1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2008 Steven Rostedt <[email protected]> 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 #define STACK_TRACE_ENTRIES 500 22 23 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES]; 24 static unsigned stack_trace_index[STACK_TRACE_ENTRIES]; 25 26 static unsigned int stack_trace_nr_entries; 27 static unsigned long stack_trace_max_size; 28 static arch_spinlock_t stack_trace_max_lock = 29 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; 30 31 DEFINE_PER_CPU(int, disable_stack_tracer); 32 static DEFINE_MUTEX(stack_sysctl_mutex); 33 34 int stack_tracer_enabled; 35 36 static void print_max_stack(void) 37 { 38 long i; 39 int size; 40 41 pr_emerg(" Depth Size Location (%d entries)\n" 42 " ----- ---- --------\n", 43 stack_trace_nr_entries); 44 45 for (i = 0; i < stack_trace_nr_entries; i++) { 46 if (i + 1 == stack_trace_nr_entries) 47 size = stack_trace_index[i]; 48 else 49 size = stack_trace_index[i] - stack_trace_index[i+1]; 50 51 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i], 52 size, (void *)stack_dump_trace[i]); 53 } 54 } 55 56 static void check_stack(unsigned long ip, unsigned long *stack) 57 { 58 unsigned long this_size, flags; unsigned long *p, *top, *start; 59 static int tracer_frame; 60 int frame_size = READ_ONCE(tracer_frame); 61 int i, x; 62 63 this_size = ((unsigned long)stack) & (THREAD_SIZE-1); 64 this_size = THREAD_SIZE - this_size; 65 /* Remove the frame of the tracer */ 66 this_size -= frame_size; 67 68 if (this_size <= stack_trace_max_size) 69 return; 70 71 /* we do not handle interrupt stacks yet */ 72 if (!object_is_on_stack(stack)) 73 return; 74 75 /* Can't do this from NMI context (can cause deadlocks) */ 76 if (in_nmi()) 77 return; 78 79 local_irq_save(flags); 80 arch_spin_lock(&stack_trace_max_lock); 81 82 /* In case another CPU set the tracer_frame on us */ 83 if (unlikely(!frame_size)) 84 this_size -= tracer_frame; 85 86 /* a race could have already updated it */ 87 if (this_size <= stack_trace_max_size) 88 goto out; 89 90 stack_trace_max_size = this_size; 91 92 stack_trace_nr_entries = stack_trace_save(stack_dump_trace, 93 ARRAY_SIZE(stack_dump_trace) - 1, 94 0); 95 96 /* Skip over the overhead of the stack tracer itself */ 97 for (i = 0; i < stack_trace_nr_entries; i++) { 98 if (stack_dump_trace[i] == ip) 99 break; 100 } 101 102 /* 103 * Some archs may not have the passed in ip in the dump. 104 * If that happens, we need to show everything. 105 */ 106 if (i == stack_trace_nr_entries) 107 i = 0; 108 109 /* 110 * Now find where in the stack these are. 111 */ 112 x = 0; 113 start = stack; 114 top = (unsigned long *) 115 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); 116 117 /* 118 * Loop through all the entries. One of the entries may 119 * for some reason be missed on the stack, so we may 120 * have to account for them. If they are all there, this 121 * loop will only happen once. This code only takes place 122 * on a new max, so it is far from a fast path. 123 */ 124 while (i < stack_trace_nr_entries) { 125 int found = 0; 126 127 stack_trace_index[x] = this_size; 128 p = start; 129 130 for (; p < top && i < stack_trace_nr_entries; p++) { 131 /* 132 * The READ_ONCE_NOCHECK is used to let KASAN know that 133 * this is not a stack-out-of-bounds error. 