arch/arm/kernel/unwind.c

   1 /*
   2  * arch/arm/kernel/unwind.c
   3  *
   4  * Copyright (C) 2008 ARM Limited
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  18  *
  19  *
  20  * Stack unwinding support for ARM
  21  *
  22  * An ARM EABI version of gcc is required to generate the unwind
  23  * tables. For information about the structure of the unwind tables,
  24  * see "Exception Handling ABI for the ARM Architecture" at:
  25  *
  26  * http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html
  27  */
  28
  29 #ifndef __CHECKER__
  30 #if !defined (__ARM_EABI__)
  31 #warning Your compiler does not have EABI support.
  32 #warning    ARM unwind is known to compile only with EABI compilers.
  33 #warning    Change compiler or disable ARM_UNWIND option.
  34 #elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2)
  35 #warning Your compiler is too buggy; it is known to not compile ARM unwind support.
  36 #warning    Change compiler or disable ARM_UNWIND option.
  37 #endif
  38 #endif /* __CHECKER__ */
  39
  40 #include <linux/kernel.h>
  41 #include <linux/init.h>
  42 #include <linux/export.h>
  43 #include <linux/sched.h>
  44 #include <linux/slab.h>
  45 #include <linux/spinlock.h>
  46 #include <linux/list.h>
  47
  48 #include <asm/stacktrace.h>
  49 #include <asm/traps.h>
  50 #include <asm/unwind.h>
  51
  52 /* Dummy functions to avoid linker complaints */
  53 void __aeabi_unwind_cpp_pr0(void)
  54 {
  55 };
  56 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
  57
  58 void __aeabi_unwind_cpp_pr1(void)
  59 {
  60 };
  61 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
  62
  63 void __aeabi_unwind_cpp_pr2(void)
  64 {
  65 };
  66 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
  67
  68 struct unwind_ctrl_block {
  69         unsigned long vrs[16];          /* virtual register set */
  70         const unsigned long *insn;      /* pointer to the current instructions word */
  71         int entries;                    /* number of entries left to interpret */
  72         int byte;                       /* current byte number in the instructions word */
  73 };
  74
  75 enum regs {
  76 #ifdef CONFIG_THUMB2_KERNEL
  77         FP = 7,
  78 #else
  79         FP = 11,
  80 #endif
  81         SP = 13,
  82         LR = 14,
  83         PC = 15
  84 };
  85
  86 extern const struct unwind_idx __start_unwind_idx[];
  87 static const struct unwind_idx *__origin_unwind_idx;
  88 extern const struct unwind_idx __stop_unwind_idx[];
  89
  90 static DEFINE_SPINLOCK(unwind_lock);
  91 static LIST_HEAD(unwind_tables);
  92
  93 /* Convert a prel31 symbol to an absolute address */
  94 #define prel31_to_addr(ptr)                             \
  95 ({                                                      \
  96         /* sign-extend to 32 bits */                    \
  97         long offset = (((long)*(ptr)) << 1) >> 1;       \
  98         (unsigned long)(ptr) + offset;                  \
  99 })
 100
 101 /*
 102  * Binary search in the unwind index. The entries are
 103  * guaranteed to be sorted in ascending order by the linker.
 104  *
 105  * start = first entry
 106  * origin = first entry with positive offset (or stop if there is no such entry)
 107  * stop - 1 = last entry
 108  */
 109 static const struct unwind_idx *search_index(unsigned long addr,
 110                                        const struct unwind_idx *start,
 111                                        const struct unwind_idx *origin,
 112                                        const struct unwind_idx *stop)
 113 {
 114         unsigned long addr_prel31;
 115
 116         pr_debug("%s(%08lx, %p, %p, %p)\n",
 117                         __func__, addr, start, origin, stop);
 118
 119         /*
 120          * only search in the section with the matching sign. This way the
 121          * prel31 numbers can be compared as unsigned longs.
 122          */
 123         if (addr < (unsigned long)start)
 124                 /* negative offsets: [start; origin) */
 125                 stop = origin;
 126         else
 127                 /* positive offsets: [origin; stop) */
 128                 start = origin;
 129
 130         /* prel31 for address relavive to start */
 131         addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff;
 132
 133         while (start < stop - 1) {
 134                 const struct unwind_idx *mid = start + ((stop - start) >> 1);
 135
 136                 /*
 137                  * As addr_prel31 is relative to start an offset is needed to
 138                  * make it relative to mid.
