Provide the missing LIBUSB_LOG_LEVEL_* for older libusb or FreeBSD. Providing just...
[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 3
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 static CompatGMutex trace_lock;
44 static CompatGCond trace_available_cond;
45 static CompatGCond trace_empty_cond;
46
47 static bool trace_available;
48 static bool trace_writeout_enabled;
49
50 enum {
51 TRACE_BUF_LEN = 4096 * 64,
52 TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
53 };
54
55 uint8_t trace_buf[TRACE_BUF_LEN];
56 static volatile gint trace_idx;
57 static unsigned int writeout_idx;
58 static volatile gint dropped_events;
59 static uint32_t trace_pid;
60 static FILE *trace_fp;
61 static char *trace_file_name;
62
63 /* * Trace buffer entry */
64 typedef struct {
65 uint64_t event; /* TraceEventID */
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); /* dont 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
168 for (;;) {
169 wait_for_trace_records_available();
170
171 if (g_atomic_int_get(&dropped_events)) {
172 dropped.rec.event = DROPPED_EVENT_ID,
173 dropped.rec.timestamp_ns = get_clock();
174 dropped.rec.length = sizeof(TraceRecord) + sizeof(uint64_t),
175 dropped.rec.pid = trace_pid;
176 do {
177 dropped_count = g_atomic_int_get(&dropped_events);
178 } while (!g_atomic_int_compare_and_exchange(&dropped_events,
179 dropped_count, 0));
180 dropped.rec.arguments[0] = dropped_count;
181 unused = fwrite(&dropped.rec, dropped.rec.length, 1, trace_fp);
182 }
183
184 while (get_trace_record(idx, &recordptr)) {
185 unused = fwrite(recordptr, recordptr->length, 1, trace_fp);
186 writeout_idx += recordptr->length;
187 free(recordptr); /* dont use g_free, can deadlock when traced */
188 idx = writeout_idx % TRACE_BUF_LEN;
189 }
190
191 fflush(trace_fp);
192 }
193 return NULL;
194 }
195
196 void trace_record_write_u64(TraceBufferRecord *rec, uint64_t val)
197 {
198 rec->rec_off = write_to_buffer(rec->rec_off, &val, sizeof(uint64_t));
199 }
200
201 void trace_record_write_str(TraceBufferRecord *rec, const char *s, uint32_t slen)
202 {
203 /* Write string length first */
204 rec->rec_off = write_to_buffer(rec->rec_off, &slen, sizeof(slen));
205 /* Write actual string now */
206 rec->rec_off = write_to_buffer(rec->rec_off, (void*)s, slen);
207 }
208
209 int trace_record_start(TraceBufferRecord *rec, TraceEventID event, size_t datasize)
210 {
211 unsigned int idx, rec_off, old_idx, new_idx;
212 uint32_t rec_len = sizeof(TraceRecord) + datasize;
213 uint64_t event_u64 = event;
214 uint64_t timestamp_ns = get_clock();
215
216 do {
217 old_idx = g_atomic_int_get(&trace_idx);
218 smp_rmb();
219 new_idx = old_idx + rec_len;
220
221 if (new_idx - writeout_idx > TRACE_BUF_LEN) {
222 /* Trace Buffer Full, Event dropped ! */
223 g_atomic_int_inc(&dropped_events);
224 return -ENOSPC;
225 }
226 } while (!g_atomic_int_compare_and_exchange(&trace_idx, old_idx, new_idx));
227
228 idx = old_idx % TRACE_BUF_LEN;
229
230 rec_off = idx;
231 rec_off = write_to_buffer(rec_off, &event_u64, sizeof(event_u64));
232 rec_off = write_to_buffer(rec_off, &timestamp_ns, sizeof(timestamp_ns));
233 rec_off = write_to_buffer(rec_off, &rec_len, sizeof(rec_len));
234 rec_off = write_to_buffer(rec_off, &trace_pid, sizeof(trace_pid));
235
236 rec->tbuf_idx = idx;
237 rec->rec_off = (idx + sizeof(TraceRecord)) % TRACE_BUF_LEN;
238 return 0;
239 }
240
241 static void read_from_buffer(unsigned int idx, void *dataptr, size_t size)
242 {
243 uint8_t *data_ptr = dataptr;
244 uint32_t x = 0;
245 while (x < size) {
246 if (idx >= TRACE_BUF_LEN) {
