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 #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 stack_trace_nr_entries = x; 162 163 if (task_stack_end_corrupted(current)) { 164 print_max_stack(); 165 BUG(); 166 } 167 168 out: 169 arch_spin_unlock(&stack_trace_max_lock); 170 local_irq_restore(flags); 171 } 172 173 static void 174 stack_trace_call(unsigned long ip, unsigned long parent_ip, 175 struct ftrace_ops *op, struct pt_regs *pt_regs) 176 { 177 unsigned long stack; 178 179 preempt_disable_notrace(); 180 181 /* no atomic needed, we only modify this variable by this cpu */ 182 __this_cpu_inc(disable_stack_tracer); 183 if (__this_cpu_read(disable_stack_tracer) != 1) 184 goto out; 185 186 /* If rcu is not watching, then save stack trace can fail */ 187 if (!rcu_is_watching()) 188 goto out; 189 190 ip += MCOUNT_INSN_SIZE; 191 192 check_stack(ip, &stack); 193 194 out: 195 __this_cpu_dec(disable_stack_tracer); 196 /* prevent recursion in schedule */ 197 preempt_enable_notrace(); 198 } 199 200 static struct ftrace_ops trace_ops __read_mostly = 201 { 202 .func = stack_trace_call, 203 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 204 }; 205 206 static ssize_t 207 stack_max_size_read(struct file *filp, char __user *ubuf, 208 size_t count, loff_t *ppos) 209 { 210 unsigned long *ptr = filp->private_data; 211 char buf[64]; 212 int r; 213 214 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 215 if (r > sizeof(buf)) 216 r = sizeof(buf); 217 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 218 } 219 220 static ssize_t 221 stack_max_size_write(struct file *filp, const char __user *ubuf, 222 size_t count, loff_t *ppos) 223 { 224 long *ptr = filp->private_data; 225 unsigned long val, flags; 226 int ret; 227 228 ret = kstrtoul_from_user(ubuf, count, 10, &val); 229 if (ret) 230 return ret; 231 232 local_irq_save(flags); 233 234 /* 235 * In case we trace inside arch_spin_lock() or after (NMI), 236 * we will cause circular lock, so we also need to increase 237 * the percpu disable_stack_tracer here. 238 */ 239 __this_cpu_inc(disable_stack_tracer); 240 241 arch_spin_lock(&stack_trace_max_lock); 242 *ptr = val; 243 arch_spin_unlock(&stack_trace_max_lock); 244 245 __this_cpu_dec(disable_stack_tracer); 246 local_irq_restore(flags); 247 248 return count; 249 } 250 251 static const struct file_operations stack_max_size_fops = { 252 .open = tracing_open_generic, 253 .read = stack_max_size_read, 254 .write = stack_max_size_write, 255 .llseek = default_llseek, 256 }; 257 258 static void * 259 __next(struct seq_file *m, loff_t *pos) 260 { 261 long n = *pos - 1; 262 263 if (n >= stack_trace_nr_entries) 264 return NULL; 265 266 m->private = (void *)n; 267 return &m->private; 268 } 269 270 static void * 271 t_next(struct seq_file *m, void *v, loff_t *pos) 272 { 273 (*pos)++; 274 return __next(m, pos); 275 } 276 277 static void *t_start(struct seq_file *m, loff_t *pos) 278 { 279 local_irq_disable(); 280 281 __this_cpu_inc(disable_stack_tracer); 282 283 arch_spin_lock(&stack_trace_max_lock); 284 285 if (*pos == 0) 286 return SEQ_START_TOKEN; 287 288 return __next(m, pos); 289 } 290 291 static void t_stop(struct seq_file *m, void *p) 292 { 293 arch_spin_unlock(&stack_trace_max_lock); 294 295 __this_cpu_dec(disable_stack_tracer); 296 297 local_irq_enable(); 298 } 299 300 static void trace_lookup_stack(struct seq_file *m, long i) 301 { 302 unsigned long addr = stack_dump_trace[i]; 303 304 seq_printf(m, "%pS\n", (void *)addr); 305 } 306 307 static void print_disabled(struct seq_file *m) 308 { 309 seq_puts(m, "#\n" 310 "# Stack tracer disabled\n" 