1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> 4 * 5 */ 6 #include <linux/sched/task_stack.h> 7 #include <linux/stacktrace.h> 8 #include <linux/kallsyms.h> 9 #include <linux/seq_file.h> 10 #include <linux/spinlock.h> 11 #include <linux/uaccess.h> 12 #include <linux/ftrace.h> 13 #include <linux/module.h> 14 #include <linux/sysctl.h> 15 #include <linux/init.h> 16 17 #include <asm/setup.h> 18 19 #include "trace.h" 20 21 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] = 22 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX }; 23 unsigned stack_trace_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 struct stack_trace stack_trace_max = { 31 .max_entries = STACK_TRACE_ENTRIES - 1, 32 .entries = &stack_dump_trace[0], 33 }; 34 35 unsigned long stack_trace_max_size; 36 arch_spinlock_t stack_trace_max_lock = 37 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; 38 39 DEFINE_PER_CPU(int, disable_stack_tracer); 40 static DEFINE_MUTEX(stack_sysctl_mutex); 41 42 int stack_tracer_enabled; 43 static int last_stack_tracer_enabled; 44 45 void stack_trace_print(void) 46 { 47 long i; 48 int size; 49 50 pr_emerg(" Depth Size Location (%d entries)\n" 51 " ----- ---- --------\n", 52 stack_trace_max.nr_entries); 53 54 for (i = 0; i < stack_trace_max.nr_entries; i++) { 55 if (stack_dump_trace[i] == ULONG_MAX) 56 break; 57 if (i+1 == stack_trace_max.nr_entries || 58 stack_dump_trace[i+1] == ULONG_MAX) 59 size = stack_trace_index[i]; 60 else 61 size = stack_trace_index[i] - stack_trace_index[i+1]; 62 63 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i], 64 size, (void *)stack_dump_trace[i]); 65 } 66 } 67 68 /* 69 * When arch-specific code overrides this function, the following 70 * data should be filled up, assuming stack_trace_max_lock is held to 71 * prevent concurrent updates. 72 * stack_trace_index[] 73 * stack_trace_max 74 * stack_trace_max_size 75 */ 76 void __weak 77 check_stack(unsigned long ip, unsigned long *stack) 78 { 79 unsigned long this_size, flags; unsigned long *p, *top, *start; 80 static int tracer_frame; 81 int frame_size = READ_ONCE(tracer_frame); 82 int i, x; 83 84 this_size = ((unsigned long)stack) & (THREAD_SIZE-1); 85 this_size = THREAD_SIZE - this_size; 86 /* Remove the frame of the tracer */ 87 this_size -= frame_size; 88 89 if (this_size <= stack_trace_max_size) 90 return; 91 92 /* we do not handle interrupt stacks yet */ 93 if (!object_is_on_stack(stack)) 94 return; 95 96 /* Can't do this from NMI context (can cause deadlocks) */ 97 if (in_nmi()) 98 return; 99 100 local_irq_save(flags); 101 arch_spin_lock(&stack_trace_max_lock); 102 103 /* In case another CPU set the tracer_frame on us */ 104 if (unlikely(!frame_size)) 105 this_size -= tracer_frame; 106 107 /* a race could have already updated it */ 108 if (this_size <= stack_trace_max_size) 109 goto out; 110 111 stack_trace_max_size = this_size; 112 113 stack_trace_max.nr_entries = 0; 114 stack_trace_max.skip = 0; 115 116 save_stack_trace(&stack_trace_max); 117 118 /* Skip over the overhead of the stack tracer itself */ 119 for (i = 0; i < stack_trace_max.nr_entries; i++) { 120 if (stack_dump_trace[i] == ip) 121 break; 122 } 123 124 /* 125 * Some archs may not have the passed in ip in the dump. 126 * If that happens, we need to show everything. 127 */ 128 if (i == stack_trace_max.nr_entries) 129 i = 0; 130 131 /* 132 * Now find where in the stack these are. 133 */ 134 x = 0; 135 start = stack; 136 top = (unsigned long *) 137 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); 138 139 /* 140 * Loop through all the entries. One of the entries may 141 * for some reason be missed on the stack, so we may 142 * have to account for them. If they are all there, this 143 * loop will only happen once. This code only takes place 144 * on a new max, so it is far from a fast path. 145 */ 146 while (i < stack_trace_max.nr_entries) { 147 int found = 0; 148 149 stack_trace_index[x] = this_size; 150 p = start; 151 152 for (; p < top && i < stack_trace_max.nr_entries; p++) { 153 if (stack_dump_trace[i] == ULONG_MAX) 154 break; 155 /* 156 * The READ_ONCE_NOCHECK is used to let KASAN know that 157 * this is not a stack-out-of-bounds error. 