1 /* 2 * Kernel unwinding support 3 * 4 * (c) 2002-2004 Randolph Chung <tausq@debian.org> 5 * 6 * Derived partially from the IA64 implementation. The PA-RISC 7 * Runtime Architecture Document is also a useful reference to 8 * understand what is happening here 9 */ 10 11 #include <linux/config.h> 12 #include <linux/kernel.h> 13 #include <linux/init.h> 14 #include <linux/slab.h> 15 #include <linux/kallsyms.h> 16 17 #include <asm/uaccess.h> 18 #include <asm/assembly.h> 19 20 #include <asm/unwind.h> 21 22 /* #define DEBUG 1 */ 23 #ifdef DEBUG 24 #define dbg(x...) printk(x) 25 #else 26 #define dbg(x...) 27 #endif 28 29 extern struct unwind_table_entry __start___unwind[]; 30 extern struct unwind_table_entry __stop___unwind[]; 31 32 static spinlock_t unwind_lock; 33 /* 34 * the kernel unwind block is not dynamically allocated so that 35 * we can call unwind_init as early in the bootup process as 36 * possible (before the slab allocator is initialized) 37 */ 38 static struct unwind_table kernel_unwind_table; 39 static LIST_HEAD(unwind_tables); 40 41 static inline const struct unwind_table_entry * 42 find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr) 43 { 44 const struct unwind_table_entry *e = NULL; 45 unsigned long lo, hi, mid; 46 47 lo = 0; 48 hi = table->length - 1; 49 50 while (lo <= hi) { 51 mid = (hi - lo) / 2 + lo; 52 e = &table->table[mid]; 53 if (addr < e->region_start) 54 hi = mid - 1; 55 else if (addr > e->region_end) 56 lo = mid + 1; 57 else 58 return e; 59 } 60 61 return NULL; 62 } 63 64 static const struct unwind_table_entry * 65 find_unwind_entry(unsigned long addr) 66 { 67 struct unwind_table *table; 68 const struct unwind_table_entry *e = NULL; 69 70 if (addr >= kernel_unwind_table.start && 71 addr <= kernel_unwind_table.end) 72 e = find_unwind_entry_in_table(&kernel_unwind_table, addr); 73 else 74 list_for_each_entry(table, &unwind_tables, list) { 75 if (addr >= table->start && 76 addr <= table->end) 77 e = find_unwind_entry_in_table(table, addr); 78 if (e) 79 break; 80 } 81 82 return e; 83 } 84 85 static void 86 unwind_table_init(struct unwind_table *table, const char *name, 87 unsigned long base_addr, unsigned long gp, 88 void *table_start, void *table_end) 89 { 90 struct unwind_table_entry *start = table_start; 91 struct unwind_table_entry *end = 92 (struct unwind_table_entry *)table_end - 1; 93 94 table->name = name; 95 table->base_addr = base_addr; 96 table->gp = gp; 97 table->start = base_addr + start->region_start; 98 table->end = base_addr + end->region_end; 99 table->table = (struct unwind_table_entry *)table_start; 100 table->length = end - start + 1; 101 INIT_LIST_HEAD(&table->list); 102 103 for (; start <= end; start++) { 104 if (start < end && 105 start->region_end > (start+1)->region_start) { 106 printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1); 107 } 108 109 start->region_start += base_addr; 110 start->region_end += base_addr; 111 } 112 } 113 114 static void 115 unwind_table_sort(struct unwind_table_entry *start, 116 struct unwind_table_entry *finish) 117 { 118 struct unwind_table_entry el, *p, *q; 119 120 for (p = start + 1; p < finish; ++p) { 121 if (p[0].region_start < p[-1].region_start) { 122 el = *p; 123 q = p; 124 do { 125 q[0] = q[-1]; 126 --q; 127 } while (q > start && 128 el.region_start < q[-1].region_start); 129 *q = el; 130 } 131 } 132 } 133 134 struct unwind_table * 135 unwind_table_add(const char *name, unsigned long base_addr, 136 unsigned long gp, 137 void *start, void *end) 138 { 139 struct unwind_table *table; 140 unsigned long flags; 