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 #endif 22 #endif /* __CHECKER__ */ 23 24 #include <linux/kernel.h> 25 #include <linux/init.h> 26 #include <linux/export.h> 27 #include <linux/sched.h> 28 #include <linux/slab.h> 29 #include <linux/spinlock.h> 30 #include <linux/list.h> 31 32 #include <asm/stacktrace.h> 33 #include <asm/traps.h> 34 #include <asm/unwind.h> 35 36 /* Dummy functions to avoid linker complaints */ 37 void __aeabi_unwind_cpp_pr0(void) 38 { 39 }; 40 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0); 41 42 void __aeabi_unwind_cpp_pr1(void) 43 { 44 }; 45 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1); 46 47 void __aeabi_unwind_cpp_pr2(void) 48 { 49 }; 50 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2); 51 52 struct unwind_ctrl_block { 53 unsigned long vrs[16]; /* virtual register set */ 54 const unsigned long *insn; /* pointer to the current instructions word */ 55 unsigned long sp_high; /* highest value of sp allowed */ 56 /* 57 * 1 : check for stack overflow for each register pop. 58 * 0 : save overhead if there is plenty of stack remaining. 59 */ 60 int check_each_pop; 61 int entries; /* number of entries left to interpret */ 62 int byte; /* current byte number in the instructions word */ 63 }; 64 65 enum regs { 66 #ifdef CONFIG_THUMB2_KERNEL 67 FP = 7, 68 #else 69 FP = 11, 70 #endif 71 SP = 13, 72 LR = 14, 73 PC = 15 74 }; 75 76 extern const struct unwind_idx __start_unwind_idx[]; 77 static const struct unwind_idx *__origin_unwind_idx; 78 extern const struct unwind_idx __stop_unwind_idx[]; 79 80 static DEFINE_RAW_SPINLOCK(unwind_lock); 81 static LIST_HEAD(unwind_tables); 82 83 /* Convert a prel31 symbol to an absolute address */ 84 #define prel31_to_addr(ptr) \ 85 ({ \ 86 /* sign-extend to 32 bits */ \ 87 long offset = (((long)*(ptr)) << 1) >> 1; \ 88 (unsigned long)(ptr) + offset; \ 89 }) 90 91 /* 92 * Binary search in the unwind index. The entries are 93 * guaranteed to be sorted in ascending order by the linker. 94 * 95 * start = first entry 96 * origin = first entry with positive offset (or stop if there is no such entry) 97 * stop - 1 = last entry 98 */ 99 static const struct unwind_idx *search_index(unsigned long addr, 100 const struct unwind_idx *start, 101 const struct unwind_idx *origin, 102 const struct unwind_idx *stop) 103 { 104 unsigned long addr_prel31; 105 106 pr_debug("%s(%08lx, %p, %p, %p)\n", 107 __func__, addr, start, origin, stop); 108 109 /* 110 * only search in the section with the matching sign. This way the 111 * prel31 numbers can be compared as unsigned longs. 112 */ 113 if (addr < (unsigned long)start) 114 /* negative offsets: [start; origin) */ 115 stop = origin; 116 else 117 /* positive offsets: [origin; stop) */ 118 start = origin; 119 120 /* prel31 for address relavive to start */ 121 addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff; 122 123 while (start < stop - 1) { 124 const struct unwind_idx *mid = start + ((stop - start) >> 1); 125 126 /* 127 * As addr_prel31 is relative to start an offset is needed to 128 * make it relative to mid. 129 */ 130 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) < 131 mid->addr_offset) 132 stop = mid; 133 else { 134 /* keep addr_prel31 relative to start */ 135 addr_prel31 -= ((unsigned long)mid - 136 (unsigned long)start); 137 start = mid; 138 } 139 } 140 141 if (likely(start->addr_offset <= addr_prel31)) 142 return start; 143 else { 144 pr_warn("unwind: Unknown symbol address %08lx\n", addr); 145 