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/module.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         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 struct unwind_idx __start_unwind_idx[];
  87 extern struct unwind_idx __stop_unwind_idx[];
  88
  89 static DEFINE_SPINLOCK(unwind_lock);
  90 static LIST_HEAD(unwind_tables);
  91
  92 /* Convert a prel31 symbol to an absolute address */
  93 #define prel31_to_addr(ptr)                             \
  94 ({                                                      \
  95         /* sign-extend to 32 bits */                    \
  96         long offset = (((long)*(ptr)) << 1) >> 1;       \
  97         (unsigned long)(ptr) + offset;                  \
  98 })
  99
 100 /*
 101  * Binary search in the unwind index. The entries entries are
 102  * guaranteed to be sorted in ascending order by the linker.
 103  */
 104 static struct unwind_idx *search_index(unsigned long addr,
 105                                        struct unwind_idx *first,
 106                                        struct unwind_idx *last)
 107 {
 108         pr_debug("%s(%08lx, %p, %p)\n", __func__, addr, first, last);
 109
 110         if (addr < first->addr) {
 111                 pr_warning("unwind: Unknown symbol address %08lx\n", addr);
 112                 return NULL;
 113         } else if (addr >= last->addr)
 114                 return last;
 115
 116         while (first < last - 1) {
 117                 struct unwind_idx *mid = first + ((last - first + 1) >> 1);
 118
 119                 if (addr < mid->addr)
 120                         last = mid;
 121                 else
 122                         first = mid;
 123         }
 124
 125         return first;
 126 }
 127
 128 static struct unwind_idx *unwind_find_idx(unsigned long addr)
 129 {
 130         struct unwind_idx *idx = NULL;
 131         unsigned long flags;
 132
 133         pr_debug("%s(%08lx)\n", __func__, addr);
 134
 135         if (core_kernel_text(addr))
 136                 /* main unwind table */
 137                 idx = search_index(addr, __start_unwind_idx,
 138                                    __stop_unwind_idx - 1);
 139         else {
 140                 /* module unwind tables */
 141                 struct unwind_table *table;
 142
 143                 spin_lock_irqsave(&unwind_lock, flags);
 144                 list_for_each_entry(table, &unwind_tables, list) {
 145                         if (addr >= table->begin_addr &&
 146                             addr < table->end_addr) {
 147                                 idx = search_index(addr, table->start,
 148                                                    table->stop - 1);
 149                                 break;
 150                         }
 151                 }
 152                 spin_unlock_irqrestore(&unwind_lock, flags);
 153         }
 154
 155         pr_debug("%s: idx = %p\n", __func__, idx);
 156         return idx;
 157 }
 158
 159 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
 160 {
 161         unsigned long ret;
 162
 163         if (ctrl->entries <= 0) {
 164                 pr_warning("unwind: Corrupt unwind table\n");
 165                 return 0;
 166         }
 167
 168         ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
 169
 170         if (ctrl->byte == 0) {
 171                 ctrl->insn++;
 172                 ctrl->entries--;
 173                 ctrl->byte = 3;
 174         } else
 175                 ctrl->byte--;
 176
 177         return ret;
 178 }
 179
 180 /*
 181  * Execute the current unwind instruction.
