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 DEFINE_PER_CPU(int, disable_stack_tracer); 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 /* In case another CPU set the tracer_frame on us */ 103 if (unlikely(!frame_size)) 104 this_size -= tracer_frame; 105 106 /* a race could have already updated it */ 107 if (this_size <= stack_trace_max_size) 108 goto out; 109 110 stack_trace_max_size = this_size; 111 112 stack_trace_max.nr_entries = 0; 113 stack_trace_max.skip = 3; 114 115 save_stack_trace(&stack_trace_max); 116 117 /* Skip over the overhead of the stack tracer itself */ 118 for (i = 0; i < stack_trace_max.nr_entries; i++) { 119 if (stack_dump_trace[i] == ip) 120 break; 121 } 122 123 /* 124 * Some archs may not have the passed in ip in the dump. 125 * If that happens, we need to show everything. 126 */ 127 if (i == stack_trace_max.nr_entries) 128 i = 0; 129 130 /* 131 * Now find where in the stack these are. 132 */ 133 x = 0; 134 start = stack; 135 top = (unsigned long *) 136 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); 137 138 /* 139 * Loop through all the entries. One of the entries may 140 * for some reason be missed on the stack, so we may 141 * have to account for them. If they are all there, this 142 * loop will only happen once. This code only takes place 143 * on a new max, so it is far from a fast path. 144 */ 145 while (i < stack_trace_max.nr_entries) { 146 int found = 0; 147 148 stack_trace_index[x] = this_size; 149 p = start; 150 151 for (; p < top && i < stack_trace_max.nr_entries; p++) { 152 if (stack_dump_trace[i] == ULONG_MAX) 153 break; 154 /* 155 * The READ_ONCE_NOCHECK is used to let KASAN know that 156 * this is not a stack-out-of-bounds error. 157 */ 158 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) { 159 stack_dump_trace[x] = stack_dump_trace[i++]; 160 this_size = stack_trace_index[x++] = 161 (top - p) * sizeof(unsigned long); 162 found = 1; 163 /* Start the search from here */ 164 start = p + 1; 165 /* 166 * We do not want to show the overhead 167 * of the stack tracer stack in the 168 * max stack. If we haven't figured 169 * out what that is, then figure it out 170 * now. 171 */ 172 if (unlikely(!tracer_frame)) { 173 tracer_frame = (p - stack) * 174 sizeof(unsigned long); 175 stack_trace_max_size -= tracer_frame; 176 } 177 } 178 } 179 180 if (!found) 181 i++; 182 } 183 184 stack_trace_max.nr_entries = x; 185 for (; x < i; x++) 186 stack_dump_trace[x] = ULONG_MAX; 187 188 if (task_stack_end_corrupted(current)) { 189 stack_trace_print(); 190 BUG(); 191 } 192 193 out: 194 arch_spin_unlock(&stack_trace_max_lock); 195 local_irq_restore(flags); 196 } 197 198 static void 199 stack_trace_call(unsigned long ip, unsigned long parent_ip, 200 struct ftrace_ops *op, struct pt_regs *pt_regs) 201 { 202 unsigned long stack; 203 204 preempt_disable_notrace(); 205 206 /* no atomic needed, we only modify this variable by this cpu */ 207 __this_cpu_inc(disable_stack_tracer); 208 if (__this_cpu_read(disable_stack_tracer) != 1) 209 goto out; 210 211 ip += MCOUNT_INSN_SIZE; 212 213 check_stack(ip, &stack); 214 215 out: 216 __this_cpu_dec(disable_stack_tracer); 217 /* prevent recursion in schedule */ 218 preempt_enable_notrace(); 219 } 220 221 static struct ftrace_ops trace_ops __read_mostly = 222 { 223 .func = stack_trace_call, 224 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 225 }; 226 227 static ssize_t 228 stack_max_size_read(struct file *filp, char __user *ubuf, 229 size_t count, loff_t *ppos) 230 { 231 unsigned long *ptr = filp->private_data; 232 char buf[64]; 233 int r; 234 235 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 236 if (r > sizeof(buf)) 237 r = sizeof(buf); 238 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 239 } 240 241 static ssize_t 242 stack_max_size_write(struct file *filp, const char __user *ubuf, 243 size_t count, loff_t *ppos) 244 { 245 long *ptr = filp->private_data; 246 unsigned long val, flags; 247 int ret; 248 249 ret = kstrtoul_from_user(ubuf, count, 10, &val); 250 if (ret) 251 return ret; 252 253 local_irq_save(flags); 254 255 /* 256 * In case we trace inside arch_spin_lock() or after (NMI), 257 * we will cause circular lock, so we also need to increase 258 * the percpu disable_stack_tracer here. 259 */ 260 __this_cpu_inc(disable_stack_tracer); 261 262 arch_spin_lock(&stack_trace_max_lock); 263 *ptr = val; 264 arch_spin_unlock(&stack_trace_max_lock); 265 266 __this_cpu_dec(disable_stack_tracer); 267 local_irq_restore(flags); 268 269 return count; 270 } 271 272 static const struct file_operations stack_max_size_fops = { 273 .open = tracing_open_generic, 274 .read = stack_max_size_read, 275 .write = stack_max_size_write, 276 .llseek = default_llseek, 277 }; 278 279 static void * 280 __next(struct seq_file *m, loff_t *pos) 281 { 282 long n = *pos - 1; 283 284 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX) 285 return NULL; 286 287 m->private = (void *)n; 288 return &m->private; 289 } 290 291 static void * 292 t_next(struct seq_file *m, void *v, loff_t *pos) 293 { 294 (*pos)++; 295 return __next(m, pos); 296 } 297 298 static void *t_start(struct seq_file *m, loff_t *pos) 299 { 300 local_irq_disable(); 301 302 __this_cpu_inc(disable_stack_tracer); 303 304 arch_spin_lock(&stack_trace_max_lock); 305 306 if (*pos == 0) 307 return SEQ_START_TOKEN; 308 309 return __next(m, pos); 310 } 311 312 static void t_stop(struct seq_file *m, void *p) 313 { 314 arch_spin_unlock(&stack_trace_max_lock); 315 316 __this_cpu_dec(disable_stack_tracer); 317 318 local_irq_enable(); 319 } 320 321 static void trace_lookup_stack(struct seq_file *m, long i) 322 { 323 unsigned long addr = stack_dump_trace[i]; 324 325 seq_printf(m, "%pS\n", (void *)addr); 326 } 327 328 static void print_disabled(struct seq_file *m) 329 { 330 seq_puts(m, "#\n" 331 "# Stack tracer disabled\n" 332 "#\n" 333 "# To enable the stack tracer, either add 'stacktrace' to the\n" 334 "# kernel command line\n" 335 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 336 "#\n"); 337 } 338 339 static int t_show(struct seq_file *m, void *v) 340 { 341 long i; 342 int size; 343 344 if (v == SEQ_START_TOKEN) { 345 seq_printf(m, " Depth Size Location" 346 " (%d entries)\n" 347 " ----- ---- --------\n", 348 stack_trace_max.nr_entries); 349 350 if (!stack_tracer_enabled && !stack_trace_max_size) 351 print_disabled(m); 352 353 return 0; 354 } 355 356 i = *(long *)v; 357 358 if (i >= stack_trace_max.nr_entries || 359 stack_dump_trace[i] == ULONG_MAX) 360 return 0; 361 362 if (i+1 == stack_trace_max.nr_entries || 363 stack_dump_trace[i+1] == ULONG_MAX) 364 size = stack_trace_index[i]; 365 else 366 size = stack_trace_index[i] - stack_trace_index[i+1]; 367 368 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size); 369 370 trace_lookup_stack(m, i); 371 372 return 0; 373 } 374 375 static const struct seq_operations stack_trace_seq_ops = { 376 .start = t_start, 377 .next = t_next, 378 .stop = t_stop, 379 .show = t_show, 380 }; 381 382 static int stack_trace_open(struct inode *inode, struct file *file) 383 { 384 return seq_open(file, &stack_trace_seq_ops); 385 } 386 387 static const struct file_operations stack_trace_fops = { 388 .open = stack_trace_open, 389 .read = seq_read, 390 .llseek = seq_lseek, 391 .release = seq_release, 392 }; 393 394 #ifdef CONFIG_DYNAMIC_FTRACE 395 396 static int 397 stack_trace_filter_open(struct inode *inode, struct file *file) 398 { 399 struct ftrace_ops *ops = inode->i_private; 400 401 return ftrace_regex_open(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 #endif /* CONFIG_DYNAMIC_FTRACE */ 414 415 int 416 stack_trace_sysctl(struct ctl_table *table, int write, 417 void __user *buffer, size_t *lenp, 418 loff_t *ppos) 419 { 420 int ret; 421 422 mutex_lock(&stack_sysctl_mutex); 423 424 ret = proc_dointvec(table, write, buffer, lenp, ppos); 425 426 if (ret || !write || 427 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 428 goto out; 429 430 last_stack_tracer_enabled = !!stack_tracer_enabled; 431 432 if (stack_tracer_enabled) 433 register_ftrace_function(&trace_ops); 434 else 435 unregister_ftrace_function(&trace_ops); 436 437 out: 438 mutex_unlock(&stack_sysctl_mutex); 439 return ret; 440 } 441 442 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 443 444 static __init int enable_stacktrace(char *str) 445 { 446 if (strncmp(str, "_filter=", 8) == 0) 447 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE); 448 449 stack_tracer_enabled = 1; 450 last_stack_tracer_enabled = 1; 451 return 1; 452 } 453 __setup("stacktrace", enable_stacktrace); 454 455 static __init int stack_trace_init(void) 456 { 457 struct dentry *d_tracer; 458 459 d_tracer = tracing_init_dentry(); 460 if (IS_ERR(d_tracer)) 461 return 0; 462 463 trace_create_file("stack_max_size", 0644, d_tracer, 464 &stack_trace_max_size, &stack_max_size_fops); 465 466 trace_create_file("stack_trace", 0444, d_tracer, 467 NULL, &stack_trace_fops); 468 469 #ifdef CONFIG_DYNAMIC_FTRACE 470 trace_create_file("stack_trace_filter", 0444, d_tracer, 471 &trace_ops, &stack_trace_filter_fops); 472 #endif 473 474 if (stack_trace_filter_buf[0]) 475 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); 476 477 if (stack_tracer_enabled) 478 register_ftrace_function(&trace_ops); 479 480 return 0; 481 } 482 483 device_initcall(stack_trace_init); 484