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/sched/debug.h>
  18 #include <linux/errno.h>
  19 #include <linux/string.h>
  20 #include <linux/proc_fs.h>
  21 #include <linux/seq_file.h>
  22 #include <linux/init.h>
  23 #include <linux/sched/signal.h>
  24 #include <linux/uaccess.h>
  25
  26 #include <asm/cp15.h>
  27 #include <asm/system_info.h>
  28 #include <asm/unaligned.h>
  29 #include <asm/opcodes.h>
  30
  31 #include "fault.h"
  32 #include "mm.h"
  33
  34 /*
  35  * 32-bit misaligned trap handler (c) 1998 San Mehat (CCC) -July 1998
  36  * /proc/sys/debug/alignment, modified and integrated into
  37  * Linux 2.1 by Russell King
  38  *
  39  * Speed optimisations and better fault handling by Russell King.
  40  *
  41  * *** NOTE ***
  42  * This code is not portable to processors with late data abort handling.
  43  */
  44 #define CODING_BITS(i)  (i & 0x0e000000)
  45 #define COND_BITS(i)    (i & 0xf0000000)
  46
  47 #define LDST_I_BIT(i)   (i & (1 << 26))         /* Immediate constant   */
  48 #define LDST_P_BIT(i)   (i & (1 << 24))         /* Preindex             */
  49 #define LDST_U_BIT(i)   (i & (1 << 23))         /* Add offset           */
  50 #define LDST_W_BIT(i)   (i & (1 << 21))         /* Writeback            */
  51 #define LDST_L_BIT(i)   (i & (1 << 20))         /* Load                 */
  52
  53 #define LDST_P_EQ_U(i)  ((((i) ^ ((i) >> 1)) & (1 << 23)) == 0)
  54
  55 #define LDSTHD_I_BIT(i) (i & (1 << 22))         /* double/half-word immed */
  56 #define LDM_S_BIT(i)    (i & (1 << 22))         /* write CPSR from SPSR */
  57
  58 #define RN_BITS(i)      ((i >> 16) & 15)        /* Rn                   */
  59 #define RD_BITS(i)      ((i >> 12) & 15)        /* Rd                   */
  60 #define RM_BITS(i)      (i & 15)                /* Rm                   */
  61
  62 #define REGMASK_BITS(i) (i & 0xffff)
  63 #define OFFSET_BITS(i)  (i & 0x0fff)
  64
  65 #define IS_SHIFT(i)     (i & 0x0ff0)
  66 #define SHIFT_BITS(i)   ((i >> 7) & 0x1f)
  67 #define SHIFT_TYPE(i)   (i & 0x60)
  68 #define SHIFT_LSL       0x00
  69 #define SHIFT_LSR       0x20
  70 #define SHIFT_ASR       0x40
  71 #define SHIFT_RORRRX    0x60
  72
  73 #define BAD_INSTR       0xdeadc0de
  74
  75 /* Thumb-2 32 bit format per ARMv7 DDI0406A A6.3, either f800h,e800h,f800h */
  76 #define IS_T32(hi16) \
  77         (((hi16) & 0xe000) == 0xe000 && ((hi16) & 0x1800))
  78
  79 static unsigned long ai_user;
  80 static unsigned long ai_sys;
  81 static void *ai_sys_last_pc;
  82 static unsigned long ai_skipped;
  83 static unsigned long ai_half;
  84 static unsigned long ai_word;
  85 static unsigned long ai_dword;
  86 static unsigned long ai_multi;
  87 static int ai_usermode;
  88 static unsigned long cr_no_alignment;
  89
  90 core_param(alignment, ai_usermode, int, 0600);
  91
  92 #define UM_WARN         (1 << 0)
  93 #define UM_FIXUP        (1 << 1)
  94 #define UM_SIGNAL       (1 << 2)
  95
  96 /* Return true if and only if the ARMv6 unaligned access model is in use. */
  97 static bool cpu_is_v6_unaligned(void)
  98 {
  99         return cpu_architecture() >= CPU_ARCH_ARMv6 && get_cr() & CR_U;
 100 }
 101
 102 static int safe_usermode(int new_usermode, bool warn)
 103 {
 104         /*
 105          * ARMv6 and later CPUs can perform unaligned accesses for
 106          * most single load and store instructions up to word size.
 107          * LDM, STM, LDRD and STRD still need to be handled.
 108          *
 109          * Ignoring the alignment fault is not an option on these
 110          * CPUs since we spin re-faulting the instruction without
 111          * making any progress.
