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) && !defined(__clang__) 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 unsigned long sp_high; /* highest value of sp allowed */ 72 /* 73 * 1 : check for stack overflow for each register pop. 74 * 0 : save overhead if there is plenty of stack remaining. 75 */ 76 int check_each_pop; 77 int entries; /* number of entries left to interpret */ 78 int byte; /* current byte number in the instructions word */ 79 }; 80 81 enum regs { 82 #ifdef CONFIG_THUMB2_KERNEL 83 FP = 7, 84 #else 85 FP = 11, 86 #endif 87 SP = 13, 88 LR = 14, 89 PC = 15 90 }; 91 92 extern const struct unwind_idx __start_unwind_idx[]; 93 static const struct unwind_idx *__origin_unwind_idx; 94 extern const struct unwind_idx __stop_unwind_idx[]; 95 96 static DEFINE_SPINLOCK(unwind_lock); 97 static LIST_HEAD(unwind_tables); 98 99 /* Convert a prel31 symbol to an absolute address */ 100 #define prel31_to_addr(ptr) \ 101 ({ \ 102 /* sign-extend to 32 bits */ \ 103 long offset = (((long)*(ptr)) << 1) >> 1; \ 104 (unsigned long)(ptr) + offset; \ 105 }) 106 107 /* 108 * Binary search in the unwind index. The entries are 109 * guaranteed to be sorted in ascending order by the linker. 110 * 111 * start = first entry 112 * origin = first entry with positive offset (or stop if there is no such entry) 113 * stop - 1 = last entry 114 */ 115 static const struct unwind_idx *search_index(unsigned long addr, 116 const struct unwind_idx *start, 117 const struct unwind_idx *origin, 118 const struct unwind_idx *stop) 119 { 120 unsigned long addr_prel31; 121 122 pr_debug("%s(%08lx, %p, %p, %p)\n", 123 __func__, addr, start, origin, stop); 124 125 /* 126 * only search in the section with the matching sign. This way the 127 * prel31 numbers can be compared as unsigned longs. 128 */ 129 if (addr < (unsigned long)start) 130 /* negative offsets: [start; origin) */ 131 stop = origin; 132 else 133 /* positive offsets: [origin; stop) */ 134 start = origin; 135 136 /* prel31 for address relavive to start */ 137 addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff; 138 139 while (start < stop - 1) { 140 const struct unwind_idx *mid = start + ((stop - start) >> 1); 141 142 /* 143 * As addr_prel31 is relative to start an offset is needed to 144 * make it relative to mid. 145 */ 146 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) < 147 mid->addr_offset) 148 stop = mid; 149 else { 150 /* keep addr_prel31 relative to start */ 151 addr_prel31 -= ((unsigned long)mid - 152 (unsigned long)start); 153 start = mid; 154 } 155 } 156 157 if (likely(start->addr_offset <= addr_prel31)) 158 return start; 159 else { 160 pr_warn("unwind: Unknown symbol address %08lx\n", addr); 161 return NULL; 162 } 163 } 164 165 static const struct unwind_idx *unwind_find_origin( 166 const struct unwind_idx *start, const struct unwind_idx *stop) 167 { 168 pr_debug("%s(%p, %p)\n", __func__, start, stop); 169 while (start < stop) { 170 const struct unwind_idx *mid = start + ((stop - start) >> 1); 171 172 if (mid->addr_offset >= 0x40000000) 173 /* negative offset */ 174 start = mid + 1; 175 else 176 /* positive offset */ 177 stop = mid; 178 } 179 pr_debug("%s -> %p\n", __func__, stop); 180 return stop; 181 } 182 183 static const struct unwind_idx *unwind_find_idx(unsigned long addr) 184 { 185 const struct unwind_idx *idx = NULL; 186 unsigned long flags; 187 188 pr_debug("%s(%08lx)\n", __func__, addr); 189 190 if (core_kernel_text(addr)) { 191 if (unlikely(!__origin_unwind_idx)) 192 __origin_unwind_idx = 193 unwind_find_origin(__start_unwind_idx, 194 __stop_unwind_idx); 195 196 /* main unwind table */ 197 idx = search_index(addr, __start_unwind_idx, 198 __origin_unwind_idx, 199 __stop_unwind_idx); 200 } else { 201 /* module unwind tables */ 202 struct unwind_table *table; 203 204 spin_lock_irqsave(&unwind_lock, flags); 205 list_for_each_entry(table, &unwind_tables, list) { 206 if (addr >= table->begin_addr && 207 addr < table->end_addr) { 208 idx = search_index(addr, table->start, 209 table->origin, 210 table->stop); 211 /* Move-to-front to exploit common traces */ 212 list_move(&table->list, &unwind_tables); 213 break; 214 } 215 } 216 spin_unlock_irqrestore(&unwind_lock, flags); 217 } 218 219 pr_debug("%s: idx = %p\n", __func__, idx); 220 return idx; 221 } 222 223 