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                                 /* Move-to-front to exploit common traces */
 150                                 list_move(&table->list, &unwind_tables);
 151                                 break;
 152                         }
 153                 }
 154                 spin_unlock_irqrestore(&unwind_lock, flags);
 155         }
 156
 157         pr_debug("%s: idx = %p\n", __func__, idx);
 158         return idx;
 159 }
 160
 161 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
 162 {
 163         unsigned long ret;
 164
 165         if (ctrl->entries <= 0) {
 166                 pr_warning("unwind: Corrupt unwind table\n");
 167                 return 0;
 168         }
 169
 170         ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
 171
 172         if (ctrl->byte == 0) {
 173                 ctrl->insn++;
 174                 ctrl->entries--;
 175                 ctrl->byte = 3;
 176         } else
 177                 ctrl->byte--;
 178
 179         return ret;
 180 }
 181
 182 /*
 183  * Execute the current unwind instruction.
 184  */
 185 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
 186 {
 187         unsigned long insn = unwind_get_byte(ctrl);
 188
 189         pr_debug("%s: insn = %08lx\n", __func__, insn);
 190
 191         if ((insn & 0xc0) == 0x00)
 192                 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
 193         else if ((insn & 0xc0) == 0x40)
 194                 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
 195         else if ((insn & 0xf0) == 0x80) {
 196                 unsigned long mask;
 197                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 198                 int load_sp, reg = 4;
 199
 200                 insn = (insn << 8) | unwind_get_byte(ctrl);
 201                 mask = insn & 0x0fff;
 202                 if (mask == 0) {
 203                         pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n",
 204                                    insn);
 205                         return -URC_FAILURE;
 206                 }
 207
 208                 /* pop R4-R15 according to mask */
 209                 load_sp = mask & (1 << (13 - 4));
 210                 while (mask) {
 211                         if (mask & 1)
 212                                 ctrl->vrs[reg] = *vsp++;
 213                         mask >>= 1;
 214                         reg++;
 215                 }
 216                 if (!load_sp)
 217                         ctrl->vrs[SP] = (unsigned long)vsp;
 218         } else if ((insn & 0xf0) == 0x90 &&
 219                    (insn & 0x0d) != 0x0d)
 220                 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
 221         else if ((insn & 0xf0) == 0xa0) {
 222                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 223                 int reg;
 224
 225                 /* pop R4-R[4+bbb] */
 226                 for (reg = 4; reg <= 4 + (insn & 7); reg++)
 227                         ctrl->vrs[reg] = *vsp++;
 228                 if (insn & 0x80)
 229                         ctrl->vrs[14] = *vsp++;
 230                 ctrl->vrs[SP] = (unsigned long)vsp;
 231         } else if (insn == 0xb0) {
 232                 if (ctrl->vrs[PC] == 0)
 233                         ctrl->vrs[PC] = ctrl->vrs[LR];
 234                 /* no further processing */
 235                 ctrl->entries = 0;
 236         } else if (insn == 0xb1) {
 237                 unsigned long mask = unwind_get_byte(ctrl);
 238                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
 239                 int reg = 0;
 240
 241                 if (mask == 0 || mask & 0xf0) {
 242                         pr_warning("unwind: Spare encoding %04lx\n",
 243                                (insn << 8) | mask);
 244                         return -URC_FAILURE;
 245                 }
 246
 247                 /* pop R0-R3 according to mask */
 248                 while (mask) {
 249                         if (mask & 1)
 250                                 ctrl->vrs[reg] = *vsp++;
 251                         mask >>= 1;
 252                         reg++;
 253                 }
 254                 ctrl->vrs[SP] = (unsigned long)vsp;
 255         } else if (insn == 0xb2) {
 256                 unsigned long uleb128 = unwind_get_byte(ctrl);
 257
 258                 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
 259         } else {
 260                 pr_warning("unwind: Unhandled instruction %02lx\n", insn);
 261                 return -URC_FAILURE;
 262         }
 263
 264         pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
 265                  ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
 266
 267         return URC_OK;
 268 }
 269
 270 /*
 271  * Unwind a single frame starting with *sp for the symbol at *pc. It
 272  * updates the *pc and *sp with the new values.
