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/export.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 const 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 const struct unwind_idx __start_unwind_idx[]; 87 static const struct unwind_idx *__origin_unwind_idx; 88 extern const struct unwind_idx __stop_unwind_idx[]; 89 90 static DEFINE_SPINLOCK(unwind_lock); 91 static LIST_HEAD(unwind_tables); 92 93 /* Convert a prel31 symbol to an absolute address */ 94 #define prel31_to_addr(ptr) \ 95 ({ \ 96 /* sign-extend to 32 bits */ \ 97 long offset = (((long)*(ptr)) << 1) >> 1; \ 98 (unsigned long)(ptr) + offset; \ 99 }) 100 101 /* 102 * Binary search in the unwind index. The entries are 103 * guaranteed to be sorted in ascending order by the linker. 104 * 105 * start = first entry 106 * origin = first entry with positive offset (or stop if there is no such entry) 107 * stop - 1 = last entry 108 */ 109 static const struct unwind_idx *search_index(unsigned long addr, 110 const struct unwind_idx *start, 111 const struct unwind_idx *origin, 112 const struct unwind_idx *stop) 113 { 114 unsigned long addr_prel31; 115 116 pr_debug("%s(%08lx, %p, %p, %p)\n", 117 __func__, addr, start, origin, stop); 118 119 /* 120 * only search in the section with the matching sign. This way the 121 * prel31 numbers can be compared as unsigned longs. 122 */ 123 if (addr < (unsigned long)start) 124 /* negative offsets: [start; origin) */ 125 stop = origin; 126 else 127 /* positive offsets: [origin; stop) */ 128 start = origin; 129 130 /* prel31 for address relavive to start */ 131 addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff; 132 133 while (start < stop - 1) { 134 const struct unwind_idx *mid = start + ((stop - start) >> 1); 135 136 /* 137 * As addr_prel31 is relative to start an offset is needed to 138 * make it relative to mid. 139 */ 140 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) < 141 mid->addr_offset) 142 stop = mid; 143 else { 144 /* keep addr_prel31 relative to start */ 145 addr_prel31 -= ((unsigned long)mid - 146 (unsigned long)start); 147 start = mid; 148 } 149 } 150 151 if (likely(start->addr_offset <= addr_prel31)) 152 return start; 153 else { 154 pr_warning("unwind: Unknown symbol address %08lx\n", addr); 155 return NULL; 156 } 157 } 158 159 static const struct unwind_idx *unwind_find_origin( 160 const struct unwind_idx *start, const struct unwind_idx *stop) 161 { 162 pr_debug("%s(%p, %p)\n", __func__, start, stop); 163 while (start < stop) { 164 const struct unwind_idx *mid = start + ((stop - start) >> 1); 165 166 if (mid->addr_offset >= 0x40000000) 167 /* negative offset */ 168 start = mid + 1; 169 else 170 /* positive offset */ 171 stop = mid; 172 } 173 pr_debug("%s -> %p\n", __func__, stop); 174 return stop; 175 } 176 177 static const struct unwind_idx *unwind_find_idx(unsigned long addr) 178 { 179 const struct unwind_idx *idx = NULL; 180 unsigned long flags; 181 182 pr_debug("%s(%08lx)\n", __func__, addr); 183 184 if (core_kernel_text(addr)) { 185 if (unlikely(!__origin_unwind_idx)) 186 __origin_unwind_idx = 187 unwind_find_origin(__start_unwind_idx, 188 __stop_unwind_idx); 189 190 /* main unwind table */ 191 idx = search_index(addr, __start_unwind_idx, 192 __origin_unwind_idx, 193 __stop_unwind_idx); 194 } else { 195 /* module unwind tables */ 196 struct unwind_table *table; 197 198 spin_lock_irqsave(&unwind_lock, flags); 199 list_for_each_entry(table, &unwind_tables, list) { 200 if (addr >= table->begin_addr && 201 addr < table->end_addr) { 202 idx = search_index(addr, table->start, 203 table->origin, 204 table->stop); 205 /* Move-to-front to exploit common traces */ 206 list_move(&table->list, &unwind_tables); 207 break; 208 } 209 } 210 