 182  */
 183 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
 184 {
 185         unsigned long insn = unwind_get_byte(ctrl);
 186
 187         pr_debug("%s: insn = %08lx\n", __func__, insn);
 188
 189         if ((insn & 0xc0) == 0x00)
 190                 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
 191         else if ((insn & 0xc0) == 0x40)
 192                 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
 193         else if ((insn & 0xf0) == 0x80) {
 194                 unsigned long mask;
 195                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 196                 int load_sp, reg = 4;
 197
 198                 insn = (insn << 8) | unwind_get_byte(ctrl);
 199                 mask = insn & 0x0fff;
 200                 if (mask == 0) {
 201                         pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n",
 202                                    insn);
 203                         return -URC_FAILURE;
 204                 }
 205
 206                 /* pop R4-R15 according to mask */
 207                 load_sp = mask & (1 << (13 - 4));
 208                 while (mask) {
 209                         if (mask & 1)
 210                                 ctrl->vrs[reg] = *vsp++;
 211                         mask >>= 1;
 212                         reg++;
 213                 }
 214                 if (!load_sp)
 215                         ctrl->vrs[SP] = (unsigned long)vsp;
 216         } else if ((insn & 0xf0) == 0x90 &&
 217                    (insn & 0x0d) != 0x0d)
 218                 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
 219         else if ((insn & 0xf0) == 0xa0) {
 220                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 221                 int reg;
 222
 223                 /* pop R4-R[4+bbb] */
 224                 for (reg = 4; reg <= 4 + (insn & 7); reg++)
 225                         ctrl->vrs[reg] = *vsp++;
 226                 if (insn & 0x80)
 227                         ctrl->vrs[14] = *vsp++;
 228                 ctrl->vrs[SP] = (unsigned long)vsp;
 229         } else if (insn == 0xb0) {
 230                 if (ctrl->vrs[PC] == 0)
 231                         ctrl->vrs[PC] = ctrl->vrs[LR];
 232                 /* no further processing */
 233                 ctrl->entries = 0;
 234         } else if (insn == 0xb1) {
 235                 unsigned long mask = unwind_get_byte(ctrl);
 236                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 237                 int reg = 0;
 238
 239                 if (mask == 0 || mask & 0xf0) {
 240                         pr_warning("unwind: Spare encoding %04lx\n",
 241                                (insn << 8) | mask);
 242                         return -URC_FAILURE;
 243                 }
 244
 245                 /* pop R0-R3 according to mask */
 246                 while (mask) {
 247                         if (mask & 1)
 248                                 ctrl->vrs[reg] = *vsp++;
 249                         mask >>= 1;
 250                         reg++;
 251                 }
 252                 ctrl->vrs[SP] = (unsigned long)vsp;
 253         } else if (insn == 0xb2) {
 254                 unsigned long uleb128 = unwind_get_byte(ctrl);
 255
 256                 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
 257         } else {
 258                 pr_warning("unwind: Unhandled instruction %02lx\n", insn);
 259                 return -URC_FAILURE;
 260         }
 261
 262         pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
 263                  ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
 264
 265         return URC_OK;
 266 }
 267
 268 /*
 269  * Unwind a single frame starting with *sp for the symbol at *pc. It
 270  * updates the *pc and *sp with the new values.
 271  */
 272 int unwind_frame(struct stackframe *frame)
 273 {
 274         unsigned long high, low;
 275         struct unwind_idx *idx;
 276         struct unwind_ctrl_block ctrl;
 277
 278         /* only go to a higher address on the stack */
 279         low = frame->sp;
 280         high = ALIGN(low, THREAD_SIZE) + THREAD_SIZE;
 281
 282         pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
 283                  frame->pc, frame->lr, frame->sp);
 284
 285         if (!kernel_text_address(frame->pc))
 286                 return -URC_FAILURE;
 287
 288         idx = unwind_find_idx(frame->pc);
 289         if (!idx) {
 290                 pr_warning("unwind: Index not found %08lx\n", frame->pc);
 291                 return -URC_FAILURE;
 292         }
 293
 294         ctrl.vrs[FP] = frame->fp;
 295         ctrl.vrs[SP] = frame->sp;
 296         ctrl.vrs[LR] = frame->lr;
 297         ctrl.vrs[PC] = 0;
 298
 299         if (idx->insn == 1)
 300                 /* can't unwind */
 301                 return -URC_FAILURE;
 302         else if ((idx->insn & 0x80000000) == 0)
 303                 /* prel31 to the unwind table */
 304                 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
 305         else if ((idx->insn & 0xff000000) == 0x80000000)
 306                 /* only personality routine 0 supported in the index */
 307                 ctrl.insn = &idx->insn;
