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 #include "reboot.h" 37 38 /* Dummy functions to avoid linker complaints */ 39 void __aeabi_unwind_cpp_pr0(void) 40 { 41 }; 42 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0); 43 44 void __aeabi_unwind_cpp_pr1(void) 45 { 46 }; 47 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1); 48 49 void __aeabi_unwind_cpp_pr2(void) 50 { 51 }; 52 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2); 53 54 struct unwind_ctrl_block { 55 unsigned long vrs[16]; /* virtual register set */ 56 const unsigned long *insn; /* pointer to the current instructions word */ 57 unsigned long sp_high; /* highest value of sp allowed */ 58 unsigned long *lr_addr; /* address of LR value on the stack */ 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 /* Use READ_ONCE_NOCHECK here to avoid this memory access 240 * from being tracked by KASAN. 241 */ 242 ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp)); 243 if (reg == 14) 244 ctrl->lr_addr = *vsp; 245 (*vsp)++; 246 return URC_OK; 247 } 248 249 /* Helper functions to execute the instructions */ 250 static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl, 251 unsigned long mask) 252 { 253 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 254 int load_sp, reg = 4; 255 256 load_sp = mask & (1 << (13 - 4)); 257 while (mask) { 258 if (mask & 1) 259 if (unwind_pop_register(ctrl, &vsp, reg)) 260 return -URC_FAILURE; 261 mask >>= 1; 262 reg++; 263 } 264 if (!load_sp) { 265 ctrl->vrs[SP] = (unsigned long)vsp; 266 } 267 268 return URC_OK; 269 } 270 271 static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl, 272 unsigned long insn) 273 { 274 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 275 int reg; 276 277 /* pop R4-R[4+bbb] */ 278 for (reg = 4; reg <= 4 + (insn & 7); reg++) 279 if (unwind_pop_register(ctrl, &vsp, reg)) 280 return -URC_FAILURE; 281 282 if (insn & 0x8) 283 if (unwind_pop_register(ctrl, &vsp, 14)) 284 return -URC_FAILURE; 285 286 ctrl->vrs[SP] = (unsigned long)vsp; 287 288 return URC_OK; 289 } 290 291 static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl, 292 unsigned long mask) 293 { 294 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 295 int reg = 0; 296 297 /* pop R0-R3 according to mask */ 298 while (mask) { 299 if (mask & 1) 300 if (unwind_pop_register(ctrl, &vsp, reg)) 301 return -URC_FAILURE; 302 mask >>= 1; 303 reg++; 304 } 305 ctrl->vrs[SP] = (unsigned long)vsp; 306 307 return URC_OK; 308 } 309 310 /* 311 * Execute the current unwind instruction. 312 */ 313 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) 314 { 315 unsigned long insn = unwind_get_byte(ctrl); 316 int ret = URC_OK; 317 318 pr_debug("%s: insn = %08lx\n", __func__, insn); 319 320 if ((insn & 0xc0) == 0x00) 321 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; 322 else if ((insn & 0xc0) == 0x40) { 323 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; 324 } else if ((insn & 0xf0) == 0x80) { 325 unsigned long mask; 326 327 insn = (insn << 8) | unwind_get_byte(ctrl); 328 mask = insn & 0x0fff; 329 if (mask == 0) { 330 pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n", 331 insn); 332 return -URC_FAILURE; 333 } 334 335 ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask); 336 if (ret) 337 goto error; 338 } else if ((insn & 0xf0) == 0x90 && 339 (insn & 0x0d) != 0x0d) { 340 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; 341 } else if ((insn & 0xf0) == 0xa0) { 342 ret = unwind_exec_pop_r4_to_rN(ctrl, insn); 343 if (ret) 344 goto error; 345 } else if (insn == 0xb0) { 346 if (ctrl->vrs[PC] == 0) 347 ctrl->vrs[PC] = ctrl->vrs[LR]; 348 /* no further processing */ 349 ctrl->entries = 0; 350 } else if (insn == 0xb1) { 351 unsigned long mask = unwind_get_byte(ctrl); 352 353 if (mask == 0 || mask & 0xf0) { 354 pr_warn("unwind: Spare encoding %04lx\n", 355 (insn << 8) | mask); 356 return -URC_FAILURE; 357 } 358 359 ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask); 360 if (ret) 361 goto error; 362 } else if (insn == 0xb2) { 363 unsigned long uleb128 = unwind_get_byte(ctrl); 364 365 ctrl->vrs[SP] += 0x204 + (uleb128 << 2); 366 } else { 367 pr_warn("unwind: Unhandled instruction %02lx\n", insn); 368 return -URC_FAILURE; 369 } 370 371 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, 372 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); 373 374 error: 375 return ret; 376 } 377 378 /* 379 * Unwind a single frame starting with *sp for the symbol at *pc. It 380 * updates the *pc and *sp with the new values. 