134 */ 135 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) { 136 stack_dump_trace[x] = stack_dump_trace[i++]; 137 this_size = stack_trace_index[x++] = 138 (top - p) * sizeof(unsigned long); 139 found = 1; 140 /* Start the search from here */ 141 start = p + 1; 142 /* 143 * We do not want to show the overhead 144 * of the stack tracer stack in the 145 * max stack. If we haven't figured 146 * out what that is, then figure it out 147 * now. 148 */ 149 if (unlikely(!tracer_frame)) { 150 tracer_frame = (p - stack) * 151 sizeof(unsigned long); 152 stack_trace_max_size -= tracer_frame; 153 } 154 } 155 } 156 157 if (!found) 158 i++; 159 } 160 161 #ifdef ARCH_FTRACE_SHIFT_STACK_TRACER 162 /* 163 * Some archs will store the link register before calling 164 * nested functions. This means the saved return address 165 * comes after the local storage, and we need to shift 166 * for that. 167 */ 168 if (x > 1) { 169 memmove(&stack_trace_index[0], &stack_trace_index[1], 170 sizeof(stack_trace_index[0]) * (x - 1)); 171 x--; 172 } 173 #endif 174 175 stack_trace_nr_entries = x; 176 177 if (task_stack_end_corrupted(current)) { 178 print_max_stack(); 179 BUG(); 180 } 181 182 out: 183 arch_spin_unlock(&stack_trace_max_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; 192 193 preempt_disable_notrace(); 194 195 /* no atomic needed, we only modify this variable by this cpu */ 196 __this_cpu_inc(disable_stack_tracer); 197 if (__this_cpu_read(disable_stack_tracer) != 1) 198 goto out; 199 200 /* If rcu is not watching, then save stack trace can fail */ 201 if (!rcu_is_watching()) 202 goto out; 203 204 ip += MCOUNT_INSN_SIZE; 205 206 check_stack(ip, &stack); 207 208 out: 209 __this_cpu_dec(disable_stack_tracer); 210 /* prevent recursion in schedule */ 211 preempt_enable_notrace(); 212 } 213 214 static struct ftrace_ops trace_ops __read_mostly = 215 { 216 .func = stack_trace_call, 217 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 218 }; 219 220 static ssize_t 221 stack_max_size_read(struct file *filp, char __user *ubuf, 222 size_t count, loff_t *ppos) 223 { 224 unsigned long *ptr = filp->private_data; 225 char buf[64]; 226 int r; 227 228 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 229 if (r > sizeof(buf)) 230 r = sizeof(buf); 231 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 232 } 233 234 static ssize_t 235 stack_max_size_write(struct file *filp, const char __user *ubuf, 236 size_t count, loff_t *ppos) 237 { 238 long *ptr = filp->private_data; 239 unsigned long val, flags; 240 int ret; 241 242 ret = kstrtoul_from_user(ubuf, count, 10, &val); 243 if (ret) 244 return ret; 245 246 local_irq_save(flags); 247 248 /* 249 * In case we trace inside arch_spin_lock() or after (NMI), 250 * we will cause circular lock, so we also need to increase 251 * the percpu disable_stack_tracer here. 252 */ 253 __this_cpu_inc(disable_stack_tracer); 254 255 arch_spin_lock(&stack_trace_max_lock); 256 *ptr = val; 257 arch_spin_unlock(&stack_trace_max_lock); 258 259 __this_cpu_dec(disable_stack_tracer); 260 local_irq_restore(flags); 261 262 return count; 263 } 264 265 static const struct file_operations stack_max_size_fops = { 266 .open = tracing_open_generic, 267 .read = stack_max_size_read, 268 .write = stack_max_size_write, 269 .llseek = default_llseek, 270 }; 271 272 static void * 273 __next(struct seq_file *m, loff_t *pos) 274 { 275 long n = *pos - 1; 276 277 if (n >= stack_trace_nr_entries) 278 return NULL; 279 280 m->private = (void *)n; 281 return &m->private; 282 } 283 284 static void * 285 t_next(struct seq_file *m, void *v, loff_t *pos) 286 { 287 (*pos)++; 288 return __next(m, pos); 289 } 290 291 static void *t_start(struct seq_file *m, loff_t *pos) 292 { 293 local_irq_disable(); 294 295 __this_cpu_inc(disable_stack_tracer); 296 297 arch_spin_lock(&stack_trace_max_lock); 298 299 if (*pos == 0) 300 return SEQ_START_TOKEN; 301 302 return __next(m, pos); 303 } 304 305 static void t_stop(struct seq_file *m, void *p) 306 { 307 arch_spin_unlock(&stack_trace_max_lock); 308 309 __this_cpu_dec(disable_stack_tracer); 310 311 local_irq_enable(); 