1 /*
2 * trace stack traces
3 *
4 * Copyright (C) 2004-2008, Soeren Sandmann
5 * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
6 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
7 */
8 #include <linux/kallsyms.h>
9 #include <linux/debugfs.h>
10 #include <linux/hrtimer.h>
11 #include <linux/uaccess.h>
12 #include <linux/ftrace.h>
13 #include <linux/module.h>
14 #include <linux/irq.h>
15 #include <linux/fs.h>
16
17 #include <asm/stacktrace.h>
18
19 #include "trace.h"
20
21 static struct trace_array *sysprof_trace;
22 static int __read_mostly tracer_enabled;
23
24 /*
25 * 1 msec sample interval by default:
26 */
27 static unsigned long sample_period = 1000000;
28 static const unsigned int sample_max_depth = 512;
29
30 static DEFINE_MUTEX(sample_timer_lock);
31 /*
32 * Per CPU hrtimers that do the profiling:
33 */
34 static DEFINE_PER_CPU(struct hrtimer, stack_trace_hrtimer);
35
36 struct stack_frame {
37 const void __user *next_fp;
38 unsigned long return_address;
39 };
40
copy_stack_frame(const void __user * fp,struct stack_frame * frame)41 static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
42 {
43 int ret;
44
45 if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
46 return 0;
47
48 ret = 1;
49 pagefault_disable();
50 if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
51 ret = 0;
52 pagefault_enable();
53
54 return ret;
55 }
56
57 struct backtrace_info {
58 struct trace_array_cpu *data;
59 struct trace_array *tr;
60 int pos;
61 };
62
63 static void
backtrace_warning_symbol(void * data,char * msg,unsigned long symbol)64 backtrace_warning_symbol(void *data, char *msg, unsigned long symbol)
65 {
66 /* Ignore warnings */
67 }
68
backtrace_warning(void * data,char * msg)69 static void backtrace_warning(void *data, char *msg)
70 {
71 /* Ignore warnings */
72 }
73
backtrace_stack(void * data,char * name)74 static int backtrace_stack(void *data, char *name)
75 {
76 /* Don't bother with IRQ stacks for now */
77 return -1;
78 }
79
backtrace_address(void * data,unsigned long addr,int reliable)80 static void backtrace_address(void *data, unsigned long addr, int reliable)
81 {
82 struct backtrace_info *info = data;
83
84 if (info->pos < sample_max_depth && reliable) {
85 __trace_special(info->tr, info->data, 1, addr, 0);
86
87 info->pos++;
88 }
89 }
90
91 const static struct stacktrace_ops backtrace_ops = {
92 .warning = backtrace_warning,
93 .warning_symbol = backtrace_warning_symbol,
94 .stack = backtrace_stack,
95 .address = backtrace_address,
96 };
97
98 static int
trace_kernel(struct pt_regs * regs,struct trace_array * tr,struct trace_array_cpu * data)99 trace_kernel(struct pt_regs *regs, struct trace_array *tr,
100 struct trace_array_cpu *data)
101 {
102 struct backtrace_info info;
103 unsigned long bp;
104 char *stack;
105
106 info.tr = tr;
107 info.data = data;
108 info.pos = 1;
109
110 __trace_special(info.tr, info.data, 1, regs->ip, 0);
111
112 stack = ((char *)regs + sizeof(struct pt_regs));
113 #ifdef CONFIG_FRAME_POINTER
114 bp = regs->bp;
115 #else
116 bp = 0;
117 #endif
118
119 dump_trace(NULL, regs, (void *)stack, bp, &backtrace_ops, &info);
120
121 return info.pos;
122 }
123
timer_notify(struct pt_regs * regs,int cpu)124 static void timer_notify(struct pt_regs *regs, int cpu)
125 {
126 struct trace_array_cpu *data;
127 struct stack_frame frame;
128 struct trace_array *tr;
129 const void __user *fp;
130 int is_user;
131 int i;
132
133 if (!regs)
134 return;
135
136 tr = sysprof_trace;
137 data = tr->data[cpu];
138 is_user = user_mode(regs);
139
140 if (!current || current->pid == 0)
141 return;
142
143 if (is_user && current->state != TASK_RUNNING)
144 return;
145
146 __trace_special(tr, data, 0, 0, current->pid);
147
148 if (!is_user)
149 i = trace_kernel(regs, tr, data);
150 else
151 i = 0;
152
153 /*
154 * Trace user stack if we are not a kernel thread
155 */
156 if (current->mm && i < sample_max_depth) {
157 regs = (struct pt_regs *)current->thread.sp0 - 1;
158
159 fp = (void __user *)regs->bp;
160
161 __trace_special(tr, data, 2, regs->ip, 0);
162
163 while (i < sample_max_depth) {
164 frame.next_fp = NULL;
165 frame.return_address = 0;
166 if (!copy_stack_frame(fp, &frame))
167 break;
168 if ((unsigned long)fp < regs->sp)
169 break;
170
171 __trace_special(tr, data, 2, frame.return_address,
