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