312 } 313 314 static void trace_lookup_stack(struct seq_file *m, long i) 315 { 316 unsigned long addr = stack_dump_trace[i]; 317 318 seq_printf(m, "%pS\n", (void *)addr); 319 } 320 321 static void print_disabled(struct seq_file *m) 322 { 323 seq_puts(m, "#\n" 324 "# Stack tracer disabled\n" 325 "#\n" 326 "# To enable the stack tracer, either add 'stacktrace' to the\n" 327 "# kernel command line\n" 328 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 329 "#\n"); 330 } 331 332 static int t_show(struct seq_file *m, void *v) 333 { 334 long i; 335 int size; 336 337 if (v == SEQ_START_TOKEN) { 338 seq_printf(m, " Depth Size Location" 339 " (%d entries)\n" 340 " ----- ---- --------\n", 341 stack_trace_nr_entries); 342 343 if (!stack_tracer_enabled && !stack_trace_max_size) 344 print_disabled(m); 345 346 return 0; 347 } 348 349 i = *(long *)v; 350 351 if (i >= stack_trace_nr_entries) 352 return 0; 353 354 if (i + 1 == stack_trace_nr_entries) 355 size = stack_trace_index[i]; 356 else 357 size = stack_trace_index[i] - stack_trace_index[i+1]; 358 359 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size); 360 361 trace_lookup_stack(m, i); 362 363 return 0; 364 } 365 366 static const struct seq_operations stack_trace_seq_ops = { 367 .start = t_start, 368 .next = t_next, 369 .stop = t_stop, 370 .show = t_show, 371 }; 372 373 static int stack_trace_open(struct inode *inode, struct file *file) 374 { 375 return seq_open(file, &stack_trace_seq_ops); 376 } 377 378 static const struct file_operations stack_trace_fops = { 379 .open = stack_trace_open, 380 .read = seq_read, 381 .llseek = seq_lseek, 382 .release = seq_release, 383 }; 384 385 #ifdef CONFIG_DYNAMIC_FTRACE 386 387 static int 388 stack_trace_filter_open(struct inode *inode, struct file *file) 389 { 390 struct ftrace_ops *ops = inode->i_private; 391 392 return ftrace_regex_open(ops, FTRACE_ITER_FILTER, 393 inode, file); 394 } 395 396 static const struct file_operations stack_trace_filter_fops = { 397 .open = stack_trace_filter_open, 398 .read = seq_read, 399 .write = ftrace_filter_write, 400 .llseek = tracing_lseek, 401 .release = ftrace_regex_release, 402 }; 403 404 #endif /* CONFIG_DYNAMIC_FTRACE */ 405 406 int 407 stack_trace_sysctl(struct ctl_table *table, int write, 408 void __user *buffer, size_t *lenp, 409 loff_t *ppos) 410 { 411 int was_enabled; 412 int ret; 413 414 mutex_lock(&stack_sysctl_mutex); 415 was_enabled = !!stack_tracer_enabled; 416 417 ret = proc_dointvec(table, write, buffer, lenp, ppos); 418 419 if (ret || !write || (was_enabled == !!stack_tracer_enabled)) 420 goto out; 421 422 if (stack_tracer_enabled) 423 register_ftrace_function(&trace_ops); 424 else 425 unregister_ftrace_function(&trace_ops); 426 out: 427 mutex_unlock(&stack_sysctl_mutex); 428 return ret; 429 } 430 431 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 432 433 static __init int enable_stacktrace(char *str) 434 { 435 int len; 436 437 if ((len = str_has_prefix(str, "_filter="))) 438 strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE); 439 440 stack_tracer_enabled = 1; 441 return 1; 442 } 443 __setup("stacktrace", enable_stacktrace); 444 445 static __init int stack_trace_init(void) 446 { 447 struct dentry *d_tracer; 448 449 d_tracer = tracing_init_dentry(); 450 if (IS_ERR(d_tracer)) 451 return 0; 452 453 trace_create_file("stack_max_size", 0644, d_tracer, 454 &stack_trace_max_size, &stack_max_size_fops); 455 456 trace_create_file("stack_trace", 0444, d_tracer, 457 NULL, &stack_trace_fops); 458 459 #ifdef CONFIG_DYNAMIC_FTRACE 460 trace_create_file("stack_trace_filter", 0644, d_tracer, 461 &trace_ops, &stack_trace_filter_fops); 462 #endif 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