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 /* 160 * The READ_ONCE_NOCHECK is used to let KASAN know that 161 * this is not a stack-out-of-bounds error. 162 */ 163 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) { 164 stack_dump_trace[x] = stack_dump_trace[i++]; 165 this_size = stack_trace_index[x++] = 166 (top - p) * sizeof(unsigned long); 167 found = 1; 168 /* Start the search from here */ 169 start = p + 1; 170 /* 171 * We do not want to show the overhead 172 * of the stack tracer stack in the 173 * max stack. If we haven't figured 174 * out what that is, then figure it out 175 * now. 176 */ 177 if (unlikely(!tracer_frame)) { 178 tracer_frame = (p - stack) * 179 sizeof(unsigned long); 180 stack_trace_max_size -= tracer_frame; 181 } 182 } 183 } 184 185 if (!found) 186 i++; 187 } 188 189 stack_trace_max.nr_entries = x; 190 for (; x < i; x++) 191 stack_dump_trace[x] = ULONG_MAX; 192 193 if (task_stack_end_corrupted(current)) { 194 stack_trace_print(); 195 BUG(); 196 } 197 198 out: 199 rcu_irq_exit(); 200 arch_spin_unlock(&stack_trace_max_lock); 201 local_irq_restore(flags); 202 } 203 204 static void 205 stack_trace_call(unsigned long ip, unsigned long parent_ip, 206 struct ftrace_ops *op, struct pt_regs *pt_regs) 207 { 208 unsigned long stack; 209 int cpu; 210 211 preempt_disable_notrace(); 212 213 cpu = raw_smp_processor_id(); 214 /* no atomic needed, we only modify this variable by this cpu */ 215 if (per_cpu(trace_active, cpu)++ != 0) 216 goto out; 217 218 ip += MCOUNT_INSN_SIZE; 219 220 check_stack(ip, &stack); 221 222 out: 223 per_cpu(trace_active, cpu)--; 224 /* prevent recursion in schedule */ 225 preempt_enable_notrace(); 226 } 227 228 static struct ftrace_ops trace_ops __read_mostly = 229 { 230 .func = stack_trace_call, 231 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 232 }; 233 234 static ssize_t 235 stack_max_size_read(struct file *filp, char __user *ubuf, 236 size_t count, loff_t *ppos) 237 { 238 unsigned long *ptr = filp->private_data; 239 char buf[64]; 240 int r; 241 242 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 243 if (r > sizeof(buf)) 244 r = sizeof(buf); 245 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 246 } 247 248 static ssize_t 249 stack_max_size_write(struct file *filp, const char __user *ubuf, 250 size_t count, loff_t *ppos) 251 { 252 long *ptr = filp->private_data; 253 unsigned long val, flags; 254 int ret; 255 int cpu; 256 257 ret = kstrtoul_from_user(ubuf, count, 10, &val); 258 if (ret) 259 return ret; 260 261 local_irq_save(flags); 262 263 /* 264 * In case we trace inside arch_spin_lock() or after (NMI), 265 * we will cause circular lock, so we also need to increase 266 * the percpu trace_active here. 267 */ 268 cpu = smp_processor_id(); 269 per_cpu(trace_active, cpu)++; 270 271 arch_spin_lock(&stack_trace_max_lock); 272 *ptr = val; 273 arch_spin_unlock(&stack_trace_max_lock); 274 275 per_cpu(trace_active, cpu)--; 276 local_irq_restore(flags); 277 278 return count; 279 } 280 281 static const struct file_operations stack_max_size_fops = { 282 .open = tracing_open_generic, 283 .read = stack_max_size_read, 284 .write = stack_max_size_write, 285 .llseek = default_llseek, 286 }; 287 288 static void * 289 __next(struct seq_file *m, loff_t *pos) 290 { 291 long n = *pos - 1; 292 293 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX) 294 return NULL; 295 296 m->private = (void *)n; 297 return &m->private; 298 } 299 300 static void * 301 t_next(struct seq_file *m, void *v, loff_t *pos) 302 { 303 (*pos)++; 304 return __next(m, pos); 305 } 306 307 static void *t_start(struct seq_file *m, loff_t *pos) 308 { 309 int cpu; 310 311 local_irq_disable(); 312 313 cpu = smp_processor_id(); 314 per_cpu(trace_active, cpu)++; 315 316 arch_spin_lock(&stack_trace_max_lock); 317 318 if (*pos == 0) 319 return SEQ_START_TOKEN; 320 321 return __next(m, pos); 322 } 323 324 static void t_stop(struct seq_file *m, void *p) 325 { 326 int cpu; 327 328 