1 /* 2 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> 3 * 4 */ 5 #include <linux/stacktrace.h> 6 #include <linux/kallsyms.h> 7 #include <linux/seq_file.h> 8 #include <linux/spinlock.h> 9 #include <linux/uaccess.h> 10 #include <linux/ftrace.h> 11 #include <linux/module.h> 12 #include <linux/sysctl.h> 13 #include <linux/init.h> 14 15 #include <asm/setup.h> 16 17 #include "trace.h" 18 19 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] = 20 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX }; 21 unsigned stack_trace_index[STACK_TRACE_ENTRIES]; 22 23 /* 24 * Reserve one entry for the passed in ip. This will allow 25 * us to remove most or all of the stack size overhead 26 * added by the stack tracer itself. 27 */ 28 struct stack_trace stack_trace_max = { 29 .max_entries = STACK_TRACE_ENTRIES - 1, 30 .entries = &stack_dump_trace[0], 31 }; 32 33 unsigned long stack_trace_max_size; 34 arch_spinlock_t stack_trace_max_lock = 35 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; 36 37 static DEFINE_PER_CPU(int, trace_active); 38 static DEFINE_MUTEX(stack_sysctl_mutex); 39 40 int stack_tracer_enabled; 41 static int last_stack_tracer_enabled; 42 43 void stack_trace_print(void) 44 { 45 long i; 46 int size; 47 48 pr_emerg(" Depth Size Location (%d entries)\n" 49 " ----- ---- --------\n", 50 stack_trace_max.nr_entries); 51 52 for (i = 0; i < stack_trace_max.nr_entries; i++) { 53 if (stack_dump_trace[i] == ULONG_MAX) 54 break; 55 if (i+1 == stack_trace_max.nr_entries || 56 stack_dump_trace[i+1] == ULONG_MAX) 57 size = stack_trace_index[i]; 58 else 59 size = stack_trace_index[i] - stack_trace_index[i+1]; 60 61 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i], 62 size, (void *)stack_dump_trace[i]); 63 } 64 } 65 66 /* 67 * When arch-specific code overides this function, the following 68 * data should be filled up, assuming stack_trace_max_lock is held to 69 * prevent concurrent updates. 70 * stack_trace_index[] 71 * stack_trace_max 72 * stack_trace_max_size 73 */ 74 void __weak 75 check_stack(unsigned long ip, unsigned long *stack) 76 { 77 unsigned long this_size, flags; unsigned long *p, *top, *start; 78 static int tracer_frame; 79 int frame_size = ACCESS_ONCE(tracer_frame); 80 int i, x; 81 82 this_size = ((unsigned long)stack) & (THREAD_SIZE-1); 83 this_size = THREAD_SIZE - this_size; 84 /* Remove the frame of the tracer */ 85 this_size -= frame_size; 86 87 if (this_size <= stack_trace_max_size) 88 return; 89 90 /* we do not handle interrupt stacks yet */ 91 if (!object_is_on_stack(stack)) 92 return; 93 94 /* Can't do this from NMI context (can cause deadlocks) */ 95 if (in_nmi()) 96 return; 97 98 local_irq_save(flags); 99 arch_spin_lock(&stack_trace_max_lock); 100 101 /* 102 * RCU may not be watching, make it see us. 103 * The stack trace code uses rcu_sched. 104 */ 105 rcu_irq_enter(); 106 107 /* In case another CPU set the tracer_frame on us */ 108 if (unlikely(!frame_size)) 109 this_size -= tracer_frame; 110 111 /* a race could have already updated it */ 112 if (this_size <= stack_trace_max_size) 113 goto out; 114 115 stack_trace_max_size = this_size; 116 117 stack_trace_max.nr_entries = 0; 118 stack_trace_max.skip = 3; 119 120 save_stack_trace(&stack_trace_max); 121 122 /* Skip over the overhead of the stack tracer itself */ 123 for (i = 0; i < stack_trace_max.nr_entries; i++) { 124 if (stack_dump_trace[i] == ip) 125 break; 126 } 127 128 /* 129 * Some archs may not have the passed in ip in the dump. 130 * If that happens, we need to show everything. 