 112          */
 113         if (cpu_is_v6_unaligned() && !(new_usermode & (UM_FIXUP | UM_SIGNAL))) {
 114                 new_usermode |= UM_FIXUP;
 115
 116                 if (warn)
 117                         pr_warn("alignment: ignoring faults is unsafe on this CPU.  Defaulting to fixup mode.\n");
 118         }
 119
 120         return new_usermode;
 121 }
 122
 123 #ifdef CONFIG_PROC_FS
 124 static const char *usermode_action[] = {
 125         "ignored",
 126         "warn",
 127         "fixup",
 128         "fixup+warn",
 129         "signal",
 130         "signal+warn"
 131 };
 132
 133 static int alignment_proc_show(struct seq_file *m, void *v)
 134 {
 135         seq_printf(m, "User:\t\t%lu\n", ai_user);
 136         seq_printf(m, "System:\t\t%lu (%pF)\n", ai_sys, ai_sys_last_pc);
 137         seq_printf(m, "Skipped:\t%lu\n", ai_skipped);
 138         seq_printf(m, "Half:\t\t%lu\n", ai_half);
 139         seq_printf(m, "Word:\t\t%lu\n", ai_word);
 140         if (cpu_architecture() >= CPU_ARCH_ARMv5TE)
 141                 seq_printf(m, "DWord:\t\t%lu\n", ai_dword);
 142         seq_printf(m, "Multi:\t\t%lu\n", ai_multi);
 143         seq_printf(m, "User faults:\t%i (%s)\n", ai_usermode,
 144                         usermode_action[ai_usermode]);
 145
 146         return 0;
 147 }
 148
 149 static int alignment_proc_open(struct inode *inode, struct file *file)
 150 {
 151         return single_open(file, alignment_proc_show, NULL);
 152 }
 153
 154 static ssize_t alignment_proc_write(struct file *file, const char __user *buffer,
 155                                     size_t count, loff_t *pos)
 156 {
 157         char mode;
 158
 159         if (count > 0) {
 160                 if (get_user(mode, buffer))
 161                         return -EFAULT;
 162                 if (mode >= '0' && mode <= '5')
 163                         ai_usermode = safe_usermode(mode - '0', true);
 164         }
 165         return count;
 166 }
 167
 168 static const struct file_operations alignment_proc_fops = {
 169         .open           = alignment_proc_open,
 170         .read           = seq_read,
 171         .llseek         = seq_lseek,
 172         .release        = single_release,
 173         .write          = alignment_proc_write,
 174 };
 175 #endif /* CONFIG_PROC_FS */
 176
 177 union offset_union {
 178         unsigned long un;
 179           signed long sn;
 180 };
 181
 182 #define TYPE_ERROR      0
 183 #define TYPE_FAULT      1
 184 #define TYPE_LDST       2
 185 #define TYPE_DONE       3
 186
 187 #ifdef __ARMEB__
 188 #define BE              1
 189 #define FIRST_BYTE_16   "mov    %1, %1, ror #8\n"
 190 #define FIRST_BYTE_32   "mov    %1, %1, ror #24\n"
 191 #define NEXT_BYTE       "ror #24"
 192 #else
 193 #define BE              0
 194 #define FIRST_BYTE_16
 195 #define FIRST_BYTE_32
 196 #define NEXT_BYTE       "lsr #8"
 197 #endif
 198
 199 #define __get8_unaligned_check(ins,val,addr,err)        \
 200         __asm__(                                        \
 201  ARM(   "1:     "ins"   %1, [%2], #1\n" )               \
 202  THUMB( "1:     "ins"   %1, [%2]\n"     )               \
 203  THUMB( "       add     %2, %2, #1\n"   )               \
 204         "2:\n"                                          \
 205         "       .pushsection .text.fixup,\"ax\"\n"      \
 206         "       .align  2\n"                            \
 207         "3:     mov     %0, #1\n"                       \
 208         "       b       2b\n"                           \
 209         "       .popsection\n"                          \
 210         "       .pushsection __ex_table,\"a\"\n"        \
 211         "       .align  3\n"                            \
 212         "       .long   1b, 3b\n"                       \
 213         "       .popsection\n"                          \
 214         : "=r" (err), "=&r" (val), "=r" (addr)          \
 215         : "0" (err), "2" (addr))
 216
 217 #define __get16_unaligned_check(ins,val,addr)                   \
 218         do {                                                    \
 219                 unsigned int err = 0, v, a = addr;              \
 220                 __get8_unaligned_check(ins,v,a,err);            \
 221                 val =  v << ((BE) ? 8 : 0);                     \
 222                 __get8_unaligned_check(ins,v,a,err);            \
 223                 val |= v << ((BE) ? 0 : 8);                     \
 224                 if (err)                                        \
 225                         goto fault;                             \
 226         } while (0)
 227
 228 #define get16_unaligned_check(val,addr) \
 229         __get16_unaligned_check("ldrb",val,addr)
 230
 231 #define get16t_unaligned_check(val,addr) \
 232         __get16_unaligned_check("ldrbt",val,addr)
 233
 234 #define __get32_unaligned_check(ins,val,addr)                   \
 235         do {                                                    \
 236                 unsigned int err = 0, v, a = addr;              \
 237                 __get8_unaligned_check(ins,v,a,err);            \
 238                 val =  v << ((BE) ? 24 :  0);                   \
 239                 __get8_unaligned_check(ins,v,a,err);            \
 240                 val |= v << ((BE) ? 16 :  8);                   \
 241                 __get8_unaligned_check(ins,v,a,err);            \
 242                 val |= v << ((BE) ?  8 : 16);                   \
 243                 __get8_unaligned_check(ins,v,a,err);            \
 244                 val |= v << ((BE) ?  0 : 24);                   \
 245                 if (err)                                        \
 246                         goto fault;                             \
 247         } while (0)
 248
 249 #define get32_unaligned_check(val,addr) \
 250         __get32_unaligned_check("ldrb",val,addr)