return NULL; 146 } 147 } 148 149 static const struct unwind_idx *unwind_find_origin( 150 const struct unwind_idx *start, const struct unwind_idx *stop) 151 { 152 pr_debug("%s(%p, %p)\n", __func__, start, stop); 153 while (start < stop) { 154 const struct unwind_idx *mid = start + ((stop - start) >> 1); 155 156 if (mid->addr_offset >= 0x40000000) 157 /* negative offset */ 158 start = mid + 1; 159 else 160 /* positive offset */ 161 stop = mid; 162 } 163 pr_debug("%s -> %p\n", __func__, stop); 164 return stop; 165 } 166 167 static const struct unwind_idx *unwind_find_idx(unsigned long addr) 168 { 169 const struct unwind_idx *idx = NULL; 170 unsigned long flags; 171 172 pr_debug("%s(%08lx)\n", __func__, addr); 173 174 if (core_kernel_text(addr)) { 175 if (unlikely(!__origin_unwind_idx)) 176 __origin_unwind_idx = 177 unwind_find_origin(__start_unwind_idx, 178 __stop_unwind_idx); 179 180 /* main unwind table */ 181 idx = search_index(addr, __start_unwind_idx, 182 __origin_unwind_idx, 183 __stop_unwind_idx); 184 } else { 185 /* module unwind tables */ 186 struct unwind_table *table; 187 188 raw_spin_lock_irqsave(&unwind_lock, flags); 189 list_for_each_entry(table, &unwind_tables, list) { 190 if (addr >= table->begin_addr && 191 addr < table->end_addr) { 192 idx = search_index(addr, table->start, 193 table->origin, 194 table->stop); 195 /* Move-to-front to exploit common traces */ 196 list_move(&table->list, &unwind_tables); 197 break; 198 } 199 } 200 raw_spin_unlock_irqrestore(&unwind_lock, flags); 201 } 202 203 pr_debug("%s: idx = %p\n", __func__, idx); 204 return idx; 205 } 206 207 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl) 208 { 209 unsigned long ret; 210 211 if (ctrl->entries <= 0) { 212 pr_warn("unwind: Corrupt unwind table\n"); 213 return 0; 214 } 215 216 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff; 217 218 if (ctrl->byte == 0) { 219 ctrl->insn++; 220 ctrl->entries--; 221 ctrl->byte = 3; 222 } else 223 ctrl->byte--; 224 225 return ret; 226 } 227 228 /* Before poping a register check whether it is feasible or not */ 229 static int unwind_pop_register(struct unwind_ctrl_block *ctrl, 230 unsigned long **vsp, unsigned int reg) 231 { 232 if (unlikely(ctrl->check_each_pop)) 233 if (*vsp >= (unsigned long *)ctrl->sp_high) 234 return -URC_FAILURE; 235 236 /* Use READ_ONCE_NOCHECK here to avoid this memory access 237 * from being tracked by KASAN. 238 */ 239 ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp)); 240 (*vsp)++; 241 return URC_OK; 242 } 243 244 /* Helper functions to execute the instructions */ 245 static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl, 246 unsigned long mask) 247 { 248 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 249 int load_sp, reg = 4; 250 251 load_sp = mask & (1 << (13 - 4)); 252 while (mask) { 253 if (mask & 1) 254 if (unwind_pop_register(ctrl, &vsp, reg)) 255 return -URC_FAILURE; 256 mask >>= 1; 257 reg++; 258 } 259 if (!load_sp) 260 ctrl->vrs[SP] = (unsigned long)vsp; 261 262 return URC_OK; 263 } 264 265 static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl, 266 unsigned long insn) 267 { 268 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 269 int reg; 270 271 /* pop R4-R[4+bbb] */ 272 for (reg = 4; reg <= 4 + (insn & 7); reg++) 273 if (unwind_pop_register(ctrl, &vsp, reg)) 274 return -URC_FAILURE; 275 276 if (insn & 0x8) 277 if (unwind_pop_register(ctrl, &vsp, 14)) 278 return -URC_FAILURE; 279 280 ctrl->vrs[SP] = (unsigned long)vsp; 281 282 return URC_OK; 283 } 284 285 static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl, 286 unsigned long mask) 287 { 288 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 289 int reg = 0; 290 291 /* pop R0-R3 according to mask */ 292 while (mask) { 293 if (mask & 1) 294 if (unwind_pop_register(ctrl, &vsp, reg)) 295 return -URC_FAILURE; 296 mask >>= 1; 297 reg++; 298 } 299 ctrl->vrs[SP] = (unsigned long)vsp; 300 301 return URC_OK; 302 } 303 304 /* 305 * Execute the current unwind instruction. 