Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging
[qemu.git] / trace / simple.c
1 /*
2 * Simple trace backend
3 *
4 * Copyright IBM, Corp. 2010
5 *
6 * This work is licensed under the terms of the GNU GPL, version 2. See
7 * the COPYING file in the top-level directory.
8 *
9 */
10
11 #include <stdlib.h>
12 #include <stdint.h>
13 #include <stdio.h>
14 #include <time.h>
15 #ifndef _WIN32
16 #include <signal.h>
17 #include <pthread.h>
18 #endif
19 #include "qemu/timer.h"
20 #include "trace.h"
21 #include "trace/control.h"
22 #include "trace/simple.h"
23
24 /** Trace file header event ID */
25 #define HEADER_EVENT_ID (~(uint64_t)0) /* avoids conflicting with TraceEventIDs */
26
27 /** Trace file magic number */
28 #define HEADER_MAGIC 0xf2b177cb0aa429b4ULL
29
30 /** Trace file version number, bump if format changes */
31 #define HEADER_VERSION 2
32
33 /** Records were dropped event ID */
34 #define DROPPED_EVENT_ID (~(uint64_t)0 - 1)
35
36 /** Trace record is valid */
37 #define TRACE_RECORD_VALID ((uint64_t)1 << 63)
38
39 /*
40 * Trace records are written out by a dedicated thread. The thread waits for
41 * records to become available, writes them out, and then waits again.
42 */
43 #if GLIB_CHECK_VERSION(2, 32, 0)
44 static GMutex trace_lock;
45 #define lock_trace_lock() g_mutex_lock(&trace_lock)
46 #define unlock_trace_lock() g_mutex_unlock(&trace_lock)
47 #define get_trace_lock_mutex() (&trace_lock)
48 #else
49 static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
50 #define lock_trace_lock() g_static_mutex_lock(&trace_lock)
51 #define unlock_trace_lock() g_static_mutex_unlock(&trace_lock)
52 #define get_trace_lock_mutex() g_static_mutex_get_mutex(&trace_lock)
53 #endif
54
55 /* g_cond_new() was deprecated in glib 2.31 but we still need to support it */
56 #if GLIB_CHECK_VERSION(2, 31, 0)
57 static GCond the_trace_available_cond;
58 static GCond the_trace_empty_cond;
59 static GCond *trace_available_cond = &the_trace_available_cond;
60 static GCond *trace_empty_cond = &the_trace_empty_cond;
61 #else
62 static GCond *trace_available_cond;
63 static GCond *trace_empty_cond;
64 #endif
65
66 static bool trace_available;
67 static bool trace_writeout_enabled;
68
69 enum {
70 TRACE_BUF_LEN = 4096 * 64,
71 TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
72 };
73
74 uint8_t trace_buf[TRACE_BUF_LEN];
75 static volatile gint trace_idx;
76 static unsigned int writeout_idx;
77 static volatile gint dropped_events;
78 static FILE *trace_fp;
79 static char *trace_file_name;
80
81 /* * Trace buffer entry */
82 typedef struct {
83 uint64_t event; /* TraceEventID */
84 uint64_t timestamp_ns;
85 uint32_t length; /* in bytes */
86 uint32_t reserved; /* unused */
87 uint64_t arguments[];
88 } TraceRecord;
89
90 typedef struct {
91 uint64_t header_event_id; /* HEADER_EVENT_ID */
92 uint64_t header_magic; /* HEADER_MAGIC */
93 uint64_t header_version; /* HEADER_VERSION */
94 } TraceLogHeader;
95
96
97 static void read_from_buffer(unsigned int idx, void *dataptr, size_t size);
98 static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size);
99
100 static void clear_buffer_range(unsigned int idx, size_t len)
101 {
102 uint32_t num = 0;
103 while (num < len) {
104 if (idx >= TRACE_BUF_LEN) {
105 idx = idx % TRACE_BUF_LEN;
106 }
107 trace_buf[idx++] = 0;
108 num++;
109 }
110 }
111 /**
112 * Read a trace record from the trace buffer
113 *
114 * @idx Trace buffer index
115 * @record Trace record to fill
116 *
117 * Returns false if the record is not valid.
118 */
119 static bool get_trace_record(unsigned int idx, TraceRecord **recordptr)
120 {
121 uint64_t event_flag = 0;
122 TraceRecord record;
123 /* read the event flag to see if its a valid record */
124 read_from_buffer(idx, &record, sizeof(event_flag));
125
126 if (!(record.event & TRACE_RECORD_VALID)) {
127 return false;
128 }
129
130 smp_rmb(); /* read memory barrier before accessing record */
131 /* read the record header to know record length */
132 read_from_buffer(idx, &record, sizeof(TraceRecord));
133 *recordptr = malloc(record.length); /* dont use g_malloc, can deadlock when traced */
134 /* make a copy of record to avoid being overwritten */
135 read_from_buffer(idx, *recordptr, record.length);
136 smp_rmb(); /* memory barrier before clearing valid flag */
137 (*recordptr)->event &= ~TRACE_RECORD_VALID;
138 /* clear the trace buffer range for consumed record otherwise any byte
139 * with its MSB set may be considered as a valid event id when the writer
140 * thread crosses this range of buffer again.