381 */ 382 int unwind_frame(struct stackframe *frame) 383 { 384 const struct unwind_idx *idx; 385 struct unwind_ctrl_block ctrl; 386 unsigned long sp_low; 387 388 /* store the highest address on the stack to avoid crossing it*/ 389 sp_low = frame->sp; 390 ctrl.sp_high = ALIGN(sp_low - THREAD_SIZE, THREAD_ALIGN) 391 + THREAD_SIZE; 392 393 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, 394 frame->pc, frame->lr, frame->sp); 395 396 idx = unwind_find_idx(frame->pc); 397 if (!idx) { 398 if (frame->pc && kernel_text_address(frame->pc)) 399 pr_warn("unwind: Index not found %08lx\n", frame->pc); 400 return -URC_FAILURE; 401 } 402 403 ctrl.vrs[FP] = frame->fp; 404 ctrl.vrs[SP] = frame->sp; 405 ctrl.vrs[LR] = frame->lr; 406 ctrl.vrs[PC] = 0; 407 408 if (idx->insn == 1) 409 /* can't unwind */ 410 return -URC_FAILURE; 411 else if (frame->pc == prel31_to_addr(&idx->addr_offset)) { 412 /* 413 * Unwinding is tricky when we're halfway through the prologue, 414 * since the stack frame that the unwinder expects may not be 415 * fully set up yet. However, one thing we do know for sure is 416 * that if we are unwinding from the very first instruction of 417 * a function, we are still effectively in the stack frame of 418 * the caller, and the unwind info has no relevance yet. 419 */ 420 if (frame->pc == frame->lr) 421 return -URC_FAILURE; 422 frame->pc = frame->lr; 423 return URC_OK; 424 } else if ((idx->insn & 0x80000000) == 0) 425 /* prel31 to the unwind table */ 426 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); 427 else if ((idx->insn & 0xff000000) == 0x80000000) 428 /* only personality routine 0 supported in the index */ 429 ctrl.insn = &idx->insn; 430 else { 431 pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n", 432 idx->insn, idx); 433 return -URC_FAILURE; 434 } 435 436 /* check the personality routine */ 437 if ((*ctrl.insn & 0xff000000) == 0x80000000) { 438 ctrl.byte = 2; 439 ctrl.entries = 1; 440 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) { 441 ctrl.byte = 1; 442 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); 443 } else { 444 pr_warn("unwind: Unsupported personality routine %08lx at %p\n", 445 *ctrl.insn, ctrl.insn); 446 return -URC_FAILURE; 447 } 448 449 ctrl.check_each_pop = 0; 450 451 if (prel31_to_addr(&idx->addr_offset) == (u32)&call_with_stack) { 452 /* 453 * call_with_stack() is the only place where we permit SP to 454 * jump from one stack to another, and since we know it is 455 * guaranteed to happen, set up the SP bounds accordingly. 456 */ 457 sp_low = frame->fp; 458 ctrl.sp_high = ALIGN(frame->fp, THREAD_SIZE); 459 } 460 461 while (ctrl.entries > 0) { 462 int urc; 463 if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs)) 464 ctrl.check_each_pop = 1; 465 urc = unwind_exec_insn(&ctrl); 466 if (urc < 0) 467 return urc; 468 if (ctrl.vrs[SP] < sp_low || ctrl.vrs[SP] > ctrl.sp_high) 469 return -URC_FAILURE; 470 } 471 472 if (ctrl.vrs[PC] == 0) 473 ctrl.vrs[PC] = ctrl.vrs[LR]; 474 475 /* check for infinite loop */ 476 if (frame->pc == ctrl.vrs[PC] && frame->sp == ctrl.vrs[SP]) 477 return -URC_FAILURE; 478 479 frame->fp = ctrl.vrs[FP]; 480 frame->sp = ctrl.vrs[SP]; 481 frame->lr = ctrl.vrs[LR]; 482 frame->pc = ctrl.vrs[PC]; 483 frame->lr_addr = ctrl.lr_addr; 484 485 return URC_OK; 486 } 487 488 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk, 489 const char *loglvl) 490 { 491 struct stackframe frame; 492 493 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 494 495 if (!tsk) 496 tsk = current; 497 498 if (regs) { 499 arm_get_current_stackframe(regs, &frame); 500 /* PC might be corrupted, use LR in that case. */ 501 if (!kernel_text_address(regs->ARM_pc)) 502 frame.pc = regs->ARM_lr; 503 } else if (tsk == current) { 504 frame.fp = (unsigned long)__builtin_frame_address(0); 505 frame.sp = current_stack_pointer; 506 frame.lr = (unsigned long)__builtin_return_address(0); 507 /* We are saving the stack and execution state at this 508 * point, so we should ensure that frame.pc is within 509 * this block of code. 510 */ 511 here: 512 frame.pc = (unsigned long)&&here; 513 } else { 514 /* task blocked in __switch_to */ 515 frame.fp = thread_saved_fp(tsk); 516 frame.sp = thread_saved_sp(tsk); 517 /* 518 * The function calling __switch_to cannot be a leaf function 519 * so LR is recovered from the stack. 520 */ 521 frame.lr = 0; 522 frame.pc = thread_saved_pc(tsk); 523 } 524 525 while (1) { 526 int urc; 527 unsigned long where = frame.pc; 528 529 urc = unwind_frame(&frame); 530 if (urc < 0) 531 break; 532 dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl); 533 } 534 } 535 536 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, 537 unsigned long text_addr, 538 unsigned long text_size) 539 { 540 unsigned long flags; 541 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); 542 543 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, 544 text_addr, text_size); 545 546 if (!tab) 547 return tab; 548 549 tab->start = (const struct unwind_idx *)start; 550 tab->stop = (const struct unwind_idx *)(start + size); 551 tab->origin = unwind_find_origin(tab->start, tab->stop); 552 tab->begin_addr = text_addr; 553 tab->end_addr = text_addr + text_size; 554 555 raw_spin_lock_irqsave(&unwind_lock, flags); 556 list_add_tail(&tab->list, &unwind_tables); 557 raw_spin_unlock_irqrestore(&unwind_lock, flags); 558 559 return tab; 560 } 561 562 void unwind_table_del(struct unwind_table *tab) 563 { 564 unsigned long flags; 565 566 if (!tab) 567 return; 568 569 raw_spin_lock_irqsave(&unwind_lock, flags); 570 list_del(&tab->list); 571 raw_spin_unlock_irqrestore(&unwind_lock, flags); 572 573 kfree(tab); 574 } 575