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