1 /* 2 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> 3 * 4 */ 5 #include <linux/sched/task_stack.h> 6 #include <linux/stacktrace.h> 7 #include <linux/kallsyms.h> 8 #include <linux/seq_file.h> 9 #include <linux/spinlock.h> 10 #include <linux/uaccess.h> 11 #include <linux/ftrace.h> 12 #include <linux/module.h> 13 #include <linux/sysctl.h> 14 #include <linux/init.h> 15 16 #include <asm/setup.h> 17 18 #include "trace.h" 19 20 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] = 21 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX }; 22 unsigned stack_trace_index[STACK_TRACE_ENTRIES]; 23 24 /* 25 * Reserve one entry for the passed in ip. This will allow 26 * us to remove most or all of the stack size overhead 27 * added by the stack tracer itself. 28 */ 29 struct stack_trace stack_trace_max = { 30 .max_entries = STACK_TRACE_ENTRIES - 1, 31 .entries = &stack_dump_trace[0], 32 }; 33 34 unsigned long stack_trace_max_size; 35 arch_spinlock_t stack_trace_max_lock = 36 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; 37 38 static DEFINE_PER_CPU(int, trace_active); 39 static DEFINE_MUTEX(stack_sysctl_mutex); 40 41 int stack_tracer_enabled; 42 static int last_stack_tracer_enabled; 43 44 void stack_trace_print(void) 45 { 46 long i; 47 int size; 48 49 pr_emerg(" Depth Size Location (%d entries)\n" 50 " ----- ---- --------\n", 51 stack_trace_max.nr_entries); 52 53 for (i = 0; i < stack_trace_max.nr_entries; i++) { 54 if (stack_dump_trace[i] == ULONG_MAX) 55 break; 56 if (i+1 == stack_trace_max.nr_entries || 57 stack_dump_trace[i+1] == ULONG_MAX) 58 size = stack_trace_index[i]; 59 else 60 size = stack_trace_index[i] - stack_trace_index[i+1]; 61 62 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i], 63 size, (void *)stack_dump_trace[i]); 64 } 65 } 66 67 /* 68 * When arch-specific code overrides this function, the following 69 * data should be filled up, assuming stack_trace_max_lock is held to 70 * prevent concurrent updates. 71 * stack_trace_index[] 72 * stack_trace_max 73 * stack_trace_max_size 74 */ 75 void __weak 76 check_stack(unsigned long ip, unsigned long *stack) 77 { 78 unsigned long this_size, flags; unsigned long *p, *top, *start; 79 static int tracer_frame; 80 int frame_size = ACCESS_ONCE(tracer_frame); 81 int i, x; 82 83 this_size = ((unsigned long)stack) & (THREAD_SIZE-1); 84 this_size = THREAD_SIZE - this_size; 85 /* Remove the frame of the tracer */ 86 this_size -= frame_size; 87 88 if (this_size <= stack_trace_max_size) 89 return; 90 91 /* we do not handle interrupt stacks yet */ 92 if (!object_is_on_stack(stack)) 93 return; 94 95 /* Can't do this from NMI context (can cause deadlocks) */ 96 if (in_nmi()) 97 return; 98 99 local_irq_save(flags); 100 arch_spin_lock(&stack_trace_max_lock); 101 102 /* 103 * RCU may not be watching, make it see us. 104 * The stack trace code uses rcu_sched. 105 */ 106 rcu_irq_enter(); 107 108 /* In case another CPU set the tracer_frame on us */ 109 if (unlikely(!frame_size)) 110 this_size -= tracer_frame; 111 112 /* a race could have already updated it */ 113 if (this_size <= stack_trace_max_size) 114 goto out; 115 116 stack_trace_max_size = this_size; 117 118 stack_trace_max.nr_entries = 0; 119 stack_trace_max.skip = 3; 120 121 save_stack_trace(&stack_trace_max); 122 123 /* Skip over the overhead of the stack tracer itself */ 124 for (i = 0; i < stack_trace_max.nr_entries; i++) { 125 if (stack_dump_trace[i] == ip) 126 break; 127 } 128 129 /* 130 * Some archs may not have the passed in ip in the dump. 131 * If that happens, we need to show everything. 132 */ 133 if (i == stack_trace_max.nr_entries) 134 i = 0; 135 136 /* 137 * Now find where in the stack these are. 138 */ 139 x = 0; 140 start = stack; 141 top = (unsigned long *) 142 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); 143 144 /* 145 * Loop through all the entries. One of the entries may 146 * for some reason be missed on the stack, so we may 147 * have to account for them. If they are all there, this 148 * loop will only happen once. This code only takes place 149 * on a new max, so it is far from a fast path. 150 */ 151 while (i < stack_trace_max.nr_entries) { 152 int found = 0; 153 154 stack_trace_index[x] = this_size; 155 p = start; 156 157 for (; p < top && i < stack_trace_max.nr_entries; p++) { 158 if (stack_dump_trace[i] == ULONG_MAX) 159 break; 160 /* 161 * The READ_ONCE_NOCHECK is used to let KASAN know that 162 * this is not a stack-out-of-bounds error. 