1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * arch/arm/kernel/unwind.c 4 * 5 * Copyright (C) 2008 ARM Limited 6 * 7 * Stack unwinding support for ARM 8 * 9 * An ARM EABI version of gcc is required to generate the unwind 10 * tables. For information about the structure of the unwind tables, 11 * see "Exception Handling ABI for the ARM Architecture" at: 12 * 13 * http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html 14 */ 15 16 #ifndef __CHECKER__ 17 #if !defined (__ARM_EABI__) 18 #warning Your compiler does not have EABI support. 19 #warning ARM unwind is known to compile only with EABI compilers. 20 #warning Change compiler or disable ARM_UNWIND option. 21 #elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2) && !defined(__clang__) 22 #warning Your compiler is too buggy; it is known to not compile ARM unwind support. 23 #warning Change compiler or disable ARM_UNWIND option. 24 #endif 25 #endif /* __CHECKER__ */ 26 27 #include <linux/kernel.h> 28 #include <linux/init.h> 29 #include <linux/export.h> 30 #include <linux/sched.h> 31 #include <linux/slab.h> 32 #include <linux/spinlock.h> 33 #include <linux/list.h> 34 35 #include <asm/stacktrace.h> 36 #include <asm/traps.h> 37 #include <asm/unwind.h> 38 39 /* Dummy functions to avoid linker complaints */ 40 void __aeabi_unwind_cpp_pr0(void) 41 { 42 }; 43 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0); 44 45 void __aeabi_unwind_cpp_pr1(void) 46 { 47 }; 48 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1); 49 50 void __aeabi_unwind_cpp_pr2(void) 51 { 52 }; 53 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2); 54 55 struct unwind_ctrl_block { 56 unsigned long vrs[16]; /* virtual register set */ 57 const unsigned long *insn; /* pointer to the current instructions word */ 58 unsigned long sp_high; /* highest value of sp allowed */ 59 /* 60 * 1 : check for stack overflow for each register pop. 61 * 0 : save overhead if there is plenty of stack remaining. 62 */ 63 int check_each_pop; 64 int entries; /* number of entries left to interpret */ 65 int byte; /* current byte number in the instructions word */ 66 }; 67 68 enum regs { 69 #ifdef CONFIG_THUMB2_KERNEL 70 FP = 7, 71 #else 72 FP = 11, 73 #endif 74 SP = 13, 75 LR = 14, 76 PC = 15 77 }; 78 79 extern const struct unwind_idx __start_unwind_idx[]; 80 static const struct unwind_idx *__origin_unwind_idx; 81 extern const struct unwind_idx __stop_unwind_idx[]; 82 83 static DEFINE_RAW_SPINLOCK(unwind_lock); 84 static LIST_HEAD(unwind_tables); 85 86 /* Convert a prel31 symbol to an absolute address */ 87 #define prel31_to_addr(ptr) \ 88 ({ \ 89 /* sign-extend to 32 bits */ \ 90 long offset = (((long)*(ptr)) << 1) >> 1; \ 91 (unsigned long)(ptr) + offset; \ 92 }) 93 94 /* 95 * Binary search in the unwind index. The entries are 96 * guaranteed to be sorted in ascending order by the linker. 97 * 98 * start = first entry 99 * origin = first entry with positive offset (or stop if there is no such entry) 100 * stop - 1 = last entry 101 */ 102 static const struct unwind_idx *search_index(unsigned long addr, 103 const struct unwind_idx *start, 104 const struct unwind_idx *origin, 105 const struct unwind_idx *stop) 106 { 107 unsigned long addr_prel31; 108 109 pr_debug("%s(%08lx, %p, %p, %p)\n", 110 __func__, addr, start, origin, stop); 111 112 /* 113 * only search in the section with the matching sign. This way the 114 * prel31 numbers can be compared as unsigned longs. 