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 #include <linux/module.h> 32 33 #include <asm/stacktrace.h> 34 #include <asm/traps.h> 35 #include <asm/unwind.h> 36 37 #include "reboot.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 unsigned long *lr_addr; /* address of LR value on the stack */ 60 /* 61 * 1 : check for stack overflow for each register pop. 62 * 0 : save overhead if there is plenty of stack remaining. 63 */ 64 int check_each_pop; 65 int entries; /* number of entries left to interpret */ 66 int byte; /* current byte number in the instructions word */ 67 }; 68 69 enum regs { 70 #ifdef CONFIG_THUMB2_KERNEL 71 FP = 7, 72 #else 73 FP = 11, 74 #endif 75 SP = 13, 76 LR = 14, 77 PC = 15 78 }; 79 80 extern const struct unwind_idx __start_unwind_idx[]; 81 static const struct unwind_idx *__origin_unwind_idx; 82 extern const struct unwind_idx __stop_unwind_idx[]; 83 84 static DEFINE_RAW_SPINLOCK(unwind_lock); 85 static LIST_HEAD(unwind_tables); 86 87 /* Convert a prel31 symbol to an absolute address */ 88 #define prel31_to_addr(ptr) \ 89 ({ \ 90 /* sign-extend to 32 bits */ \ 91 long offset = (((long)*(ptr)) << 1) >> 1; \ 92 (unsigned long)(ptr) + offset; \ 93 }) 94 95 /* 96 * Binary search in the unwind index. The entries are 97 * guaranteed to be sorted in ascending order by the linker. 98 * 99 * start = first entry 100 * origin = first entry with positive offset (or stop if there is no such entry) 101 * stop - 1 = last entry 102 */ 103 static const struct unwind_idx *search_index(unsigned long addr, 104 const struct unwind_idx *start, 105 const struct unwind_idx *origin, 106 const struct unwind_idx *stop) 107 { 108 unsigned long addr_prel31; 109 110 pr_debug("%s(%08lx, %p, %p, %p)\n", 111 __func__, addr, start, origin, stop); 112 113 /* 114 * only search in the section with the matching sign. This way the 115 * prel31 numbers can be compared as unsigned longs. 116 */ 117 if (addr < (unsigned long)start) 118 /* negative offsets: [start; origin) */ 119 stop = origin; 120 else 121 /* positive offsets: [origin; stop) */ 122 start = origin; 123 124 /* prel31 for address relavive to start */ 125 addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff; 126 127 while (start < stop - 1) { 128 const struct unwind_idx *mid = start + ((stop - start) >> 1); 129 130 /* 131 * As addr_prel31 is relative to start an offset is needed to 132 * make it relative to mid. 133 */ 134 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) < 135 mid->addr_offset) 136 stop = mid; 137 else { 138 /* keep addr_prel31 relative to start */ 139 addr_prel31 -= ((unsigned long)mid - 140 (unsigned long)start); 141 start = mid; 142 } 143 } 144 145 if (likely(start->addr_offset <= addr_prel31)) 146 return start; 147 else { 148 pr_warn("unwind: Unknown symbol address %08lx\n", addr); 149 return NULL; 150 } 151 } 152 153 static const struct unwind_idx *unwind_find_origin( 154 const struct unwind_idx *start, const struct unwind_idx *stop) 155 { 156 pr_debug("%s(%p, %p)\n", __func__, start, stop); 157 while (start < stop) { 158 const struct unwind_idx *mid = start + ((stop - start) >> 1); 159 160 if (mid->addr_offset >= 0x40000000) 161 /* negative offset */ 162 start = mid + 1; 163 else 164 /* positive offset */ 165 stop = mid; 166 } 167 pr_debug("%s -> %p\n", __func__, stop); 168 return stop; 169 } 170 171 static const struct unwind_idx *unwind_find_idx(unsigned long addr) 172 { 173 const struct unwind_idx *idx = NULL; 174 unsigned long flags; 175 176 pr_debug("%s(%08lx)\n", __func__, addr); 177 178 if (core_kernel_text(addr)) { 179 if (unlikely(!