Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20200117-1' into...
[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 "qemu/osdep.h"
12 #ifndef _WIN32
13 #include <pthread.h>
14 #endif
15 #include "qemu/timer.h"
16 #include "trace/control.h"
17 #include "trace/simple.h"
18 #include "qemu/error-report.h"
19 #include "qemu/qemu-print.h"
20
21 /** Trace file header event ID, picked to avoid conflict with real event IDs */
22 #define HEADER_EVENT_ID (~(uint64_t)0)
23
24 /** Trace file magic number */
25 #define HEADER_MAGIC 0xf2b177cb0aa429b4ULL
26
27 /** Trace file version number, bump if format changes */
28 #define HEADER_VERSION 4
29
30 /** Records were dropped event ID */
31 #define DROPPED_EVENT_ID (~(uint64_t)0 - 1)
32
33 /** Trace record is valid */
34 #define TRACE_RECORD_VALID ((uint64_t)1 << 63)
35
36 /*
37 * Trace records are written out by a dedicated thread. The thread waits for
38 * records to become available, writes them out, and then waits again.
39 */
40 static GMutex trace_lock;
41 static GCond trace_available_cond;
42 static GCond trace_empty_cond;
43
44 static bool trace_available;
45 static bool trace_writeout_enabled;
46
47 enum {
48 TRACE_BUF_LEN = 4096 * 64,
49 TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
50 };
51
52 uint8_t trace_buf[TRACE_BUF_LEN];
53 static volatile gint trace_idx;
54 static unsigned int writeout_idx;
55 static volatile gint dropped_events;
56 static uint32_t trace_pid;
57 static FILE *trace_fp;
58 static char *trace_file_name;
59
60 #define TRACE_RECORD_TYPE_MAPPING 0
61 #define TRACE_RECORD_TYPE_EVENT 1
62
63 /* * Trace buffer entry */
64 typedef struct {
65 uint64_t event; /* event ID value */
66 uint64_t timestamp_ns;
67 uint32_t length; /* in bytes */
68 uint32_t pid;
69 uint64_t arguments[];
70 } TraceRecord;
71
72 typedef struct {
73 uint64_t header_event_id; /* HEADER_EVENT_ID */
74 uint64_t header_magic; /* HEADER_MAGIC */
75 uint64_t header_version; /* HEADER_VERSION */
76 } TraceLogHeader;
77
78
79 static void read_from_buffer(unsigned int idx, void *dataptr, size_t size);
80 static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size);
81
82 static void clear_buffer_range(unsigned int idx, size_t len)
83 {
84 uint32_t num = 0;
85 while (num < len) {
86 if (idx >= TRACE_BUF_LEN) {
87 idx = idx % TRACE_BUF_LEN;
88 }
89 trace_buf[idx++] = 0;
90 num++;
91 }
92 }
93 /**
94 * Read a trace record from the trace buffer
95 *
96 * @idx Trace buffer index
97 * @record Trace record to fill
98 *
99 * Returns false if the record is not valid.
100 */
101 static bool get_trace_record(unsigned int idx, TraceRecord **recordptr)
102 {
103 uint64_t event_flag = 0;
104 TraceRecord record;
105 /* read the event flag to see if its a valid record */
106 read_from_buffer(idx, &record, sizeof(event_flag));
107
108 if (!(record.event & TRACE_RECORD_VALID)) {
109 return false;
110 }
111
112 smp_rmb(); /* read memory barrier before accessing record */
113 /* read the record header to know record length */
114 read_from_buffer(idx, &record, sizeof(TraceRecord));
115 *recordptr = malloc(record.length); /* don't use g_malloc, can deadlock when traced */
116 /* make a copy of record to avoid being overwritten */
117 read_from_buffer(idx, *recordptr, record.length);
118 smp_rmb(); /* memory barrier before clearing valid flag */
119 (*recordptr)->event &= ~TRACE_RECORD_VALID;
120 /* clear the trace buffer range for consumed record otherwise any byte
121 * with its MSB set may be considered as a valid event id when the writer
122 * thread crosses this range of buffer again.