115 */ 116 if (addr < (unsigned long)start) 117 /* negative offsets: [start; origin) */ 118 stop = origin; 119 else 120 /* positive offsets: [origin; stop) */ 121 start = origin; 122 123 /* prel31 for address relavive to start */ 124 addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff; 125 126 while (start < stop - 1) { 127 const struct unwind_idx *mid = start + ((stop - start) >> 1); 128 129 /* 130 * As addr_prel31 is relative to start an offset is needed to 131 * make it relative to mid. 132 */ 133 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) < 134 mid->addr_offset) 135 stop = mid; 136 else { 137 /* keep addr_prel31 relative to start */ 138 addr_prel31 -= ((unsigned long)mid - 139 (unsigned long)start); 140 start = mid; 141 } 142 } 143 144 if (likely(start->addr_offset <= addr_prel31)) 145 return start; 146 else { 147 pr_warn("unwind: Unknown symbol address %08lx\n", addr); 148 return NULL; 149 } 150 } 151 152 static const struct unwind_idx *unwind_find_origin( 153 const struct unwind_idx *start, const struct unwind_idx *stop) 154 { 155 pr_debug("%s(%p, %p)\n", __func__, start, stop); 156 while (start < stop) { 157 const struct unwind_idx *mid = start + ((stop - start) >> 1); 158 159 if (mid->addr_offset >= 0x40000000) 160 /* negative offset */ 161 start = mid + 1; 162 else 163 /* positive offset */ 164 stop = mid; 165 } 166 pr_debug("%s -> %p\n", __func__, stop); 167 return stop; 168 } 169 170 static const struct unwind_idx *unwind_find_idx(unsigned long addr) 171 { 172 const struct unwind_idx *idx = NULL; 173 unsigned long flags; 174 175 pr_debug("%s(%08lx)\n", __func__, addr); 176 177 if (core_kernel_text(addr)) { 178 if (unlikely(!__origin_unwind_idx)) 179 __origin_unwind_idx = 180 unwind_find_origin(__start_unwind_idx, 181 __stop_unwind_idx); 182 183 /* main unwind table */ 184 idx = search_index(addr, __start_unwind_idx, 185 __origin_unwind_idx, 186 __stop_unwind_idx); 187 } else { 188 /* module unwind tables */ 189 struct unwind_table *table; 190 191 raw_spin_lock_irqsave(&unwind_lock, flags); 192 list_for_each_entry(table, &unwind_tables, list) { 193 if (addr >= table->begin_addr && 194 addr < table->end_addr) { 195 idx = search_index(addr, table->start, 196 table->origin, 197 table->stop); 198 /* Move-to-front to exploit common traces */ 199 list_move(&table->list, &unwind_tables); 200 break; 201 } 202 } 203 raw_spin_unlock_irqrestore(&unwind_lock, flags); 204 } 205 206 pr_debug("%s: idx = %p\n", __func__, idx); 207 return idx; 208 } 209 210 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl) 211 { 212 unsigned long ret; 213 214 if (ctrl->entries <= 0) { 215 pr_warn("unwind: Corrupt unwind table\n"); 216 return 0; 217 } 218 219 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff; 220 221 if (ctrl->byte == 0) { 222 ctrl->insn++; 223 ctrl->entries--; 224 ctrl->byte = 3; 225 } else 226 ctrl->byte--; 227 228 return ret; 229 } 230 231 /* Before poping a register check whether it is feasible or not */ 232 static int unwind_pop_register(struct unwind_ctrl_block *ctrl, 233 unsigned long **vsp, unsigned int reg) 234 { 235 if (unlikely(ctrl->check_each_pop)) 236 if (*vsp >= (unsigned long *)ctrl->sp_high) 237 return -URC_FAILURE; 238 239 ctrl->vrs[reg] = *(*vsp)++; 240 return URC_OK; 241 } 242 243 /* Helper functions to execute the instructions */ 244 static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl, 245 unsigned long mask) 246 { 247 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 248 int load_sp, reg = 4; 249 250 load_sp = mask & (1 << (13 - 4)); 251 while (mask) { 252 if (mask & 1) 253 if (unwind_pop_register(ctrl, &vsp, reg)) 254 return -URC_FAILURE; 255 mask >>= 1; 256 reg++; 257 } 258 if (!load_sp) 259 ctrl->vrs[SP] = (unsigned long)vsp; 260 261 return URC_OK; 262 } 263 264 static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl, 265 unsigned long insn) 