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