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 * Now find where in the stack these are. 130 */ 131 x = 0; 132 start = stack; 133 top = (unsigned long *) 134 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); 135 136 /* 137 * Loop through all the entries. One of the entries may 138 * for some reason be missed on the stack, so we may 139 * have to account for them. If they are all there, this 140 * loop will only happen once. This code only takes place 141 * on a new max, so it is far from a fast path. 142 */ 143 while (i < stack_trace_max.nr_entries) { 144 int found = 0; 145 146 stack_trace_index[x] = this_size; 147 p = start; 148 149 for (; p < top && i < stack_trace_max.nr_entries; p++) { 150 if (stack_dump_trace[i] == ULONG_MAX) 151 break; 152 if (*p == stack_dump_trace[i]) { 153 stack_dump_trace[x] = stack_dump_trace[i++]; 154 this_size = stack_trace_index[x++] = 155 (top - p) * sizeof(unsigned long); 156 found = 1; 157 /* Start the search from here */ 158 start = p + 1; 159 /* 160 * We do not want to show the overhead 161 * of the stack tracer stack in the 162 * max stack. If we haven't figured 163 * out what that is, then figure it out 164 * now. 165 */ 166 if (unlikely(!tracer_frame)) { 167 tracer_frame = (p - stack) * 168 sizeof(unsigned long); 169 stack_trace_max_size -= tracer_frame; 170 } 171 } 172 } 173 174 if (!found) 175 i++; 176 } 177 178 stack_trace_max.nr_entries = x; 179 for (; x < i; x++) 180 stack_dump_trace[x] = ULONG_MAX; 181 182 if (task_stack_end_corrupted(current)) { 183 stack_trace_print(); 184 BUG(); 185 } 186 187 out: 188 rcu_irq_exit(); 189 arch_spin_unlock(&stack_trace_max_lock); 190 local_irq_restore(flags); 191 } 192 193 static void 194 stack_trace_call(unsigned long ip, unsigned long parent_ip, 195 struct ftrace_ops *op, struct pt_regs *pt_regs) 196 { 197 unsigned long stack; 198 int cpu; 199 200 preempt_disable_notrace(); 201 202 cpu = raw_smp_processor_id(); 203 /* no atomic needed, we only modify this variable by this cpu */ 204 if (per_cpu(trace_active, cpu)++ != 0) 205 goto out; 206 207 ip += MCOUNT_INSN_SIZE; 208 209 check_stack(ip, &stack); 210 211 out: 212 per_cpu(trace_active, cpu)--; 213 /* prevent recursion in schedule */ 214 preempt_enable_notrace(); 215 } 216 217 static struct ftrace_ops trace_ops __read_mostly = 218 { 219 .func = stack_trace_call, 220 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 221 }; 222 223 static ssize_t 224 stack_max_size_read(struct file *filp, char __user *ubuf, 225 size_t count, loff_t *ppos) 226 { 227 unsigned long *ptr = filp->private_data; 228 char buf[64]; 229 int r; 230 231 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 232 if (r > sizeof(buf)) 233 r = sizeof(buf); 234 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 235 } 236 237 static ssize_t 238 stack_max_size_write(struct file *filp, const char __user *ubuf, 239 size_t count, loff_t *ppos) 240 { 241 long *ptr = filp->private_data; 242 unsigned long val, flags; 243 int ret; 244 int cpu; 245 246 ret = kstrtoul_from_user(ubuf, count, 10, &val); 247 if (ret) 248 return ret; 249 250 local_irq_save(flags); 251 252 /* 253 * In case we trace inside arch_spin_lock() or after (NMI), 254 * we will cause circular lock, so we also need to increase 255 * the percpu trace_active here. 256 */ 257 cpu = smp_processor_id(); 258 per_cpu(trace_active, cpu)++; 259 260 arch_spin_lock(&stack_trace_max_lock); 261 *ptr = val; 262 arch_spin_unlock(&stack_trace_max_lock); 263 264 per_cpu(trace_active, cpu)--; 265 local_irq_restore(flags); 266 267 return count; 268 } 269 270 static const struct file_operations stack_max_size_fops = { 271 .open = tracing_open_generic, 272 .read = stack_max_size_read, 273 .write = stack_max_size_write, 274 .llseek = default_llseek, 275 }; 276 277 static void * 278 __next(struct seq_file *m, loff_t *pos) 279 { 280 long n = *pos - 1; 281 282 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX) 283 return NULL; 284 285 m->private = (void *)n; 286 return &m->private; 287 } 288 289 static void * 290 t_next(struct seq_file *m, void *v, loff_t *pos) 291 { 292 (*pos)++; 293 return __next(m, pos); 294 } 295 296 static void *t_start(struct seq_file *m, loff_t *pos) 297 { 298 int cpu; 299 300 local_irq_disable(); 301 302 