         } else {
 928                 /*
 929                  * We're about to disable the alignment trap and return to
 930                  * user space.  But if an interrupt occurs before actually
 931                  * reaching user space, then the IRQ vector entry code will
 932                  * notice that we were still in kernel space and therefore
 933                  * the alignment trap won't be re-enabled in that case as it
 934                  * is presumed to be always on from kernel space.
 935                  * Let's prevent that race by disabling interrupts here (they
 936                  * are disabled on the way back to user space anyway in
 937                  * entry-common.S) and disable the alignment trap only if
 938                  * there is no work pending for this thread.
 939                  */
 940                 raw_local_irq_disable();
 941                 if (!(current_thread_info()->flags & _TIF_WORK_MASK))
 942                         set_cr(cr_no_alignment);
 943         }
 944
 945         return 0;
 946 }
 947
 948 /*
 949  * This needs to be done after sysctl_init, otherwise sys/ will be
 950  * overwritten.  Actually, this shouldn't be in sys/ at all since
 951  * it isn't a sysctl, and it doesn't contain sysctl information.
 952  * We now locate it in /proc/cpu/alignment instead.
 953  */
 954 static int __init alignment_init(void)
 955 {
 956 #ifdef CONFIG_PROC_FS
 957         struct proc_dir_entry *res;
 958
 959         res = proc_create("cpu/alignment", S_IWUSR | S_IRUGO, NULL,
 960                           &alignment_proc_fops);
 961         if (!res)
 962                 return -ENOMEM;
 963 #endif
 964
 965         if (cpu_is_v6_unaligned()) {
 966                 cr_alignment &= ~CR_A;
 967                 cr_no_alignment &= ~CR_A;
 968                 set_cr(cr_alignment);
 969                 ai_usermode = safe_usermode(ai_usermode, false);
 970         }
 971
 972         hook_fault_code(FAULT_CODE_ALIGNMENT, do_alignment, SIGBUS, BUS_ADRALN,
 973                         "alignment exception");
 974
 975         /*
 976          * ARMv6K and ARMv7 use fault status 3 (0b00011) as Access Flag section
 977          * fault, not as alignment error.
 978          *
 979          * TODO: handle ARMv6K properly. Runtime check for 'K' extension is
 980          * needed.
 981          */
 982         if (cpu_architecture() <= CPU_ARCH_ARMv6) {
 983                 hook_fault_code(3, do_alignment, SIGBUS, BUS_ADRALN,
 984                                 "alignment exception");
 985         }
 986
 987         return 0;
 988 }
 989
 990 fs_initcall(alignment_init);