 251
 252 #define get32t_unaligned_check(val,addr) \
 253         __get32_unaligned_check("ldrbt",val,addr)
 254
 255 #define __put16_unaligned_check(ins,val,addr)                   \
 256         do {                                                    \
 257                 unsigned int err = 0, v = val, a = addr;        \
 258                 __asm__( FIRST_BYTE_16                          \
 259          ARM(   "1:     "ins"   %1, [%2], #1\n" )               \
 260          THUMB( "1:     "ins"   %1, [%2]\n"     )               \
 261          THUMB( "       add     %2, %2, #1\n"   )               \
 262                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 263                 "2:     "ins"   %1, [%2]\n"                     \
 264                 "3:\n"                                          \
 265                 "       .pushsection .text.fixup,\"ax\"\n"      \
 266                 "       .align  2\n"                            \
 267                 "4:     mov     %0, #1\n"                       \
 268                 "       b       3b\n"                           \
 269                 "       .popsection\n"                          \
 270                 "       .pushsection __ex_table,\"a\"\n"        \
 271                 "       .align  3\n"                            \
 272                 "       .long   1b, 4b\n"                       \
 273                 "       .long   2b, 4b\n"                       \
 274                 "       .popsection\n"                          \
 275                 : "=r" (err), "=&r" (v), "=&r" (a)              \
 276                 : "0" (err), "1" (v), "2" (a));                 \
 277                 if (err)                                        \
 278                         goto fault;                             \
 279         } while (0)
 280
 281 #define put16_unaligned_check(val,addr)  \
 282         __put16_unaligned_check("strb",val,addr)
 283
 284 #define put16t_unaligned_check(val,addr) \
 285         __put16_unaligned_check("strbt",val,addr)
 286
 287 #define __put32_unaligned_check(ins,val,addr)                   \
 288         do {                                                    \
 289                 unsigned int err = 0, v = val, a = addr;        \
 290                 __asm__( FIRST_BYTE_32                          \
 291          ARM(   "1:     "ins"   %1, [%2], #1\n" )               \
 292          THUMB( "1:     "ins"   %1, [%2]\n"     )               \
 293          THUMB( "       add     %2, %2, #1\n"   )               \
 294                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 295          ARM(   "2:     "ins"   %1, [%2], #1\n" )               \
 296          THUMB( "2:     "ins"   %1, [%2]\n"     )               \
 297          THUMB( "       add     %2, %2, #1\n"   )               \
 298                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 299          ARM(   "3:     "ins"   %1, [%2], #1\n" )               \
 300          THUMB( "3:     "ins"   %1, [%2]\n"     )               \
 301          THUMB( "       add     %2, %2, #1\n"   )               \
 302                 "       mov     %1, %1, "NEXT_BYTE"\n"          \
 303                 "4:     "ins"   %1, [%2]\n"                     \
 304                 "5:\n"                                          \
 305                 "       .pushsection .text.fixup,\"ax\"\n"      \
 306                 "       .align  2\n"                            \
 307                 "6:     mov     %0, #1\n"                       \
 308                 "       b       5b\n"                           \
 309                 "       .popsection\n"                          \
 310                 "       .pushsection __ex_table,\"a\"\n"        \
 311                 "       .align  3\n"                            \
 312                 "       .long   1b, 6b\n"                       \
 313                 "       .long   2b, 6b\n"                       \
 314                 "       .long   3b, 6b\n"                       \
 315                 "       .long   4b, 6b\n"                       \
 316                 "       .popsection\n"                          \
 317                 : "=r" (err), "=&r" (v), "=&r" (a)              \
 318                 : "0" (err), "1" (v), "2" (a));                 \
 319                 if (err)                                        \
 320                         goto fault;                             \
 321         } while (0)
 322
 323 #define put32_unaligned_check(val,addr) \
 324         __put32_unaligned_check("strb", val, addr)
 325
 326 #define put32t_unaligned_check(val,addr) \
 327         __put32_unaligned_check("strbt", val, addr)
 328
 329 static void
 330 do_alignment_finish_ldst(unsigned long addr, unsigned long instr, struct pt_regs *regs, union offset_union offset)
 331 {
 332         if (!LDST_U_BIT(instr))
 333                 offset.un = -offset.un;
 334
 335         if (!LDST_P_BIT(instr))
 336                 addr += offset.un;
 337
 338         if (!LDST_P_BIT(instr) || LDST_W_BIT(instr))
 339                 regs->uregs[RN_BITS(instr)] = addr;
 340 }
 341
 342 static int
 343 do_alignment_ldrhstrh(unsigned long addr, unsigned long instr, struct pt_regs *regs)
 344 {
 345         unsigned int rd = RD_BITS(instr);
 346
 347         ai_half += 1;
 348
 349         if (user_mode(regs))
 350                 goto user;
 351
 352         if (LDST_L_BIT(instr)) {
 353                 unsigned long val;
 354                 get16_unaligned_check(val, addr);
 355
 356                 /* signed half-word? */
 357                 if (instr & 0x40)
 358                         val = (signed long)((signed short) val);
 359
 360                 regs->uregs[rd] = val;
 361         } else
 362                 put16_unaligned_check(regs->uregs[rd], addr);
 363
