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