158 */ 159 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) { 160 stack_dump_trace[x] = stack_dump_trace[i++]; 161 this_size = stack_trace_index[x++] = 162 (top - p) * sizeof(unsigned long); 163 found = 1; 164 /* Start the search from here */ 165 start = p + 1; 166 /* 167 * We do not want to show the overhead 168 * of the stack tracer stack in the 169 * max stack. If we haven't figured 170 * out what that is, then figure it out 171 * now. 172 */ 173 if (unlikely(!tracer_frame)) { 174 tracer_frame = (p - stack) * 175 sizeof(unsigned long); 176 stack_trace_max_size -= tracer_frame; 177 } 178 } 179 } 180 181 if (!found) 182 i++; 183 } 184 185 stack_trace_max.nr_entries = x; 186 for (; x < i; x++) 187 stack_dump_trace[x] = ULONG_MAX; 188 189 if (task_stack_end_corrupted(current)) { 190 stack_trace_print(); 191 BUG(); 192 } 193 194 out: 195 arch_spin_unlock(&stack_trace_max_lock); 196 local_irq_restore(flags); 197 } 198 199 static void 200 stack_trace_call(unsigned long ip, unsigned long parent_ip, 201 struct ftrace_ops *op, struct pt_regs *pt_regs) 202 { 203 unsigned long stack; 204 205 preempt_disable_notrace(); 206 207 /* no atomic needed, we only modify this variable by this cpu */ 208 __this_cpu_inc(disable_stack_tracer); 209 if (__this_cpu_read(disable_stack_tracer) != 1) 210 goto out; 211 212 /* If rcu is not watching, then save stack trace can fail */ 213 if (!rcu_is_watching()) 214 goto out; 215 216 ip += MCOUNT_INSN_SIZE; 217 218 check_stack(ip, &stack); 219 220 out: 221 __this_cpu_dec(disable_stack_tracer); 222 /* prevent recursion in schedule */ 223 preempt_enable_notrace(); 224 } 225 226 static struct ftrace_ops trace_ops __read_mostly = 227 { 228 .func = stack_trace_call, 229 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 230 }; 231 232 static ssize_t 233 stack_max_size_read(struct file *filp, char __user *ubuf, 234 size_t count, loff_t *ppos) 235 { 236 unsigned long *ptr = filp->private_data; 237 char buf[64]; 238 int r; 239 240 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 241 if (r > sizeof(buf)) 242 r = sizeof(buf); 243 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 244 } 245 246 static ssize_t 247 stack_max_size_write(struct file *filp, const char __user *ubuf, 248 size_t count, loff_t *ppos) 249 { 250 long *ptr = filp->private_data; 251 unsigned long val, flags; 252 int ret; 253 254 ret = kstrtoul_from_user(ubuf, count, 10, &val); 255 if (ret) 256 return ret; 257 258 local_irq_save(flags); 259 260 /* 261 * In case we trace inside arch_spin_lock() or after (NMI), 262 * we will cause circular lock, so we also need to increase 263 * the percpu disable_stack_tracer here. 264 */ 265 __this_cpu_inc(disable_stack_tracer); 266 267 arch_spin_lock(&stack_trace_max_lock); 268 *ptr = val; 269 arch_spin_unlock(&stack_trace_max_lock); 270 271 __this_cpu_dec(disable_stack_tracer); 272 local_irq_restore(flags); 273 274 return count; 275 } 276 277 static const struct file_operations stack_max_size_fops = { 278 .open = tracing_open_generic, 279 .read = stack_max_size_read, 280 .write = stack_max_size_write, 281 .llseek = default_llseek, 282 }; 283 284 static void * 285 __next(struct seq_file *m, loff_t *pos) 286 { 287 long n = *pos - 1; 288 289 if (n >= stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX) 290 return NULL; 291 292 m->private = (void *)n; 293 return &m->private; 294 } 295 296 static void * 297 t_next(struct seq_file *m, void *v, loff_t *pos) 298 { 299 (*pos)++; 300 return __next(m, pos); 301 } 302 303 static void *t_start(struct seq_file *m, loff_t *pos) 304 { 305 local_irq_disable(); 306 307 __this_cpu_inc(disable_stack_tracer); 308 309 arch_spin_lock(&stack_trace_max_lock); 310 311 if (*pos == 0) 312 return SEQ_START_TOKEN; 313 314 return __next(m, pos); 315 } 316 317 static void t_stop(struct seq_file *m, void *p) 318 { 319 arch_spin_unlock(&stack_trace_max_lock); 320 321 __this_cpu_dec(disable_stack_tracer); 322 323 