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 #if !defined (__ARM_EABI__) 30 #warning Your compiler does not have EABI support. 31 #warning ARM unwind is known to compile only with EABI compilers. 32 #warning Change compiler or disable ARM_UNWIND option. 33 #elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2) 34 #warning Your compiler is too buggy; it is known to not compile ARM unwind support. 35 #warning Change compiler or disable ARM_UNWIND option. 36 #endif 37 38 #include <linux/kernel.h> 39 #include <linux/init.h> 40 #include <linux/module.h> 41 #include <linux/sched.h> 42 #include <linux/slab.h> 43 #include <linux/spinlock.h> 44 #include <linux/list.h> 45 46 #include <asm/stacktrace.h> 47 #include <asm/traps.h> 48 #include <asm/unwind.h> 49 50 /* Dummy functions to avoid linker complaints */ 51 void __aeabi_unwind_cpp_pr0(void) 52 { 53 }; 54 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0); 55 56 void __aeabi_unwind_cpp_pr1(void) 57 { 58 }; 59 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1); 60 61 void __aeabi_unwind_cpp_pr2(void) 62 { 63 }; 64 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2); 65 66 struct unwind_ctrl_block { 67 unsigned long vrs[16]; /* virtual register set */ 68 unsigned long *insn; /* pointer to the current instructions word */ 69 int entries; /* number of entries left to interpret */ 70 int byte; /* current byte number in the instructions word */ 71 }; 72 73 enum regs { 74 #ifdef CONFIG_THUMB2_KERNEL 75 FP = 7, 76 #else 77 FP = 11, 78 #endif 79 SP = 13, 80 LR = 14, 81 PC = 15 82 }; 83 84 extern struct unwind_idx __start_unwind_idx[]; 85 extern struct unwind_idx __stop_unwind_idx[]; 86 87 static DEFINE_SPINLOCK(unwind_lock); 88 static LIST_HEAD(unwind_tables); 89 90 /* Convert a prel31 symbol to an absolute address */ 91 #define prel31_to_addr(ptr) \ 92 ({ \ 93 /* sign-extend to 32 bits */ \ 94 long offset = (((long)*(ptr)) << 1) >> 1; \ 95 (unsigned long)(ptr) + offset; \ 96 }) 97 98 /* 99 * Binary search in the unwind index. The entries entries are 100 * guaranteed to be sorted in ascending order by the linker. 101 */ 102 static struct unwind_idx *search_index(unsigned long addr, 103 struct unwind_idx *first, 104 struct unwind_idx *last) 105 { 106 pr_debug("%s(%08lx, %p, %p)\n", __func__, addr, first, last); 107 108 if (addr < first->addr) { 109 pr_warning("unwind: Unknown symbol address %08lx\n", addr); 110 return NULL; 111 } else if (addr >= last->addr) 112 return last; 113 114 while (first < last - 1) { 115 struct unwind_idx *mid = first + ((last - first + 1) >> 1); 116 117 if (addr < mid->addr) 118 last = mid; 119 else 120 first = mid; 121 } 122 123 return first; 124 } 125 126 static struct unwind_idx *unwind_find_idx(unsigned long addr) 127 { 128 struct unwind_idx *idx = NULL; 129 unsigned long flags; 130 131 pr_debug("%s(%08lx)\n", __func__, addr); 132 133 if (core_kernel_text(addr)) 134 /* main unwind table */ 135 idx = search_index(addr, __start_unwind_idx, 136 __stop_unwind_idx - 1); 137 else { 138 /* module unwind tables */ 139 struct unwind_table *table; 140 141 spin_lock_irqsave(&unwind_lock, flags); 142 list_for_each_entry(table, &unwind_tables, list) { 143 if (addr >= table->begin_addr && 144 addr < table->end_addr) { 145 idx = search_index(addr, table->start, 146 table->stop - 1); 147 break; 148 } 149 } 150 spin_unlock_irqrestore(&unwind_lock, flags); 151 } 152 153 pr_debug("%s: idx = %p\n", __func__, idx); 154 return idx; 155 } 156 157 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl) 158 { 159 unsigned long ret; 160 161 if (ctrl->entries <= 0) { 162 pr_warning("unwind: Corrupt unwind table\n"); 163 return 0; 164 } 165 166 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff; 167 168 if (ctrl->byte == 0) { 169 ctrl->insn++; 170 ctrl->entries--; 171 ctrl->byte = 3; 172 } else 173 ctrl->byte--; 174 175 return ret; 176 } 177 178 /* 179 * Execute the current unwind instruction. 