123 */
124 clear_buffer_range(idx, record.length);
125 return true;
126 }
127
128 /**
129 * Kick writeout thread
130 *
131 * @wait Whether to wait for writeout thread to complete
132 */
133 static void flush_trace_file(bool wait)
134 {
135 g_mutex_lock(&trace_lock);
136 trace_available = true;
137 g_cond_signal(&trace_available_cond);
138
139 if (wait) {
140 g_cond_wait(&trace_empty_cond, &trace_lock);
141 }
142
143 g_mutex_unlock(&trace_lock);
144 }
145
146 static void wait_for_trace_records_available(void)
147 {
148 g_mutex_lock(&trace_lock);
149 while (!(trace_available && trace_writeout_enabled)) {
150 g_cond_signal(&trace_empty_cond);
151 g_cond_wait(&trace_available_cond, &trace_lock);
152 }
153 trace_available = false;
154 g_mutex_unlock(&trace_lock);
155 }
156
157 static gpointer writeout_thread(gpointer opaque)
158 {
159 TraceRecord *recordptr;
160 union {
161 TraceRecord rec;
162 uint8_t bytes[sizeof(TraceRecord) + sizeof(uint64_t)];
163 } dropped;
164 unsigned int idx = 0;
165 int dropped_count;
166 size_t unused __attribute__ ((unused));
167 uint64_t type = TRACE_RECORD_TYPE_EVENT;
168
169 for (;;) {
170 wait_for_trace_records_available();
171
172 if (g_atomic_int_get(&dropped_events)) {
173 dropped.rec.event = DROPPED_EVENT_ID;
174 dropped.rec.timestamp_ns = get_clock();
175 dropped.rec.length = sizeof(TraceRecord) + sizeof(uint64_t);
176 dropped.rec.pid = trace_pid;
177 do {
178 dropped_count = g_atomic_int_get(&dropped_events);
179 } while (!g_atomic_int_compare_and_exchange(&dropped_events,
180 dropped_count, 0));
181 dropped.rec.arguments[0] = dropped_count;
182 unused = fwrite(&type, sizeof(type), 1, trace_fp);
183 unused = fwrite(&dropped.rec, dropped.rec.length, 1, trace_fp);
184 }
185
186 while (get_trace_record(idx, &recordptr)) {
187 unused = fwrite(&type, sizeof(type), 1, trace_fp);
188 unused = fwrite(recordptr, recordptr->length, 1, trace_fp);
189 writeout_idx += recordptr->length;
190 free(recordptr); /* don't use g_free, can deadlock when traced */
191 idx = writeout_idx % TRACE_BUF_LEN;
192 }
193
194 fflush(trace_fp);
195 }
196 return NULL;
197 }
198
199 void trace_record_write_u64(TraceBufferRecord *rec, uint64_t val)
200 {
201 rec->rec_off = write_to_buffer(rec->rec_off, &val, sizeof(uint64_t));
202 }
203
204 void trace_record_write_str(TraceBufferRecord *rec, const char *s, uint32_t slen)
205 {
206 /* Write string length first */
207 rec->rec_off = write_to_buffer(rec->rec_off, &slen, sizeof(slen));
208 /* Write actual string now */
209 rec->rec_off = write_to_buffer(rec->rec_off, (void*)s, slen);
210 }
211
212 int trace_record_start(TraceBufferRecord *rec, uint32_t event, size_t datasize)
213 {
214 unsigned int idx, rec_off, old_idx, new_idx;
215 uint32_t rec_len = sizeof(TraceRecord) + datasize;
216 uint64_t event_u64 = event;
217 uint64_t timestamp_ns = get_clock();
218
219 do {
220 old_idx = g_atomic_int_get(&trace_idx);
221 smp_rmb();
222 new_idx = old_idx + rec_len;
223
224 if (new_idx - writeout_idx > TRACE_BUF_LEN) {
225 /* Trace Buffer Full, Event dropped ! */
226 g_atomic_int_inc(&dropped_events);
227 return -ENOSPC;
228 }
229 } while (!g_atomic_int_compare_and_exchange(&trace_idx, old_idx, new_idx));
230
231 idx = old_idx % TRACE_BUF_LEN;
232
233 rec_off = idx;
234 rec_off = write_to_buffer(rec_off, &event_u64, sizeof(event_u64));
235 rec_off = write_to_buffer(rec_off, &timestamp_ns, sizeof(timestamp_ns));
236 rec_off = write_to_buffer(rec_off, &rec_len, sizeof(rec_len));
237 rec_off = write_to_buffer(rec_off, &trace_pid, sizeof(trace_pid));
238
239 rec->tbuf_idx = idx;
240 rec->rec_off = (idx + sizeof(TraceRecord)) % TRACE_BUF_LEN;
241 return 0;
242 }
243
244 static void read_from_buffer(unsigned int idx, void *dataptr, size_t size)
245 {
246 uint8_t *data_ptr = dataptr;
247 uint32_t x = 0;
248 while (x < size) {
249 if (idx >= TRACE_BUF_LEN) {
250 idx = idx % TRACE_BUF_LEN;
251 }
252 data_ptr[x++] = trace_buf[idx++];
253 }
254 }
255
256 static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size)
257 {
258 uint8_t *data_ptr = dataptr;