__origin_unwind_idx)) 180 __origin_unwind_idx = 181 unwind_find_origin(__start_unwind_idx, 182 __stop_unwind_idx); 183 184 /* main unwind table */ 185 idx = search_index(addr, __start_unwind_idx, 186 __origin_unwind_idx, 187 __stop_unwind_idx); 188 } else { 189 /* module unwind tables */ 190 struct unwind_table *table; 191 192 raw_spin_lock_irqsave(&unwind_lock, flags); 193 list_for_each_entry(table, &unwind_tables, list) { 194 if (addr >= table->begin_addr && 195 addr < table->end_addr) { 196 idx = search_index(addr, table->start, 197 table->origin, 198 table->stop); 199 /* Move-to-front to exploit common traces */ 200 list_move(&table->list, &unwind_tables); 201 break; 202 } 203 } 204 raw_spin_unlock_irqrestore(&unwind_lock, flags); 205 } 206 207 pr_debug("%s: idx = %p\n", __func__, idx); 208 return idx; 209 } 210 211 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl) 212 { 213 unsigned long ret; 214 215 if (ctrl->entries <= 0) { 216 pr_warn("unwind: Corrupt unwind table\n"); 217 return 0; 218 } 219 220 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff; 221 222 if (ctrl->byte == 0) { 223 ctrl->insn++; 224 ctrl->entries--; 225 ctrl->byte = 3; 226 } else 227 ctrl->byte--; 228 229 return ret; 230 } 231 232 /* Before poping a register check whether it is feasible or not */ 233 static int unwind_pop_register(struct unwind_ctrl_block *ctrl, 234 unsigned long **vsp, unsigned int reg) 235 { 236 if (unlikely(ctrl->check_each_pop)) 237 if (*vsp >= (unsigned long *)ctrl->sp_high) 238 return -URC_FAILURE; 239 240 /* Use READ_ONCE_NOCHECK here to avoid this memory access 241 * from being tracked by KASAN. 242 */ 243 ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp)); 244 if (reg == 14) 245 ctrl->lr_addr = *vsp; 246 (*vsp)++; 247 return URC_OK; 248 } 249 250 /* Helper functions to execute the instructions */ 251 static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl, 252 unsigned long mask) 253 { 254 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 255 int load_sp, reg = 4; 256 257 load_sp = mask & (1 << (13 - 4)); 258 while (mask) { 259 if (mask & 1) 260 if (unwind_pop_register(ctrl, &vsp, reg)) 261 return -URC_FAILURE; 262 mask >>= 1; 263 reg++; 264 } 265 if (!load_sp) { 266 ctrl->vrs[SP] = (unsigned long)vsp; 267 } 268 269 return URC_OK; 270 } 271 272 static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl, 273 unsigned long insn) 274 { 275 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 276 int reg; 277 278 /* pop R4-R[4+bbb] */ 279 for (reg = 4; reg <= 4 + (insn & 7); reg++) 280 if (unwind_pop_register(ctrl, &vsp, reg)) 281 return -URC_FAILURE; 282 283 if (insn & 0x8) 284 if (unwind_pop_register(ctrl, &vsp, 14)) 285 return -URC_FAILURE; 286 287 ctrl->vrs[SP] = (unsigned long)vsp; 288 289 return URC_OK; 290 } 291 292 static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl, 293 unsigned long mask) 294 { 295 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 296 int reg = 0; 297 298 /* pop R0-R3 according to mask */ 299 while (mask) { 300 if (mask & 1) 301 if (unwind_pop_register(ctrl, &vsp, reg)) 302 return -URC_FAILURE; 303 mask >>= 1; 304 reg++; 305 } 306 ctrl->vrs[SP] = (unsigned long)vsp; 307 308 return URC_OK; 309 } 310 311 /* 312 * Execute the current unwind instruction. 