 273  */
 274 int unwind_frame(struct stackframe *frame)
 275 {
 276         unsigned long high, low;
 277         struct unwind_idx *idx;
 278         struct unwind_ctrl_block ctrl;
 279
 280         /* only go to a higher address on the stack */
 281         low = frame->sp;
 282         high = ALIGN(low, THREAD_SIZE) + THREAD_SIZE;
 283
 284         pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
 285                  frame->pc, frame->lr, frame->sp);
 286
 287         if (!kernel_text_address(frame->pc))
 288                 return -URC_FAILURE;
 289
 290         idx = unwind_find_idx(frame->pc);
 291         if (!idx) {
 292                 pr_warning("unwind: Index not found %08lx\n", frame->pc);
 293                 return -URC_FAILURE;
 294         }
 295
 296         ctrl.vrs[FP] = frame->fp;
 297         ctrl.vrs[SP] = frame->sp;
 298         ctrl.vrs[LR] = frame->lr;
 299         ctrl.vrs[PC] = 0;
 300
 301         if (idx->insn == 1)
 302                 /* can't unwind */
 303                 return -URC_FAILURE;
 304         else if ((idx->insn & 0x80000000) == 0)
 305                 /* prel31 to the unwind table */
 306                 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
 307         else if ((idx->insn & 0xff000000) == 0x80000000)
 308                 /* only personality routine 0 supported in the index */
 309                 ctrl.insn = &idx->insn;
 310         else {
 311                 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n",
 312                            idx->insn, idx);
 313                 return -URC_FAILURE;
 314         }
 315
 316         /* check the personality routine */
 317         if ((*ctrl.insn & 0xff000000) == 0x80000000) {
 318                 ctrl.byte = 2;
 319                 ctrl.entries = 1;
 320         } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
 321                 ctrl.byte = 1;
 322                 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
 323         } else {
 324                 pr_warning("unwind: Unsupported personality routine %08lx at %p\n",
 325                            *ctrl.insn, ctrl.insn);
 326                 return -URC_FAILURE;
 327         }
 328
 329         while (ctrl.entries > 0) {
 330                 int urc = unwind_exec_insn(&ctrl);
 331                 if (urc < 0)
 332                         return urc;
 333                 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
 334                         return -URC_FAILURE;
 335         }
 336
 337         if (ctrl.vrs[PC] == 0)
 338                 ctrl.vrs[PC] = ctrl.vrs[LR];
 339
 340         /* check for infinite loop */
 341         if (frame->pc == ctrl.vrs[PC])
 342                 return -URC_FAILURE;
 343
 344         frame->fp = ctrl.vrs[FP];
 345         frame->sp = ctrl.vrs[SP];
 346         frame->lr = ctrl.vrs[LR];
 347         frame->pc = ctrl.vrs[PC];
 348
 349         return URC_OK;
 350 }
 351
 352 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 353 {
 354         struct stackframe frame;
 355         register unsigned long current_sp asm ("sp");
 356
 357         pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 358
 359         if (!tsk)
 360                 tsk = current;
 361
 362         if (regs) {
 363                 frame.fp = regs->ARM_fp;
 364                 frame.sp = regs->ARM_sp;
 365                 frame.lr = regs->ARM_lr;
 366                 /* PC might be corrupted, use LR in that case. */
 367                 frame.pc = kernel_text_address(regs->ARM_pc)
 368                          ? regs->ARM_pc : regs->ARM_lr;
 369         } else if (tsk == current) {
 370                 frame.fp = (unsigned long)__builtin_frame_address(0);
 371                 frame.sp = current_sp;
 372                 frame.lr = (unsigned long)__builtin_return_address(0);
 373                 frame.pc = (unsigned long)unwind_backtrace;
 374         } else {
 375                 /* task blocked in __switch_to */
 376                 frame.fp = thread_saved_fp(tsk);
 377                 frame.sp = thread_saved_sp(tsk);
 378                 /*
 379                  * The function calling __switch_to cannot be a leaf function
 380                  * so LR is recovered from the stack.
 381                  */
 382                 frame.lr = 0;
 383                 frame.pc = thread_saved_pc(tsk);
 384         }
 385
 386         while (1) {
 387                 int urc;
 388                 unsigned long where = frame.pc;
 389
 390                 urc = unwind_frame(&frame);
 391                 if (urc < 0)
 392                         break;
 393                 dump_backtrace_entry(where, frame.pc, frame.sp - 4);
 394         }
 395 }
 396
 397 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
 398                                       unsigned long text_addr,
 399                                       unsigned long text_size)
 400 {
 401         unsigned long flags;
 402         struct unwind_idx *idx;
 403         struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
 404
 405         pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
 406                  text_addr, text_size);
 407
 408         if (!tab)
 409                 return tab;
 410
 411         tab->start = (struct unwind_idx *)start;
 412         tab->stop = (struct unwind_idx *)(start + size);
 413         tab->begin_addr = text_addr;
 414         tab->end_addr = text_addr + text_size;
 415
 416         /* Convert the symbol addresses to absolute values */
 417         for (idx = tab->start; idx < tab->stop; idx++)
 418                 idx->addr = prel31_to_addr(&idx->addr);
 419
 420         spin_lock_irqsave(&unwind_lock, flags);
 421         list_add_tail(&tab->list, &unwind_tables);
 422         spin_unlock_irqrestore(&unwind_lock, flags);
 423
 424         return tab;
 425 }
 426
 427 void unwind_table_del(struct unwind_table *tab)
 428 {
 429         unsigned long flags;
 430
 431         if (!tab)
 432                 return;
 433
 434         spin_lock_irqsave(&unwind_lock, flags);
 435         list_del(&tab->list);
 436         spin_unlock_irqrestore(&unwind_lock, flags);
 437
 438         kfree(tab);
 439 }
 440
 441 int __init unwind_init(void)
 442 {
 443         struct unwind_idx *idx;
 444
 445         /* Convert the symbol addresses to absolute values */
 446         for (idx = __start_unwind_idx; idx < __stop_unwind_idx; idx++)
 447                 idx->addr = prel31_to_addr(&idx->addr);
 448
 449         pr_debug("unwind: ARM stack unwinding initialised\n");
 450
 451         return 0;
 452 }