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 #define STACK_TRACE_ENTRIES 500 20 21 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] = 22 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX }; 23 static unsigned stack_dump_index[STACK_TRACE_ENTRIES]; 24 25 /* 26 * Reserve one entry for the passed in ip. This will allow 27 * us to remove most or all of the stack size overhead 28 * added by the stack tracer itself. 29 */ 30 static struct stack_trace max_stack_trace = { 31 .max_entries = STACK_TRACE_ENTRIES - 1, 32 .entries = &stack_dump_trace[0], 33 }; 34 35 static unsigned long max_stack_size; 36 static arch_spinlock_t max_stack_lock = 37 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; 38 39 static DEFINE_PER_CPU(int, trace_active); 40 static DEFINE_MUTEX(stack_sysctl_mutex); 41 42 int stack_tracer_enabled; 43 static int last_stack_tracer_enabled; 44 45 static inline void print_max_stack(void) 46 { 47 long i; 48 int size; 49 50 pr_emerg(" Depth Size Location (%d entries)\n" 51 " ----- ---- --------\n", 52 max_stack_trace.nr_entries); 53 54 for (i = 0; i < max_stack_trace.nr_entries; i++) { 55 if (stack_dump_trace[i] == ULONG_MAX) 56 break; 57 if (i+1 == max_stack_trace.nr_entries || 58 stack_dump_trace[i+1] == ULONG_MAX) 59 size = stack_dump_index[i]; 60 else 61 size = stack_dump_index[i] - stack_dump_index[i+1]; 62 63 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_dump_index[i], 64 size, (void *)stack_dump_trace[i]); 65 } 66 } 67 68 static inline void 69 check_stack(unsigned long ip, unsigned long *stack) 70 { 71 unsigned long this_size, flags; unsigned long *p, *top, *start; 72 static int tracer_frame; 73 int frame_size = ACCESS_ONCE(tracer_frame); 74 int i, x; 75 76 this_size = ((unsigned long)stack) & (THREAD_SIZE-1); 77 this_size = THREAD_SIZE - this_size; 78 /* Remove the frame of the tracer */ 79 this_size -= frame_size; 80 81 if (this_size <= max_stack_size) 82 return; 83 84 /* we do not handle interrupt stacks yet */ 85 if (!object_is_on_stack(stack)) 86 return; 87 88 /* Can't do this from NMI context (can cause deadlocks) */ 89 if (in_nmi()) 90 return; 91 92 local_irq_save(flags); 93 arch_spin_lock(&max_stack_lock); 94 95 /* 96 * RCU may not be watching, make it see us. 97 * The stack trace code uses rcu_sched. 98 */ 99 rcu_irq_enter(); 100 101 /* In case another CPU set the tracer_frame on us */ 102 if (unlikely(!frame_size)) 103 this_size -= tracer_frame; 104 105 /* a race could have already updated it */ 106 if (this_size <= max_stack_size) 107 goto out; 108 109 max_stack_size = this_size; 110 111 max_stack_trace.nr_entries = 0; 112 max_stack_trace.skip = 3; 113 114 save_stack_trace(&max_stack_trace); 115 116 /* Skip over the overhead of the stack tracer itself */ 117 for (i = 0; i < max_stack_trace.nr_entries; i++) { 118 if (stack_dump_trace[i] == ip) 119 break; 120 } 121 122 /* 123 * Now find where in the stack these are. 124 */ 125 x = 0; 126 start = stack; 127 top = (unsigned long *) 128 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); 129 130 /* 131 * Loop through all the entries. One of the entries may 132 * for some reason be missed on the stack, so we may 133 * have to account for them. If they are all there, this 134 * loop will only happen once. This code only takes place 135 * on a new max, so it is far from a fast path. 136 */ 137 while (i < max_stack_trace.nr_entries) { 138 int found = 0; 139 140 stack_dump_index[x] = this_size; 141 p = start; 142 143 for (; p < top && i < max_stack_trace.nr_entries; p++) { 144 if (stack_dump_trace[i] == ULONG_MAX) 145 break; 146 if (*p == stack_dump_trace[i]) { 147 stack_dump_trace[x] = stack_dump_trace[i++]; 148 this_size = stack_dump_index[x++] = 149 (top - p) * sizeof(unsigned long); 150 found = 