spin_unlock_irqrestore(&unwind_lock, flags); 211 } 212 213 pr_debug("%s: idx = %p\n", __func__, idx); 214 return idx; 215 } 216 217 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl) 218 { 219 unsigned long ret; 220 221 if (ctrl->entries <= 0) { 222 pr_warning("unwind: Corrupt unwind table\n"); 223 return 0; 224 } 225 226 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff; 227 228 if (ctrl->byte == 0) { 229 ctrl->insn++; 230 ctrl->entries--; 231 ctrl->byte = 3; 232 } else 233 ctrl->byte--; 234 235 return ret; 236 } 237 238 /* 239 * Execute the current unwind instruction. 240 */ 241 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) 242 { 243 unsigned long insn = unwind_get_byte(ctrl); 244 245 pr_debug("%s: insn = %08lx\n", __func__, insn); 246 247 if ((insn & 0xc0) == 0x00) 248 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; 249 else if ((insn & 0xc0) == 0x40) 250 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; 251 else if ((insn & 0xf0) == 0x80) { 252 unsigned long mask; 253 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 254 int load_sp, reg = 4; 255 256 insn = (insn << 8) | unwind_get_byte(ctrl); 257 mask = insn & 0x0fff; 258 if (mask == 0) { 259 pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n", 260 insn); 261 return -URC_FAILURE; 262 } 263 264 /* pop R4-R15 according to mask */ 265 load_sp = mask & (1 << (13 - 4)); 266 while (mask) { 267 if (mask & 1) 268 ctrl->vrs[reg] = *vsp++; 269 mask >>= 1; 270 reg++; 271 } 272 if (!load_sp) 273 ctrl->vrs[SP] = (unsigned long)vsp; 274 } else if ((insn & 0xf0) == 0x90 && 275 (insn & 0x0d) != 0x0d) 276 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; 277 else if ((insn & 0xf0) == 0xa0) { 278 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 279 int reg; 280 281 /* pop R4-R[4+bbb] */ 282 for (reg = 4; reg <= 4 + (insn & 7); reg++) 283 ctrl->vrs[reg] = *vsp++; 284 if (insn & 0x80) 285 ctrl->vrs[14] = *vsp++; 286 ctrl->vrs[SP] = (unsigned long)vsp; 287 } else if (insn == 0xb0) { 288 if (ctrl->vrs[PC] == 0) 289 ctrl->vrs[PC] = ctrl->vrs[LR]; 290 /* no further processing */ 291 ctrl->entries = 0; 292 } else if (insn == 0xb1) { 293 unsigned long mask = unwind_get_byte(ctrl); 294 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 295 int reg = 0; 296 297 if (mask == 0 || mask & 0xf0) { 298 pr_warning("unwind: Spare encoding %04lx\n", 299 (insn << 8) | mask); 300 return -URC_FAILURE; 301 } 302 303 /* pop R0-R3 according to mask */ 304 while (mask) { 305 if (mask & 1) 306 ctrl->vrs[reg] = *vsp++; 307 mask >>= 1; 308 reg++; 309 } 310 ctrl->vrs[SP] = (unsigned long)vsp; 311 } else if (insn == 0xb2) { 312 unsigned long uleb128 = unwind_get_byte(ctrl); 313 314 ctrl->vrs[SP] += 0x204 + (uleb128 << 2); 315 } else { 316 pr_warning("unwind: Unhandled instruction %02lx\n", insn); 317 return -URC_FAILURE; 318 } 319 320 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, 321 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); 322 323 return URC_OK; 324 } 325 326 /* 327 * Unwind a single frame starting with *sp for the symbol at *pc. It 328 * updates the *pc and *sp with the new values. 329 */ 330 int unwind_frame(struct stackframe *frame) 331 { 332 unsigned long high, low; 333 const struct unwind_idx *idx; 334 struct unwind_ctrl_block ctrl; 335 336 /* only go to a higher address on the stack */ 337 low = frame->sp; 338 high = ALIGN(low, THREAD_SIZE); 339 340 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, 341 frame->pc, frame->lr, frame->sp); 342 343 if (!kernel_text_address(frame->pc)) 344 return -URC_FAILURE; 345 346 idx = unwind_find_idx(frame->pc); 347 if (!idx) { 348 pr_warning("unwind: Index not found %08lx\n", frame->pc); 349 return -URC_FAILURE; 350 } 351 352 ctrl.vrs[FP] = frame->fp; 353 