311 "#\n" 312 "# To enable the stack tracer, either add 'stacktrace' to the\n" 313 "# kernel command line\n" 314 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 315 "#\n"); 316 } 317 318 static int t_show(struct seq_file *m, void *v) 319 { 320 long i; 321 int size; 322 323 if (v == SEQ_START_TOKEN) { 324 seq_printf(m, " Depth Size Location" 325 " (%d entries)\n" 326 " ----- ---- --------\n", 327 stack_trace_nr_entries); 328 329 if (!stack_tracer_enabled && !stack_trace_max_size) 330 print_disabled(m); 331 332 return 0; 333 } 334 335 i = *(long *)v; 336 337 if (i >= stack_trace_nr_entries) 338 return 0; 339 340 if (i + 1 == stack_trace_nr_entries) 341 size = stack_trace_index[i]; 342 else 343 size = stack_trace_index[i] - stack_trace_index[i+1]; 344 345 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size); 346 347 trace_lookup_stack(m, i); 348 349 return 0; 350 } 351 352 static const struct seq_operations stack_trace_seq_ops = { 353 .start = t_start, 354 .next = t_next, 355 .stop = t_stop, 356 .show = t_show, 357 }; 358 359 static int stack_trace_open(struct inode *inode, struct file *file) 360 { 361 return seq_open(file, &stack_trace_seq_ops); 362 } 363 364 static const struct file_operations stack_trace_fops = { 365 .open = stack_trace_open, 366 .read = seq_read, 367 .llseek = seq_lseek, 368 .release = seq_release, 369 }; 370 371 #ifdef CONFIG_DYNAMIC_FTRACE 372 373 static int 374 stack_trace_filter_open(struct inode *inode, struct file *file) 375 { 376 struct ftrace_ops *ops = inode->i_private; 377 378 return ftrace_regex_open(ops, FTRACE_ITER_FILTER, 379 inode, file); 380 } 381 382 static const struct file_operations stack_trace_filter_fops = { 383 .open = stack_trace_filter_open, 384 .read = seq_read, 385 .write = ftrace_filter_write, 386 .llseek = tracing_lseek, 387 .release = ftrace_regex_release, 388 }; 389 390 #endif /* CONFIG_DYNAMIC_FTRACE */ 391 392 int 393 stack_trace_sysctl(struct ctl_table *table, int write, 394 void __user *buffer, size_t *lenp, 395 loff_t *ppos) 396 { 397 int was_enabled; 398 int ret; 399 400 mutex_lock(&stack_sysctl_mutex); 401 was_enabled = !!stack_tracer_enabled; 402 403 ret = proc_dointvec(table, write, buffer, lenp, ppos); 404 405 if (ret || !write || (was_enabled == !!stack_tracer_enabled)) 406 goto out; 407 408 if (stack_tracer_enabled) 409 register_ftrace_function(&trace_ops); 410 else 411 unregister_ftrace_function(&trace_ops); 412 out: 413 mutex_unlock(&stack_sysctl_mutex); 414 return ret; 415 } 416 417 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; 418 419 static __init int enable_stacktrace(char *str) 420 { 421 int len; 422 423 if ((len = str_has_prefix(str, "_filter="))) 424 strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE); 425 426 stack_tracer_enabled = 1; 427 return 1; 428 } 429 __setup("stacktrace", enable_stacktrace); 430 431 static __init int stack_trace_init(void) 432 { 433 struct dentry *d_tracer; 434 435 d_tracer = tracing_init_dentry(); 436 if (IS_ERR(d_tracer)) 437 return 0; 438 439 trace_create_file("stack_max_size", 0644, d_tracer, 440 &stack_trace_max_size, &stack_max_size_fops); 441 442 trace_create_file("stack_trace", 0444, d_tracer, 443 NULL, &stack_trace_fops); 444 445 #ifdef CONFIG_DYNAMIC_FTRACE 446 trace_create_file("stack_trace_filter", 0644, d_tracer, 447 &trace_ops, &stack_trace_filter_fops); 448 #endif 449 450 if (stack_trace_filter_buf[0]) 451 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); 452 453 if (stack_tracer_enabled) 454 register_ftrace_function(&trace_ops); 455 456 return 0; 457 } 458 459 device_initcall(stack_trace_init); 460