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, resched; 114 115 if (unlikely(!ftrace_enabled || stack_trace_disabled)) 116 return; 117 118 resched = ftrace_preempt_disable(); 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 ftrace_preempt_enable(resched); 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 }; 199 200 static void * 201 __next(struct seq_file *m, loff_t *pos) 202 { 203 long n = *pos - 1; 204 205 if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX) 206 return NULL; 207 208 m->private = (void *)n; 209 return &m->private; 210 } 211 212 static void * 213 t_next(struct seq_file *m, void *v, loff_t *pos) 214 { 215 (*pos)++; 216 return __next(m, pos); 217 } 218 219 static void *t_start(struct seq_file *m, loff_t *pos) 220 { 221 int cpu; 222 223 local_irq_disable(); 224 225 cpu = smp_processor_id(); 226 per_cpu(trace_active, cpu)++; 227 228 arch_spin_lock(&max_stack_lock); 229 230 if (*pos == 0) 231 return SEQ_START_TOKEN; 232 233 return __next(m, pos); 234 } 235 236 static void t_stop(struct seq_file *m, void *p) 237 { 238 int cpu; 239 240 arch_spin_unlock(&max_stack_lock); 241 242 cpu = smp_processor_id(); 243 per_cpu(trace_active, cpu)--; 244 245 local_irq_enable(); 246 } 247 248 static int trace_lookup_stack(struct seq_file *m, long i) 249 { 250 unsigned long addr = stack_dump_trace[i]; 251 252 return seq_printf(m, "%pF\n", (void *)addr); 253 } 254 255 static void print_disabled(struct seq_file *m) 256 { 257 seq_puts(m, "#\n" 258 "# Stack tracer disabled\n" 259 "#\n" 260 "# To enable the stack tracer, either add 'stacktrace' to the\n" 261 "# kernel command line\n" 262 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" 263 "#\n"); 264 } 265 266 static int t_show(struct seq_file *m, void *v) 267 { 268 long i; 269 int size; 270 271 if (v == SEQ_START_TOKEN) { 272 seq_printf(m, " Depth Size Location" 273 " (%d entries)\n" 274 " ----- ---- --------\n", 275 max_stack_trace.nr_entries - 1); 276 277 if (!stack_tracer_enabled && !max_stack_size) 278 print_disabled(m); 279 280 return 0; 281 } 282 283 i = *(long *)v; 284 285 if (i >= max_stack_trace.nr_entries || 286 stack_dump_trace[i] == ULONG_MAX) 287 return 0; 288 289 if (i+1 == max_stack_trace.nr_entries || 290 stack_dump_trace[i+1] == ULONG_MAX) 291 size = stack_dump_index[i]; 292 else 293 size = stack_dump_index[i] - stack_dump_index[i+1]; 294 295 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size); 296 297 trace_lookup_stack(m, i); 298 299 return 0; 300 } 301 302 static const struct seq_operations stack_trace_seq_ops = { 303 .start = t_start, 304 .next = t_next, 305 .stop = t_stop, 306 .show = t_show, 307 }; 308 309 static int stack_trace_open(struct inode *inode, struct file *file) 310 { 311 return seq_open(file, &stack_trace_seq_ops); 312 } 313 314 static const struct file_operations stack_trace_fops = { 315 .open = stack_trace_open, 316 .read = seq_read, 317 .llseek = seq_lseek, 318 .release = seq_release, 319 }; 320 321 int 322 stack_trace_sysctl(struct ctl_table *table, int write, 323 void __user *buffer, size_t *lenp, 324 loff_t *ppos) 325 { 326 int ret; 327 328 mutex_lock(&stack_sysctl_mutex); 329 330 ret = proc_dointvec(table, write, buffer, lenp, ppos); 331 332 if (ret || !write || 333 (last_stack_tracer_enabled == !!stack_tracer_enabled)) 334 goto out; 335 336 last_stack_tracer_enabled = !!stack_tracer_enabled; 337 338 if (stack_tracer_enabled) 339 register_ftrace_function(&trace_ops); 340 else 341 unregister_ftrace_function(&trace_ops); 342 343 out: 344 mutex_unlock(&stack_sysctl_mutex); 345 return ret; 346 } 347 348 static __init int enable_stacktrace(char *str) 349 { 350 stack_tracer_enabled = 1; 351 last_stack_tracer_enabled = 1; 352 return 1; 353 } 354 __setup("stacktrace", enable_stacktrace); 355 356 static __init int stack_trace_init(void) 357 { 358 struct dentry *d_tracer; 359 360 d_tracer = tracing_init_dentry(); 361 362 trace_create_file("stack_max_size", 0644, d_tracer, 363 &max_stack_size, &stack_max_size_fops); 364 365 trace_create_file("stack_trace", 0444, d_tracer, 366 NULL, &stack_trace_fops); 367 368 if (stack_tracer_enabled) 369 register_ftrace_function(&trace_ops); 370 371 return 0; 372 } 373 374 device_initcall(stack_trace_init); 375