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