 364         return TYPE_LDST;
 365
 366  user:
 367         if (LDST_L_BIT(instr)) {
 368                 unsigned long val;
 369                 unsigned int __ua_flags = uaccess_save_and_enable();
 370
 371                 get16t_unaligned_check(val, addr);
 372                 uaccess_restore(__ua_flags);
 373
 374                 /* signed half-word? */
 375                 if (instr & 0x40)
 376                         val = (signed long)((signed short) val);
 377
 378                 regs->uregs[rd] = val;
 379         } else {
 380                 unsigned int __ua_flags = uaccess_save_and_enable();
 381                 put16t_unaligned_check(regs->uregs[rd], addr);
 382                 uaccess_restore(__ua_flags);
 383         }
 384
 385         return TYPE_LDST;
 386
 387  fault:
 388         return TYPE_FAULT;
 389 }
 390
 391 static int
 392 do_alignment_ldrdstrd(unsigned long addr, unsigned long instr,
 393                       struct pt_regs *regs)
 394 {
 395         unsigned int rd = RD_BITS(instr);
 396         unsigned int rd2;
 397         int load;
 398
 399         if ((instr & 0xfe000000) == 0xe8000000) {
 400                 /* ARMv7 Thumb-2 32-bit LDRD/STRD */
 401                 rd2 = (instr >> 8) & 0xf;
 402                 load = !!(LDST_L_BIT(instr));
 403         } else if (((rd & 1) == 1) || (rd == 14))
 404                 goto bad;
 405         else {
 406                 load = ((instr & 0xf0) == 0xd0);
 407                 rd2 = rd + 1;
 408         }
 409
 410         ai_dword += 1;
 411
 412         if (user_mode(regs))
 413                 goto user;
 414
 415         if (load) {
 416                 unsigned long val;
 417                 get32_unaligned_check(val, addr);
 418                 regs->uregs[rd] = val;
 419                 get32_unaligned_check(val, addr + 4);
 420                 regs->uregs[rd2] = val;
 421         } else {
 422                 put32_unaligned_check(regs->uregs[rd], addr);
 423                 put32_unaligned_check(regs->uregs[rd2], addr + 4);
 424         }
 425
 426         return TYPE_LDST;
 427
 428  user:
 429         if (load) {
 430                 unsigned long val, val2;
 431                 unsigned int __ua_flags = uaccess_save_and_enable();
 432
 433                 get32t_unaligned_check(val, addr);
 434                 get32t_unaligned_check(val2, addr + 4);
 435
 436                 uaccess_restore(__ua_flags);
 437
 438                 regs->uregs[rd] = val;
 439                 regs->uregs[rd2] = val2;
 440         } else {
 441                 unsigned int __ua_flags = uaccess_save_and_enable();
 442                 put32t_unaligned_check(regs->uregs[rd], addr);
 443                 put32t_unaligned_check(regs->uregs[rd2], addr + 4);
 444                 uaccess_restore(__ua_flags);
 445         }
 446
 447         return TYPE_LDST;
 448  bad:
 449         return TYPE_ERROR;
 450  fault:
 451         return TYPE_FAULT;
 452 }
 453
 454 static int
 455 do_alignment_ldrstr(unsigned long addr, unsigned long instr, struct pt_regs *regs)
 456 {
 457         unsigned int rd = RD_BITS(instr);
 458
 459         ai_word += 1;
 460
 461         if ((!LDST_P_BIT(instr) && LDST_W_BIT(instr)) || user_mode(regs))
 462                 goto trans;
 463
 464         if (LDST_L_BIT(instr)) {
 465                 unsigned int val;
 466                 get32_unaligned_check(val, addr);
 467                 regs->uregs[rd] = val;
 468         } else
 469                 put32_unaligned_check(regs->uregs[rd], addr);
 470         return TYPE_LDST;
 471
 472  trans:
 473         if (LDST_L_BIT(instr)) {
 474                 unsigned int val;
 475                 unsigned int __ua_flags = uaccess_save_and_enable();
 476                 get32t_unaligned_check(val, addr);
 477                 uaccess_restore(__ua_flags);
 478                 regs->uregs[rd] = val;
 479         } else {
 480                 unsigned int __ua_flags = uaccess_save_and_enable();
 481                 put32t_unaligned_check(regs->uregs[rd], addr);
 482                 uaccess_restore(__ua_flags);
 483         }
 484         return TYPE_LDST;
 485
 486  fault:
 487         return TYPE_FAULT;
 488 }
 489
 490 /*
 491  * LDM/STM alignment handler.
 492  *
 493  * There are 4 variants of this instruction:
 494  *
 495  * B = rn pointer before instruction, A = rn pointer after instruction
 496  *              ------ increasing address ----->
 497  *              |    | r0 | r1 | ... | rx |    |
 498  * PU = 01             B                    A
 499  * PU = 11        B                    A
 500  * PU = 00        A                    B
 501  * PU = 10             A                    B
 502  */
 503 static int
 504 do_alignment_ldmstm(unsigned long addr, unsigned long instr, struct pt_regs *regs)
 505 {
 506         unsigned int rd, rn, correction, nr_regs, regbits;
 507         unsigned long eaddr, newaddr;
 508
 509         if (LDM_S_BIT(instr))
 510                 goto bad;
 511
 512         correction = 4; /* processor implementation defined */
 513         regs->ARM_pc += correction;
 514
 515         ai_multi += 1;
 516
 517         /* count the number of registers in the mask to be transferred */
 518         nr_regs = hweight16(REGMASK_BITS(instr)) * 4;
 519
 520         rn = RN_BITS(instr);
 521         newaddr = eaddr = regs->uregs[rn];
 522
 523         if (!LDST_U_BIT(instr))
 524                 nr_regs = -nr_regs;
 525         newaddr += nr_regs;
 526         if (!LDST_U_BIT(instr))
 527                 eaddr = newaddr;
 528
 529         if (LDST_P_EQ_U(instr)) /* U = P */
 530                 eaddr += 4;
 531
 532         /*
 533          * For alignment faults on the ARM922T/ARM920T the MMU  makes
 534          * the FSR (and hence addr) equal to the updated base address
 535          * of the multiple access rather than the restored value.