141 */
142 clear_buffer_range(idx, record.length);
143 return true;
144 }
145
146 /**
147 * Kick writeout thread
148 *
149 * @wait Whether to wait for writeout thread to complete
150 */
151 static void flush_trace_file(bool wait)
152 {
153 lock_trace_lock();
154 trace_available = true;
155 g_cond_signal(trace_available_cond);
156
157 if (wait) {
158 g_cond_wait(trace_empty_cond, get_trace_lock_mutex());
159 }
160
161 unlock_trace_lock();
162 }
163
164 static void wait_for_trace_records_available(void)
165 {
166 lock_trace_lock();
167 while (!(trace_available && trace_writeout_enabled)) {
168 g_cond_signal(trace_empty_cond);
169 g_cond_wait(trace_available_cond, get_trace_lock_mutex());
170 }
171 trace_available = false;
172 unlock_trace_lock();
173 }
174
175 static gpointer writeout_thread(gpointer opaque)
176 {
177 TraceRecord *recordptr;
178 union {
179 TraceRecord rec;
180 uint8_t bytes[sizeof(TraceRecord) + sizeof(uint64_t)];
181 } dropped;
182 unsigned int idx = 0;
183 int dropped_count;
184 size_t unused __attribute__ ((unused));
185
186 for (;;) {
187 wait_for_trace_records_available();
188
189 if (g_atomic_int_get(&dropped_events)) {
190 dropped.rec.event = DROPPED_EVENT_ID,
191 dropped.rec.timestamp_ns = get_clock();
192 dropped.rec.length = sizeof(TraceRecord) + sizeof(uint64_t),
193 dropped.rec.reserved = 0;
194 do {
195 dropped_count = g_atomic_int_get(&dropped_events);
196 } while (!g_atomic_int_compare_and_exchange(&dropped_events,
197 dropped_count, 0));
198 dropped.rec.arguments[0] = dropped_count;
199 unused = fwrite(&dropped.rec, dropped.rec.length, 1, trace_fp);
200 }
201
202 while (get_trace_record(idx, &recordptr)) {
203 unused = fwrite(recordptr, recordptr->length, 1, trace_fp);
204 writeout_idx += recordptr->length;
205 free(recordptr); /* dont use g_free, can deadlock when traced */
206 idx = writeout_idx % TRACE_BUF_LEN;
207 }
208
209 fflush(trace_fp);
210 }
211 return NULL;
212 }
213
214 void trace_record_write_u64(TraceBufferRecord *rec, uint64_t val)
215 {
216 rec->rec_off = write_to_buffer(rec->rec_off, &val, sizeof(uint64_t));
217 }
218
219 void trace_record_write_str(TraceBufferRecord *rec, const char *s, uint32_t slen)
220 {
221 /* Write string length first */
222 rec->rec_off = write_to_buffer(rec->rec_off, &slen, sizeof(slen));
223 /* Write actual string now */
224 rec->rec_off = write_to_buffer(rec->rec_off, (void*)s, slen);
225 }
226
227 int trace_record_start(TraceBufferRecord *rec, TraceEventID event, size_t datasize)
228 {
229 unsigned int idx, rec_off, old_idx, new_idx;
230 uint32_t rec_len = sizeof(TraceRecord) + datasize;
231 uint64_t event_u64 = event;
232 uint64_t timestamp_ns = get_clock();
233
234 do {
235 old_idx = g_atomic_int_get(&trace_idx);
236 smp_rmb();
237 new_idx = old_idx + rec_len;
238
239 if (new_idx - writeout_idx > TRACE_BUF_LEN) {
240 /* Trace Buffer Full, Event dropped ! */
241 g_atomic_int_inc(&dropped_events);
242 return -ENOSPC;
243 }
244 } while (!g_atomic_int_compare_and_exchange(&trace_idx, old_idx, new_idx));
245
246 idx = old_idx % TRACE_BUF_LEN;
247
248 rec_off = idx;
249 rec_off = write_to_buffer(rec_off, &event_u64, sizeof(event_u64));
250 rec_off = write_to_buffer(rec_off, &timestamp_ns, sizeof(timestamp_ns));
251 rec_off = write_to_buffer(rec_off, &rec_len, sizeof(rec_len));
252
253 rec->tbuf_idx = idx;
254 rec->rec_off = (idx + sizeof(TraceRecord)) % TRACE_BUF_LEN;
255 return 0;
256 }
257
258 static void read_from_buffer(unsigned int idx, void *dataptr, size_t size)
259 {
260 uint8_t *data_ptr = dataptr;
261 uint32_t x = 0;
262 while (x < size) {
263 if (idx >= TRACE_BUF_LEN) {
264 idx = idx % TRACE_BUF_LEN;
265 }
266 data_ptr[x++] = trace_buf[idx++];
267 }
268 }
269
270 static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size)
271 {
272 uint8_t *data_ptr = dataptr;
273 uint32_t x = 0;
274 while (x < size) {
275 if (idx >= TRACE_BUF_LEN) {
276 idx = idx % TRACE_BUF_LEN;
277 }
278 trace_buf[idx++] = data_ptr[x++];
279 }
280 return idx; /* most callers wants to know where to write next */
281 }
282