306 */ 307 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) 308 { 309 unsigned long insn = unwind_get_byte(ctrl); 310 int ret = URC_OK; 311 312 pr_debug("%s: insn = %08lx\n", __func__, insn); 313 314 if ((insn & 0xc0) == 0x00) 315 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; 316 else if ((insn & 0xc0) == 0x40) 317 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; 318 else if ((insn & 0xf0) == 0x80) { 319 unsigned long mask; 320 321 insn = (insn << 8) | unwind_get_byte(ctrl); 322 mask = insn & 0x0fff; 323 if (mask == 0) { 324 pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n", 325 insn); 326 return -URC_FAILURE; 327 } 328 329 ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask); 330 if (ret) 331 goto error; 332 } else if ((insn & 0xf0) == 0x90 && 333 (insn & 0x0d) != 0x0d) 334 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; 335 else if ((insn & 0xf0) == 0xa0) { 336 ret = unwind_exec_pop_r4_to_rN(ctrl, insn); 337 if (ret) 338 goto error; 339 } else if (insn == 0xb0) { 340 if (ctrl->vrs[PC] == 0) 341 ctrl->vrs[PC] = ctrl->vrs[LR]; 342 /* no further processing */ 343 ctrl->entries = 0; 344 } else if (insn == 0xb1) { 345 unsigned long mask = unwind_get_byte(ctrl); 346 347 if (mask == 0 || mask & 0xf0) { 348 pr_warn("unwind: Spare encoding %04lx\n", 349 (insn << 8) | mask); 350 return -URC_FAILURE; 351 } 352 353 ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask); 354 if (ret) 355 goto error; 356 } else if (insn == 0xb2) { 357 unsigned long uleb128 = unwind_get_byte(ctrl); 358 359 ctrl->vrs[SP] += 0x204 + (uleb128 << 2); 360 } else { 361 pr_warn("unwind: Unhandled instruction %02lx\n", insn); 362 return -URC_FAILURE; 363 } 364 365 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, 366 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); 367 368 error: 369 return ret; 370 } 371 372 /* 373 * Unwind a single frame starting with *sp for the symbol at *pc. It 374 * updates the *pc and *sp with the new values. 375 */ 376 int unwind_frame(struct stackframe *frame) 377 { 378 unsigned long low; 379 const struct unwind_idx *idx; 380 struct unwind_ctrl_block ctrl; 381 382 /* store the highest address on the stack to avoid crossing it*/ 383 low = frame->sp; 384 ctrl.sp_high = ALIGN(low, THREAD_SIZE); 385 386 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, 387 frame->pc, frame->lr, frame->sp); 388 389 if (!kernel_text_address(frame->pc)) 390 return -URC_FAILURE; 391 392 idx = unwind_find_idx(frame->pc); 393 if (!idx) { 394 pr_warn("unwind: Index not found %08lx\n", frame->pc); 395 return -URC_FAILURE; 396 } 397 398 ctrl.vrs[FP] = frame->fp; 399 ctrl.vrs[SP] = frame->sp; 400 ctrl.vrs[LR] = frame->lr; 401 ctrl.vrs[PC] = 0; 402 403 if (idx->insn == 1) 404 /* can't unwind */ 405 return -URC_FAILURE; 406 else if ((idx->insn & 0x80000000) == 0) 407 /* prel31 to the unwind table */ 408 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); 409 else if ((idx->insn & 0xff000000) == 0x80000000) 410 /* only personality