 536          * Switch this message off if we've got a ARM92[02], otherwise
 537          * [ls]dm alignment faults are noisy!
 538          */
 539 #if !(defined CONFIG_CPU_ARM922T)  && !(defined CONFIG_CPU_ARM920T)
 540         /*
 541          * This is a "hint" - we already have eaddr worked out by the
 542          * processor for us.
 543          */
 544         if (addr != eaddr) {
 545                 pr_err("LDMSTM: PC = %08lx, instr = %08lx, "
 546                         "addr = %08lx, eaddr = %08lx\n",
 547                          instruction_pointer(regs), instr, addr, eaddr);
 548                 show_regs(regs);
 549         }
 550 #endif
 551
 552         if (user_mode(regs)) {
 553                 unsigned int __ua_flags = uaccess_save_and_enable();
 554                 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
 555                      regbits >>= 1, rd += 1)
 556                         if (regbits & 1) {
 557                                 if (LDST_L_BIT(instr)) {
 558                                         unsigned int val;
 559                                         get32t_unaligned_check(val, eaddr);
 560                                         regs->uregs[rd] = val;
 561                                 } else
 562                                         put32t_unaligned_check(regs->uregs[rd], eaddr);
 563                                 eaddr += 4;
 564                         }
 565                 uaccess_restore(__ua_flags);
 566         } else {
 567                 for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
 568                      regbits >>= 1, rd += 1)
 569                         if (regbits & 1) {
 570                                 if (LDST_L_BIT(instr)) {
 571                                         unsigned int val;
 572                                         get32_unaligned_check(val, eaddr);
 573                                         regs->uregs[rd] = val;
 574                                 } else
 575                                         put32_unaligned_check(regs->uregs[rd], eaddr);
 576                                 eaddr += 4;
 577                         }
 578         }
 579
 580         if (LDST_W_BIT(instr))
 581                 regs->uregs[rn] = newaddr;
 582         if (!LDST_L_BIT(instr) || !(REGMASK_BITS(instr) & (1 << 15)))
 583                 regs->ARM_pc -= correction;
 584         return TYPE_DONE;
 585
 586 fault:
 587         regs->ARM_pc -= correction;
 588         return TYPE_FAULT;
 589
 590 bad:
 591         pr_err("Alignment trap: not handling ldm with s-bit set\n");
 592         return TYPE_ERROR;
 593 }
 594
 595 /*
 596  * Convert Thumb ld/st instruction forms to equivalent ARM instructions so
 597  * we can reuse ARM userland alignment fault fixups for Thumb.
 598  *
 599  * This implementation was initially based on the algorithm found in
 600  * gdb/sim/arm/thumbemu.c. It is basically just a code reduction of same
 601  * to convert only Thumb ld/st instruction forms to equivalent ARM forms.
 602  *
 603  * NOTES:
 604  * 1. Comments below refer to ARM ARM DDI0100E Thumb Instruction sections.
 605  * 2. If for some reason we're passed an non-ld/st Thumb instruction to
 606  *    decode, we return 0xdeadc0de. This should never happen under normal
 607  *    circumstances but if it does, we've got other problems to deal with
 608  *    elsewhere and we obviously can't fix those problems here.
 609  */
 610
 611 static unsigned long
 612 thumb2arm(u16 tinstr)
 613 {
 614         u32 L = (tinstr & (1<<11)) >> 11;
 615
 616         switch ((tinstr & 0xf800) >> 11) {
 617         /* 6.5.1 Format 1: */
 618         case 0x6000 >> 11:                              /* 7.1.52 STR(1) */
 619         case 0x6800 >> 11:                              /* 7.1.26 LDR(1) */
 620         case 0x7000 >> 11:                              /* 7.1.55 STRB(1) */
 621         case 0x7800 >> 11:                              /* 7.1.30 LDRB(1) */
 622                 return 0xe5800000 |
 623                         ((tinstr & (1<<12)) << (22-12)) |       /* fixup */
 624                         (L<<20) |                               /* L==1? */
 625                         ((tinstr & (7<<0)) << (12-0)) |         /* Rd */
 626                         ((tinstr & (7<<3)) << (16-3)) |         /* Rn */
 627                         ((tinstr & (31<<6)) >>                  /* immed_5 */
 628                                 (6 - ((tinstr & (1<<12)) ? 0 : 2)));
 629         case 0x8000 >> 11:                              /* 7.1.57 STRH(1) */
 630         case 0x8800 >> 11:                              /* 7.1.32 LDRH(1) */
 631                 return 0xe1c000b0 |
 632                         (L<<20) |                               /* L==1? */
 633                         ((tinstr & (7<<0)) << (12-0)) |         /* Rd */
 634                         ((tinstr & (7<<3)) << (16-3)) |         /* Rn */
 635                         ((tinstr & (7<<6)) >> (6-1)) |   /* immed_5[2:0] */
 636                         ((tinstr & (3<<9)) >> (9-8));    /* immed_5[4:3] */
 637
 638         /* 6.5.1 Format 2: */
 639         case 0x5000 >> 11:
 640         case 0x5800 >> 11:
 641                 {
 642                         static const u32 subset[8] = {
 643                                 0xe7800000,             /* 7.1.53 STR(2) */
 644                                 0xe18000b0,             /* 7.1.58 STRH(2) */
 645                                 0xe7c00000,             /* 7.1.56 STRB(2) */
 646                                 0xe19000d0,             /* 7.1.34 LDRSB */
 647                                 0xe7900000,             /* 7.1.27 LDR(2) */
 648                                 0xe19000b0,             /* 7.1.33 LDRH(2) */
 649                                 0xe7d00000,             /* 7.1.31 LDRB(2) */
 650                                 0xe19000f0              /* 7.1.35 LDRSH */
 651                         };
 652                         return subset[(tinstr & (7<<9)) >> 9] |
 653                             ((tinstr & (7<<0)) << (12-0)) |     /* Rd */
 654                             ((tinstr & (7<<3)) << (16-3)) |     /* Rn */
 655                             ((tinstr & (7<<6)) >> (6-0));       /* Rm */
 656                 }
 657
 658         /* 6.5.1 Format 3: */
 659         case 0x4800 >> 11:                              /* 7.1.28 LDR(3) */
 660                 /* NOTE: This case is not technically possible. We're
 661                  *       loading 32-bit memory data via PC relative
 662                  *       addressing mode. So we can and should eliminate
 663                  *       this case. But I'll leave it here for now.