259 uint32_t x = 0;
260 while (x < size) {
261 if (idx >= TRACE_BUF_LEN) {
262 idx = idx % TRACE_BUF_LEN;
263 }
264 trace_buf[idx++] = data_ptr[x++];
265 }
266 return idx; /* most callers wants to know where to write next */
267 }
268
269 void trace_record_finish(TraceBufferRecord *rec)
270 {
271 TraceRecord record;
272 read_from_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
273 smp_wmb(); /* write barrier before marking as valid */
274 record.event |= TRACE_RECORD_VALID;
275 write_to_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
276
277 if (((unsigned int)g_atomic_int_get(&trace_idx) - writeout_idx)
278 > TRACE_BUF_FLUSH_THRESHOLD) {
279 flush_trace_file(false);
280 }
281 }
282
283 static int st_write_event_mapping(void)
284 {
285 uint64_t type = TRACE_RECORD_TYPE_MAPPING;
286 TraceEventIter iter;
287 TraceEvent *ev;
288
289 trace_event_iter_init(&iter, NULL);
290 while ((ev = trace_event_iter_next(&iter)) != NULL) {
291 uint64_t id = trace_event_get_id(ev);
292 const char *name = trace_event_get_name(ev);
293 uint32_t len = strlen(name);
294 if (fwrite(&type, sizeof(type), 1, trace_fp) != 1 ||
295 fwrite(&id, sizeof(id), 1, trace_fp) != 1 ||
296 fwrite(&len, sizeof(len), 1, trace_fp) != 1 ||
297 fwrite(name, len, 1, trace_fp) != 1) {
298 return -1;
299 }
300 }
301
302 return 0;
303 }
304
305 void st_set_trace_file_enabled(bool enable)
306 {
307 if (enable == !!trace_fp) {
308 return; /* no change */
309 }
310
311 /* Halt trace writeout */
312 flush_trace_file(true);
313 trace_writeout_enabled = false;
314 flush_trace_file(true);
315
316 if (enable) {
317 static const TraceLogHeader header = {
318 .header_event_id = HEADER_EVENT_ID,
319 .header_magic = HEADER_MAGIC,
320 /* Older log readers will check for version at next location */
321 .header_version = HEADER_VERSION,
322 };
323
324 trace_fp = fopen(trace_file_name, "wb");
325 if (!trace_fp) {
326 return;
327 }
328
329 if (fwrite(&header, sizeof header, 1, trace_fp) != 1 ||
330 st_write_event_mapping() < 0) {
331 fclose(trace_fp);
332 trace_fp = NULL;
333 return;
334 }
335
336 /* Resume trace writeout */
337 trace_writeout_enabled = true;
338 flush_trace_file(false);
339 } else {
340 fclose(trace_fp);
341 trace_fp = NULL;
342 }
343 }
344
345 /**
346 * Set the name of a trace file
347 *
348 * @file The trace file name or NULL for the default name-<pid> set at
349 * config time
350 */
351 void st_set_trace_file(const char *file)
352 {
353 st_set_trace_file_enabled(false);
354
355 g_free(trace_file_name);
356
357 if (!file) {
358 /* Type cast needed for Windows where getpid() returns an int. */
359 trace_file_name = g_strdup_printf(CONFIG_TRACE_FILE, (pid_t)getpid());
360 } else {
361 trace_file_name = g_strdup_printf("%s", file);
362 }
363
364 st_set_trace_file_enabled(true);
365 }
366
367 void st_print_trace_file_status(void)
368 {
369 qemu_printf("Trace file \"%s\" %s.\n",
370 trace_file_name, trace_fp ? "on" : "off");
371 }
372
373 void st_flush_trace_buffer(void)
374 {
375 flush_trace_file(true);
376 }
377
378 /* Helper function to create a thread with signals blocked. Use glib's
379 * portable threads since QEMU abstractions cannot be used due to reentrancy in
380 * the tracer. Also note the signal masking on POSIX hosts so that the thread
381 * does not steal signals when the rest of the program wants them blocked.
382 */
383 static GThread *trace_thread_create(GThreadFunc fn)
384 {
385 GThread *thread;
386 #ifndef _WIN32
387 sigset_t set, oldset;
388
389 sigfillset(&set);
390 pthread_sigmask(SIG_SETMASK, &set, &oldset);
391 #endif
392
393 thread = g_thread_new("trace-thread", fn, NULL);
394
395 #ifndef _WIN32
396 pthread_sigmask(SIG_SETMASK, &oldset, NULL);
397 #endif
398
399 return thread;
400 }
401
402 bool st_init(void)
403 {
404 GThread *thread;
405
406 trace_pid = getpid();
407
408 thread = trace_thread_create(writeout_thread);
409 if (!thread) {
410 warn_report("unable to initialize simple trace backend");
411 return false;
412 }
413
414 atexit(st_flush_trace_buffer);
415 return true;
416 }