routine 0 supported in the index */ 411 ctrl.insn = &idx->insn; 412 else { 413 pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n", 414 idx->insn, idx); 415 return -URC_FAILURE; 416 } 417 418 /* check the personality routine */ 419 if ((*ctrl.insn & 0xff000000) == 0x80000000) { 420 ctrl.byte = 2; 421 ctrl.entries = 1; 422 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) { 423 ctrl.byte = 1; 424 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); 425 } else { 426 pr_warn("unwind: Unsupported personality routine %08lx at %p\n", 427 *ctrl.insn, ctrl.insn); 428 return -URC_FAILURE; 429 } 430 431 ctrl.check_each_pop = 0; 432 433 while (ctrl.entries > 0) { 434 int urc; 435 if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs)) 436 ctrl.check_each_pop = 1; 437 urc = unwind_exec_insn(&ctrl); 438 if (urc < 0) 439 return urc; 440 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= ctrl.sp_high) 441 return -URC_FAILURE; 442 } 443 444 if (ctrl.vrs[PC] == 0) 445 ctrl.vrs[PC] = ctrl.vrs[LR]; 446 447 /* check for infinite loop */ 448 if (frame->pc == ctrl.vrs[PC] && frame->sp == ctrl.vrs[SP]) 449 return -URC_FAILURE; 450 451 frame->fp = ctrl.vrs[FP]; 452 frame->sp = ctrl.vrs[SP]; 453 frame->lr = ctrl.vrs[LR]; 454 frame->pc = ctrl.vrs[PC]; 455 456 return URC_OK; 457 } 458 459 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk, 460 const char *loglvl) 461 { 462 struct stackframe frame; 463 464 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 465 466 if (!tsk) 467 tsk = current; 468 469 if (regs) { 470 arm_get_current_stackframe(regs, &frame); 471 /* PC might be corrupted, use LR in that case. */ 472 if (!kernel_text_address(regs->ARM_pc)) 473 frame.pc = regs->ARM_lr; 474 } else if (tsk == current) { 475 frame.fp = (unsigned long)__builtin_frame_address(0); 476 frame.sp = current_stack_pointer; 477 frame.lr = (unsigned long)__builtin_return_address(0); 478 frame.pc = (unsigned long)unwind_backtrace; 479 } else { 480 /* task blocked in __switch_to */ 481 frame.fp = thread_saved_fp(tsk); 482 frame.sp = thread_saved_sp(tsk); 483 /* 484 * The function calling __switch_to cannot be a leaf function 485 * so LR is recovered from the stack. 486 */ 487 frame.lr = 0; 488 frame.pc = thread_saved_pc(tsk); 489 } 490 491 while (1) { 492 int urc; 493 unsigned long where = frame.pc; 494 495 urc = unwind_frame(&frame); 496 if (urc < 0) 497 break; 498 dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl); 499 } 500 } 501 502 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, 503 unsigned long text_addr, 504 unsigned long text_size) 505 { 506 unsigned long flags; 507 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); 508 509 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, 510 text_addr, text_size); 511 512 if (!tab) 513 return tab; 514 515 tab->start = (const struct unwind_idx *)start; 516 tab->stop = (const struct unwind_idx *)(start + size); 517 tab->origin = unwind_find_origin(tab->start, tab->stop); 518 tab->begin_addr = text_addr; 519 tab->end_addr = text_addr + text_size; 520 521 raw_spin_lock_irqsave(&unwind_lock, flags); 522 list_add_tail(&tab->list, &unwind_tables); 523 raw_spin_unlock_irqrestore(&unwind_lock, flags); 524 525 return tab; 526 } 527 528 void unwind_table_del(struct unwind_table *tab) 529 { 530 unsigned long flags; 531 532 if (!tab) 533 return; 534 535 raw_spin_lock_irqsave(&unwind_lock, flags); 536 list_del(&tab->list); 537 raw_spin_unlock_irqrestore(&unwind_lock, flags); 538 539 kfree(tab); 540 } 541