ctrl.vrs[SP] = frame->sp; 354 ctrl.vrs[LR] = frame->lr; 355 ctrl.vrs[PC] = 0; 356 357 if (idx->insn == 1) 358 /* can't unwind */ 359 return -URC_FAILURE; 360 else if ((idx->insn & 0x80000000) == 0) 361 /* prel31 to the unwind table */ 362 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); 363 else if ((idx->insn & 0xff000000) == 0x80000000) 364 /* only personality routine 0 supported in the index */ 365 ctrl.insn = &idx->insn; 366 else { 367 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n", 368 idx->insn, idx); 369 return -URC_FAILURE; 370 } 371 372 /* check the personality routine */ 373 if ((*ctrl.insn & 0xff000000) == 0x80000000) { 374 ctrl.byte = 2; 375 ctrl.entries = 1; 376 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) { 377 ctrl.byte = 1; 378 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); 379 } else { 380 pr_warning("unwind: Unsupported personality routine %08lx at %p\n", 381 *ctrl.insn, ctrl.insn); 382 return -URC_FAILURE; 383 } 384 385 while (ctrl.entries > 0) { 386 int urc = unwind_exec_insn(&ctrl); 387 if (urc < 0) 388 return urc; 389 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high) 390 return -URC_FAILURE; 391 } 392 393 if (ctrl.vrs[PC] == 0) 394 ctrl.vrs[PC] = ctrl.vrs[LR]; 395 396 /* check for infinite loop */ 397 if (frame->pc == ctrl.vrs[PC]) 398 return -URC_FAILURE; 399 400 frame->fp = ctrl.vrs[FP]; 401 frame->sp = ctrl.vrs[SP]; 402 frame->lr = ctrl.vrs[LR]; 403 frame->pc = ctrl.vrs[PC]; 404 405 return URC_OK; 406 } 407 408 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk) 409 { 410 struct stackframe frame; 411 register unsigned long current_sp asm ("sp"); 412 413 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 414 415 if (!tsk) 416 tsk = current; 417 418 if (regs) { 419 frame.fp = regs->ARM_fp; 420 frame.sp = regs->ARM_sp; 421 frame.lr = regs->ARM_lr; 422 /* PC might be corrupted, use LR in that case. */ 423 frame.pc = kernel_text_address(regs->ARM_pc) 424 ? regs->ARM_pc : regs->ARM_lr; 425 } else if (tsk == current) { 426 frame.fp = (unsigned long)__builtin_frame_address(0); 427 frame.sp = current_sp; 428 frame.lr = (unsigned long)__builtin_return_address(0); 429 frame.pc = (unsigned long)unwind_backtrace; 430 } else { 431 /* task blocked in __switch_to */ 432 frame.fp = thread_saved_fp(tsk); 433 frame.sp = thread_saved_sp(tsk); 434 /* 435 * The function calling __switch_to cannot be a leaf function 436 * so LR is recovered from the stack. 437 */ 438 frame.lr = 0; 439 frame.pc = thread_saved_pc(tsk); 440 } 441 442 while (1) { 443 int urc; 444 unsigned long where = frame.pc; 445 446 urc = unwind_frame(&frame); 447 if (urc < 0) 448 break; 449 dump_backtrace_entry(where, frame.pc, frame.sp - 4); 450 } 451 } 452 453 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, 454 unsigned long text_addr, 455 unsigned long text_size) 456 { 457 unsigned long flags; 458 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); 459 460 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, 461 text_addr, text_size); 462 463 if (!tab) 464 return tab; 465 466 tab->start = (const struct unwind_idx *)start; 467 tab->stop = (const struct unwind_idx *)(start + size); 468 tab->origin = unwind_find_origin(tab->start, tab->stop); 469 tab->begin_addr = text_addr; 470 tab->end_addr = text_addr + text_size; 471 472 spin_lock_irqsave(&unwind_lock, flags); 473 list_add_tail(&tab->list, &unwind_tables); 474 spin_unlock_irqrestore(&unwind_lock, flags); 475 476 return tab; 477 } 478 479 void unwind_table_del(struct unwind_table *tab) 480 { 481 unsigned long flags; 482 483 if (!tab) 484 return; 485 486 spin_lock_irqsave(&unwind_lock, flags); 487 list_del(&tab->list); 488 spin_unlock_irqrestore(&unwind_lock, flags); 489 490 kfree(tab); 491 } 492