163 */ 164 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) { 165 stack_dump_trace[x] = stack_dump_trace[i++]; 166 this_size = stack_trace_index[x++] = 167 (top - p) * sizeof(unsigned long); 168 found = 1; 169 /* Start the search from here */ 170 start = p + 1; 171 /* 172 * We do not want to show the overhead 173 * of the stack tracer stack in the 174 * max stack. If we haven't figured 175 * out what that is, then figure it out 176 * now. 177 */ 178 if (unlikely(!tracer_frame)) { 179 tracer_frame = (p - stack) * 180 sizeof(unsigned long); 181 stack_trace_max_size -= tracer_frame; 182 } 183 } 184 } 185 186 if (!found) 187 i++; 188 } 189 190 stack_trace_max.nr_entries = x; 191 for (; x < i; x++) 192 stack_dump_trace[x] = ULONG_MAX; 193 194 if (task_stack_end_corrupted(current)) { 195 stack_trace_print(); 196 BUG(); 197 } 198 199 out: 200 rcu_irq_exit(); 201 arch_spin_unlock(&stack_trace_max_lock); 202 local_irq_restore(flags); 203 } 204 205 static void 206 stack_trace_call(unsigned long ip, unsigned long parent_ip, 207 struct ftrace_ops *op, struct pt_regs *pt_regs) 208 { 209 unsigned long stack; 210 int cpu; 211 212 preempt_disable_notrace(); 213 214 cpu = raw_smp_processor_id(); 215 /* no atomic needed, we only modify this variable by this cpu */ 216 if (per_cpu(trace_active, cpu)++ != 0) 217 goto out; 218 219 ip += MCOUNT_INSN_SIZE; 220 221 check_stack(ip, &stack); 222 223 out: 224 per_cpu(trace_active, cpu)--; 225 /* prevent recursion in schedule */ 226 preempt_enable_notrace(); 227 } 228 229 static struct ftrace_ops trace_ops __read_mostly = 230 { 231 .func = stack_trace_call, 232 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 233 }; 234 235 static ssize_t 236 stack_max_size_read(struct file *filp, char __user *ubuf, 237 size_t count, loff_t *ppos) 238 { 239 unsigned long *ptr = filp->private_data; 240 char buf[64]; 241 int r; 242 243 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 244 if (r > sizeof(buf)) 245 r = sizeof(buf); 246 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 247 } 248 249 static ssize_t 250 stack_max_size_write(struct file *filp, const char __user *ubuf, 251 size_t count, loff_t *ppos) 252 { 253 long *ptr = filp->private_data; 254 unsigned long val, flags; 255 int ret; 256 int cpu; 257 258 ret = kstrtoul_from_user(ubuf, count, 10, &val); 259 if (ret) 260 return ret; 261 262 local_irq_save(flags); 263 264 /* 265 * In case we trace inside arch_spin_lock() or after (NMI), 266 * we will cause circular lock, so we also need to increase 267 * the percpu trace_active here. 268 */ 269 cpu = smp_processor_id(); 270 per_cpu(trace_active, cpu)++; 271 272 arch_spin_lock(&stack_trace_max_lock); 273 *ptr = val; 274 arch_spin_unlock(&stack_trace_max_lock); 275 276 per_cpu(trace_active, cpu)--; 277 local_irq_restore(flags); 278 279 return count; 280 } 281 282 static const struct file_operations stack_max_size_fops = { 283 .open = tracing_open_generic, 284 .read = stack_max_size_read, 285 .write = stack_max_size_write, 286 .llseek = default_llseek, 287 }; 288 289 static void * 290 __next(struct seq_file *m, loff_t *pos) 291 { 292 long n = *pos - 1; 293 294 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX) 295 return NULL; 296 297 m->private = (void *)n; 298 return &m->private; 299 } 300 301 static void * 302 t_next(struct seq_file *m, void *v, loff_t *pos) 303 { 304 (*pos)++; 305 return __next(m, pos); 306 } 307 308 static void *t_start(struct seq_file *m, loff_t *pos) 309 { 310 int cpu; 311 312 local_irq_disable(); 313 314 cpu = smp_processor_id(); 315 per_cpu(trace_active, cpu)++; 316 317 arch_spin_lock(&stack_trace_max_lock); 318 319 if (*pos == 0) 320 return SEQ_START_TOKEN; 321 322 return __next(m, pos); 323 } 324 325 static void t_stop(struct seq_file *m, void *p) 326 { 327 int cpu; 328 329 arch_spin_unlock(&stack_trace_max_lock); 330 331 cpu = smp_processor_id(); 332 per_cpu(trace_active, cpu)--; 333 334 local_irq_enable(); 335 } 336 337 static void trace_lookup_stack(struct seq_file *m, long i) 338 { 339 unsigned long addr = stack_dump_trace[i]; 340 341 seq_printf(m, "%pS\n", (void *)addr); 342 } 343 344 static void print_disabled(struct seq_file *m) 345 { 346 seq_puts(m, "#\n" 347 "# Stack tracer disabled\n" 348 "#\n" 349 "# To enable the stack tracer, either add 'stacktrace' to the\n" 350 "# kernel command line\n" 351 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 352 "#\n"); 353 } 354 355 static int t_show(struct seq_file *m, void *v) 356 { 357 long i; 358 int size; 359 360 if (v == SEQ_START_TOKEN) { 361 seq_printf(m, " Depth Size Location" 362 " (%d entries)\n" 363 " ----- ---- --------\n", 364 stack_trace_max.nr_entries); 365 366 if (!stack_tracer_enabled && !stack_trace_max_size) 367 print_disabled(m); 368 369 return 0; 370 } 371 372 i = *(long *)v; 373 374 if (i >= stack_trace_max.nr_entries || 375 stack_dump_trace[i] == ULONG_MAX) 376 return 0; 377 378 if (i+1 == stack_trace_max.nr_entries || 379 stack_dump_trace[i+1] == ULONG_MAX) 380 size = stack_trace_index[i]; 381 else 382 size = stack_trace_index[i] - stack_trace_index[i+1]; 383 384 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size); 385 386 trace_lookup_stack(m, i); 387 388 return 0; 389 } 390 391 static const struct seq_operations stack_trace_seq_ops = { 392 .start = t_start, 393 .next = t_next, 394 .stop = t_stop, 395 .show = t_show, 396 }; 397 398 static int stack_trace_open(struct inode *inode, struct file *file) 399 { 400 return seq_open(file, &stack_trace_seq_ops); 401 } 402 403 static const struct file_operations stack_trace_fops = { 404 .open = stack_trace_open, 405 .read = seq_read, 406 .llseek = seq_lseek, 407 .release = seq_release, 408 }; 409 410 static int 411 stack_trace_filter_open(struct inode *inode, struct file *file) 412 { 413 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER, 414 inode, file); 415 } 416 417 static const struct file_operations stack_trace_filter_fops = { 418 .open = stack_trace_filter_open, 419 .read = seq_read, 420 .write = ftrace_filter_write, 421 .llseek = tracing_lseek, 422 .release = ftrace_regex_release, 423 }; 424 425 int 426 stack_trace_sysctl(struct ctl_table *table, int write, 427 void __user *buffer, size_t *lenp, 428 loff_t *ppos) 429 { 430 int ret; 431 432 mutex_lock(&stack_sysctl_mutex); 433 434 ret = proc_dointvec(table, write, buffer, lenp, ppos); 435 436 if (ret || !write || 437 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 438 goto out; 439 440 last_stack_tracer_enabled = !!stack_tracer_enabled; 441 442 if (stack_tracer_enabled) 443 register_ftrace_function(&trace_ops); 444 else 445 unregister_ftrace_function(&trace_ops); 446 447 out: 448 mutex_unlock(&stack_sysctl_mutex); 449 return ret; 450 } 451 452 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 453 454 static __init int enable_stacktrace(char *str) 455 { 456 if (strncmp(str, "_filter=", 8) == 0) 457 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE); 458 459 stack_tracer_enabled = 1; 460 last_stack_tracer_enabled = 1; 461 return 1; 462 } 463 __setup("stacktrace", enable_stacktrace); 464 465 static __init int stack_trace_init(void) 466 { 467 struct dentry *d_tracer; 468 469 d_tracer = tracing_init_dentry(); 470 if (IS_ERR(d_tracer)) 471 return 0; 472 473 trace_create_file("stack_max_size", 0644, d_tracer, 474 &stack_trace_max_size, &stack_max_size_fops); 475 476 trace_create_file("stack_trace", 0444, d_tracer, 477 NULL, &stack_trace_fops); 478 479 trace_create_file("stack_trace_filter", 0444, d_tracer, 480 NULL, &stack_trace_filter_fops); 481 482 if (stack_trace_filter_buf[0]) 483 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); 484 485 if (stack_tracer_enabled) 486 register_ftrace_function(&trace_ops); 487 488 return 0; 489 } 490 491 device_initcall(stack_trace_init); 492