1; 151 /* Start the search from here */ 152 start = p + 1; 153 /* 154 * We do not want to show the overhead 155 * of the stack tracer stack in the 156 * max stack. If we haven't figured 157 * out what that is, then figure it out 158 * now. 159 */ 160 if (unlikely(!tracer_frame)) { 161 tracer_frame = (p - stack) * 162 sizeof(unsigned long); 163 max_stack_size -= tracer_frame; 164 } 165 } 166 } 167 168 if (!found) 169 i++; 170 } 171 172 max_stack_trace.nr_entries = x; 173 for (; x < i; x++) 174 stack_dump_trace[x] = ULONG_MAX; 175 176 if (task_stack_end_corrupted(current)) { 177 print_max_stack(); 178 BUG(); 179 } 180 181 out: 182 rcu_irq_exit(); 183 arch_spin_unlock(&max_stack_lock); 184 local_irq_restore(flags); 185 } 186 187 static void 188 stack_trace_call(unsigned long ip, unsigned long parent_ip, 189 struct ftrace_ops *op, struct pt_regs *pt_regs) 190 { 191 unsigned long stack; 192 int cpu; 193 194 preempt_disable_notrace(); 195 196 cpu = raw_smp_processor_id(); 197 /* no atomic needed, we only modify this variable by this cpu */ 198 if (per_cpu(trace_active, cpu)++ != 0) 199 goto out; 200 201 ip += MCOUNT_INSN_SIZE; 202 203 check_stack(ip, &stack); 204 205 out: 206 per_cpu(trace_active, cpu)--; 207 /* prevent recursion in schedule */ 208 preempt_enable_notrace(); 209 } 210 211 static struct ftrace_ops trace_ops __read_mostly = 212 { 213 .func = stack_trace_call, 214 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 215 }; 216 217 static ssize_t 218 stack_max_size_read(struct file *filp, char __user *ubuf, 219 size_t count, loff_t *ppos) 220 { 221 unsigned long *ptr = filp->private_data; 222 char buf[64]; 223 int r; 224 225 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 226 if (r > sizeof(buf)) 227 r = sizeof(buf); 228 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 229 } 230 231 static ssize_t 232 stack_max_size_write(struct file *filp, const char __user *ubuf, 233 size_t count, loff_t *ppos) 234 { 235 long *ptr = filp->private_data; 236 unsigned long val, flags; 237 int ret; 238 int cpu; 239 240 ret = kstrtoul_from_user(ubuf, count, 10, &val); 241 if (ret) 242 return ret; 243 244 local_irq_save(flags); 245 246 /* 247 * In case we trace inside arch_spin_lock() or after (NMI), 248 * we will cause circular lock, so we also need to increase 249 * the percpu trace_active here. 250 */ 251 cpu = smp_processor_id(); 252 per_cpu(trace_active, cpu)++; 253 254 arch_spin_lock(&max_stack_lock); 255 *ptr = val; 256 arch_spin_unlock(&max_stack_lock); 257 258 per_cpu(trace_active, cpu)--; 259 local_irq_restore(flags); 260 261 return count; 262 } 263 264 static const struct file_operations stack_max_size_fops = { 265 .open = tracing_open_generic, 266 .read = stack_max_size_read, 267 .write = stack_max_size_write, 268 .llseek = default_llseek, 269 }; 270 271 static void * 272 __next(struct seq_file *m, loff_t *pos) 273 { 274 long n = *pos - 1; 275 276 if (n > max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX) 277 return NULL; 278 279 m->private = (void *)n; 280 return &m->private; 281 } 282 283 static void * 284 t_next(struct seq_file *m, void *v, loff_t *pos) 285 { 286 (*pos)++; 287 return __next(m, pos); 288 } 289 290 static void *t_start(struct seq_file *m, loff_t *pos) 291 { 292 int cpu; 293 294 local_irq_disable(); 295 296 cpu = smp_processor_id(); 297 per_cpu(trace_active, cpu)++; 298 299 arch_spin_lock(&max_stack_lock); 300 301 if (*pos == 0) 302 return SEQ_START_TOKEN; 303 304 return __next(m, pos); 305 } 306 307 static void t_stop(struct seq_file *m, void *p) 308 { 309 int cpu; 310 311 arch_spin_unlock(&max_stack_lock); 312 313 cpu = smp_processor_id(); 314 per_cpu(trace_active, cpu)--; 315 316 local_irq_enable(); 317 } 318 319 static void trace_lookup_stack(struct seq_file *m, long i) 320 { 321 unsigned long addr = stack_dump_trace[i]; 322 323 seq_printf(m, "%pS\n", (void *)addr); 324 } 325 326 static void print_disabled(struct seq_file *m) 327 { 328 seq_puts(m, "#\n" 329 "# Stack tracer disabled\n" 330 "#\n" 331 "# To enable the stack tracer, either add 'stacktrace' to the\n" 332 "# kernel command line\n" 333 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 334 "#\n"); 335 } 336 337 static int t_show(struct seq_file *m, void *v) 338 { 339 long i; 340 int size; 341 342 if (v == SEQ_START_TOKEN) { 343 seq_printf(m, " Depth Size Location" 344 " (%d entries)\n" 345 " ----- ---- --------\n", 346 max_stack_trace.nr_entries); 347 348 if (!stack_tracer_enabled && !max_stack_size) 349 print_disabled(m); 350 351 return 0; 352 } 353 354 i = *(long *)v; 355 356 if (i >= max_stack_trace.nr_entries || 357 stack_dump_trace[i] == ULONG_MAX) 358 return 0; 359 360 if (i+1 == max_stack_trace.nr_entries || 361 stack_dump_trace[i+1] == ULONG_MAX) 362 size = stack_dump_index[i]; 363 else 364 size = stack_dump_index[i] - stack_dump_index[i+1]; 365 366 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size); 367 368 trace_lookup_stack(m, i); 369 370 return 0; 371 } 372 373 static const struct seq_operations stack_trace_seq_ops = { 374 .start = t_start, 375 .next = t_next, 376 .stop = t_stop, 377 .show = t_show, 378 }; 379 380 static int stack_trace_open(struct inode *inode, struct file *file) 381 { 382 return seq_open(file, &stack_trace_seq_ops); 383 } 384 385 static const struct file_operations stack_trace_fops = { 386 .open = stack_trace_open, 387 .read = seq_read, 388 .llseek = seq_lseek, 389 .release = seq_release, 390 }; 391 392 static int 393 stack_trace_filter_open(struct inode *inode, struct file *file) 394 { 395 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER, 396 inode, file); 397 } 398 399 static const struct file_operations stack_trace_filter_fops = { 400 .open = stack_trace_filter_open, 401 .read = seq_read, 402 .write = ftrace_filter_write, 403 .llseek = tracing_lseek, 404 .release = ftrace_regex_release, 405 }; 406 407 int 408 stack_trace_sysctl(struct ctl_table *table, int write, 409 void __user *buffer, size_t *lenp, 410 loff_t *ppos) 411 { 412 int ret; 413 414 mutex_lock(&stack_sysctl_mutex); 415 416 ret = proc_dointvec(table, write, buffer, lenp, ppos); 417 418 if (ret || !write || 419 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 420 goto out; 421 422 last_stack_tracer_enabled = !!stack_tracer_enabled; 423 424 if (stack_tracer_enabled) 425 register_ftrace_function(&trace_ops); 426 else 427 unregister_ftrace_function(&trace_ops); 428 429 out: 430 mutex_unlock(&stack_sysctl_mutex); 431 return ret; 432 } 433 434 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 435 436 static __init int enable_stacktrace(char *str) 437 { 438 if (strncmp(str, "_filter=", 8) == 0) 439 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE); 440 441 stack_tracer_enabled = 1; 442 last_stack_tracer_enabled = 1; 443 return 1; 444 } 445 __setup("stacktrace", enable_stacktrace); 446 447 static __init int stack_trace_init(void) 448 { 449 struct dentry *d_tracer; 450 451 d_tracer = tracing_init_dentry(); 452 if (IS_ERR(d_tracer)) 453 return 0; 454 455 trace_create_file("stack_max_size", 0644, d_tracer, 456 &max_stack_size, &stack_max_size_fops); 457 458 trace_create_file("stack_trace", 0444, d_tracer, 459 NULL, &stack_trace_fops); 460 461 trace_create_file("stack_trace_filter", 0444, d_tracer, 462 NULL, &stack_trace_filter_fops); 463 464 if (stack_trace_filter_buf[0]) 465 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); 466 467 if (stack_tracer_enabled) 468 register_ftrace_function(&trace_ops); 469 470 return 0; 471 } 472 473 device_initcall(stack_trace_init); 474