1 /* 2 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> 3 * 4 */ 5 #include <linux/stacktrace.h> 6 #include <linux/kallsyms.h> 7 #include <linux/seq_file.h> 8 #include <linux/spinlock.h> 9 #include <linux/uaccess.h> 10 #include <linux/debugfs.h> 11 #include <linux/ftrace.h> 12 #include <linux/module.h> 13 #include <linux/sysctl.h> 14 #include <linux/init.h> 15 #include <linux/fs.h> 16 #include "trace.h" 17 18 #define STACK_TRACE_ENTRIES 500 19 20 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] = 21 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX }; 22 static unsigned stack_dump_index[STACK_TRACE_ENTRIES]; 23 24 static struct stack_trace max_stack_trace = { 25 .max_entries = STACK_TRACE_ENTRIES, 26 .entries = stack_dump_trace, 27 }; 28 29 static unsigned long max_stack_size; 30 static arch_spinlock_t max_stack_lock = 31 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; 32 33 static int stack_trace_disabled __read_mostly; 34 static DEFINE_PER_CPU(int, trace_active); 35 static DEFINE_MUTEX(stack_sysctl_mutex); 36 37 int stack_tracer_enabled; 38 static int last_stack_tracer_enabled; 39 40 static inline void check_stack(void) 41 { 42 unsigned long this_size, flags; 43 unsigned long *p, *top, *start; 44 int i; 45 46 this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1); 47 this_size = THREAD_SIZE - this_size; 48 49 if (this_size <= max_stack_size) 50 return; 51 52 /* we do not handle interrupt stacks yet */ 53 if (!object_is_on_stack(&this_size)) 54 return; 55 56 local_irq_save(flags); 57 arch_spin_lock(&max_stack_lock); 58 59 /* a race could have already updated it */ 60 if (this_size <= max_stack_size) 61 goto out; 62 63 max_stack_size = this_size; 64 65 max_stack_trace.nr_entries = 0; 66 max_stack_trace.skip = 3; 67 68 save_stack_trace(&max_stack_trace); 69 70 /* 71 * Now find where in the stack these are. 72 */ 73 i = 0; 74 start = &this_size; 75 top = (unsigned long *) 76 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); 77 78 /* 79 * Loop through all the entries. One of the entries may 80 * for some reason be missed on the stack, so we may 81 * have to account for them. If they are all there, this 82 * loop will only happen once. This code only takes place 83 * on a new max, so it is far from a fast path. 84 */ 85 while (i < max_stack_trace.nr_entries) { 86 int found = 0; 87 88 stack_dump_index[i] = this_size; 89 p = start; 90 91 for (; p < top && i < max_stack_trace.nr_entries; p++) { 92 if (*p == stack_dump_trace[i]) { 93 this_size = stack_dump_index[i++] = 94 (top - p) * sizeof(unsigned long); 95 found = 1; 96 /* Start the search from here */ 97 start = p + 1; 98 } 99 } 100 101 if (!found) 102 i++; 103 } 104 105 out: 106 arch_spin_unlock(&max_stack_lock); 107 local_irq_restore(flags); 108 } 109 110 static void 111 stack_trace_call(unsigned long ip, unsigned long parent_ip) 112 { 113 int cpu; 114 115 if (unlikely(!ftrace_enabled || stack_trace_disabled)) 116 return; 117 118 preempt_disable_notrace(); 119 120 cpu = raw_smp_processor_id(); 121 /* no atomic needed, we only modify this variable by this cpu */ 122 if (per_cpu(trace_active, cpu)++ != 0) 123 goto out; 124 125 check_stack(); 126 127 out: 128 per_cpu(trace_active, cpu)--; 129 /* prevent recursion in schedule */ 130 preempt_enable_notrace(); 131 } 132 133 static struct ftrace_ops trace_ops __read_mostly = 134 { 135 .func = stack_trace_call, 136 }; 137 138 static ssize_t 139 stack_max_size_read(struct file *filp, char __user *ubuf, 140 size_t count, loff_t *ppos) 141 { 142 unsigned long *ptr = filp->private_data; 143 char buf[64]; 144 int r; 145 146 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 147 if (r > sizeof(buf)) 148 r = sizeof(buf); 149 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 150 } 151 152 static ssize_t 153 stack_max_size_write(struct file *filp, const char __user *ubuf, 154 size_t count, loff_t *ppos) 155 { 156 long *ptr = filp->private_data; 157 unsigned long val, flags; 158 char buf[64]; 159 int ret; 160 int cpu; 161 162 if (count >= sizeof(buf)) 163 return -EINVAL; 164 165 if (copy_from_user(&buf, ubuf, count)) 166 return -EFAULT; 167 168 buf[count] = 0; 169 170 ret = strict_strtoul(buf, 10, &val); 171 if (ret < 0) 172 return ret; 173 174 local_irq_save(flags); 175 176 /* 177 * In case we trace inside arch_spin_lock() or after (NMI), 178 * we will cause circular lock, so we also need to increase 