cpu = smp_processor_id(); 303 per_cpu(trace_active, cpu)++; 304 305 arch_spin_lock(&stack_trace_max_lock); 306 307 if (*pos == 0) 308 return SEQ_START_TOKEN; 309 310 return __next(m, pos); 311 } 312 313 static void t_stop(struct seq_file *m, void *p) 314 { 315 int cpu; 316 317 arch_spin_unlock(&stack_trace_max_lock); 318 319 cpu = smp_processor_id(); 320 per_cpu(trace_active, cpu)--; 321 322 local_irq_enable(); 323 } 324 325 static void trace_lookup_stack(struct seq_file *m, long i) 326 { 327 unsigned long addr = stack_dump_trace[i]; 328 329 seq_printf(m, "%pS\n", (void *)addr); 330 } 331 332 static void print_disabled(struct seq_file *m) 333 { 334 seq_puts(m, "#\n" 335 "# Stack tracer disabled\n" 336 "#\n" 337 "# To enable the stack tracer, either add 'stacktrace' to the\n" 338 "# kernel command line\n" 339 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 340 "#\n"); 341 } 342 343 static int t_show(struct seq_file *m, void *v) 344 { 345 long i; 346 int size; 347 348 if (v == SEQ_START_TOKEN) { 349 seq_printf(m, " Depth Size Location" 350 " (%d entries)\n" 351 " ----- ---- --------\n", 352 stack_trace_max.nr_entries); 353 354 if (!stack_tracer_enabled && !stack_trace_max_size) 355 print_disabled(m); 356 357 return 0; 358 } 359 360 i = *(long *)v; 361 362 if (i >= stack_trace_max.nr_entries || 363 stack_dump_trace[i] == ULONG_MAX) 364 return 0; 365 366 if (i+1 == stack_trace_max.nr_entries || 367 stack_dump_trace[i+1] == ULONG_MAX) 368 size = stack_trace_index[i]; 369 else 370 size = stack_trace_index[i] - stack_trace_index[i+1]; 371 372 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size); 373 374 trace_lookup_stack(m, i); 375 376 return 0; 377 } 378 379 static const struct seq_operations stack_trace_seq_ops = { 380 .start = t_start, 381 .next = t_next, 382 .stop = t_stop, 383 .show = t_show, 384 }; 385 386 static int stack_trace_open(struct inode *inode, struct file *file) 387 { 388 return seq_open(file, &stack_trace_seq_ops); 389 } 390 391 static const struct file_operations stack_trace_fops = { 392 .open = stack_trace_open, 393 .read = seq_read, 394 .llseek = seq_lseek, 395 .release = seq_release, 396 }; 397 398 static int 399 stack_trace_filter_open(struct inode *inode, struct file *file) 400 { 401 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER, 402 inode, file); 403 } 404 405 static const struct file_operations stack_trace_filter_fops = { 406 .open = stack_trace_filter_open, 407 .read = seq_read, 408 .write = ftrace_filter_write, 409 .llseek = tracing_lseek, 410 .release = ftrace_regex_release, 411 }; 412 413 int 414 stack_trace_sysctl(struct ctl_table *table, int write, 415 void __user *buffer, size_t *lenp, 416 loff_t *ppos) 417 { 418 int ret; 419 420 mutex_lock(&stack_sysctl_mutex); 421 422 ret = proc_dointvec(table, write, buffer, lenp, ppos); 423 424 if (ret || !write || 425 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 426 goto out; 427 428 last_stack_tracer_enabled = !!stack_tracer_enabled; 429 430 if (stack_tracer_enabled) 431 register_ftrace_function(&trace_ops); 432 else 433 unregister_ftrace_function(&trace_ops); 434 435 out: 436 mutex_unlock(&stack_sysctl_mutex); 437 return ret; 438 } 439 440 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 441 442 static __init int enable_stacktrace(char *str) 443 { 444 if (strncmp(str, "_filter=", 8) == 0) 445 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE); 446 447 stack_tracer_enabled = 1; 448 last_stack_tracer_enabled = 1; 449 return 1; 450 } 451 __setup("stacktrace", enable_stacktrace); 452 453 static __init int stack_trace_init(void) 454 { 455 struct dentry *d_tracer; 456 457 d_tracer = tracing_init_dentry(); 458 if (IS_ERR(d_tracer)) 459 return 0; 460 461 trace_create_file("stack_max_size", 0644, d_tracer, 462 &stack_trace_max_size, &stack_max_size_fops); 463 464 trace_create_file("stack_trace", 0444, d_tracer, 465 NULL, &stack_trace_fops); 466 467 trace_create_file("stack_trace_filter", 0444, d_tracer, 468 NULL, &stack_trace_filter_fops); 469 470 if (stack_trace_filter_buf[0]) 471 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); 472 473 if (stack_tracer_enabled) 474 register_ftrace_function(&trace_ops); 475 476 return 0; 477 } 478 479 device_initcall(stack_trace_init); 480