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 .flags = FTRACE_OPS_FL_GLOBAL, 137 }; 138 139 static ssize_t 140 stack_max_size_read(struct file *filp, char __user *ubuf, 141 size_t count, loff_t *ppos) 142 { 143 unsigned long *ptr = filp->private_data; 144 char buf[64]; 145 int r; 146 147 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); 148 if (r > sizeof(buf)) 149 r = sizeof(buf); 150 return simple_read_from_buffer(ubuf, count, ppos, buf, r); 151 } 152 153 static ssize_t 154 stack_max_size_write(struct file *filp, const char __user *ubuf, 155 size_t count, loff_t *ppos) 156 { 157 long *ptr = filp->private_data; 158 unsigned long val, flags; 159 char buf[64]; 160 int ret; 161 int cpu; 162 163 if (count >= sizeof(buf)) 164 return -EINVAL; 165 166 if (copy_from_user(&buf, ubuf, count)) 167 return -EFAULT; 168 169 buf[count] = 0; 170 171 ret = strict_strtoul(buf, 10, &val); 172 if (ret < 0) 173 return ret; 174 175 local_irq_save(flags); 176 177 /* 178 * In case we trace inside arch_spin_lock() or after (NMI), 179 * we will cause circular lock, so we also need to increase 180 * the percpu trace_active here. 181 */ 182 cpu = smp_processor_id(); 183 per_cpu(trace_active, cpu)++; 184 185 arch_spin_lock(&max_stack_lock); 186 *ptr = val; 187 arch_spin_unlock(&max_stack_lock); 188 189 per_cpu(trace_active, cpu)--; 190 local_irq_restore(flags); 191 192 return count; 193 } 194 195 static const struct file_operations stack_max_size_fops = { 196 .open = tracing_open_generic, 197 .read = stack_max_size_read, 198 .write = stack_max_size_write, 199 .llseek = default_llseek, 200 }; 201 202 static void * 203 __next(struct seq_file *m, loff_t *pos) 204 { 205 long n = *pos - 1; 206 207 if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX) 208 return NULL; 209 210 m->private = (void *)n; 211 return &m->private; 212 } 213 214 static void * 215 t_next(struct seq_file *m, void *v, loff_t *pos) 216 { 217 (*pos)++; 218 return __next(m, pos); 219 } 220 221 static void *t_start(struct seq_file *m, loff_t *pos) 222 { 223 int cpu; 224 225 local_irq_disable(); 226 227 cpu = smp_processor_id(); 228 per_cpu(trace_active, cpu)++; 229 230 arch_spin_lock(&max_stack_lock); 231 232 if (*pos == 0) 233 return SEQ_START_TOKEN; 234 235 return __next(m, pos); 236 } 237 238 static void t_stop(struct seq_file *m, void *p) 239 { 240 int cpu; 241 242 arch_spin_unlock(&max_stack_lock); 243 244 cpu = smp_processor_id(); 245 per_cpu(trace_active, cpu)--; 246 247 local_irq_enable(); 248 } 249 250 static int trace_lookup_stack(struct seq_file *m, long i) 251 { 252 unsigned long addr = stack_dump_trace[i]; 253 254 return seq_printf(m, "%pS\n", (void *)addr); 255 } 256 257 static void print_disabled(struct seq_file *m) 258 { 259 seq_puts(m, "#\n" 260 "# Stack tracer disabled\n" 261 "#\n" 262 "# To enable the stack tracer, either add 'stacktrace' to the\n" 263 "# kernel command line\n" 264 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 265 "#\n"); 266 } 267 268 static int t_show(struct seq_file *m, void *v) 269 { 270 long i; 271 int size; 272 273 if (v == SEQ_START_TOKEN) { 274 seq_printf(m, " Depth Size Location" 275 " (%d entries)\n" 276 " ----- ---- --------\n", 277 max_stack_trace.nr_entries - 1); 278 279 if (!stack_tracer_enabled && !max_stack_size) 280 print_disabled(m); 281 282 return 0; 283 } 284 285 i = *(long *)v; 286 287 if (i >= max_stack_trace.nr_entries || 288 stack_dump_trace[i] == ULONG_MAX) 289 return 0; 290 291 if (i+1 == max_stack_trace.nr_entries || 292 stack_dump_trace[i+1] == ULONG_MAX) 293 size = stack_dump_index[i]; 294 else 295 size = stack_dump_index[i] - stack_dump_index[i+1]; 296 297 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size); 298 299 trace_lookup_stack(m, i); 300 301 return 0; 302 } 303 304 static const struct seq_operations stack_trace_seq_ops = { 305 .start = t_start, 306 .next = t_next, 307 .stop = t_stop, 308 .show = t_show, 309 }; 310 311 static int stack_trace_open(struct inode *inode, struct file *file) 312 { 313 return seq_open(file, &stack_trace_seq_ops); 314 } 315 316 static const struct file_operations stack_trace_fops = { 317 .open = stack_trace_open, 318 .read = seq_read, 319 .llseek = seq_lseek, 320 .release = seq_release, 321 }; 322 323 int 324 stack_trace_sysctl(struct ctl_table *table, int write, 325 void __user *buffer, size_t *lenp, 326 loff_t *ppos) 327 { 328 int ret; 329 330 mutex_lock(&stack_sysctl_mutex); 331 332 ret = proc_dointvec(table, write, buffer, lenp, ppos); 333 334 if (ret || !write || 335 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 336 goto out; 337 338 last_stack_tracer_enabled = !!stack_tracer_enabled; 339 340 if (stack_tracer_enabled) 341 register_ftrace_function(&trace_ops); 342 else 343 unregister_ftrace_function(&trace_ops); 344 345 out: 346 mutex_unlock(&stack_sysctl_mutex); 347 return ret; 348 } 349 350 static __init int enable_stacktrace(char *str) 351 { 352 stack_tracer_enabled = 1; 353 last_stack_tracer_enabled = 1; 354 return 1; 355 } 356 __setup("stacktrace", enable_stacktrace); 357 358 static __init int stack_trace_init(void) 359 { 360 struct dentry *d_tracer; 361 362 d_tracer = tracing_init_dentry(); 363 364 trace_create_file("stack_max_size", 0644, d_tracer, 365 &max_stack_size, &stack_max_size_fops); 366 367 trace_create_file("stack_trace", 0444, d_tracer, 368 NULL, &stack_trace_fops); 369 370 if (stack_tracer_enabled) 371 register_ftrace_function(&trace_ops); 372 373 return 0; 374 } 375 376 device_initcall(stack_trace_init); 377