313 */ 314 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) 315 { 316 unsigned long insn = unwind_get_byte(ctrl); 317 int ret = URC_OK; 318 319 pr_debug("%s: insn = %08lx\n", __func__, insn); 320 321 if ((insn & 0xc0) == 0x00) 322 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; 323 else if ((insn & 0xc0) == 0x40) { 324 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; 325 } else if ((insn & 0xf0) == 0x80) { 326 unsigned long mask; 327 328 insn = (insn << 8) | unwind_get_byte(ctrl); 329 mask = insn & 0x0fff; 330 if (mask == 0) { 331 pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n", 332 insn); 333 return -URC_FAILURE; 334 } 335 336 ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask); 337 if (ret) 338 goto error; 339 } else if ((insn & 0xf0) == 0x90 && 340 (insn & 0x0d) != 0x0d) { 341 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; 342 } else if ((insn & 0xf0) == 0xa0) { 343 ret = unwind_exec_pop_r4_to_rN(ctrl, insn); 344 if (ret) 345 goto error; 346 } else if (insn == 0xb0) { 347 if (ctrl->vrs[PC] == 0) 348 ctrl->vrs[PC] = ctrl->vrs[LR]; 349 /* no further processing */ 350 ctrl->entries = 0; 351 } else if (insn == 0xb1) { 352 unsigned long mask = unwind_get_byte(ctrl); 353 354 if (mask == 0 || mask & 0xf0) { 355 pr_warn("unwind: Spare encoding %04lx\n", 356 (insn << 8) | mask); 357 return -URC_FAILURE; 358 } 359 360 ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask); 361 if (ret) 362 goto error; 363 } else if (insn == 0xb2) { 364 unsigned long uleb128 = unwind_get_byte(ctrl); 365 366 ctrl->vrs[SP] += 0x204 + (uleb128 << 2); 367 } else { 368 pr_warn("unwind: Unhandled instruction %02lx\n", insn); 369 return -URC_FAILURE; 370 } 371 372 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, 373 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); 374 375 error: 376 return ret; 377 } 378 379 /* 380 * Unwind a single frame starting with *sp for the symbol at *pc. It 381 * updates the *pc and *sp with the new values. 382 */ 383 int unwind_frame(struct stackframe *frame) 384 { 385 const struct unwind_idx *idx; 386 struct unwind_ctrl_block ctrl; 387 unsigned long sp_low; 388 389 /* store the highest address on the stack to avoid crossing it*/ 390 sp_low = frame->sp; 391 ctrl.sp_high = ALIGN(sp_low - THREAD_SIZE, THREAD_ALIGN) 392 + THREAD_SIZE; 393 394 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, 395 frame->pc, frame->lr, frame->sp); 396 397 idx = unwind_find_idx(frame->pc); 398 if (!idx) { 399 if (frame->pc && kernel_text_address(frame->pc)) { 400 if (in_module_plt(frame->pc) && frame->pc != frame->lr) { 401 /* 402 * Quoting Ard: Veneers only set PC using a 403 * PC+immediate LDR, and so they don't affect 404 * the state of the stack or the register file 405 */ 406 frame->pc = frame->lr; 407 return URC_OK; 408 } 409 pr_warn("unwind: Index not found %08lx\n", frame->pc); 410 } 411 return -URC_FAILURE; 412 } 413 414 ctrl.vrs[FP] = frame->fp; 415 ctrl.vrs[SP] = frame->sp; 416 ctrl.vrs[LR] = frame->lr; 417 ctrl.vrs[PC] = 0; 418 419 if (idx->insn == 1) 420 /* can't unwind */ 421 return -URC_FAILURE; 422 else if (frame->pc == prel31_to_addr(&idx->addr_offset)) { 423 /* 424 * Unwinding is tricky when we're halfway through the prologue, 425 * since the stack frame that the unwinder expects may not be 426 * fully set up yet. However, one thing we do know for sure is 427 * that if we are unwinding from the very first instruction of 428 * a function, we are still effectively in the stack frame of 429 * the caller, and the unwind info has no relevance yet. 430 */ 431 if (frame->pc == frame->lr) 432 return -URC_FAILURE; 433 frame->pc = frame->lr; 434 return URC_OK; 435 } else if ((idx->insn & 0x80000000) == 0) 436 /* prel31 to the unwind table */ 437 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); 438 else if ((idx->insn & 0xff000000) == 0x80000000) 439 /* only personality routine 0 supported in the index */ 440 ctrl.insn = &idx->insn; 441 else { 442 pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n", 443 idx->insn, idx); 444 return -URC_FAILURE; 445 } 446 447 /* check the personality routine */ 448 if ((*ctrl.insn & 0xff000000) == 0x80000000) { 449 ctrl.byte = 2; 450 ctrl.entries = 1; 451 