172 (unsigned long)fp);
173 fp = frame.next_fp;
174
175 i++;
176 }
177
178 }
179
180 /*
181 * Special trace entry if we overflow the max depth:
182 */
183 if (i == sample_max_depth)
184 __trace_special(tr, data, -1, -1, -1);
185
186 __trace_special(tr, data, 3, current->pid, i);
187 }
188
stack_trace_timer_fn(struct hrtimer * hrtimer)189 static enum hrtimer_restart stack_trace_timer_fn(struct hrtimer *hrtimer)
190 {
191 /* trace here */
192 timer_notify(get_irq_regs(), smp_processor_id());
193
194 hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
195
196 return HRTIMER_RESTART;
197 }
198
start_stack_timer(void * unused)199 static void start_stack_timer(void *unused)
200 {
201 struct hrtimer *hrtimer = &__get_cpu_var(stack_trace_hrtimer);
202
203 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
204 hrtimer->function = stack_trace_timer_fn;
205
206 hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL);
207 }
208
start_stack_timers(void)209 static void start_stack_timers(void)
210 {
211 on_each_cpu(start_stack_timer, NULL, 1);
212 }
213
stop_stack_timer(int cpu)214 static void stop_stack_timer(int cpu)
215 {
216 struct hrtimer *hrtimer = &per_cpu(stack_trace_hrtimer, cpu);
217
218 hrtimer_cancel(hrtimer);
219 }
220
stop_stack_timers(void)221 static void stop_stack_timers(void)
222 {
223 int cpu;
224
225 for_each_online_cpu(cpu)
226 stop_stack_timer(cpu);
227 }
228
start_stack_trace(struct trace_array * tr)229 static void start_stack_trace(struct trace_array *tr)
230 {
231 mutex_lock(&sample_timer_lock);
232 tracing_reset_online_cpus(tr);
233 start_stack_timers();
234 tracer_enabled = 1;
235 mutex_unlock(&sample_timer_lock);
236 }
237
stop_stack_trace(struct trace_array * tr)238 static void stop_stack_trace(struct trace_array *tr)
239 {
240 mutex_lock(&sample_timer_lock);
241 stop_stack_timers();
242 tracer_enabled = 0;
243 mutex_unlock(&sample_timer_lock);
244 }
245
stack_trace_init(struct trace_array * tr)246 static int stack_trace_init(struct trace_array *tr)
247 {
248 sysprof_trace = tr;
249
250 start_stack_trace(tr);
251 return 0;
252 }
253
stack_trace_reset(struct trace_array * tr)254 static void stack_trace_reset(struct trace_array *tr)
255 {
256 stop_stack_trace(tr);
257 }
258
259 static struct tracer stack_trace __read_mostly =
260 {
261 .name = "sysprof",
262 .init = stack_trace_init,
263 .reset = stack_trace_reset,
264 #ifdef CONFIG_FTRACE_SELFTEST
265 .selftest = trace_selftest_startup_sysprof,
266 #endif
267 };
268
init_stack_trace(void)269 __init static int init_stack_trace(void)
270 {
271 return register_tracer(&stack_trace);
272 }
273 device_initcall(init_stack_trace);
274
275 #define MAX_LONG_DIGITS 22
276
277 static ssize_t
sysprof_sample_read(struct file * filp,char __user * ubuf,size_t cnt,loff_t * ppos)278 sysprof_sample_read(struct file *filp, char __user *ubuf,
279 size_t cnt, loff_t *ppos)
280 {
281 char buf[MAX_LONG_DIGITS];
282 int r;
283
284 r = sprintf(buf, "%ld\n", nsecs_to_usecs(sample_period));
285
286 return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
287 }
288
289 static ssize_t
sysprof_sample_write(struct file * filp,const char __user * ubuf,size_t cnt,loff_t * ppos)290 sysprof_sample_write(struct file *filp, const char __user *ubuf,
291 size_t cnt, loff_t *ppos)
292 {
293 char buf[MAX_LONG_DIGITS];
294 unsigned long val;
295
296 if (cnt > MAX_LONG_DIGITS-1)
297 cnt = MAX_LONG_DIGITS-1;
298
299 if (copy_from_user(&buf, ubuf, cnt))
300 return -EFAULT;
301
302 buf[cnt] = 0;
303
304 val = simple_strtoul(buf, NULL, 10);
305 /*
306 * Enforce a minimum sample period of 100 usecs:
307 */
308 if (val < 100)
309 val = 100;
310
311 mutex_lock(&sample_timer_lock);
312 stop_stack_timers();
313 sample_period = val * 1000;
314 start_stack_timers();
315 mutex_unlock(&sample_timer_lock);
316
317 return cnt;
318 }
319
320 static struct file_operations sysprof_sample_fops = {
321 .read = sysprof_sample_read,
322 .write = sysprof_sample_write,
323 };
324
init_tracer_sysprof_debugfs(struct dentry * d_tracer)325 void init_tracer_sysprof_debugfs(struct dentry *d_tracer)
326 {
327 struct dentry *entry;
328
329 entry = debugfs_create_file("sysprof_sample_period", 0644,
330 d_tracer, NULL, &sysprof_sample_fops);
331 if (entry)
332 return;
333 pr_warning("Could not create debugfs 'dyn_ftrace_total_info' entry\n");
334 }
335