247 idx = idx % TRACE_BUF_LEN;
248 }
249 data_ptr[x++] = trace_buf[idx++];
250 }
251 }
252
253 static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size)
254 {
255 uint8_t *data_ptr = dataptr;
256 uint32_t x = 0;
257 while (x < size) {
258 if (idx >= TRACE_BUF_LEN) {
259 idx = idx % TRACE_BUF_LEN;
260 }
261 trace_buf[idx++] = data_ptr[x++];
262 }
263 return idx; /* most callers wants to know where to write next */
264 }
265
266 void trace_record_finish(TraceBufferRecord *rec)
267 {
268 TraceRecord record;
269 read_from_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
270 smp_wmb(); /* write barrier before marking as valid */
271 record.event |= TRACE_RECORD_VALID;
272 write_to_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
273
274 if (((unsigned int)g_atomic_int_get(&trace_idx) - writeout_idx)
275 > TRACE_BUF_FLUSH_THRESHOLD) {
276 flush_trace_file(false);
277 }
278 }
279
280 void st_set_trace_file_enabled(bool enable)
281 {
282 if (enable == !!trace_fp) {
283 return; /* no change */
284 }
285
286 /* Halt trace writeout */
287 flush_trace_file(true);
288 trace_writeout_enabled = false;
289 flush_trace_file(true);
290
291 if (enable) {
292 static const TraceLogHeader header = {
293 .header_event_id = HEADER_EVENT_ID,
294 .header_magic = HEADER_MAGIC,
295 /* Older log readers will check for version at next location */
296 .header_version = HEADER_VERSION,
297 };
298
299 trace_fp = fopen(trace_file_name, "wb");
300 if (!trace_fp) {
301 return;
302 }
303
304 if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
305 fclose(trace_fp);
306 trace_fp = NULL;
307 return;
308 }
309
310 /* Resume trace writeout */
311 trace_writeout_enabled = true;
312 flush_trace_file(false);
313 } else {
314 fclose(trace_fp);
315 trace_fp = NULL;
316 }
317 }
318
319 /**
320 * Set the name of a trace file
321 *
322 * @file The trace file name or NULL for the default name-<pid> set at
323 * config time
324 */
325 bool st_set_trace_file(const char *file)
326 {
327 st_set_trace_file_enabled(false);
328
329 g_free(trace_file_name);
330
331 if (!file) {
332 trace_file_name = g_strdup_printf(CONFIG_TRACE_FILE, getpid());
333 } else {
334 trace_file_name = g_strdup_printf("%s", file);
335 }
336
337 st_set_trace_file_enabled(true);
338 return true;
339 }
340
341 void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
342 {
343 stream_printf(stream, "Trace file \"%s\" %s.\n",
344 trace_file_name, trace_fp ? "on" : "off");
345 }
346
347 void st_flush_trace_buffer(void)
348 {
349 flush_trace_file(true);
350 }
351
352 /* Helper function to create a thread with signals blocked. Use glib's
353 * portable threads since QEMU abstractions cannot be used due to reentrancy in
354 * the tracer. Also note the signal masking on POSIX hosts so that the thread
355 * does not steal signals when the rest of the program wants them blocked.
356 */
357 static GThread *trace_thread_create(GThreadFunc fn)
358 {
359 GThread *thread;
360 #ifndef _WIN32
361 sigset_t set, oldset;
362
363 sigfillset(&set);
364 pthread_sigmask(SIG_SETMASK, &set, &oldset);
365 #endif
366
367 thread = g_thread_new("trace-thread", fn, NULL);
368
369 #ifndef _WIN32
370 pthread_sigmask(SIG_SETMASK, &oldset, NULL);
371 #endif
372
373 return thread;
374 }
375
376 bool st_init(const char *file)
377 {
378 GThread *thread;
379
380 trace_pid = getpid();
381
382 thread = trace_thread_create(writeout_thread);
383 if (!thread) {
384 fprintf(stderr, "warning: unable to initialize simple trace backend\n");
385 return false;
386 }
387
388 atexit(st_flush_trace_buffer);
389 st_set_trace_file(file);
390 return true;
391 }