 139                  */
 140                 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) <
 141                                 mid->addr_offset)
 142                         stop = mid;
 143                 else {
 144                         /* keep addr_prel31 relative to start */
 145                         addr_prel31 -= ((unsigned long)mid -
 146                                         (unsigned long)start);
 147                         start = mid;
 148                 }
 149         }
 150
 151         if (likely(start->addr_offset <= addr_prel31))
 152                 return start;
 153         else {
 154                 pr_warning("unwind: Unknown symbol address %08lx\n", addr);
 155                 return NULL;
 156         }
 157 }
 158
 159 static const struct unwind_idx *unwind_find_origin(
 160                 const struct unwind_idx *start, const struct unwind_idx *stop)
 161 {
 162         pr_debug("%s(%p, %p)\n", __func__, start, stop);
 163         while (start < stop) {
 164                 const struct unwind_idx *mid = start + ((stop - start) >> 1);
 165
 166                 if (mid->addr_offset >= 0x40000000)
 167                         /* negative offset */
 168                         start = mid + 1;
 169                 else
 170                         /* positive offset */
 171                         stop = mid;
 172         }
 173         pr_debug("%s -> %p\n", __func__, stop);
 174         return stop;
 175 }
 176
 177 static const struct unwind_idx *unwind_find_idx(unsigned long addr)
 178 {
 179         const struct unwind_idx *idx = NULL;
 180         unsigned long flags;
 181
 182         pr_debug("%s(%08lx)\n", __func__, addr);
 183
 184         if (core_kernel_text(addr)) {
 185                 if (unlikely(!__origin_unwind_idx))
 186                         __origin_unwind_idx =
 187                                 unwind_find_origin(__start_unwind_idx,
 188                                                 __stop_unwind_idx);
 189
 190                 /* main unwind table */
 191                 idx = search_index(addr, __start_unwind_idx,
 192                                    __origin_unwind_idx,
 193                                    __stop_unwind_idx);
 194         } else {
 195                 /* module unwind tables */
 196                 struct unwind_table *table;
 197
 198                 spin_lock_irqsave(&unwind_lock, flags);
 199                 list_for_each_entry(table, &unwind_tables, list) {
 200                         if (addr >= table->begin_addr &&
 201                             addr < table->end_addr) {
 202                                 idx = search_index(addr, table->start,
 203                                                    table->origin,
 204                                                    table->stop);
 205                                 /* Move-to-front to exploit common traces */
 206                                 list_move(&table->list, &unwind_tables);
 207                                 break;
 208                         }
 209                 }
 210                 spin_unlock_irqrestore(&unwind_lock, flags);
 211         }
 212
 213         pr_debug("%s: idx = %p\n", __func__, idx);
 214         return idx;
 215 }
 216
 217 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
 218 {
 219         unsigned long ret;
 220
 221         if (ctrl->entries <= 0) {
 222                 pr_warning("unwind: Corrupt unwind table\n");
 223                 return 0;
 224         }
 225
 226         ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
 227
 228         if (ctrl->byte == 0) {
 229                 ctrl->insn++;
 230                 ctrl->entries--;
 231                 ctrl->byte = 3;
 232         } else
 233                 ctrl->byte--;
 234
 235         return ret;
 236 }
 237
 238 /*
 239  * Execute the current unwind instruction.