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl) 224 { 225 unsigned long ret; 226 227 if (ctrl->entries <= 0) { 228 pr_warn("unwind: Corrupt unwind table\n"); 229 return 0; 230 } 231 232 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff; 233 234 if (ctrl->byte == 0) { 235 ctrl->insn++; 236 ctrl->entries--; 237 ctrl->byte = 3; 238 } else 239 ctrl->byte--; 240 241 return ret; 242 } 243 244 /* Before poping a register check whether it is feasible or not */ 245 static int unwind_pop_register(struct unwind_ctrl_block *ctrl, 246 unsigned long **vsp, unsigned int reg) 247 { 248 if (unlikely(ctrl->check_each_pop)) 249 if (*vsp >= (unsigned long *)ctrl->sp_high) 250 return -URC_FAILURE; 251 252 ctrl->vrs[reg] = *(*vsp)++; 253 return URC_OK; 254 } 255 256 /* Helper functions to execute the instructions */ 257 static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl, 258 unsigned long mask) 259 { 260 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 261 int load_sp, reg = 4; 262 263 load_sp = mask & (1 << (13 - 4)); 264 while (mask) { 265 if (mask & 1) 266 if (unwind_pop_register(ctrl, &vsp, reg)) 267 return -URC_FAILURE; 268 mask >>= 1; 269 reg++; 270 } 271 if (!load_sp) 272 ctrl->vrs[SP] = (unsigned long)vsp; 273 274 return URC_OK; 275 } 276 277 static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl, 278 unsigned long insn) 279 { 280 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 281 int reg; 282 283 /* pop R4-R[4+bbb] */ 284 for (reg = 4; reg <= 4 + (insn & 7); reg++) 285 if (unwind_pop_register(ctrl, &vsp, reg)) 286 return -URC_FAILURE; 287 288 if (insn & 0x8) 289 if (unwind_pop_register(ctrl, &vsp, 14)) 290 return -URC_FAILURE; 291 292 ctrl->vrs[SP] = (unsigned long)vsp; 293 294 return URC_OK; 295 } 296 297 static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl, 298 unsigned long mask) 299 { 300 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 301 int reg = 0; 302 303 /* pop R0-R3 according to mask */ 304 while (mask) { 305 if (mask & 1) 306 if (unwind_pop_register(ctrl, &vsp, reg)) 307 return -URC_FAILURE; 308 mask >>= 1; 309 reg++; 310 } 311 ctrl->vrs[SP] = (unsigned long)vsp; 312 313 return URC_OK; 314 } 315 316 /* 317 * Execute the current unwind instruction. 318 */ 319 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) 320 { 321 unsigned long insn = unwind_get_byte(ctrl); 322 int ret = URC_OK; 323 324 pr_debug("%s: insn = %08lx\n", __func__, insn); 325 326 if ((insn & 0xc0) == 0x00) 327 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; 328 else if ((insn & 0xc0) == 0x40) 329 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; 330 else if ((insn & 0xf0) == 0x80) { 331 unsigned long mask; 332 333 insn = (insn << 8) | unwind_get_byte(ctrl); 334 mask = insn & 0x0fff; 335 if (mask == 0) { 336 pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n", 337 insn); 338 return -URC_FAILURE; 339 } 340 341 ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask); 342 if (ret) 343 goto error; 344 } else if ((insn & 0xf0) == 0x90 && 345 (insn & 0x0d) != 0x0d) 346 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; 347 else if ((insn & 0xf0) == 0xa0) { 348 ret = unwind_exec_pop_r4_to_rN(ctrl, insn); 349 if (ret) 350 goto error; 351 } else if (insn == 0xb0) { 352 if (ctrl->vrs[PC] == 0) 353 ctrl->vrs[PC] = ctrl->vrs[LR]; 354 /* no further processing */ 355 ctrl->entries = 0; 356 } else if (insn == 0xb1) { 357 unsigned long mask = unwind_get_byte(ctrl); 358 359 if (mask == 0 || mask & 0xf0) { 360 pr_warn("unwind: Spare encoding %04lx\n", 361 (insn << 8) | mask); 362 return -URC_FAILURE; 363 } 364 365 ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask); 366 if (ret) 367 goto error; 368 } else if (insn == 0xb2) { 369 unsigned long uleb128 = unwind_get_byte(ctrl); 370 371 ctrl->vrs[SP] += 0x204 + (uleb128 << 2); 372 } else { 373 pr_warn("unwind: Unhandled instruction %02lx\n", insn); 374 return -URC_FAILURE; 375 } 376 377 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, 378 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); 379 380 error: 381 return ret; 382 } 383 384 /* 385 * Unwind a single frame starting with *sp for the symbol at *pc. It 386 * updates the *pc and *sp with the new values. 