283 void trace_record_finish(TraceBufferRecord *rec)
284 {
285 TraceRecord record;
286 read_from_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
287 smp_wmb(); /* write barrier before marking as valid */
288 record.event |= TRACE_RECORD_VALID;
289 write_to_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
290
291 if (((unsigned int)g_atomic_int_get(&trace_idx) - writeout_idx)
292 > TRACE_BUF_FLUSH_THRESHOLD) {
293 flush_trace_file(false);
294 }
295 }
296
297 void st_set_trace_file_enabled(bool enable)
298 {
299 if (enable == !!trace_fp) {
300 return; /* no change */
301 }
302
303 /* Halt trace writeout */
304 flush_trace_file(true);
305 trace_writeout_enabled = false;
306 flush_trace_file(true);
307
308 if (enable) {
309 static const TraceLogHeader header = {
310 .header_event_id = HEADER_EVENT_ID,
311 .header_magic = HEADER_MAGIC,
312 /* Older log readers will check for version at next location */
313 .header_version = HEADER_VERSION,
314 };
315
316 trace_fp = fopen(trace_file_name, "wb");
317 if (!trace_fp) {
318 return;
319 }
320
321 if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
322 fclose(trace_fp);
323 trace_fp = NULL;
324 return;
325 }
326
327 /* Resume trace writeout */
328 trace_writeout_enabled = true;
329 flush_trace_file(false);
330 } else {
331 fclose(trace_fp);
332 trace_fp = NULL;
333 }
334 }
335
336 /**
337 * Set the name of a trace file
338 *
339 * @file The trace file name or NULL for the default name-<pid> set at
340 * config time
341 */
342 bool st_set_trace_file(const char *file)
343 {
344 st_set_trace_file_enabled(false);
345
346 g_free(trace_file_name);
347
348 if (!file) {
349 trace_file_name = g_strdup_printf(CONFIG_TRACE_FILE, getpid());
350 } else {
351 trace_file_name = g_strdup_printf("%s", file);
352 }
353
354 st_set_trace_file_enabled(true);
355 return true;
356 }
357
358 void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
359 {
360 stream_printf(stream, "Trace file \"%s\" %s.\n",
361 trace_file_name, trace_fp ? "on" : "off");
362 }
363
364 void st_flush_trace_buffer(void)
365 {
366 flush_trace_file(true);
367 }
368
369 void trace_print_events(FILE *stream, fprintf_function stream_printf)
370 {
371 unsigned int i;
372
373 for (i = 0; i < trace_event_count(); i++) {
374 TraceEvent *ev = trace_event_id(i);
375 stream_printf(stream, "%s [Event ID %u] : state %u\n",
376 trace_event_get_name(ev), i, trace_event_get_state_dynamic(ev));
377 }
378 }
379
380 void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state)
381 {
382 ev->dstate = state;
383 }
384
385 /* Helper function to create a thread with signals blocked. Use glib's
386 * portable threads since QEMU abstractions cannot be used due to reentrancy in
387 * the tracer. Also note the signal masking on POSIX hosts so that the thread
388 * does not steal signals when the rest of the program wants them blocked.
389 */
390 static GThread *trace_thread_create(GThreadFunc fn)
391 {
392 GThread *thread;
393 #ifndef _WIN32
394 sigset_t set, oldset;
395
396 sigfillset(&set);
397 pthread_sigmask(SIG_SETMASK, &set, &oldset);
398 #endif
399
400 #if GLIB_CHECK_VERSION(2, 31, 0)
401 thread = g_thread_new("trace-thread", fn, NULL);
402 #else
403 thread = g_thread_create(fn, NULL, FALSE, NULL);
404 #endif
405
406 #ifndef _WIN32
407 pthread_sigmask(SIG_SETMASK, &oldset, NULL);
408 #endif
409
410 return thread;
411 }
412
413 bool trace_backend_init(const char *events, const char *file)
414 {
415 GThread *thread;
416
417 if (!g_thread_supported()) {
418 #if !GLIB_CHECK_VERSION(2, 31, 0)
419 g_thread_init(NULL);
420 #else
421 fprintf(stderr, "glib threading failed to initialize.\n");
422 exit(1);
423 #endif
424 }
425
426 #if !GLIB_CHECK_VERSION(2, 31, 0)
427 trace_available_cond = g_cond_new();
428 trace_empty_cond = g_cond_new();
429 #endif
430
431 thread = trace_thread_create(writeout_thread);
432 if (!thread) {
433 fprintf(stderr, "warning: unable to initialize simple trace backend\n");
434 return false;
435 }
436
437 atexit(st_flush_trace_buffer);
438 trace_backend_init_events(events);
439 st_set_trace_file(file);
440 return true;
441 }