 240  */
 241 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
 242 {
 243         unsigned long insn = unwind_get_byte(ctrl);
 244
 245         pr_debug("%s: insn = %08lx\n", __func__, insn);
 246
 247         if ((insn & 0xc0) == 0x00)
 248                 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
 249         else if ((insn & 0xc0) == 0x40)
 250                 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
 251         else if ((insn & 0xf0) == 0x80) {
 252                 unsigned long mask;
 253                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 254                 int load_sp, reg = 4;
 255
 256                 insn = (insn << 8) | unwind_get_byte(ctrl);
 257                 mask = insn & 0x0fff;
 258                 if (mask == 0) {
 259                         pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n",
 260                                    insn);
 261                         return -URC_FAILURE;
 262                 }
 263
 264                 /* pop R4-R15 according to mask */
 265                 load_sp = mask & (1 << (13 - 4));
 266                 while (mask) {
 267                         if (mask & 1)
 268                                 ctrl->vrs[reg] = *vsp++;
 269                         mask >>= 1;
 270                         reg++;
 271                 }
 272                 if (!load_sp)
 273                         ctrl->vrs[SP] = (unsigned long)vsp;
 274         } else if ((insn & 0xf0) == 0x90 &&
 275                    (insn & 0x0d) != 0x0d)
 276                 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
 277         else if ((insn & 0xf0) == 0xa0) {
 278                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 279                 int reg;
 280
 281                 /* pop R4-R[4+bbb] */
 282                 for (reg = 4; reg <= 4 + (insn & 7); reg++)
 283                         ctrl->vrs[reg] = *vsp++;
 284                 if (insn & 0x80)
 285                         ctrl->vrs[14] = *vsp++;
 286                 ctrl->vrs[SP] = (unsigned long)vsp;
 287         } else if (insn == 0xb0) {
 288                 if (ctrl->vrs[PC] == 0)
 289                         ctrl->vrs[PC] = ctrl->vrs[LR];
 290                 /* no further processing */
 291                 ctrl->entries = 0;
 292         } else if (insn == 0xb1) {
 293                 unsigned long mask = unwind_get_byte(ctrl);
 294                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 295                 int reg = 0;
 296
 297                 if (mask == 0 || mask & 0xf0) {
 298                         pr_warning("unwind: Spare encoding %04lx\n",
 299                                (insn << 8) | mask);
 300                         return -URC_FAILURE;
 301                 }
 302
 303                 /* pop R0-R3 according to mask */
 304                 while (mask) {
 305                         if (mask & 1)
 306                                 ctrl->vrs[reg] = *vsp++;
 307                         mask >>= 1;
 308                         reg++;
 309                 }
 310                 ctrl->vrs[SP] = (unsigned long)vsp;
 311         } else if (insn == 0xb2) {
 312                 unsigned long uleb128 = unwind_get_byte(ctrl);
 313
 314                 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
 315         } else {
 316                 pr_warning("unwind: Unhandled instruction %02lx\n", insn);
 317                 return -URC_FAILURE;
 318         }
 319
 320         pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
 321                  ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
 322
 323         return URC_OK;
 324 }
 325
 326 /*
 327  * Unwind a single frame starting with *sp for the symbol at *pc. It
 328  * updates the *pc and *sp with the new values.
 329  */
 330 int unwind_frame(struct stackframe *frame)
 331 {
 332         unsigned long high, low;
 333         const struct unwind_idx *idx;
 334         struct unwind_ctrl_block ctrl;
 335
 336         /* only go to a higher address on the stack */
 337         low = frame->sp;
 338         high = ALIGN(low, THREAD_SIZE);
 339
 340         pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
 341                  frame->pc, frame->lr, frame->sp);
 342
 343         if (!kernel_text_address(frame->pc))
 344                 return -URC_FAILURE;
 345
 346         idx = unwind_find_idx(frame->pc);
 347         if (!idx) {
 348                 pr_warning("unwind: Index not found %08lx\n", frame->pc);
 349                 return -URC_FAILURE;
 350         }
 351
 352         ctrl.vrs[FP] = frame->fp;
 353         ctrl.vrs[SP] = frame->sp;
 354         ctrl.vrs[LR] = frame->lr;
 355         ctrl.vrs[PC] = 0;
 356
 357         if (idx->insn == 1)
 358                 /* can't unwind */
 359                 return -URC_FAILURE;
 360         else if ((idx->insn & 0x80000000) == 0)