131 */ 132 if (i == stack_trace_max.nr_entries) 133 i = 0; 134 135 /* 136 * Now find where in the stack these are. 137 */ 138 x = 0; 139 start = stack; 140 top = (unsigned long *) 141 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); 142 143 /* 144 * Loop through all the entries. One of the entries may 145 * for some reason be missed on the stack, so we may 146 * have to account for them. If they are all there, this 147 * loop will only happen once. This code only takes place 148 * on a new max, so it is far from a fast path. 149 */ 150 while (i < stack_trace_max.nr_entries) { 151 int found = 0; 152 153 stack_trace_index[x] = this_size; 154 p = start; 155 156 for (; p < top && i < stack_trace_max.nr_entries; p++) { 157 if (stack_dump_trace[i] == ULONG_MAX) 158 break; 159 if (*p == stack_dump_trace[i]) { 160 stack_dump_trace[x] = stack_dump_trace[i++]; 161 this_size = stack_trace_index[x++] = 162 (top - p) * sizeof(unsigned long); 163 found = 1; 164 /* Start the search from here */ 165 start = p + 1; 166 /* 167 * We do not want to show the overhead 168 * of the stack tracer stack in the 169 * max stack. If we haven't figured 170 * out what that is, then figure it out 171 * now. 172 */ 173 if (unlikely(!tracer_frame)) { 174 tracer_frame = (p - stack) * 175 sizeof(unsigned long); 176 stack_trace_max_size -= tracer_frame; 177 } 178 } 179 } 180 181 if (!found) 182 i++; 183 } 184 185 stack_trace_max.nr_entries = x; 186 for (; x < i; x++) 187 stack_dump_trace[x] = ULONG_MAX; 188 189 if (task_stack_end_corrupted(current)) { 190 stack_trace_print(); 191 BUG(); 192 } 193 194 out: 195 rcu_irq_exit(); 196 arch_spin_unlock(&stack_trace_max_lock); 197 local_irq_restore(flags); 198 } 199 200 static void 201 stack_trace_call(unsigned long ip, unsigned long parent_ip, 202 struct ftrace_ops *op, struct pt_regs *pt_regs) 203 { 204 unsigned long stack; 205 int cpu; 206 207 preempt_disable_notrace(); 208 209 cpu = raw_smp_processor_id(); 210 /* no atomic needed, we only modify this variable by this cpu */ 211 if (per_cpu(trace_active, cpu)++ != 0) 212 goto out; 213 214 ip += MCOUNT_INSN_SIZE; 215 216 check_stack(ip, &stack); 217 218 out: 219 per_cpu(trace_active, cpu)--; 220 /* prevent recursion in schedule */ 221 preempt_enable_notrace(); 222 } 223 224 static struct ftrace_ops trace_ops __read_mostly = 225 { 226 .func = stack_trace_call, 227 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 228 }; 229 230 static ssize_t 231 stack_max_size_read(struct file *filp, char __user *ubuf, 232 size_t count, loff_t *ppos) 233 { 234 unsigned long *ptr = filp->private_data; 235 char buf[64]; 236 int r; 237 238 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 239 if (r > sizeof(buf)) 240 r = sizeof(buf); 241 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 242 } 243 244 static ssize_t 245 stack_max_size_write(struct file *filp, const char __user *ubuf, 246 size_t count, loff_t *ppos) 247 { 248 long *ptr = filp->private_data; 249 unsigned long val, flags; 250 int ret; 251 int cpu; 252 253 ret = kstrtoul_from_user(ubuf, count, 10, &val); 254 if (ret) 255 return ret; 256 257 local_irq_save(flags); 258 259 /* 260 * In case we trace inside arch_spin_lock() or after (NMI), 261 * we will cause circular lock, so we also need to increase 262 * the percpu trace_active here. 263 */ 264 cpu = smp_processor_id(); 265 per_cpu(trace_active, cpu)++; 266 267 arch_spin_lock(&stack_trace_max_lock); 268 *ptr = val; 269 arch_spin_unlock(&stack_trace_max_lock); 270 271 per_cpu(trace_active, cpu)--; 272 local_irq_restore(flags); 273 274 return count; 275 } 276 277 static const struct file_operations stack_max_size_fops = { 278 .open = tracing_open_generic, 279 .read = stack_max_size_read, 280 .write = stack_max_size_write, 281 .llseek = default_llseek, 282 }; 283 284 static void * 285 __next(struct seq_file *m, loff_t *pos) 286 { 287 long n = *pos - 1; 288 289 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX) 290 return NULL; 291 292 m->private = (void *)n; 293 return &m->private; 294 } 295 296 static void * 297 t_next(struct seq_file *m, void *v, loff_t *pos) 298 { 299 (*pos)++; 300 return __next(m, pos); 301 } 302 303 static void *t_start(struct seq_file *m, loff_t *pos) 304 { 305 int cpu; 306 307 local_irq_disable(); 308 309 cpu = smp_processor_id(); 310 per_cpu(trace_active, cpu)++; 311 312 arch_spin_lock(&stack_trace_max_lock); 313 314 if (*pos == 0) 315 return SEQ_START_TOKEN; 316 317 return __next(m, pos); 318 } 319 320 static void t_stop(struct seq_file *m, void *p) 321 { 322 int cpu; 323 324 arch_spin_unlock(&stack_trace_max_lock); 325 326 cpu = smp_processor_id(); 327 per_cpu(trace_active, cpu)--; 328 329 local_irq_enable(); 330 } 331 332 static void trace_lookup_stack(struct seq_file *m, long i) 333 { 334 unsigned long addr = stack_dump_trace[i]; 335 336 seq_printf(m, "%pS\n", (void *)addr); 337 } 338 339 static void print_disabled(struct seq_file *m) 340 { 341 seq_puts(m, "#\n" 342 "# Stack tracer disabled\n" 343 "#\n" 344 "# To enable the stack tracer, either add 'stacktrace' to the\n" 345 "# kernel command line\n" 346 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 347 "#\n"); 348 } 349 350 static int t_show(struct seq_file *m, void *v) 351 { 352 long i; 353 int size; 354 355 if (v == SEQ_START_TOKEN) { 356 seq_printf(m, " Depth Size Location" 357 " (%d entries)\n" 358 " ----- ---- --------\n", 359 stack_trace_max.nr_entries); 360 361 if (!stack_tracer_enabled && !stack_trace_max_size) 362 print_disabled(m); 363 364 return 0; 365 } 366 367 i = *(long *)v; 368 369 if (i >= stack_trace_max.nr_entries || 370 stack_dump_trace[i] == ULONG_MAX) 371 return 0; 372 373 if (i+1 == stack_trace_max.nr_entries || 374 stack_dump_trace[i+1] == ULONG_MAX) 375 size = stack_trace_index[i]; 376 else 377 size = stack_trace_index[i] - stack_trace_index[i+1]; 378 379 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size); 380 381 trace_lookup_stack(m, i); 382 383 return 0; 384 } 385 386 static const struct seq_operations stack_trace_seq_ops = { 387 .start = t_start, 388 .next = t_next, 389 .stop = t_stop, 390 .show = t_show, 391 }; 392 393 static int stack_trace_open(struct inode *inode, struct file *file) 394 { 395 return seq_open(file, &stack_trace_seq_ops); 396 } 397 398 static const struct file_operations stack_trace_fops = { 399 .open = stack_trace_open, 400 .read = seq_read, 401 .llseek = seq_lseek, 402 .release = seq_release, 403 }; 404 405 static int 406 stack_trace_filter_open(struct inode *inode, struct file *file) 407 { 408 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER, 409 inode, file); 410 } 411 412 static const struct file_operations stack_trace_filter_fops = { 413 .open = stack_trace_filter_open, 414 .read = seq_read, 415 .write = ftrace_filter_write, 416 .llseek = tracing_lseek, 417 .release = ftrace_regex_release, 418 }; 419 420 int 421 stack_trace_sysctl(struct ctl_table *table, int write, 422 void __user *buffer, size_t *lenp, 423 loff_t *ppos) 424 { 425 int ret; 426 427 mutex_lock(&stack_sysctl_mutex); 428 429 ret = proc_dointvec(table, write, buffer, lenp, ppos); 430 431 if (ret || !write || 432 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 433 goto out; 434 435 last_stack_tracer_enabled = !!stack_tracer_enabled; 436 437 if (stack_tracer_enabled) 438 register_ftrace_function(&trace_ops); 439 else 440 unregister_ftrace_function(&trace_ops); 441 442 out: 443 mutex_unlock(&stack_sysctl_mutex); 444 return ret; 445 } 446 447 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 448 449 static __init int enable_stacktrace(char *str) 450 { 451 if (strncmp(str, "_filter=", 8) == 0) 452 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE); 453 454 stack_tracer_enabled = 1; 455 last_stack_tracer_enabled = 1; 456 return 1; 457 } 458 __setup("stacktrace", enable_stacktrace); 459 460 static __init int stack_trace_init(void) 461 { 462 struct dentry *d_tracer; 463 464 d_tracer = tracing_init_dentry(); 465 if (IS_ERR(d_tracer)) 466 return 0; 467 468 trace_create_file("stack_max_size", 0644, d_tracer, 469 &stack_trace_max_size, &stack_max_size_fops); 470 471 trace_create_file("stack_trace", 0444, d_tracer, 472 NULL, &stack_trace_fops); 473 474 trace_create_file("stack_trace_filter", 0444, d_tracer, 475 NULL, &stack_trace_filter_fops); 476 477 if (stack_trace_filter_buf[0]) 478 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); 479 480 if (stack_tracer_enabled) 481 register_ftrace_function(&trace_ops); 482 483 return 0; 484 } 485 486 device_initcall(stack_trace_init); 487