266 { 267 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 268 int reg; 269 270 /* pop R4-R[4+bbb] */ 271 for (reg = 4; reg <= 4 + (insn & 7); reg++) 272 if (unwind_pop_register(ctrl, &vsp, reg)) 273 return -URC_FAILURE; 274 275 if (insn & 0x8) 276 if (unwind_pop_register(ctrl, &vsp, 14)) 277 return -URC_FAILURE; 278 279 ctrl->vrs[SP] = (unsigned long)vsp; 280 281 return URC_OK; 282 } 283 284 static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl, 285 unsigned long mask) 286 { 287 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 288 int reg = 0; 289 290 /* pop R0-R3 according to mask */ 291 while (mask) { 292 if (mask & 1) 293 if (unwind_pop_register(ctrl, &vsp, reg)) 294 return -URC_FAILURE; 295 mask >>= 1; 296 reg++; 297 } 298 ctrl->vrs[SP] = (unsigned long)vsp; 299 300 return URC_OK; 301 } 302 303 /* 304 * Execute the current unwind instruction. 305 */ 306 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) 307 { 308 unsigned long insn = unwind_get_byte(ctrl); 309 int ret = URC_OK; 310 311 pr_debug("%s: insn = %08lx\n", __func__, insn); 312 313 if ((insn & 0xc0) == 0x00) 314 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; 315 else if ((insn & 0xc0) == 0x40) 316 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; 317 else if ((insn & 0xf0) == 0x80) { 318 unsigned long mask; 319 320 insn = (insn << 8) | unwind_get_byte(ctrl); 321 mask = insn & 0x0fff; 322 if (mask == 0) { 323 pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n", 324 insn); 325 return -URC_FAILURE; 326 } 327 328 ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask); 329 if (ret) 330 goto error; 331 } else if ((insn & 0xf0) == 0x90 && 332 (insn & 0x0d) != 0x0d) 333 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; 334 else if ((insn & 0xf0) == 0xa0) { 335 ret = unwind_exec_pop_r4_to_rN(ctrl, insn); 336 if (ret) 337 goto error; 338 } else if (insn == 0xb0) { 339 if (ctrl->vrs[PC] == 0) 340 ctrl->vrs[PC] = ctrl->vrs[LR]; 341 /* no further processing */ 342 ctrl->entries = 0; 343 } else if (insn == 0xb1) { 344 unsigned long mask = unwind_get_byte(ctrl); 345 346 if (mask == 0 || mask & 0xf0) { 347 pr_warn("unwind: Spare encoding %04lx\n", 348 (insn << 8) | mask); 349 return -URC_FAILURE; 350 } 351 352 ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask); 353 if (ret) 354 goto error; 355 } else if (insn == 0xb2) { 356 unsigned long uleb128 = unwind_get_byte(ctrl); 357 358 ctrl->vrs[SP] += 0x204 + (uleb128 << 2); 359 } else { 360 pr_warn("unwind: Unhandled instruction %02lx\n", insn); 361 return -URC_FAILURE; 362 } 363 364 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, 365 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); 366 367 error: 368 return ret; 369 } 370 371 /* 372 * Unwind a single frame starting with *sp for the symbol at *pc. It 373 * updates the *pc and *sp with the new values. 374 */ 375 int unwind_frame(struct stackframe *frame) 376 { 377 unsigned long low; 378 const struct unwind_idx *idx; 379 struct unwind_ctrl_block ctrl; 380 381 /* store the highest address on the stack to avoid crossing it*/ 382 low = frame->sp; 383 ctrl.sp_high = ALIGN(low, THREAD_SIZE); 384 385 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, 386 frame->pc, frame->lr, frame->sp); 387 388 if (!kernel_text_address(frame->pc)) 389 return -URC_FAILURE; 390 391 idx = unwind_find_idx(frame->pc); 392 if (!idx) { 393 pr_warn("unwind: Index not found %08lx\n", frame->pc); 394 return -URC_FAILURE; 395 } 396 397 ctrl.vrs[FP] = frame->fp; 398 ctrl.vrs[SP] = frame->sp; 399 ctrl.vrs[LR] = frame->lr; 400 ctrl.vrs[PC] = 0; 401 402 if (idx->insn == 1) 403 /* can't unwind */ 404 return -URC_FAILURE; 