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) 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/module.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 unsigned long *insn; /* pointer to the current instructions word */ 71 int entries; /* number of entries left to interpret */ 72 int byte; /* current byte number in the instructions word */ 73 }; 74 75 enum regs { 76 #ifdef CONFIG_THUMB2_KERNEL 77 FP = 7, 78 #else 79 FP = 11, 80 #endif 81 SP = 13, 82 LR = 14, 83 PC = 15 84 }; 85 86 extern struct unwind_idx __start_unwind_idx[]; 87 extern struct unwind_idx __stop_unwind_idx[]; 88 89 static DEFINE_SPINLOCK(unwind_lock); 90 static LIST_HEAD(unwind_tables); 91 92 /* Convert a prel31 symbol to an absolute address */ 93 #define prel31_to_addr(ptr) \ 94 ({ \ 95 /* sign-extend to 32 bits */ \ 96 long offset = (((long)*(ptr)) << 1) >> 1; \ 97 (unsigned long)(ptr) + offset; \ 98 }) 99 100 /* 101 * Binary search in the unwind index. The entries entries are 102 * guaranteed to be sorted in ascending order by the linker. 103 */ 104 static struct unwind_idx *search_index(unsigned long addr, 105 struct unwind_idx *first, 106 struct unwind_idx *last) 107 { 108 pr_debug("%s(%08lx, %p, %p)\n", __func__, addr, first, last); 109 110 if (addr < first->addr) { 111 pr_warning("unwind: Unknown symbol address %08lx\n", addr); 112 return NULL; 113 } else if (addr >= last->addr) 114 return last; 115 116 while (first < last - 1) { 117 struct unwind_idx *mid = first + ((last - first + 1) >> 1); 118 119 if (addr < mid->addr) 120 last = mid; 121 else 122 first = mid; 123 } 124 125 return first; 126 } 127 128 static struct unwind_idx *unwind_find_idx(unsigned long addr) 129 { 130 struct unwind_idx *idx = NULL; 131 unsigned long flags; 132 133 pr_debug("%s(%08lx)\n", __func__, addr); 134 135 if (core_kernel_text(addr)) 136 /* main unwind table */ 137 idx = search_index(addr, __start_unwind_idx, 138 __stop_unwind_idx - 1); 139 else { 140 /* module unwind tables */ 141 struct unwind_table *table; 142 143 spin_lock_irqsave(&unwind_lock, flags); 144 list_for_each_entry(table, &unwind_tables, list) { 145 if (addr >= table->begin_addr && 146 addr < table->end_addr) { 147 idx = search_index(addr, table->start, 148 table->stop - 1); 149 /* Move-to-front to exploit common traces */ 150 list_move(&table->list, &unwind_tables); 151 break; 152 } 153 } 154 spin_unlock_irqrestore(&unwind_lock, flags); 155 } 156 157 pr_debug("%s: idx = %p\n", __func__, idx); 158 return idx; 159 } 160 161 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl) 162 { 163 unsigned long ret; 164 165 if (ctrl->entries <= 0) { 166 pr_warning("unwind: Corrupt unwind table\n"); 167 return 0; 168 } 169 170 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff; 171 172 if (ctrl->byte == 0) { 173 ctrl->insn++; 174 ctrl->entries--; 175 ctrl->byte = 3; 176 } else 177 ctrl->byte--; 178 179 return ret; 180 } 181 182 /* 183 * Execute the current unwind instruction. 