 361                 /* prel31 to the unwind table */
 362                 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
 363         else if ((idx->insn & 0xff000000) == 0x80000000)
 364                 /* only personality routine 0 supported in the index */
 365                 ctrl.insn = &idx->insn;
 366         else {
 367                 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n",
 368                            idx->insn, idx);
 369                 return -URC_FAILURE;
 370         }
 371
 372         /* check the personality routine */
 373         if ((*ctrl.insn & 0xff000000) == 0x80000000) {
 374                 ctrl.byte = 2;
 375                 ctrl.entries = 1;
 376         } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
 377                 ctrl.byte = 1;
 378                 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
 379         } else {
 380                 pr_warning("unwind: Unsupported personality routine %08lx at %p\n",
 381                            *ctrl.insn, ctrl.insn);
 382                 return -URC_FAILURE;
 383         }
 384
 385         while (ctrl.entries > 0) {
 386                 int urc = unwind_exec_insn(&ctrl);
 387                 if (urc < 0)
 388                         return urc;
 389                 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
 390                         return -URC_FAILURE;
 391         }
 392
 393         if (ctrl.vrs[PC] == 0)
 394                 ctrl.vrs[PC] = ctrl.vrs[LR];
 395
 396         /* check for infinite loop */
 397         if (frame->pc == ctrl.vrs[PC])
 398                 return -URC_FAILURE;
 399
 400         frame->fp = ctrl.vrs[FP];
 401         frame->sp = ctrl.vrs[SP];
 402         frame->lr = ctrl.vrs[LR];
 403         frame->pc = ctrl.vrs[PC];
 404
 405         return URC_OK;
 406 }
 407
 408 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 409 {
 410         struct stackframe frame;
 411         register unsigned long current_sp asm ("sp");
 412
 413         pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 414
 415         if (!tsk)
 416                 tsk = current;
 417
 418         if (regs) {
 419                 frame.fp = regs->ARM_fp;
 420                 frame.sp = regs->ARM_sp;
 421                 frame.lr = regs->ARM_lr;
 422                 /* PC might be corrupted, use LR in that case. */
 423                 frame.pc = kernel_text_address(regs->ARM_pc)
 424                          ? regs->ARM_pc : regs->ARM_lr;
 425         } else if (tsk == current) {
 426                 frame.fp = (unsigned long)__builtin_frame_address(0);
 427                 frame.sp = current_sp;
 428                 frame.lr = (unsigned long)__builtin_return_address(0);
 429                 frame.pc = (unsigned long)unwind_backtrace;
 430         } else {
 431                 /* task blocked in __switch_to */
 432                 frame.fp = thread_saved_fp(tsk);
 433                 frame.sp = thread_saved_sp(tsk);
 434                 /*
 435                  * The function calling __switch_to cannot be a leaf function
 436                  * so LR is recovered from the stack.
 437                  */
 438                 frame.lr = 0;
 439                 frame.pc = thread_saved_pc(tsk);
 440         }
 441
 442         while (1) {
 443                 int urc;
 444                 unsigned long where = frame.pc;
 445
 446                 urc = unwind_frame(&frame);
 447                 if (urc < 0)
 448                         break;
 449                 dump_backtrace_entry(where, frame.pc, frame.sp - 4);
 450         }
 451 }
 452
 453 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
 454                                       unsigned long text_addr,
 455                                       unsigned long text_size)
 456 {
 457         unsigned long flags;
 458         struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
 459
 460         pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
 461                  text_addr, text_size);
 462
 463         if (!tab)
 464                 return tab;
 465
 466         tab->start = (const struct unwind_idx *)start;
 467         tab->stop = (const struct unwind_idx *)(start + size);
 468         tab->origin = unwind_find_origin(tab->start, tab->stop);
 469         tab->begin_addr = text_addr;
 470         tab->end_addr = text_addr + text_size;
 471
 472         spin_lock_irqsave(&unwind_lock, flags);
 473         list_add_tail(&tab->list, &unwind_tables);
 474         spin_unlock_irqrestore(&unwind_lock, flags);
 475
 476         return tab;
 477 }
 478
 479 void unwind_table_del(struct unwind_table *tab)
 480 {
 481         unsigned long flags;
 482
 483         if (!tab)
 484                 return;
 485
 486         spin_lock_irqsave(&unwind_lock, flags);
 487         list_del(&tab->list);
 488         spin_unlock_irqrestore(&unwind_lock, flags);
 489
 490         kfree(tab);
 491 }