 664                  */
 665                 return 0xe59f0000 |
 666                     ((tinstr & (7<<8)) << (12-8)) |             /* Rd */
 667                     ((tinstr & 255) << (2-0));                  /* immed_8 */
 668
 669         /* 6.5.1 Format 4: */
 670         case 0x9000 >> 11:                              /* 7.1.54 STR(3) */
 671         case 0x9800 >> 11:                              /* 7.1.29 LDR(4) */
 672                 return 0xe58d0000 |
 673                         (L<<20) |                               /* L==1? */
 674                         ((tinstr & (7<<8)) << (12-8)) |         /* Rd */
 675                         ((tinstr & 255) << 2);                  /* immed_8 */
 676
 677         /* 6.6.1 Format 1: */
 678         case 0xc000 >> 11:                              /* 7.1.51 STMIA */
 679         case 0xc800 >> 11:                              /* 7.1.25 LDMIA */
 680                 {
 681                         u32 Rn = (tinstr & (7<<8)) >> 8;
 682                         u32 W = ((L<<Rn) & (tinstr&255)) ? 0 : 1<<21;
 683
 684                         return 0xe8800000 | W | (L<<20) | (Rn<<16) |
 685                                 (tinstr&255);
 686                 }
 687
 688         /* 6.6.1 Format 2: */
 689         case 0xb000 >> 11:                              /* 7.1.48 PUSH */
 690         case 0xb800 >> 11:                              /* 7.1.47 POP */
 691                 if ((tinstr & (3 << 9)) == 0x0400) {
 692                         static const u32 subset[4] = {
 693                                 0xe92d0000,     /* STMDB sp!,{registers} */
 694                                 0xe92d4000,     /* STMDB sp!,{registers,lr} */
 695                                 0xe8bd0000,     /* LDMIA sp!,{registers} */
 696                                 0xe8bd8000      /* LDMIA sp!,{registers,pc} */
 697                         };
 698                         return subset[(L<<1) | ((tinstr & (1<<8)) >> 8)] |
 699                             (tinstr & 255);             /* register_list */
 700                 }
 701                 /* Else fall through for illegal instruction case */
 702
 703         default:
 704                 return BAD_INSTR;
 705         }
 706 }
 707
 708 /*
 709  * Convert Thumb-2 32 bit LDM, STM, LDRD, STRD to equivalent instruction
 710  * handlable by ARM alignment handler, also find the corresponding handler,
 711  * so that we can reuse ARM userland alignment fault fixups for Thumb.
 712  *
 713  * @pinstr: original Thumb-2 instruction; returns new handlable instruction
 714  * @regs: register context.
 715  * @poffset: return offset from faulted addr for later writeback
 716  *
 717  * NOTES:
 718  * 1. Comments below refer to ARMv7 DDI0406A Thumb Instruction sections.
 719  * 2. Register name Rt from ARMv7 is same as Rd from ARMv6 (Rd is Rt)
 720  */
 721 static void *
 722 do_alignment_t32_to_handler(unsigned long *pinstr, struct pt_regs *regs,
 723                             union offset_union *poffset)
 724 {
 725         unsigned long instr = *pinstr;
 726         u16 tinst1 = (instr >> 16) & 0xffff;
 727         u16 tinst2 = instr & 0xffff;
 728
 729         switch (tinst1 & 0xffe0) {
 730         /* A6.3.5 Load/Store multiple */
 731         case 0xe880:            /* STM/STMIA/STMEA,LDM/LDMIA, PUSH/POP T2 */
 732         case 0xe8a0:            /* ...above writeback version */
 733         case 0xe900:            /* STMDB/STMFD, LDMDB/LDMEA */
 734         case 0xe920:            /* ...above writeback version */
 735                 /* no need offset decision since handler calculates it */
 736                 return do_alignment_ldmstm;
 737
 738         case 0xf840:            /* POP/PUSH T3 (single register) */
 739                 if (RN_BITS(instr) == 13 && (tinst2 & 0x09ff) == 0x0904) {
 740                         u32 L = !!(LDST_L_BIT(instr));
 741                         const u32 subset[2] = {
 742                                 0xe92d0000,     /* STMDB sp!,{registers} */
 743                                 0xe8bd0000,     /* LDMIA sp!,{registers} */
 744                         };
 745                         *pinstr = subset[L] | (1<<RD_BITS(instr));
 746                         return do_alignment_ldmstm;
 747                 }
 748                 /* Else fall through for illegal instruction case */
 749                 break;
 750
 751         /* A6.3.6 Load/store double, STRD/LDRD(immed, lit, reg) */
 752         case 0xe860:
 753         case 0xe960:
 754         case 0xe8e0:
 755         case 0xe9e0:
 756                 poffset->un = (tinst2 & 0xff) << 2;
 757         case 0xe940:
 758         case 0xe9c0:
 759                 return do_alignment_ldrdstrd;
 760
 761         /*
 762          * No need to handle load/store instructions up to word size
 763          * since ARMv6 and later CPUs can perform unaligned accesses.