local_irq_enable(); 324 } 325 326 static void trace_lookup_stack(struct seq_file *m, long i) 327 { 328 unsigned long addr = stack_dump_trace[i]; 329 330 seq_printf(m, "%pS\n", (void *)addr); 331 } 332 333 static void print_disabled(struct seq_file *m) 334 { 335 seq_puts(m, "#\n" 336 "# Stack tracer disabled\n" 337 "#\n" 338 "# To enable the stack tracer, either add 'stacktrace' to the\n" 339 "# kernel command line\n" 340 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 341 "#\n"); 342 } 343 344 static int t_show(struct seq_file *m, void *v) 345 { 346 long i; 347 int size; 348 349 if (v == SEQ_START_TOKEN) { 350 seq_printf(m, " Depth Size Location" 351 " (%d entries)\n" 352 " ----- ---- --------\n", 353 stack_trace_max.nr_entries); 354 355 if (!stack_tracer_enabled && !stack_trace_max_size) 356 print_disabled(m); 357 358 return 0; 359 } 360 361 i = *(long *)v; 362 363 if (i >= stack_trace_max.nr_entries || 364 stack_dump_trace[i] == ULONG_MAX) 365 return 0; 366 367 if (i+1 == stack_trace_max.nr_entries || 368 stack_dump_trace[i+1] == ULONG_MAX) 369 size = stack_trace_index[i]; 370 else 371 size = stack_trace_index[i] - stack_trace_index[i+1]; 372 373 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size); 374 375 trace_lookup_stack(m, i); 376 377 return 0; 378 } 379 380 static const struct seq_operations stack_trace_seq_ops = { 381 .start = t_start, 382 .next = t_next, 383 .stop = t_stop, 384 .show = t_show, 385 }; 386 387 static int stack_trace_open(struct inode *inode, struct file *file) 388 { 389 return seq_open(file, &stack_trace_seq_ops); 390 } 391 392 static const struct file_operations stack_trace_fops = { 393 .open = stack_trace_open, 394 .read = seq_read, 395 .llseek = seq_lseek, 396 .release = seq_release, 397 }; 398 399 #ifdef CONFIG_DYNAMIC_FTRACE 400 401 static int 402 stack_trace_filter_open(struct inode *inode, struct file *file) 403 { 404 struct ftrace_ops *ops = inode->i_private; 405 406 return ftrace_regex_open(ops, FTRACE_ITER_FILTER, 407 inode, file); 408 } 409 410 static const struct file_operations stack_trace_filter_fops = { 411 .open = stack_trace_filter_open, 412 .read = seq_read, 413 .write = ftrace_filter_write, 414 .llseek = tracing_lseek, 415 .release = ftrace_regex_release, 416 }; 417 418 #endif /* CONFIG_DYNAMIC_FTRACE */ 419 420 int 421 stack_trace_sysctl(struct ctl_table *table, int write, 422 void __user *buffer, size_t *lenp, 423 loff_t *ppos) 424 { 425 int ret; 426 427 mutex_lock(&stack_sysctl_mutex); 428 429 ret = proc_dointvec(table, write, buffer, lenp, ppos); 430 431 if (ret || !write || 432 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 433 goto out; 434 435 last_stack_tracer_enabled = !!stack_tracer_enabled; 436 437 if (stack_tracer_enabled) 438 register_ftrace_function(&trace_ops); 439 else 440 unregister_ftrace_function(&trace_ops); 441 442 out: 443 mutex_unlock(&stack_sysctl_mutex); 444 return ret; 445 } 446 447 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 448 449 static __init int enable_stacktrace(char *str) 450 { 451 int len; 452 453 if ((len = str_has_prefix(str, "_filter="))) 454 strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE); 455 456 stack_tracer_enabled = 1; 457 last_stack_tracer_enabled = 1; 458 return 1; 459 } 460 __setup("stacktrace", enable_stacktrace); 461 462 static __init int stack_trace_init(void) 463 { 464 struct dentry *d_tracer; 465 466 d_tracer = tracing_init_dentry(); 467 if (IS_ERR(d_tracer)) 468 return 0; 469 470 trace_create_file("stack_max_size", 0644, d_tracer, 471 &stack_trace_max_size, &stack_max_size_fops); 472 473 trace_create_file("stack_trace", 0444, d_tracer, 474 NULL, &stack_trace_fops); 475 476 #ifdef CONFIG_DYNAMIC_FTRACE 477 trace_create_file("stack_trace_filter", 0644, d_tracer, 478 &trace_ops, &stack_trace_filter_fops); 479 #endif 480 481 if (stack_trace_filter_buf[0]) 482 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); 483 484 if (stack_tracer_enabled) 485 register_ftrace_function(&trace_ops); 486 487 return 0; 488 } 489 490 device_initcall(stack_trace_init); 491