 308         else {
 309                 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n",
 310                            idx->insn, idx);
 311                 return -URC_FAILURE;
 312         }
 313
 314         /* check the personality routine */
 315         if ((*ctrl.insn & 0xff000000) == 0x80000000) {
 316                 ctrl.byte = 2;
 317                 ctrl.entries = 1;
 318         } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
 319                 ctrl.byte = 1;
 320                 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
 321         } else {
 322                 pr_warning("unwind: Unsupported personality routine %08lx at %p\n",
 323                            *ctrl.insn, ctrl.insn);
 324                 return -URC_FAILURE;
 325         }
 326
 327         while (ctrl.entries > 0) {
 328                 int urc = unwind_exec_insn(&ctrl);
 329                 if (urc < 0)
 330                         return urc;
 331                 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
 332                         return -URC_FAILURE;
 333         }
 334
 335         if (ctrl.vrs[PC] == 0)
 336                 ctrl.vrs[PC] = ctrl.vrs[LR];
 337
 338         /* check for infinite loop */
 339         if (frame->pc == ctrl.vrs[PC])
 340                 return -URC_FAILURE;
 341
 342         frame->fp = ctrl.vrs[FP];
 343         frame->sp = ctrl.vrs[SP];
 344         frame->lr = ctrl.vrs[LR];
 345         frame->pc = ctrl.vrs[PC];
 346
 347         return URC_OK;
 348 }
 349
 350 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 351 {
 352         struct stackframe frame;
 353         register unsigned long current_sp asm ("sp");
 354
 355         pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 356
 357         if (!tsk)
 358                 tsk = current;
 359
 360         if (regs) {
 361                 frame.fp = regs->ARM_fp;
 362                 frame.sp = regs->ARM_sp;
 363                 frame.lr = regs->ARM_lr;
 364                 /* PC might be corrupted, use LR in that case. */
 365                 frame.pc = kernel_text_address(regs->ARM_pc)
 366                          ? regs->ARM_pc : regs->ARM_lr;
 367         } else if (tsk == current) {
 368                 frame.fp = (unsigned long)__builtin_frame_address(0);
 369                 frame.sp = current_sp;
 370                 frame.lr = (unsigned long)__builtin_return_address(0);
 371                 frame.pc = (unsigned long)unwind_backtrace;
 372         } else {
 373                 /* task blocked in __switch_to */
 374                 frame.fp = thread_saved_fp(tsk);
 375                 frame.sp = thread_saved_sp(tsk);
 376                 /*
 377                  * The function calling __switch_to cannot be a leaf function
 378                  * so LR is recovered from the stack.
 379                  */
 380                 frame.lr = 0;
 381                 frame.pc = thread_saved_pc(tsk);
 382         }
 383
 384         while (1) {
 385                 int urc;
 386                 unsigned long where = frame.pc;
 387
 388                 urc = unwind_frame(&frame);
 389                 if (urc < 0)
 390                         break;
 391                 dump_backtrace_entry(where, frame.pc, frame.sp - 4);
 392         }
 393 }
 394
 395 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
 396                                       unsigned long text_addr,
 397                                       unsigned long text_size)
 398 {
 399         unsigned long flags;
 400         struct unwind_idx *idx;
 401         struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
 402
 403         pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
 404                  text_addr, text_size);
 405
 406         if (!tab)
 407                 return tab;
 408
 409         tab->start = (struct unwind_idx *)start;
 410         tab->stop = (struct unwind_idx *)(start + size);
 411         tab->begin_addr = text_addr;
 412         tab->end_addr = text_addr + text_size;
 413
 414         /* Convert the symbol addresses to absolute values */
 415         for (idx = tab->start; idx < tab->stop; idx++)
 416                 idx->addr = prel31_to_addr(&idx->addr);
 417
 418         spin_lock_irqsave(&unwind_lock, flags);
 419         list_add_tail(&tab->list, &unwind_tables);
 420         spin_unlock_irqrestore(&unwind_lock, flags);
 421
 422         return tab;
 423 }
 424
 425 void unwind_table_del(struct unwind_table *tab)
 426 {
 427         unsigned long flags;
 428
 429         if (!tab)
 430                 return;
 431
 432         spin_lock_irqsave(&unwind_lock, flags);
 433         list_del(&tab->list);
 434         spin_unlock_irqrestore(&unwind_lock, flags);
 435
 436         kfree(tab);
 437 }
 438
 439 int __init unwind_init(void)
 440 {
 441         struct unwind_idx *idx;
 442
 443         /* Convert the symbol addresses to absolute values */
 444         for (idx = __start_unwind_idx; idx < __stop_unwind_idx; idx++)
 445                 idx->addr = prel31_to_addr(&idx->addr);
 446
 447         pr_debug("unwind: ARM stack unwinding initialised\n");
 448
 449         return 0;
 450 }