141 struct unwind_table_entry *s = (struct unwind_table_entry *)start; 142 struct unwind_table_entry *e = (struct unwind_table_entry *)end; 143 144 unwind_table_sort(s, e); 145 146 table = kmalloc(sizeof(struct unwind_table), GFP_USER); 147 if (table == NULL) 148 return NULL; 149 unwind_table_init(table, name, base_addr, gp, start, end); 150 spin_lock_irqsave(&unwind_lock, flags); 151 list_add_tail(&table->list, &unwind_tables); 152 spin_unlock_irqrestore(&unwind_lock, flags); 153 154 return table; 155 } 156 157 void unwind_table_remove(struct unwind_table *table) 158 { 159 unsigned long flags; 160 161 spin_lock_irqsave(&unwind_lock, flags); 162 list_del(&table->list); 163 spin_unlock_irqrestore(&unwind_lock, flags); 164 165 kfree(table); 166 } 167 168 /* Called from setup_arch to import the kernel unwind info */ 169 static int unwind_init(void) 170 { 171 long start, stop; 172 register unsigned long gp __asm__ ("r27"); 173 174 start = (long)&__start___unwind[0]; 175 stop = (long)&__stop___unwind[0]; 176 177 spin_lock_init(&unwind_lock); 178 179 printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n", 180 start, stop, 181 (stop - start) / sizeof(struct unwind_table_entry)); 182 183 unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START, 184 gp, 185 &__start___unwind[0], &__stop___unwind[0]); 186 #if 0 187 { 188 int i; 189 for (i = 0; i < 10; i++) 190 { 191 printk("region 0x%x-0x%x\n", 192 __start___unwind[i].region_start, 193 __start___unwind[i].region_end); 194 } 195 } 196 #endif 197 return 0; 198 } 199 200 static void unwind_frame_regs(struct unwind_frame_info *info) 201 { 202 const struct unwind_table_entry *e; 203 unsigned long npc; 204 unsigned int insn; 205 long frame_size = 0; 206 int looking_for_rp, rpoffset = 0; 207 208 e = find_unwind_entry(info->ip); 209 if (e == NULL) { 210 unsigned long sp; 211 extern char _stext[], _etext[]; 212 213 dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip); 214 215 #ifdef CONFIG_KALLSYMS 216 /* Handle some frequent special cases.... */ 217 { 218 char symname[KSYM_NAME_LEN+1]; 219 char *modname; 220 unsigned long symsize, offset; 221 222 kallsyms_lookup(info->ip, &symsize, &offset, 223 &modname, symname); 224 225 dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname); 226 227 if (strcmp(symname, "_switch_to_ret") == 0) { 228 info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE; 229 info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET); 230 dbg("_switch_to_ret @ %lx - setting " 231 "prev_sp=%lx prev_ip=%lx\n", 232 info->ip, info->prev_sp, 233 info->prev_ip); 234 return; 235 } else if (strcmp(symname, "ret_from_kernel_thread") == 0 || 236 strcmp(symname, "syscall_exit") == 0) { 237 info->prev_ip = info->prev_sp = 0; 238 return; 239 } 240 } 241 #endif 242 243 /* Since we are doing the unwinding blind, we don't know if 244 we are adjusting the stack correctly or extracting the rp 245 correctly. The rp is checked to see if it belongs to the 246 kernel text section, if not we assume we don't have a 247 correct stack frame and we continue to unwind the stack. 