184 */ 185 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) 186 { 187 unsigned long insn = unwind_get_byte(ctrl); 188 189 pr_debug("%s: insn = %08lx\n", __func__, insn); 190 191 if ((insn & 0xc0) == 0x00) 192 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; 193 else if ((insn & 0xc0) == 0x40) 194 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; 195 else if ((insn & 0xf0) == 0x80) { 196 unsigned long mask; 197 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 198 int load_sp, reg = 4; 199 200 insn = (insn << 8) | unwind_get_byte(ctrl); 201 mask = insn & 0x0fff; 202 if (mask == 0) { 203 pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n", 204 insn); 205 return -URC_FAILURE; 206 } 207 208 /* pop R4-R15 according to mask */ 209 load_sp = mask & (1 << (13 - 4)); 210 while (mask) { 211 if (mask & 1) 212 ctrl->vrs[reg] = *vsp++; 213 mask >>= 1; 214 reg++; 215 } 216 if (!load_sp) 217 ctrl->vrs[SP] = (unsigned long)vsp; 218 } else if ((insn & 0xf0) == 0x90 && 219 (insn & 0x0d) != 0x0d) 220 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; 221 else if ((insn & 0xf0) == 0xa0) { 222 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 223 int reg; 224 225 /* pop R4-R[4+bbb] */ 226 for (reg = 4; reg <= 4 + (insn & 7); reg++) 227 ctrl->vrs[reg] = *vsp++; 228 if (insn & 0x80) 229 ctrl->vrs[14] = *vsp++; 230 ctrl->vrs[SP] = (unsigned long)vsp; 231 } else if (insn == 0xb0) { 232 if (ctrl->vrs[PC] == 0) 233 ctrl->vrs[PC] = ctrl->vrs[LR]; 234 /* no further processing */ 235 ctrl->entries = 0; 236 } else if (insn == 0xb1) { 237 unsigned long mask = unwind_get_byte(ctrl); 238 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 239 int reg = 0; 240 241 if (mask == 0 || mask & 0xf0) { 242 pr_warning("unwind: Spare encoding %04lx\n", 243 (insn << 8) | mask); 244 return -URC_FAILURE; 245 } 246 247 /* pop R0-R3 according to mask */ 248 while (mask) { 249 if (mask & 1) 250 ctrl->vrs[reg] = *vsp++; 251 mask >>= 1; 252 reg++; 253 } 254 ctrl->vrs[SP] = (unsigned long)vsp; 255 } else if (insn == 0xb2) { 256 unsigned long uleb128 = unwind_get_byte(ctrl); 257 258 ctrl->vrs[SP] += 0x204 + (uleb128 << 2); 259 } else { 260 pr_warning("unwind: Unhandled instruction %02lx\n", insn); 261 return -URC_FAILURE; 262 } 263 264 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, 265 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); 266 267 return URC_OK; 268 } 269 270 /* 271 * Unwind a single frame starting with *sp for the symbol at *pc. It 272 * updates the *pc and *sp with the new values. 273 */ 274 int unwind_frame(struct stackframe *frame) 275 { 276 unsigned long high, low; 277 struct unwind_idx *idx; 278 struct unwind_ctrl_block ctrl; 279 280 /* only go to a higher address on the stack */ 281 low = frame->sp; 282 high = ALIGN(low, THREAD_SIZE); 283 284 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, 285 frame->pc, frame->lr, frame->sp); 286 287 if (!kernel_text_address(frame->pc)) 288 return -URC_FAILURE; 289 290 idx = unwind_find_idx(frame->pc); 291 if (!idx) { 292 pr_warning("unwind: Index not found %08lx\n", frame->pc); 293 return -URC_FAILURE; 294 } 295 296 ctrl.vrs[FP] = frame->fp; 297 ctrl.vrs[SP] = frame->sp; 298 ctrl.vrs[LR] = frame->lr; 299 ctrl.vrs[PC] = 0; 300 301 if (idx->insn == 1) 302 /* can't unwind */ 303 return -URC_FAILURE; 304 else if ((idx->insn & 0x80000000) == 0) 305 /* prel31 to the unwind table */ 306 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); 307 else if ((idx->insn & 0xff000000) == 0x80000000) 308 /* only personality routine 0 supported in the index */ 309 ctrl.insn = &idx->insn; 310 else { 311 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n", 312 idx->insn, idx); 313 return -URC_FAILURE; 314 } 315 316 /* check the personality routine */ 317 if ((*ctrl.insn & 0xff000000) == 0x80000000) { 318 ctrl.byte = 2; 319 ctrl.entries = 1; 320 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) { 