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 raw_spinlock_t max_stack_lock = 31 (raw_spinlock_t)__RAW_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 __raw_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 __raw_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; 160 161 if (count >= sizeof(buf)) 162 return -EINVAL; 163 164 if (copy_from_user(&buf, ubuf, count)) 165 return -EFAULT; 166 167 buf[count] = 0; 168 169 ret = strict_strtoul(buf, 10, &val); 170 if (ret < 0) 171 return ret; 172 173 local_irq_save(flags); 174 __raw_spin_lock(&max_stack_lock); 175 *ptr = val; 176 __raw_spin_unlock(&max_stack_lock); 177 local_irq_restore(flags); 178 179 return count; 180 } 181 182 static const struct file_operations stack_max_size_fops = { 183 .open = tracing_open_generic, 184 .read = stack_max_size_read, 185 .write = stack_max_size_write, 186 }; 187 188 static void * 189 t_next(struct seq_file *m, void *v, loff_t *pos) 190 { 191 long i; 192 193 (*pos)++; 194 195 if (v == SEQ_START_TOKEN) 196 i = 0; 197 else { 198 i = *(long *)v; 199 i++; 200 } 201 202 if (i >= max_stack_trace.nr_entries || 203 stack_dump_trace[i] == ULONG_MAX) 204 return NULL; 205 206 m->private = (void *)i; 207 208 return &m->private; 209 } 210 211 static void *t_start(struct seq_file *m, loff_t *pos) 212 { 213 void *t = SEQ_START_TOKEN; 214 loff_t l = 0; 215 216 local_irq_disable(); 217 __raw_spin_lock(&max_stack_lock); 218 219 if (*pos == 0) 220 return SEQ_START_TOKEN; 221 222 for (; t && l < *pos; t = t_next(m, t, &l)) 223 ; 224 225 return t; 226 } 227 228 static void t_stop(struct seq_file *m, void *p) 229 { 230 __raw_spin_unlock(&max_stack_lock); 231 local_irq_enable(); 232 } 233 234 static int trace_lookup_stack(struct seq_file *m, long i) 235 { 236 unsigned long addr = stack_dump_trace[i]; 237 #ifdef CONFIG_KALLSYMS 238 char str[KSYM_SYMBOL_LEN]; 239 240 sprint_symbol(str, addr); 241 242 return seq_printf(m, "%s\n", str); 243 #else 244 return seq_printf(m, "%p\n", (void*)addr); 245 #endif 246 } 247 248 static int t_show(struct seq_file *m, void *v) 249 { 250 long i; 251 int size; 252 253 if (v == SEQ_START_TOKEN) { 254 seq_printf(m, " Depth Size Location" 255 " (%d entries)\n" 256 " ----- ---- --------\n", 257 max_stack_trace.nr_entries); 258 return 0; 259 } 260 261 i = *(long *)v; 262 263 if (i >= max_stack_trace.nr_entries || 264 stack_dump_trace[i] == ULONG_MAX) 265 return 0; 266 267 if (i+1 == max_stack_trace.nr_entries || 268 stack_dump_trace[i+1] == ULONG_MAX) 269 size = stack_dump_index[i]; 270 else 271 size = stack_dump_index[i] - stack_dump_index[i+1]; 272 273 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size); 274 275 trace_lookup_stack(m, i); 276 277 return 0; 278 } 279 280 static const struct seq_operations stack_trace_seq_ops = { 281 .start = t_start, 282 .next = t_next, 283 .stop = t_stop, 284 .show = t_show, 285 }; 286 287 static int stack_trace_open(struct inode *inode, struct file *file) 288 { 289 int ret; 290 291 ret = seq_open(file, &stack_trace_seq_ops); 292 293 return ret; 294 } 295 296 static const struct file_operations stack_trace_fops = { 297 .open = stack_trace_open, 298 .read = seq_read, 299 .llseek = seq_lseek, 300 }; 301 302 int 303 stack_trace_sysctl(struct ctl_table *table, int write, 304 struct file *file, void __user *buffer, size_t *lenp, 305 loff_t *ppos) 306 { 307 int ret; 308 309 mutex_lock(&stack_sysctl_mutex); 310 311 ret = proc_dointvec(table, write, file, buffer, lenp, ppos); 312 313 if (ret || !write || 314 (last_stack_tracer_enabled == stack_tracer_enabled)) 315 goto out; 316 317 last_stack_tracer_enabled = stack_tracer_enabled; 318 319 if (stack_tracer_enabled) 320 register_ftrace_function(&trace_ops); 321 else 322 unregister_ftrace_function(&trace_ops); 323 324 out: 325 mutex_unlock(&stack_sysctl_mutex); 326 return ret; 327 } 328 329 static __init int enable_stacktrace(char *str) 330 { 331 stack_tracer_enabled = 1; 332 last_stack_tracer_enabled = 1; 333 return 1; 334 } 335 __setup("stacktrace", enable_stacktrace); 336 337 static __init int stack_trace_init(void) 338 { 339 struct dentry *d_tracer; 340 struct dentry *entry; 341 342 d_tracer = tracing_init_dentry(); 343 344 entry = debugfs_create_file("stack_max_size", 0644, d_tracer, 345 &max_stack_size, &stack_max_size_fops); 346 if (!entry) 347 pr_warning("Could not create debugfs 'stack_max_size' entry\n"); 348 349 entry = debugfs_create_file("stack_trace", 0444, d_tracer, 350 NULL, &stack_trace_fops); 351 if (!entry) 352 pr_warning("Could not create debugfs 'stack_trace' entry\n"); 353 354 if (stack_tracer_enabled) 355 register_ftrace_function(&trace_ops); 356 357 return 0; 358 } 359 360 device_initcall(stack_trace_init); 361