179 * the percpu trace_active here. 180 */ 181 cpu = smp_processor_id(); 182 per_cpu(trace_active, cpu)++; 183 184 arch_spin_lock(&max_stack_lock); 185 *ptr = val; 186 arch_spin_unlock(&max_stack_lock); 187 188 per_cpu(trace_active, cpu)--; 189 local_irq_restore(flags); 190 191 return count; 192 } 193 194 static const struct file_operations stack_max_size_fops = { 195 .open = tracing_open_generic, 196 .read = stack_max_size_read, 197 .write = stack_max_size_write, 198 .llseek = default_llseek, 199 }; 200 201 static void * 202 __next(struct seq_file *m, loff_t *pos) 203 { 204 long n = *pos - 1; 205 206 if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX) 207 return NULL; 208 209 m->private = (void *)n; 210 return &m->private; 211 } 212 213 static void * 214 t_next(struct seq_file *m, void *v, loff_t *pos) 215 { 216 (*pos)++; 217 return __next(m, pos); 218 } 219 220 static void *t_start(struct seq_file *m, loff_t *pos) 221 { 222 int cpu; 223 224 local_irq_disable(); 225 226 cpu = smp_processor_id(); 227 per_cpu(trace_active, cpu)++; 228 229 arch_spin_lock(&max_stack_lock); 230 231 if (*pos == 0) 232 return SEQ_START_TOKEN; 233 234 return __next(m, pos); 235 } 236 237 static void t_stop(struct seq_file *m, void *p) 238 { 239 int cpu; 240 241 arch_spin_unlock(&max_stack_lock); 242 243 cpu = smp_processor_id(); 244 per_cpu(trace_active, cpu)--; 245 246 local_irq_enable(); 247 } 248 249 static int trace_lookup_stack(struct seq_file *m, long i) 250 { 251 unsigned long addr = stack_dump_trace[i]; 252 253 return seq_printf(m, "%pS\n", (void *)addr); 254 } 255 256 static void print_disabled(struct seq_file *m) 257 { 258 seq_puts(m, "#\n" 259 "# Stack tracer disabled\n" 260 "#\n" 261 "# To enable the stack tracer, either add 'stacktrace' to the\n" 262 "# kernel command line\n" 263 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 264 "#\n"); 265 } 266 267 static int t_show(struct seq_file *m, void *v) 268 { 269 long i; 270 int size; 271 272 if (v == SEQ_START_TOKEN) { 273 seq_printf(m, " Depth Size Location" 274 " (%d entries)\n" 275 " ----- ---- --------\n", 276 max_stack_trace.nr_entries - 1); 277 278 if (!stack_tracer_enabled && !max_stack_size) 279 print_disabled(m); 280 281 return 0; 282 } 283 284 i = *(long *)v; 285 286 if (i >= max_stack_trace.nr_entries || 287 stack_dump_trace[i] == ULONG_MAX) 288 return 0; 289 290 if (i+1 == max_stack_trace.nr_entries || 291 stack_dump_trace[i+1] == ULONG_MAX) 292 size = stack_dump_index[i]; 293 else 294 size = stack_dump_index[i] - stack_dump_index[i+1]; 295 296 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size); 297 298 trace_lookup_stack(m, i); 299 300 return 0; 301 } 302 303 static const struct seq_operations stack_trace_seq_ops = { 304 .start = t_start, 305 .next = t_next, 306 .stop = t_stop, 307 .show = t_show, 308 }; 309 310 static int stack_trace_open(struct inode *inode, struct file *file) 311 { 312 return seq_open(file, &stack_trace_seq_ops); 313 } 314 315 static const struct file_operations stack_trace_fops = { 316 .open = stack_trace_open, 317 .read = seq_read, 318 .llseek = seq_lseek, 319 .release = seq_release, 320 }; 321 322 int 323 stack_trace_sysctl(struct ctl_table *table, int write, 324 void __user *buffer, size_t *lenp, 325 loff_t *ppos) 326 { 327 int ret; 328 329 mutex_lock(&stack_sysctl_mutex); 330 331 ret = proc_dointvec(table, write, buffer, lenp, ppos); 332 333 if (ret || !write || 334 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 335 goto out; 336 337 last_stack_tracer_enabled = !!stack_tracer_enabled; 338 339 if (stack_tracer_enabled) 340 register_ftrace_function(&trace_ops); 341 else 342 unregister_ftrace_function(&trace_ops); 343 344 out: 345 mutex_unlock(&stack_sysctl_mutex); 346 return ret; 347 } 348 349 static __init int enable_stacktrace(char *str) 350 { 351 stack_tracer_enabled = 1; 352 last_stack_tracer_enabled = 1; 353 return 1; 354 } 355 __setup("stacktrace", enable_stacktrace); 356 357 static __init int stack_trace_init(void) 358 { 359 struct dentry *d_tracer; 360 361 d_tracer = tracing_init_dentry(); 362 363 trace_create_file("stack_max_size", 0644, d_tracer, 364 &max_stack_size, &stack_max_size_fops); 365 366 trace_create_file("stack_trace", 0444, d_tracer, 367 NULL, &stack_trace_fops); 368 369 if (stack_tracer_enabled) 370 register_ftrace_function(&trace_ops); 371 372 return 0; 373 } 374 375 device_initcall(stack_trace_init); 376