405 else if ((idx->insn & 0x80000000) == 0) 406 /* prel31 to the unwind table */ 407 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); 408 else if ((idx->insn & 0xff000000) == 0x80000000) 409 /* only personality routine 0 supported in the index */ 410 ctrl.insn = &idx->insn; 411 else { 412 pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n", 413 idx->insn, idx); 414 return -URC_FAILURE; 415 } 416 417 /* check the personality routine */ 418 if ((*ctrl.insn & 0xff000000) == 0x80000000) { 419 ctrl.byte = 2; 420 ctrl.entries = 1; 421 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) { 422 ctrl.byte = 1; 423 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); 424 } else { 425 pr_warn("unwind: Unsupported personality routine %08lx at %p\n", 426 *ctrl.insn, ctrl.insn); 427 return -URC_FAILURE; 428 } 429 430 ctrl.check_each_pop = 0; 431 432 while (ctrl.entries > 0) { 433 int urc; 434 if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs)) 435 ctrl.check_each_pop = 1; 436 urc = unwind_exec_insn(&ctrl); 437 if (urc < 0) 438 return urc; 439 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= ctrl.sp_high) 440 return -URC_FAILURE; 441 } 442 443 if (ctrl.vrs[PC] == 0) 444 ctrl.vrs[PC] = ctrl.vrs[LR]; 445 446 /* check for infinite loop */ 447 if (frame->pc == ctrl.vrs[PC]) 448 return -URC_FAILURE; 449 450 frame->fp = ctrl.vrs[FP]; 451 frame->sp = ctrl.vrs[SP]; 452 frame->lr = ctrl.vrs[LR]; 453 frame->pc = ctrl.vrs[PC]; 454 455 return URC_OK; 456 } 457 458 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk) 459 { 460 struct stackframe frame; 461 462 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 463 464 if (!tsk) 465 tsk = current; 466 467 if (regs) { 468 arm_get_current_stackframe(regs, &frame); 469 /* PC might be corrupted, use LR in that case. */ 470 if (!kernel_text_address(regs->ARM_pc)) 471 frame.pc = regs->ARM_lr; 472 } else if (tsk == current) { 473 frame.fp = (unsigned long)__builtin_frame_address(0); 474 frame.sp = current_stack_pointer; 475 frame.lr = (unsigned long)__builtin_return_address(0); 476 frame.pc = (unsigned long)unwind_backtrace; 477 } else { 478 /* task blocked in __switch_to */ 479 frame.fp = thread_saved_fp(tsk); 480 frame.sp = thread_saved_sp(tsk); 481 /* 482 * The function calling __switch_to cannot be a leaf function 483 * so LR is recovered from the stack. 484 */ 485 frame.lr = 0; 486 frame.pc = thread_saved_pc(tsk); 487 } 488 489 while (1) { 490 int urc; 491 unsigned long where = frame.pc; 492 493 urc = unwind_frame(&frame); 494 if (urc < 0) 495 break; 496 dump_backtrace_entry(where, frame.pc, frame.sp - 4); 497 } 498 } 499 500 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, 501 unsigned long text_addr, 502 unsigned long text_size) 503 { 504 unsigned long flags; 505 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); 506 507 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, 508 text_addr, text_size); 509 510 if (!tab) 511 return tab; 512 513 tab->start = (const struct unwind_idx *)start; 514 tab->stop = (const struct unwind_idx *)(start + size); 515 tab->origin = unwind_find_origin(tab->start, tab->stop); 516 tab->begin_addr = text_addr; 517 tab->end_addr = text_addr + text_size; 518 519 raw_spin_lock_irqsave(&unwind_lock, flags); 520 list_add_tail(&tab->list, &unwind_tables); 521 raw_spin_unlock_irqrestore(&unwind_lock, flags); 522 523 return tab; 524 } 525 526 void unwind_table_del(struct unwind_table *tab) 527 { 528 unsigned long flags; 529 530 if (!tab) 531 return; 532 533 raw_spin_lock_irqsave(&unwind_lock, flags); 534 list_del(&tab->list); 535 raw_spin_unlock_irqrestore(&unwind_lock, flags); 536 537 kfree(tab); 538 } 539