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 = 3; 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 ip += MCOUNT_INSN_SIZE; 213 214 check_stack(ip, &stack); 215 216 out: 217 __this_cpu_dec(disable_stack_tracer); 218 /* prevent recursion in schedule */ 219 preempt_enable_notrace(); 220 } 221 222 static struct ftrace_ops trace_ops __read_mostly = 223 { 224 .func = stack_trace_call, 225 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 226 }; 227 228 static ssize_t 229 stack_max_size_read(struct file *filp, char __user *ubuf, 230 size_t count, loff_t *ppos) 231 { 232 unsigned long *ptr = filp->private_data; 233 char buf[64]; 234 int r; 235 236 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 237 if (r > sizeof(buf)) 238 r = sizeof(buf); 239 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 240 } 241 242 static ssize_t 243 stack_max_size_write(struct file *filp, const char __user *ubuf, 244 size_t count, loff_t *ppos) 245 { 246 long *ptr = filp->private_data; 247 unsigned long val, flags; 248 int ret; 249 250 ret = kstrtoul_from_user(ubuf, count, 10, &val); 251 if (ret) 252 return ret; 253 254 local_irq_save(flags); 255 256 /* 257 * In case we trace inside arch_spin_lock() or after (NMI), 258 * we will cause circular lock, so we also need to increase 259 * the percpu disable_stack_tracer here. 260 */ 261 __this_cpu_inc(disable_stack_tracer); 262 263 arch_spin_lock(&stack_trace_max_lock); 264 *ptr = val; 265 arch_spin_unlock(&stack_trace_max_lock); 266 267 __this_cpu_dec(disable_stack_tracer); 268 local_irq_restore(flags); 269 270 return count; 271 } 272 273 static const struct file_operations stack_max_size_fops = { 274 .open = tracing_open_generic, 275 .read = stack_max_size_read, 276 .write = stack_max_size_write, 277 .llseek = default_llseek, 278 }; 279 280 static void * 281 __next(struct seq_file *m, loff_t *pos) 282 { 283 long n = *pos - 1; 284 285 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX) 286 return NULL; 287 288 m->private = (void *)n; 289 return &m->private; 290 } 291 292 static void * 293 t_next(struct seq_file *m, void *v, loff_t *pos) 294 { 295 (*pos)++; 296 return __next(m, pos); 297 } 298 299 static void *t_start(struct seq_file *m, loff_t *pos) 300 { 301 local_irq_disable(); 302 303 __this_cpu_inc(disable_stack_tracer); 304 305 arch_spin_lock(&stack_trace_max_lock); 306 307 if (*pos == 0) 308 return SEQ_START_TOKEN; 309 310 return __next(m, pos); 311 } 312 313 static void t_stop(struct seq_file *m, void *p) 314 { 315 arch_spin_unlock(&stack_trace_max_lock); 316 317 __this_cpu_dec(disable_stack_tracer); 318 319 local_irq_enable(); 320 } 321 322 static void trace_lookup_stack(struct seq_file *m, long i) 323 { 324 unsigned long addr = stack_dump_trace[i]; 325 326 seq_printf(m, "%pS\n", (void *)addr); 327 } 328 329 static void print_disabled(struct seq_file *m) 330 { 331 seq_puts(m, "#\n" 332 "# Stack tracer disabled\n" 333 "#\n" 334 "# To enable the stack tracer, either add 'stacktrace' to the\n" 335 "# kernel command line\n" 336 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 337 "#\n"); 338 } 339 340 static int t_show(struct seq_file *m, void *v) 341 { 342 long i; 343 int size; 344 345 if (v == SEQ_START_TOKEN) { 346 seq_printf(m, " Depth Size Location" 347 " (%d entries)\n" 348 " ----- ---- --------\n", 349 stack_trace_max.nr_entries); 350 351 if (!stack_tracer_enabled && !stack_trace_max_size) 352 print_disabled(m); 353 354 return 0; 355 } 356 357 i = *(long *)v; 358 359 if (i >= stack_trace_max.nr_entries || 360 stack_dump_trace[i] == ULONG_MAX) 361 return 0; 362 363 if (i+1 == stack_trace_max.nr_entries || 364 stack_dump_trace[i+1] == ULONG_MAX) 365 size = stack_trace_index[i]; 366 else 367 size = stack_trace_index[i] - stack_trace_index[i+1]; 368 369 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size); 370 371 trace_lookup_stack(m, i); 372 373 return 0; 374 } 375 376 static const struct seq_operations stack_trace_seq_ops = { 377 .start = t_start, 378 .next = t_next, 379 .stop = t_stop, 380 .show = t_show, 381 }; 382 383 static int stack_trace_open(struct inode *inode, struct file *file) 384 { 385 return seq_open(file, &stack_trace_seq_ops); 386 } 387 388 static const struct file_operations stack_trace_fops = { 389 .open = stack_trace_open, 390 .read = seq_read, 391 .llseek = seq_lseek, 392 .release = seq_release, 393 }; 394 395 #ifdef CONFIG_DYNAMIC_FTRACE 396 397 static int 398 stack_trace_filter_open(struct inode *inode, struct file *file) 399 { 400 struct ftrace_ops *ops = inode->i_private; 401 402 return ftrace_regex_open(ops, FTRACE_ITER_FILTER, 403 inode, file); 404 } 405 406 static const struct file_operations stack_trace_filter_fops = { 407 .open = stack_trace_filter_open, 408 .read = seq_read, 409 .write = ftrace_filter_write, 410 .llseek = tracing_lseek, 411 .release = ftrace_regex_release, 412 }; 413 414 #endif /* CONFIG_DYNAMIC_FTRACE */ 415 416 int 417 stack_trace_sysctl(struct ctl_table *table, int write, 418 void __user *buffer, size_t *lenp, 419 loff_t *ppos) 420 { 421 int ret; 422 423 mutex_lock(&stack_sysctl_mutex); 424 425 ret = proc_dointvec(table, write, buffer, lenp, ppos); 426 427 if (ret || !write || 428 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 429 goto out; 430 431 last_stack_tracer_enabled = !!stack_tracer_enabled; 432 433 if (stack_tracer_enabled) 434 register_ftrace_function(&trace_ops); 435 else 436 unregister_ftrace_function(&trace_ops); 437 438 out: 439 mutex_unlock(&stack_sysctl_mutex); 440 return ret; 441 } 442 443 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 444 445 static __init int enable_stacktrace(char *str) 446 { 447 if (strncmp(str, "_filter=", 8) == 0) 448 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE); 449 450 stack_tracer_enabled = 1; 451 last_stack_tracer_enabled = 1; 452 return 1; 453 } 454 __setup("stacktrace", enable_stacktrace); 455 456 static __init int stack_trace_init(void) 457 { 458 struct dentry *d_tracer; 459 460 d_tracer = tracing_init_dentry(); 461 if (IS_ERR(d_tracer)) 462 return 0; 463 464 trace_create_file("stack_max_size", 0644, d_tracer, 465 &stack_trace_max_size, &stack_max_size_fops); 466 467 trace_create_file("stack_trace", 0444, d_tracer, 468 NULL, &stack_trace_fops); 469 470 #ifdef CONFIG_DYNAMIC_FTRACE 471 trace_create_file("stack_trace_filter", 0444, d_tracer, 472 &trace_ops, &stack_trace_filter_fops); 473 #endif 474 475 if (stack_trace_filter_buf[0]) 476 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); 477 478 if (stack_tracer_enabled) 479 register_ftrace_function(&trace_ops); 480 481 return 0; 482 } 483 484 device_initcall(stack_trace_init); 485