arch_spin_unlock(&stack_trace_max_lock); 329 330 cpu = smp_processor_id(); 331 per_cpu(trace_active, cpu)--; 332 333 local_irq_enable(); 334 } 335 336 static void trace_lookup_stack(struct seq_file *m, long i) 337 { 338 unsigned long addr = stack_dump_trace[i]; 339 340 seq_printf(m, "%pS\n", (void *)addr); 341 } 342 343 static void print_disabled(struct seq_file *m) 344 { 345 seq_puts(m, "#\n" 346 "# Stack tracer disabled\n" 347 "#\n" 348 "# To enable the stack tracer, either add 'stacktrace' to the\n" 349 "# kernel command line\n" 350 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 351 "#\n"); 352 } 353 354 static int t_show(struct seq_file *m, void *v) 355 { 356 long i; 357 int size; 358 359 if (v == SEQ_START_TOKEN) { 360 seq_printf(m, " Depth Size Location" 361 " (%d entries)\n" 362 " ----- ---- --------\n", 363 stack_trace_max.nr_entries); 364 365 if (!stack_tracer_enabled && !stack_trace_max_size) 366 print_disabled(m); 367 368 return 0; 369 } 370 371 i = *(long *)v; 372 373 if (i >= stack_trace_max.nr_entries || 374 stack_dump_trace[i] == ULONG_MAX) 375 return 0; 376 377 if (i+1 == stack_trace_max.nr_entries || 378 stack_dump_trace[i+1] == ULONG_MAX) 379 size = stack_trace_index[i]; 380 else 381 size = stack_trace_index[i] - stack_trace_index[i+1]; 382 383 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size); 384 385 trace_lookup_stack(m, i); 386 387 return 0; 388 } 389 390 static const struct seq_operations stack_trace_seq_ops = { 391 .start = t_start, 392 .next = t_next, 393 .stop = t_stop, 394 .show = t_show, 395 }; 396 397 static int stack_trace_open(struct inode *inode, struct file *file) 398 { 399 return seq_open(file, &stack_trace_seq_ops); 400 } 401 402 static const struct file_operations stack_trace_fops = { 403 .open = stack_trace_open, 404 .read = seq_read, 405 .llseek = seq_lseek, 406 .release = seq_release, 407 }; 408 409 static int 410 stack_trace_filter_open(struct inode *inode, struct file *file) 411 { 412 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER, 413 inode, file); 414 } 415 416 static const struct file_operations stack_trace_filter_fops = { 417 .open = stack_trace_filter_open, 418 .read = seq_read, 419 .write = ftrace_filter_write, 420 .llseek = tracing_lseek, 421 .release = ftrace_regex_release, 422 }; 423 424 int 425 stack_trace_sysctl(struct ctl_table *table, int write, 426 void __user *buffer, size_t *lenp, 427 loff_t *ppos) 428 { 429 int ret; 430 431 mutex_lock(&stack_sysctl_mutex); 432 433 ret = proc_dointvec(table, write, buffer, lenp, ppos); 434 435 if (ret || !write || 436 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 437 goto out; 438 439 last_stack_tracer_enabled = !!stack_tracer_enabled; 440 441 if (stack_tracer_enabled) 442 register_ftrace_function(&trace_ops); 443 else 444 unregister_ftrace_function(&trace_ops); 445 446 out: 447 mutex_unlock(&stack_sysctl_mutex); 448 return ret; 449 } 450 451 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 452 453 static __init int enable_stacktrace(char *str) 454 { 455 if (strncmp(str, "_filter=", 8) == 0) 456 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE); 457 458 stack_tracer_enabled = 1; 459 last_stack_tracer_enabled = 1; 460 return 1; 461 } 462 __setup("stacktrace", enable_stacktrace); 463 464 static __init int stack_trace_init(void) 465 { 466 struct dentry *d_tracer; 467 468 d_tracer = tracing_init_dentry(); 469 if (IS_ERR(d_tracer)) 470 return 0; 471 472 trace_create_file("stack_max_size", 0644, d_tracer, 473 &stack_trace_max_size, &stack_max_size_fops); 474 475 trace_create_file("stack_trace", 0444, d_tracer, 476 NULL, &stack_trace_fops); 477 478 trace_create_file("stack_trace_filter", 0444, d_tracer, 479 NULL, &stack_trace_filter_fops); 480 481 if (stack_trace_filter_buf[0]) 482 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); 483 484 if (stack_tracer_enabled) 485 register_ftrace_function(&trace_ops); 486 487 return 0; 488 } 489 490 device_initcall(stack_trace_init); 491