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 #if !defined (__ARM_EABI__)
  30 #warning Your compiler does not have EABI support.
  31 #warning    ARM unwind is known to compile only with EABI compilers.
  32 #warning    Change compiler or disable ARM_UNWIND option.
  33 #elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2)
  34 #warning Your compiler is too buggy; it is known to not compile ARM unwind support.
  35 #warning    Change compiler or disable ARM_UNWIND option.
  36 #endif
  37
  38 #include <linux/kernel.h>
  39 #include <linux/init.h>
  40 #include <linux/module.h>
  41 #include <linux/sched.h>
  42 #include <linux/slab.h>
  43 #include <linux/spinlock.h>
  44 #include <linux/list.h>
  45
  46 #include <asm/stacktrace.h>
  47 #include <asm/traps.h>
  48 #include <asm/unwind.h>
  49
  50 /* Dummy functions to avoid linker complaints */
  51 void __aeabi_unwind_cpp_pr0(void)
  52 {
  53 };
  54 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
  55
  56 void __aeabi_unwind_cpp_pr1(void)
  57 {
  58 };
  59 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
  60
  61 void __aeabi_unwind_cpp_pr2(void)
  62 {
  63 };
  64 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
  65
  66 struct unwind_ctrl_block {
  67         unsigned long vrs[16];          /* virtual register set */
  68         unsigned long *insn;            /* pointer to the current instructions word */
  69         int entries;                    /* number of entries left to interpret */
  70         int byte;                       /* current byte number in the instructions word */
  71 };
  72
  73 enum regs {
  74 #ifdef CONFIG_THUMB2_KERNEL
  75         FP = 7,
  76 #else
  77         FP = 11,
  78 #endif
  79         SP = 13,
  80         LR = 14,
  81         PC = 15
  82 };
  83
  84 extern struct unwind_idx __start_unwind_idx[];
  85 extern struct unwind_idx __stop_unwind_idx[];
  86
  87 static DEFINE_SPINLOCK(unwind_lock);
  88 static LIST_HEAD(unwind_tables);
  89
  90 /* Convert a prel31 symbol to an absolute address */
  91 #define prel31_to_addr(ptr)                             \
  92 ({                                                      \
  93         /* sign-extend to 32 bits */                    \
  94         long offset = (((long)*(ptr)) << 1) >> 1;       \
  95         (unsigned long)(ptr) + offset;                  \
  96 })
  97
  98 /*
  99  * Binary search in the unwind index. The entries entries are
 100  * guaranteed to be sorted in ascending order by the linker.
 101  */
 102 static struct unwind_idx *search_index(unsigned long addr,
 103                                        struct unwind_idx *first,
 104                                        struct unwind_idx *last)
 105 {
 106         pr_debug("%s(%08lx, %p, %p)\n", __func__, addr, first, last);
 107
 108         if (addr < first->addr) {
 109                 pr_warning("unwind: Unknown symbol address %08lx\n", addr);
 110                 return NULL;
 111         } else if (addr >= last->addr)
 112                 return last;
 113
 114         while (first < last - 1) {
 115                 struct unwind_idx *mid = first + ((last - first + 1) >> 1);
 116
 117                 if (addr < mid->addr)
 118                         last = mid;
 119                 else
 120                         first = mid;
 121         }
 122
 123         return first;
 124 }
 125
 126 static struct unwind_idx *unwind_find_idx(unsigned long addr)
 127 {
 128         struct unwind_idx *idx = NULL;
 129         unsigned long flags;
 130
 131         pr_debug("%s(%08lx)\n", __func__, addr);
 132
 133         if (core_kernel_text(addr))
 134                 /* main unwind table */
 135                 idx = search_index(addr, __start_unwind_idx,
 136                                    __stop_unwind_idx - 1);
 137         else {
 138                 /* module unwind tables */
 139                 struct unwind_table *table;
 140
 141                 spin_lock_irqsave(&unwind_lock, flags);
 142                 list_for_each_entry(table, &unwind_tables, list) {
 143                         if (addr >= table->begin_addr &&
 144                             addr < table->end_addr) {
 145                                 idx = search_index(addr, table->start,
 146                                                    table->stop - 1);
 147                                 break;
 148                         }
 149                 }
 150                 spin_unlock_irqrestore(&unwind_lock, flags);
 151         }
 152
 153         pr_debug("%s: idx = %p\n", __func__, idx);
 154         return idx;
 155 }
 156
 157 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
 158 {
 159         unsigned long ret;
 160
 161         if (ctrl->entries <= 0) {
 162                 pr_warning("unwind: Corrupt unwind table\n");
 163                 return 0;
 164         }
 165
 166         ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
 167
 168         if (ctrl->byte == 0) {
 169                 ctrl->insn++;
 170                 ctrl->entries--;
 171                 ctrl->byte = 3;
 172         } else
 173                 ctrl->byte--;
 174
 175         return ret;
 176 }
 177
 178 /*
 179  * Execute the current unwind instruction.