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) { 452 ctrl.byte = 1; 453 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); 454 } else { 455 pr_warn("unwind: Unsupported personality routine %08lx at %p\n", 456 *ctrl.insn, ctrl.insn); 457 return -URC_FAILURE; 458 } 459 460 ctrl.check_each_pop = 0; 461 462 if (prel31_to_addr(&idx->addr_offset) == (u32)&call_with_stack) { 463 /* 464 * call_with_stack() is the only place where we permit SP to 465 * jump from one stack to another, and since we know it is 466 * guaranteed to happen, set up the SP bounds accordingly. 467 */ 468 sp_low = frame->fp; 469 ctrl.sp_high = ALIGN(frame->fp, THREAD_SIZE); 470 } 471 472 while (ctrl.entries > 0) { 473 int urc; 474 if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs)) 475 ctrl.check_each_pop = 1; 476 urc = unwind_exec_insn(&ctrl); 477 if (urc < 0) 478 return urc; 479 if (ctrl.vrs[SP] < sp_low || ctrl.vrs[SP] > ctrl.sp_high) 480 return -URC_FAILURE; 481 } 482 483 if (ctrl.vrs[PC] == 0) 484 ctrl.vrs[PC] = ctrl.vrs[LR]; 485 486 /* check for infinite loop */ 487 if (frame->pc == ctrl.vrs[PC] && frame->sp == ctrl.vrs[SP]) 488 return -URC_FAILURE; 489 490 frame->fp = ctrl.vrs[FP]; 491 frame->sp = ctrl.vrs[SP]; 492 frame->lr = ctrl.vrs[LR]; 493 frame->pc = ctrl.vrs[PC]; 494 frame->lr_addr = ctrl.lr_addr; 495 496 return URC_OK; 497 } 498 499 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk, 500 const char *loglvl) 501 { 502 struct stackframe frame; 503 504 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 505 506 if (!tsk) 507 tsk = current; 508 509 if (regs) { 510 arm_get_current_stackframe(regs, &frame); 511 /* PC might be corrupted, use LR in that case. */ 512 if (!kernel_text_address(regs->ARM_pc)) 513 frame.pc = regs->ARM_lr; 514 } else if (tsk == current) { 515 frame.fp = (unsigned long)__builtin_frame_address(0); 516 frame.sp = current_stack_pointer; 517 frame.lr = (unsigned long)__builtin_return_address(0); 518 /* We are saving the stack and execution state at this 519 * point, so we should ensure that frame.pc is within 520 * this block of code. 521 */ 522 here: 523 frame.pc = (unsigned long)&&here; 524 } else { 525 /* task blocked in __switch_to */ 526 frame.fp = thread_saved_fp(tsk); 527 frame.sp = thread_saved_sp(tsk); 528 /* 529 * The function calling __switch_to cannot be a leaf function 530 * so LR is recovered from the stack. 531 */ 532 frame.lr = 0; 533 frame.pc = thread_saved_pc(tsk); 534 } 535 536 while (1) { 537 int urc; 538 unsigned long where = frame.pc; 539 540 urc = unwind_frame(&frame); 541 if (urc < 0) 542 break; 543 dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl); 544 } 545 } 546 547 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, 548 unsigned long text_addr, 549 unsigned long text_size) 550 { 551 unsigned long flags; 552 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); 553 554 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, 555 text_addr, text_size); 556 557 if (!tab) 558 return tab; 559 560 tab->start = (const struct unwind_idx *)start; 561 tab->stop = (const struct unwind_idx *)(start + size); 562 tab->origin = unwind_find_origin(tab->start, tab->stop); 563 tab->begin_addr = text_addr; 564 tab->end_addr = text_addr + text_size; 565 566 raw_spin_lock_irqsave(&unwind_lock, flags); 567 list_add_tail(&tab->list, &unwind_tables); 568 raw_spin_unlock_irqrestore(&unwind_lock, flags); 569 570 return tab; 571 } 572 573 void unwind_table_del(struct unwind_table *tab) 574 { 575 unsigned long flags; 576 577 if (!tab) 578 return; 579 580 raw_spin_lock_irqsave(&unwind_lock, flags); 581 list_del(&tab->list); 582 raw_spin_unlock_irqrestore(&unwind_lock, flags); 583 584 kfree(tab); 585 } 586