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