 180  */
 181 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
 182 {
 183         unsigned long insn = unwind_get_byte(ctrl);
 184
 185         pr_debug("%s: insn = %08lx\n", __func__, insn);
 186
 187         if ((insn & 0xc0) == 0x00)
 188                 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
 189         else if ((insn & 0xc0) == 0x40)
 190                 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
 191         else if ((insn & 0xf0) == 0x80) {
 192                 unsigned long mask;
 193                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 194                 int load_sp, reg = 4;
 195
 196                 insn = (insn << 8) | unwind_get_byte(ctrl);
 197                 mask = insn & 0x0fff;
 198                 if (mask == 0) {
 199                         pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n",
 200                                    insn);
 201                         return -URC_FAILURE;
 202                 }
 203
 204                 /* pop R4-R15 according to mask */
 205                 load_sp = mask & (1 << (13 - 4));
 206                 while (mask) {
 207                         if (mask & 1)
 208                                 ctrl->vrs[reg] = *vsp++;
 209                         mask >>= 1;
 210                         reg++;
 211                 }
 212                 if (!load_sp)
 213                         ctrl->vrs[SP] = (unsigned long)vsp;
 214         } else if ((insn & 0xf0) == 0x90 &&
 215                    (insn & 0x0d) != 0x0d)
 216                 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
 217         else if ((insn & 0xf0) == 0xa0) {
 218                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 219                 int reg;
 220
 221                 /* pop R4-R[4+bbb] */
 222                 for (reg = 4; reg <= 4 + (insn & 7); reg++)
 223                         ctrl->vrs[reg] = *vsp++;
 224                 if (insn & 0x80)
 225                         ctrl->vrs[14] = *vsp++;
 226                 ctrl->vrs[SP] = (unsigned long)vsp;
 227         } else if (insn == 0xb0) {
 228                 if (ctrl->vrs[PC] == 0)
 229                         ctrl->vrs[PC] = ctrl->vrs[LR];
 230                 /* no further processing */
 231                 ctrl->entries = 0;
 232         } else if (insn == 0xb1) {
 233                 unsigned long mask = unwind_get_byte(ctrl);
 234                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 235                 int reg = 0;
 236
 237                 if (mask == 0 || mask & 0xf0) {
 238                         pr_warning("unwind: Spare encoding %04lx\n",
 239                                (insn << 8) | mask);
 240                         return -URC_FAILURE;
 241                 }
 242
 243                 /* pop R0-R3 according to mask */
 244                 while (mask) {
 245                         if (mask & 1)
 246                                 ctrl->vrs[reg] = *vsp++;
 247                         mask >>= 1;
 248                         reg++;
 249                 }
 250                 ctrl->vrs[SP] = (unsigned long)vsp;
 251         } else if (insn == 0xb2) {
 252                 unsigned long uleb128 = unwind_get_byte(ctrl);
 253
 254                 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
 255         } else {
 256                 pr_warning("unwind: Unhandled instruction %02lx\n", insn);
 257                 return -URC_FAILURE;
 258         }
 259
 260         pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
 261                  ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
 262
 263         return URC_OK;
 264 }
 265
 266 /*
 267  * Unwind a single frame starting with *sp for the symbol at *pc. It
 268  * updates the *pc and *sp with the new values.