 764          */
 765         default:
 766                 break;
 767         }
 768         return NULL;
 769 }
 770
 771 static int
 772 do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 773 {
 774         union offset_union uninitialized_var(offset);
 775         unsigned long instr = 0, instrptr;
 776         int (*handler)(unsigned long addr, unsigned long instr, struct pt_regs *regs);
 777         unsigned int type;
 778         unsigned int fault;
 779         u16 tinstr = 0;
 780         int isize = 4;
 781         int thumb2_32b = 0;
 782
 783         if (interrupts_enabled(regs))
 784                 local_irq_enable();
 785
 786         instrptr = instruction_pointer(regs);
 787
 788         if (thumb_mode(regs)) {
 789                 u16 *ptr = (u16 *)(instrptr & ~1);
 790                 fault = probe_kernel_address(ptr, tinstr);
 791                 tinstr = __mem_to_opcode_thumb16(tinstr);
 792                 if (!fault) {
 793                         if (cpu_architecture() >= CPU_ARCH_ARMv7 &&
 794                             IS_T32(tinstr)) {
 795                                 /* Thumb-2 32-bit */
 796                                 u16 tinst2 = 0;
 797                                 fault = probe_kernel_address(ptr + 1, tinst2);
 798                                 tinst2 = __mem_to_opcode_thumb16(tinst2);
 799                                 instr = __opcode_thumb32_compose(tinstr, tinst2);
 800                                 thumb2_32b = 1;
 801                         } else {
 802                                 isize = 2;
 803                                 instr = thumb2arm(tinstr);
 804                         }
 805                 }
 806         } else {
 807                 fault = probe_kernel_address((void *)instrptr, instr);
 808                 instr = __mem_to_opcode_arm(instr);
 809         }
 810
 811         if (fault) {
 812                 type = TYPE_FAULT;
 813                 goto bad_or_fault;
 814         }
 815
 816         if (user_mode(regs))
 817                 goto user;
 818
 819         ai_sys += 1;
 820         ai_sys_last_pc = (void *)instruction_pointer(regs);
 821
 822  fixup:
 823
 824         regs->ARM_pc += isize;
 825
 826         switch (CODING_BITS(instr)) {
 827         case 0x00000000:        /* 3.13.4 load/store instruction extensions */
 828                 if (LDSTHD_I_BIT(instr))
 829                         offset.un = (instr & 0xf00) >> 4 | (instr & 15);
 830                 else
 831                         offset.un = regs->uregs[RM_BITS(instr)];
 832
 833                 if ((instr & 0x000000f0) == 0x000000b0 || /* LDRH, STRH */
 834                     (instr & 0x001000f0) == 0x001000f0)   /* LDRSH */
 835                         handler = do_alignment_ldrhstrh;
 836                 else if ((instr & 0x001000f0) == 0x000000d0 || /* LDRD */
 837                          (instr & 0x001000f0) == 0x000000f0)   /* STRD */
 838                         handler = do_alignment_ldrdstrd;
 839                 else if ((instr & 0x01f00ff0) == 0x01000090) /* SWP */
 840                         goto swp;
 841                 else
 842                         goto bad;
 843                 break;
 844
 845         case 0x04000000:        /* ldr or str immediate */
 846                 if (COND_BITS(instr) == 0xf0000000) /* NEON VLDn, VSTn */
 847                         goto bad;
 848                 offset.un = OFFSET_BITS(instr);
 849                 handler = do_alignment_ldrstr;
 850                 break;
 851
 852         case 0x06000000:        /* ldr or str register */
 853                 offset.un = regs->uregs[RM_BITS(instr)];
 854
 855                 if (IS_SHIFT(instr)) {
 856                         unsigned int shiftval = SHIFT_BITS(instr);
 857
 858                         switch(SHIFT_TYPE(instr)) {
 859                         case SHIFT_LSL:
 860                                 offset.un <<= shiftval;
 861                                 break;
 862
 863                         case SHIFT_LSR:
 864                                 offset.un >>= shiftval;
 865                                 break;
 866
 867                         case SHIFT_ASR:
 868                                 offset.sn >>= shiftval;
 869                                 break;
 870
 871                         case SHIFT_RORRRX:
 872                                 if (shiftval == 0) {
 873                                         offset.un >>= 1;
 874                                         if (regs->ARM_cpsr & PSR_C_BIT)
 875                                                 offset.un |= 1 << 31;
 876                                 } else
 877                                         offset.un = offset.un >> shiftval |
 878                                                           offset.un << (32 - shiftval);
 879                                 break;
 880                         }
 881                 }
 882                 handler = do_alignment_ldrstr;
 883                 break;
 884
 885         case 0x08000000:        /* ldm or stm, or thumb-2 32bit instruction */
 886                 if (thumb2_32b) {
 887                         offset.un = 0;
 888                         handler = do_alignment_t32_to_handler(&instr, regs, &offset);
 889                 } else {
 890                         offset.un = 0;
 891                         handler = do_alignment_ldmstm;
 892                 }
 893                 break;
 894
 895         default:
 896                 goto bad;
 897         }
 898
 899         if (!handler)
 900                 goto bad;
 901         type = handler(addr, instr, regs);
 902
 903         if (type == TYPE_ERROR || type == TYPE_FAULT) {
 904                 regs->ARM_pc -= isize;
 905                 goto bad_or_fault;
 906         }
 907
 908         if (type == TYPE_LDST)
 909                 do_alignment_finish_ldst(addr, instr, regs, offset);
 910
 911         return 0;
 912
 913  bad_or_fault:
 914         if (type == TYPE_ERROR)
 915                 goto bad;
 916         /*
 917          * We got a fault - fix it up, or die.