321 ctrl.byte = 1; 322 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); 323 } else { 324 pr_warning("unwind: Unsupported personality routine %08lx at %p\n", 325 *ctrl.insn, ctrl.insn); 326 return -URC_FAILURE; 327 } 328 329 while (ctrl.entries > 0) { 330 int urc = unwind_exec_insn(&ctrl); 331 if (urc < 0) 332 return urc; 333 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high) 334 return -URC_FAILURE; 335 } 336 337 if (ctrl.vrs[PC] == 0) 338 ctrl.vrs[PC] = ctrl.vrs[LR]; 339 340 /* check for infinite loop */ 341 if (frame->pc == ctrl.vrs[PC]) 342 return -URC_FAILURE; 343 344 frame->fp = ctrl.vrs[FP]; 345 frame->sp = ctrl.vrs[SP]; 346 frame->lr = ctrl.vrs[LR]; 347 frame->pc = ctrl.vrs[PC]; 348 349 return URC_OK; 350 } 351 352 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk) 353 { 354 struct stackframe frame; 355 register unsigned long current_sp asm ("sp"); 356 357 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 358 359 if (!tsk) 360 tsk = current; 361 362 if (regs) { 363 frame.fp = regs->ARM_fp; 364 frame.sp = regs->ARM_sp; 365 frame.lr = regs->ARM_lr; 366 /* PC might be corrupted, use LR in that case. */ 367 frame.pc = kernel_text_address(regs->ARM_pc) 368 ? regs->ARM_pc : regs->ARM_lr; 369 } else if (tsk == current) { 370 frame.fp = (unsigned long)__builtin_frame_address(0); 371 frame.sp = current_sp; 372 frame.lr = (unsigned long)__builtin_return_address(0); 373 frame.pc = (unsigned long)unwind_backtrace; 374 } else { 375 /* task blocked in __switch_to */ 376 frame.fp = thread_saved_fp(tsk); 377 frame.sp = thread_saved_sp(tsk); 378 /* 379 * The function calling __switch_to cannot be a leaf function 380 * so LR is recovered from the stack. 381 */ 382 frame.lr = 0; 383 frame.pc = thread_saved_pc(tsk); 384 } 385 386 while (1) { 387 int urc; 388 unsigned long where = frame.pc; 389 390 urc = unwind_frame(&frame); 391 if (urc < 0) 392 break; 393 dump_backtrace_entry(where, frame.pc, frame.sp - 4); 394 } 395 } 396 397 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, 398 unsigned long text_addr, 399 unsigned long text_size) 400 { 401 unsigned long flags; 402 struct unwind_idx *idx; 403 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); 404 405 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, 406 text_addr, text_size); 407 408 if (!tab) 409 return tab; 410 411 tab->start = (struct unwind_idx *)start; 412 tab->stop = (struct unwind_idx *)(start + size); 413 tab->begin_addr = text_addr; 414 tab->end_addr = text_addr + text_size; 415 416 /* Convert the symbol addresses to absolute values */ 417 for (idx = tab->start; idx < tab->stop; idx++) 418 idx->addr = prel31_to_addr(&idx->addr); 419 420 spin_lock_irqsave(&unwind_lock, flags); 421 list_add_tail(&tab->list, &unwind_tables); 422 spin_unlock_irqrestore(&unwind_lock, flags); 423 424 return tab; 425 } 426 427 void unwind_table_del(struct unwind_table *tab) 428 { 429 unsigned long flags; 430 431 if (!tab) 432 return; 433 434 spin_lock_irqsave(&unwind_lock, flags); 435 list_del(&tab->list); 436 spin_unlock_irqrestore(&unwind_lock, flags); 437 438 kfree(tab); 439 } 440 441 int __init unwind_init(void) 442 { 443 struct unwind_idx *idx; 444 445 /* Convert the symbol addresses to absolute values */ 446 for (idx = __start_unwind_idx; idx < __stop_unwind_idx; idx++) 447 idx->addr = prel31_to_addr(&idx->addr); 448 449 pr_debug("unwind: ARM stack unwinding initialised\n"); 450 451 return 0; 452 } 453