 269  */
 270 int unwind_frame(struct stackframe *frame)
 271 {
 272         unsigned long high, low;
 273         struct unwind_idx *idx;
 274         struct unwind_ctrl_block ctrl;
 275
 276         /* only go to a higher address on the stack */
 277         low = frame->sp;
 278         high = ALIGN(low, THREAD_SIZE) + THREAD_SIZE;
 279
 280         pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
 281                  frame->pc, frame->lr, frame->sp);
 282
 283         if (!kernel_text_address(frame->pc))
 284                 return -URC_FAILURE;
 285
 286         idx = unwind_find_idx(frame->pc);
 287         if (!idx) {
 288                 pr_warning("unwind: Index not found %08lx\n", frame->pc);
 289                 return -URC_FAILURE;
 290         }
 291
 292         ctrl.vrs[FP] = frame->fp;
 293         ctrl.vrs[SP] = frame->sp;
 294         ctrl.vrs[LR] = frame->lr;
 295         ctrl.vrs[PC] = 0;
 296
 297         if (idx->insn == 1)
 298                 /* can't unwind */
 299                 return -URC_FAILURE;
 300         else if ((idx->insn & 0x80000000) == 0)
 301                 /* prel31 to the unwind table */
 302                 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
 303         else if ((idx->insn & 0xff000000) == 0x80000000)
 304                 /* only personality routine 0 supported in the index */
 305                 ctrl.insn = &idx->insn;
 306         else {
 307                 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n",
 308                            idx->insn, idx);
 309                 return -URC_FAILURE;
 310         }
 311
 312         /* check the personality routine */
 313         if ((*ctrl.insn & 0xff000000) == 0x80000000) {
 314                 ctrl.byte = 2;
 315                 ctrl.entries = 1;
 316         } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
 317                 ctrl.byte = 1;
 318                 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
 319         } else {
 320                 pr_warning("unwind: Unsupported personality routine %08lx at %p\n",
 321                            *ctrl.insn, ctrl.insn);
 322                 return -URC_FAILURE;
 323         }
 324
 325         while (ctrl.entries > 0) {
 326                 int urc = unwind_exec_insn(&ctrl);
 327                 if (urc < 0)
 328                         return urc;
 329                 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
 330                         return -URC_FAILURE;
 331         }
 332
 333         if (ctrl.vrs[PC] == 0)
 334                 ctrl.vrs[PC] = ctrl.vrs[LR];
 335
 336         /* check for infinite loop */
 337         if (frame->pc == ctrl.vrs[PC])
 338                 return -URC_FAILURE;
 339
 340         frame->fp = ctrl.vrs[FP];
 341         frame->sp = ctrl.vrs[SP];
 342         frame->lr = ctrl.vrs[LR];
 343         frame->pc = ctrl.vrs[PC];
 344
 345         return URC_OK;
 346 }
 347
 348 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 349 {
 350         struct stackframe frame;
 351         register unsigned long current_sp asm ("sp");
 352
 353         pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 354
 355         if (!tsk)
 356                 tsk = current;
 357
 358         if (regs) {
 359                 frame.fp = regs->ARM_fp;
 360                 frame.sp = regs->ARM_sp;
 361                 frame.lr = regs->ARM_lr;
 362                 frame.pc = regs->ARM_pc;
 363         } else if (tsk == current) {
 364                 frame.fp = (unsigned long)__builtin_frame_address(0);
 365                 frame.sp = current_sp;
 366                 frame.lr = (unsigned long)__builtin_return_address(0);
 367                 frame.pc = (unsigned long)unwind_backtrace;
 368         } else {
 369                 /* task blocked in __switch_to */
 370                 frame.fp = thread_saved_fp(tsk);
 371                 frame.sp = thread_saved_sp(tsk);
 372                 /*
 373                  * The function calling __switch_to cannot be a leaf function
 374                  * so LR is recovered from the stack.
 375                  */
 376                 frame.lr = 0;
 377                 frame.pc = thread_saved_pc(tsk);
 378         }
 379
 380         while (1) {
 381                 int urc;
 382                 unsigned long where = frame.pc;
 383
 384                 urc = unwind_frame(&frame);
 385                 if (urc < 0)
 386                         break;
 387                 dump_backtrace_entry(where, frame.pc, frame.sp - 4);
 388         }
 389 }
 390
 391 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
 392                                       unsigned long text_addr,
 393                                       unsigned long text_size)
 394 {
 395         unsigned long flags;
 396         struct unwind_idx *idx;
 397         struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
 398
 399         pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
 400                  text_addr, text_size);
 401
 402         if (!tab)
 403                 return tab;
 404
 405         tab->start = (struct unwind_idx *)start;
 406         tab->stop = (struct unwind_idx *)(start + size);
 407         tab->begin_addr = text_addr;
 408         tab->end_addr = text_addr + text_size;
 409
 410         /* Convert the symbol addresses to absolute values */
 411         for (idx = tab->start; idx < tab->stop; idx++)
 412                 idx->addr = prel31_to_addr(&idx->addr);
 413
 414         spin_lock_irqsave(&unwind_lock, flags);
 415         list_add_tail(&tab->list, &unwind_tables);
 416         spin_unlock_irqrestore(&unwind_lock, flags);
 417
 418         return tab;
 419 }
 420
 421 void unwind_table_del(struct unwind_table *tab)
 422 {
 423         unsigned long flags;
 424
 425         if (!tab)
 426                 return;
 427
 428         spin_lock_irqsave(&unwind_lock, flags);
 429         list_del(&tab->list);
 430         spin_unlock_irqrestore(&unwind_lock, flags);
 431
 432         kfree(tab);
 433 }
 434
 435 int __init unwind_init(void)
 436 {
 437         struct unwind_idx *idx;
 438
 439         /* Convert the symbol addresses to absolute values */
 440         for (idx = __start_unwind_idx; idx < __stop_unwind_idx; idx++)
 441                 idx->addr = prel31_to_addr(&idx->addr);
 442
 443         pr_debug("unwind: ARM stack unwinding initialised\n");
 444
 445         return 0;
 446 }