248 This is not quite correct, and will fail for loadable 249 modules. */ 250 sp = info->sp & ~63; 251 do { 252 unsigned long tmp; 253 254 info->prev_sp = sp - 64; 255 info->prev_ip = 0; 256 if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET))) 257 break; 258 info->prev_ip = tmp; 259 sp = info->prev_sp; 260 } while (info->prev_ip < (unsigned long)_stext || 261 info->prev_ip > (unsigned long)_etext); 262 263 info->rp = 0; 264 265 dbg("analyzing func @ %lx with no unwind info, setting " 266 "prev_sp=%lx prev_ip=%lx\n", info->ip, 267 info->prev_sp, info->prev_ip); 268 } else { 269 dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, " 270 "Save_RP = %d, Millicode = %d size = %u\n", 271 e->region_start, e->region_end, e->Save_SP, e->Save_RP, 272 e->Millicode, e->Total_frame_size); 273 274 looking_for_rp = e->Save_RP; 275 276 for (npc = e->region_start; 277 (frame_size < (e->Total_frame_size << 3) || 278 looking_for_rp) && 279 npc < info->ip; 280 npc += 4) { 281 282 insn = *(unsigned int *)npc; 283 284 if ((insn & 0xffffc000) == 0x37de0000 || 285 (insn & 0xffe00000) == 0x6fc00000) { 286 /* ldo X(sp), sp, or stwm X,D(sp) */ 287 frame_size += (insn & 0x1 ? -1 << 13 : 0) | 288 ((insn & 0x3fff) >> 1); 289 dbg("analyzing func @ %lx, insn=%08x @ " 290 "%lx, frame_size = %ld\n", info->ip, 291 insn, npc, frame_size); 292 } else if ((insn & 0xffe00008) == 0x73c00008) { 293 /* std,ma X,D(sp) */ 294 frame_size += (insn & 0x1 ? -1 << 13 : 0) | 295 (((insn >> 4) & 0x3ff) << 3); 296 dbg("analyzing func @ %lx, insn=%08x @ " 297 "%lx, frame_size = %ld\n", info->ip, 298 insn, npc, frame_size); 299 } else if (insn == 0x6bc23fd9) { 300 /* stw rp,-20(sp) */ 301 rpoffset = 20; 302 looking_for_rp = 0; 303 dbg("analyzing func @ %lx, insn=stw rp," 304 "-20(sp) @ %lx\n", info->ip, npc); 305 } else if (insn == 0x0fc212c1) { 306 /* std rp,-16(sr0,sp) */ 307 rpoffset = 16; 308 looking_for_rp = 0; 309 dbg("analyzing func @ %lx, insn=std rp," 310 "-16(sp) @ %lx\n", info->ip, npc); 311 } 312 } 313 314 info->prev_sp = info->sp - frame_size; 315 if (e->Millicode) 316 info->rp = info->r31; 317 else if (rpoffset) 318 info->rp = *(unsigned long *)(info->prev_sp - rpoffset); 319 info->prev_ip = info->rp; 320 info->rp = 0; 321 322 dbg("analyzing func @ %lx, setting prev_sp=%lx " 323 "prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp, 324 info->prev_ip, npc); 325 } 326 } 327 328 void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t, 329 struct pt_regs *regs) 330 { 331 memset(info, 0, sizeof(struct unwind_frame_info)); 332 info->t = t; 333 info->sp = regs->gr[30]; 334 info->ip = regs->iaoq[0]; 335 info->rp = regs->gr[2]; 336 info->r31 = regs->gr[31]; 337 338 dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n", 339 t ? (int)t->pid : -1, info->sp, info->ip); 340 } 341 342 void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t) 343 { 344 struct pt_regs *r = &t->thread.regs; 345 struct pt_regs *r2; 346 347 r2 = (struct pt_regs *)kmalloc(sizeof(struct pt_regs), GFP_KERNEL); 348 if (!r2) 349 return; 350 *r2 = *r; 351 r2->gr[30] = r->ksp; 352 r2->iaoq[0] = r->kpc; 353 unwind_frame_init(info, t, r2); 354 kfree(r2); 355 } 356 357 void unwind_frame_init_running(struct unwind_frame_info *info, struct pt_regs *regs) 358 { 359 unwind_frame_init(info, current, regs); 360 } 361 362 int unwind_once(struct unwind_frame_info *next_frame) 363 { 364 unwind_frame_regs(next_frame); 365 366 if (next_frame->prev_sp == 0 || 367 next_frame->prev_ip == 0) 368 return -1; 369 370 next_frame->sp = next_frame->prev_sp; 371 next_frame->ip = next_frame->prev_ip; 372 next_frame->prev_sp = 0; 373 next_frame->prev_ip = 0; 374 375 dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n", 376 next_frame->t ? (int)next_frame->t->pid : -1, 377 next_frame->sp, next_frame->ip); 378 379 return 0; 380 } 381 382 int unwind_to_user(struct unwind_frame_info *info) 383 { 384 int ret; 385 386 do { 387 ret = unwind_once(info); 388 } while (!ret && !(info->ip & 3)); 389 390 return ret; 391 } 392 393 module_init(unwind_init); 394