 918          */
 919         do_bad_area(addr, fsr, regs);
 920         return 0;
 921
 922  swp:
 923         pr_err("Alignment trap: not handling swp instruction\n");
 924
 925  bad:
 926         /*
 927          * Oops, we didn't handle the instruction.
 928          */
 929         pr_err("Alignment trap: not handling instruction "
 930                 "%0*lx at [<%08lx>]\n",
 931                 isize << 1,
 932                 isize == 2 ? tinstr : instr, instrptr);
 933         ai_skipped += 1;
 934         return 1;
 935
 936  user:
 937         ai_user += 1;
 938
 939         if (ai_usermode & UM_WARN)
 940                 printk("Alignment trap: %s (%d) PC=0x%08lx Instr=0x%0*lx "
 941                        "Address=0x%08lx FSR 0x%03x\n", current->comm,
 942                         task_pid_nr(current), instrptr,
 943                         isize << 1,
 944                         isize == 2 ? tinstr : instr,
 945                         addr, fsr);
 946
 947         if (ai_usermode & UM_FIXUP)
 948                 goto fixup;
 949
 950         if (ai_usermode & UM_SIGNAL) {
 951                 siginfo_t si;
 952
 953                 clear_siginfo(&si);
 954                 si.si_signo = SIGBUS;
 955                 si.si_errno = 0;
 956                 si.si_code = BUS_ADRALN;
 957                 si.si_addr = (void __user *)addr;
 958
 959                 force_sig_info(si.si_signo, &si, current);
 960         } else {
 961                 /*
 962                  * We're about to disable the alignment trap and return to
 963                  * user space.  But if an interrupt occurs before actually
 964                  * reaching user space, then the IRQ vector entry code will
 965                  * notice that we were still in kernel space and therefore
 966                  * the alignment trap won't be re-enabled in that case as it
 967                  * is presumed to be always on from kernel space.
 968                  * Let's prevent that race by disabling interrupts here (they
 969                  * are disabled on the way back to user space anyway in
 970                  * entry-common.S) and disable the alignment trap only if
 971                  * there is no work pending for this thread.
 972                  */
 973                 raw_local_irq_disable();
 974                 if (!(current_thread_info()->flags & _TIF_WORK_MASK))
 975                         set_cr(cr_no_alignment);
 976         }
 977
 978         return 0;
 979 }
 980
 981 static int __init noalign_setup(char *__unused)
 982 {
 983         set_cr(__clear_cr(CR_A));
 984         return 1;
 985 }
 986 __setup("noalign", noalign_setup);
 987
 988 /*
 989  * This needs to be done after sysctl_init, otherwise sys/ will be
 990  * overwritten.  Actually, this shouldn't be in sys/ at all since
 991  * it isn't a sysctl, and it doesn't contain sysctl information.
 992  * We now locate it in /proc/cpu/alignment instead.
 993  */
 994 static int __init alignment_init(void)
 995 {
 996 #ifdef CONFIG_PROC_FS
 997         struct proc_dir_entry *res;
 998
 999         res = proc_create("cpu/alignment", S_IWUSR | S_IRUGO, NULL,
1000                           &alignment_proc_fops);
1001         if (!res)
1002                 return -ENOMEM;
1003 #endif
1004
1005         if (cpu_is_v6_unaligned()) {
1006                 set_cr(__clear_cr(CR_A));
1007                 ai_usermode = safe_usermode(ai_usermode, false);
1008         }
1009
1010         cr_no_alignment = get_cr() & ~CR_A;
1011
1012         hook_fault_code(FAULT_CODE_ALIGNMENT, do_alignment, SIGBUS, BUS_ADRALN,
1013                         "alignment exception");
1014
1015         /*
1016          * ARMv6K and ARMv7 use fault status 3 (0b00011) as Access Flag section
1017          * fault, not as alignment error.
1018          *
1019          * TODO: handle ARMv6K properly. Runtime check for 'K' extension is
1020          * needed.
1021          */
1022         if (cpu_architecture() <= CPU_ARCH_ARMv6) {
1023                 hook_fault_code(3, do_alignment, SIGBUS, BUS_ADRALN,
1024                                 "alignment exception");
1025         }
1026
1027         return 0;
1028 }
1029
1030 fs_initcall(alignment_init);