180 */ 181 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) 182 { 183 unsigned long insn = unwind_get_byte(ctrl); 184 185 pr_debug("%s: insn = %08lx\n", __func__, insn); 186 187 if ((insn & 0xc0) == 0x00) 188 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; 189 else if ((insn & 0xc0) == 0x40) 190 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; 191 else if ((insn & 0xf0) == 0x80) { 192 unsigned long mask; 193 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 194 int load_sp, reg = 4; 195 196 insn = (insn << 8) | unwind_get_byte(ctrl); 197 mask = insn & 0x0fff; 198 if (mask == 0) { 199 pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n", 200 insn); 201 return -URC_FAILURE; 202 } 203 204 /* pop R4-R15 according to mask */ 205 load_sp = mask & (1 << (13 - 4)); 206 while (mask) { 207 if (mask & 1) 208 ctrl->vrs[reg] = *vsp++; 209 mask >>= 1; 210 reg++; 211 } 212 if (!load_sp) 213 ctrl->vrs[SP] = (unsigned long)vsp; 214 } else if ((insn & 0xf0) == 0x90 && 215 (insn & 0x0d) != 0x0d) 216 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; 217 else if ((insn & 0xf0) == 0xa0) { 218 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 219 int reg; 220 221 /* pop R4-R[4+bbb] */ 222 for (reg = 4; reg <= 4 + (insn & 7); reg++) 223 ctrl->vrs[reg] = *vsp++; 224 if (insn & 0x80) 225 ctrl->vrs[14] = *vsp++; 226 ctrl->vrs[SP] = (unsigned long)vsp; 227 } else if (insn == 0xb0) { 228 if (ctrl->vrs[PC] == 0) 229 ctrl->vrs[PC] = ctrl->vrs[LR]; 230 /* no further processing */ 231 ctrl->entries = 0; 232 } else if (insn == 0xb1) { 233 unsigned long mask = unwind_get_byte(ctrl); 234 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; 235 int reg = 0; 236 237 if (mask == 0 || mask & 0xf0) { 238 pr_warning("unwind: Spare encoding %04lx\n", 239 (insn << 8) | mask); 240 return -URC_FAILURE; 241 } 242 243 /* pop R0-R3 according to mask */ 244 while (mask) { 245 if (mask & 1) 246 ctrl->vrs[reg] = *vsp++; 247 mask >>= 1; 248 reg++; 249 } 250 ctrl->vrs[SP] = (unsigned long)vsp; 251 } else if (insn == 0xb2) { 252 unsigned long uleb128 = unwind_get_byte(ctrl); 253 254 ctrl->vrs[SP] += 0x204 + (uleb128 << 2); 255 } else { 256 pr_warning("unwind: Unhandled instruction %02lx\n", insn); 257 return -URC_FAILURE; 258 } 259 260 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, 261 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); 262 263 return URC_OK; 264 } 265 266 /* 267 * Unwind a single frame starting with *sp for the symbol at *pc. It 268 * updates the *pc and *sp with the new values. 269 */ 270 int unwind_frame(struct stackframe *frame) 271 { 272 unsigned long high, low; 273 struct unwind_idx *idx; 274 struct unwind_ctrl_block ctrl; 275 276 /* only go to a higher address on the stack */ 277 low = frame->sp; 278 high = ALIGN(low, THREAD_SIZE) + THREAD_SIZE; 279 280 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, 281 frame->pc, frame->lr, frame->sp); 282 283 if (!kernel_text_address(frame->pc)) 284 return -URC_FAILURE; 285 286 idx = unwind_find_idx(frame->pc); 287 if (!idx) { 288 pr_warning("unwind: Index not found %08lx\n", frame->pc); 289 return -URC_FAILURE; 290 } 291 292 ctrl.vrs[FP] = frame->fp; 293 ctrl.vrs[SP] = frame->sp; 294 ctrl.vrs[LR] = frame->lr; 295 ctrl.vrs[PC] = 0; 296 297 if (idx->insn == 1) 298 /* can't unwind */ 299 return -URC_FAILURE; 300 else if ((idx->insn & 0x80000000) == 0) 301 /* prel31 to the unwind table */ 302 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); 303 else if ((idx->insn & 0xff000000) == 0x80000000) 304 /* only personality routine 0 supported in the index */ 305 ctrl.insn = &idx->insn; 306 else { 307 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n", 308 idx->insn, idx); 309 return -URC_FAILURE; 310 } 311 312 /* check the personality routine */ 313 if ((*ctrl.insn & 0xff000000) == 0x80000000) { 314 ctrl.byte = 2; 315 ctrl.entries = 1; 316 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) { 317 ctrl.byte = 1; 318 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); 319 } else { 320 pr_warning("unwind: Unsupported personality routine %08lx at %p\n", 321 *ctrl.insn, ctrl.insn); 322 return -URC_FAILURE; 323 } 324 325 while (ctrl.entries > 0) { 326 int urc = unwind_exec_insn(&ctrl); 327 if (urc < 0) 328 return urc; 329 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high) 330 return -URC_FAILURE; 331 } 332 333 if (ctrl.vrs[PC] == 0) 334 ctrl.vrs[PC] = ctrl.vrs[LR]; 335 336 /* check for infinite loop */ 337 if (frame->pc == ctrl.vrs[PC]) 338 return -URC_FAILURE; 339 340 frame->fp = ctrl.vrs[FP]; 341 frame->sp = ctrl.vrs[SP]; 342 frame->lr = ctrl.vrs[LR]; 343 frame->pc = ctrl.vrs[PC]; 344 345 return URC_OK; 346 } 347 348 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk) 349 { 350 struct stackframe frame; 351 register unsigned long current_sp asm ("sp"); 352 353 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 354 355 if (!tsk) 356 tsk = current; 357 358 if (regs) { 359 frame.fp = regs->ARM_fp; 360 frame.sp = regs->ARM_sp; 361 frame.lr = regs->ARM_lr; 362 frame.pc = regs->ARM_pc; 363 } else if (tsk == current) { 364 frame.fp = (unsigned long)__builtin_frame_address(0); 365 frame.sp = current_sp; 366 frame.lr = (unsigned long)__builtin_return_address(0); 367 frame.pc = (unsigned long)unwind_backtrace; 368 } else { 369 /* task blocked in __switch_to */ 370 frame.fp = thread_saved_fp(tsk); 371 frame.sp = thread_saved_sp(tsk); 372 /* 373 * The function calling __switch_to cannot be a leaf function 374 * so LR is recovered from the stack. 375 */ 376 frame.lr = 0; 377 frame.pc = thread_saved_pc(tsk); 378 } 379 380 while (1) { 381 int urc; 382 unsigned long where = frame.pc; 383 384 urc = unwind_frame(&frame); 385 if (urc < 0) 386 break; 387 dump_backtrace_entry(where, frame.pc, frame.sp - 4); 388 } 389 } 390 391 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, 392 unsigned long text_addr, 393 unsigned long text_size) 394 { 395 unsigned long flags; 396 struct unwind_idx *idx; 397 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); 398 399 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, 400 text_addr, text_size); 401 402 if (!tab) 403 return tab; 404 405 tab->start = (struct unwind_idx *)start; 406 tab->stop = (struct unwind_idx *)(start + size); 407 tab->begin_addr = text_addr; 408 tab->end_addr = text_addr + text_size; 409 410 /* Convert the symbol addresses to absolute values */ 411 for (idx = tab->start; idx < tab->stop; idx++) 412 idx->addr = prel31_to_addr(&idx->addr); 413 414 spin_lock_irqsave(&unwind_lock, flags); 415 list_add_tail(&tab->list, &unwind_tables); 416 spin_unlock_irqrestore(&unwind_lock, flags); 417 418 return tab; 419 } 420 421 void unwind_table_del(struct unwind_table *tab) 422 { 423 unsigned long flags; 424 425 if (!tab) 426 return; 427 428 spin_lock_irqsave(&unwind_lock, flags); 429 list_del(&tab->list); 430 spin_unlock_irqrestore(&unwind_lock, flags); 431 432 kfree(tab); 433 } 434 435 int __init unwind_init(void) 436 { 437 struct unwind_idx *idx; 438 439 /* Convert the symbol addresses to absolute values */ 440 for (idx = __start_unwind_idx; idx < __stop_unwind_idx; idx++) 441 idx->addr = prel31_to_addr(&idx->addr); 442 443 pr_debug("unwind: ARM stack unwinding initialised\n"); 444 445 return 0; 446 } 447