387 */ 388 int unwind_frame(struct stackframe *frame) 389 { 390 unsigned long low; 391 const struct unwind_idx *idx; 392 struct unwind_ctrl_block ctrl; 393 394 /* store the highest address on the stack to avoid crossing it*/ 395 low = frame->sp; 396 ctrl.sp_high = ALIGN(low, THREAD_SIZE); 397 398 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, 399 frame->pc, frame->lr, frame->sp); 400 401 if (!kernel_text_address(frame->pc)) 402 return -URC_FAILURE; 403 404 idx = unwind_find_idx(frame->pc); 405 if (!idx) { 406 pr_warn("unwind: Index not found %08lx\n", frame->pc); 407 return -URC_FAILURE; 408 } 409 410 ctrl.vrs[FP] = frame->fp; 411 ctrl.vrs[SP] = frame->sp; 412 ctrl.vrs[LR] = frame->lr; 413 ctrl.vrs[PC] = 0; 414 415 if (idx->insn == 1) 416 /* can't unwind */ 417 return -URC_FAILURE; 418 else if ((idx->insn & 0x80000000) == 0) 419 /* prel31 to the unwind table */ 420 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); 421 else if ((idx->insn & 0xff000000) == 0x80000000) 422 /* only personality routine 0 supported in the index */ 423 ctrl.insn = &idx->insn; 424 else { 425 pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n", 426 idx->insn, idx); 427 return -URC_FAILURE; 428 } 429 430 /* check the personality routine */ 431 if ((*ctrl.insn & 0xff000000) == 0x80000000) { 432 ctrl.byte = 2; 433 ctrl.entries = 1; 434 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) { 435 ctrl.byte = 1; 436 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); 437 } else { 438 pr_warn("unwind: Unsupported personality routine %08lx at %p\n", 439 *ctrl.insn, ctrl.insn); 440 return -URC_FAILURE; 441 } 442 443 ctrl.check_each_pop = 0; 444 445 while (ctrl.entries > 0) { 446 int urc; 447 if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs)) 448 ctrl.check_each_pop = 1; 449 urc = unwind_exec_insn(&ctrl); 450 if (urc < 0) 451 return urc; 452 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= ctrl.sp_high) 453 return -URC_FAILURE; 454 } 455 456 if (ctrl.vrs[PC] == 0) 457 ctrl.vrs[PC] = ctrl.vrs[LR]; 458 459 /* check for infinite loop */ 460 if (frame->pc == ctrl.vrs[PC]) 461 return -URC_FAILURE; 462 463 frame->fp = ctrl.vrs[FP]; 464 frame->sp = ctrl.vrs[SP]; 465 frame->lr = ctrl.vrs[LR]; 466 frame->pc = ctrl.vrs[PC]; 467 468 return URC_OK; 469 } 470 471 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk) 472 { 473 struct stackframe frame; 474 475 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 476 477 if (!tsk) 478 tsk = current; 479 480 if (regs) { 481 arm_get_current_stackframe(regs, &frame); 482 /* PC might be corrupted, use LR in that case. */ 483 if (!kernel_text_address(regs->ARM_pc)) 484 frame.pc = regs->ARM_lr; 485 } else if (tsk == current) { 486 frame.fp = (unsigned long)__builtin_frame_address(0); 487 frame.sp = current_stack_pointer; 488 frame.lr = (unsigned long)__builtin_return_address(0); 489 frame.pc = (unsigned long)unwind_backtrace; 490 } else { 491 /* task blocked in __switch_to */ 492 frame.fp = thread_saved_fp(tsk); 493 frame.sp = thread_saved_sp(tsk); 494 /* 495 * The function calling __switch_to cannot be a leaf function 496 * so LR is recovered from the stack. 497 */ 498 frame.lr = 0; 499 frame.pc = thread_saved_pc(tsk); 500 } 501 502 while (1) { 503 int urc; 504 unsigned long where = frame.pc; 505 506 urc = unwind_frame(&frame); 507 if (urc < 0) 508 break; 509 dump_backtrace_entry(where, frame.pc, frame.sp - 4); 510 } 511 } 512 513 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, 514 unsigned long text_addr, 515 unsigned long text_size) 516 { 517 unsigned long flags; 518 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); 519 520 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, 521 text_addr, text_size); 522 523 if (!tab) 524 return tab; 525 526 tab->start = (const struct unwind_idx *)start; 527 tab->stop = (const struct unwind_idx *)(start + size); 528 tab->origin = unwind_find_origin(tab->start, tab->stop); 529 tab->begin_addr = text_addr; 530 tab->end_addr = text_addr + text_size; 531 532 spin_lock_irqsave(&unwind_lock, flags); 533 list_add_tail(&tab->list, &unwind_tables); 534 spin_unlock_irqrestore(&unwind_lock, flags); 535 536 return tab; 537 } 538 539 void unwind_table_del(struct unwind_table *tab) 540 { 541 unsigned long flags; 542 543 if (!tab) 544 return; 545 546 spin_lock_irqsave(&unwind_lock, flags); 547 list_del(&tab->list); 548 spin_unlock_irqrestore(&unwind_lock, flags); 549 550 kfree(tab); 551 } 552