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
  23 /** Trace file header event ID */
  24 #define HEADER_EVENT_ID (~(uint64_t)0) /* avoids conflicting with TraceEventIDs */
  25
  26 /** Trace file magic number */
  27 #define HEADER_MAGIC 0xf2b177cb0aa429b4ULL
  28
  29 /** Trace file version number, bump if format changes */
  30 #define HEADER_VERSION 0
  31
  32 /** Records were dropped event ID */
  33 #define DROPPED_EVENT_ID (~(uint64_t)0 - 1)
  34
  35 /** Trace record is valid */
  36 #define TRACE_RECORD_VALID ((uint64_t)1 << 63)
  37
  38 /** Trace buffer entry */
  39 typedef struct {
  40     uint64_t event;
  41     uint64_t timestamp_ns;
  42     uint64_t x1;
  43     uint64_t x2;
  44     uint64_t x3;
  45     uint64_t x4;
  46     uint64_t x5;
  47     uint64_t x6;
  48 } TraceRecord;
  49
  50 enum {
  51     TRACE_BUF_LEN = 4096,
  52     TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
  53 };
  54
  55 /*
  56  * Trace records are written out by a dedicated thread.  The thread waits for
  57  * records to become available, writes them out, and then waits again.
  58  */
  59 static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
  60 static GCond *trace_available_cond;
  61 static GCond *trace_empty_cond;
  62 static bool trace_available;
  63 static bool trace_writeout_enabled;
  64
  65 static TraceRecord trace_buf[TRACE_BUF_LEN];
  66 static unsigned int trace_idx;
  67 static FILE *trace_fp;
  68 static char *trace_file_name = NULL;
  69
  70 /**
  71  * Read a trace record from the trace buffer
  72  *
  73  * @idx         Trace buffer index
  74  * @record      Trace record to fill
  75  *
  76  * Returns false if the record is not valid.
  77  */
  78 static bool get_trace_record(unsigned int idx, TraceRecord *record)
  79 {
  80     if (!(trace_buf[idx].event & TRACE_RECORD_VALID)) {
  81         return false;
  82     }
  83
  84     __sync_synchronize(); /* read memory barrier before accessing record */
  85
  86     *record = trace_buf[idx];
  87     record->event &= ~TRACE_RECORD_VALID;
  88     return true;
  89 }
  90
  91 /**
  92  * Kick writeout thread
  93  *
  94  * @wait        Whether to wait for writeout thread to complete
  95  */
  96 static void flush_trace_file(bool wait)
  97 {
  98     g_static_mutex_lock(&trace_lock);
  99     trace_available = true;
 100     g_cond_signal(trace_available_cond);
 101
 102     if (wait) {
 103         g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(&trace_lock));
 104     }
 105
 106     g_static_mutex_unlock(&trace_lock);
 107 }
 108
 109 static void wait_for_trace_records_available(void)
 110 {
 111     g_static_mutex_lock(&trace_lock);
 112     while (!(trace_available && trace_writeout_enabled)) {
 113         g_cond_signal(trace_empty_cond);
 114         g_cond_wait(trace_available_cond,
 115                     g_static_mutex_get_mutex(&trace_lock));
 116     }
 117     trace_available = false;
 118     g_static_mutex_unlock(&trace_lock);
 119 }
 120
 121 static gpointer writeout_thread(gpointer opaque)
 122 {
 123     TraceRecord record;
 124     unsigned int writeout_idx = 0;
 125     unsigned int num_available, idx;
 126     size_t unused __attribute__ ((unused));
 127
 128     for (;;) {
 129         wait_for_trace_records_available();
 130
 131         num_available = trace_idx - writeout_idx;
 132         if (num_available > TRACE_BUF_LEN) {
 133             record = (TraceRecord){
 134                 .event = DROPPED_EVENT_ID,
 135                 .x1 = num_available,
 136             };
 137             unused = fwrite(&record, sizeof(record), 1, trace_fp);
 138             writeout_idx += num_available;
 139         }
 140
 141         idx = writeout_idx % TRACE_BUF_LEN;
 142         while (get_trace_record(idx, &record)) {
 143             trace_buf[idx].event = 0; /* clear valid bit */
 144             unused = fwrite(&record, sizeof(record), 1, trace_fp);
 145             idx = ++writeout_idx % TRACE_BUF_LEN;
 146         }
 147
 148         fflush(trace_fp);
 149     }
 150     return NULL;
 151 }
 152
 153 static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,
 154                   uint64_t x4, uint64_t x5, uint64_t x6)
 155 {
 156     unsigned int idx;
 157     uint64_t timestamp;
 158
 159     if (!trace_list[event].state) {
 160         return;
 161     }
 162
 163     timestamp = get_clock();
 164 #if GLIB_CHECK_VERSION(2, 30, 0)
 165     idx = g_atomic_int_add((gint *)&trace_idx, 1) % TRACE_BUF_LEN;
 166 #else
 167     idx = g_atomic_int_exchange_and_add((gint *)&trace_idx, 1) % TRACE_BUF_LEN;
 168 #endif
 169     trace_buf[idx] = (TraceRecord){
 170         .event = event,
 171         .timestamp_ns = timestamp,
 172         .x1 = x1,
 173         .x2 = x2,
 174         .x3 = x3,
 175         .x4 = x4,
 176         .x5 = x5,
 177         .x6 = x6,
 178     };
 179     __sync_synchronize(); /* write barrier before marking as valid */
 180     trace_buf[idx].event |= TRACE_RECORD_VALID;
 181
 182     if ((idx + 1) % TRACE_BUF_FLUSH_THRESHOLD == 0) {
 183         flush_trace_file(false);
 184     }
 185 }
 186
 187 void trace0(TraceEventID event)
 188 {
 189     trace(event, 0, 0, 0, 0, 0, 0);
 190 }
 191
 192 void trace1(TraceEventID event, uint64_t x1)
 193 {
 194     trace(event, x1, 0, 0, 0, 0, 0);
 195 }
 196
 197 void trace2(TraceEventID event, uint64_t x1, uint64_t x2)
 198 {
 199     trace(event, x1, x2, 0, 0, 0, 0);
 200 }
 201
 202 void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3)
 203 {
 204     trace(event, x1, x2, x3, 0, 0, 0);
 205 }
 206
 207 void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4)
 208 {
 209     trace(event, x1, x2, x3, x4, 0, 0);
 210 }
 211
 212 void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5)
 213 {
 214     trace(event, x1, x2, x3, x4, x5, 0);
 215 }
 216
 217 void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6)
 218 {
 219     trace(event, x1, x2, x3, x4, x5, x6);
 220 }
 221
 222 void st_set_trace_file_enabled(bool enable)
 223 {
 224     if (enable == !!trace_fp) {
 225         return; /* no change */
 226     }
 227
 228     /* Halt trace writeout */
 229     flush_trace_file(true);
 230     trace_writeout_enabled = false;
 231     flush_trace_file(true);
 232
 233     if (enable) {
 234         static const TraceRecord header = {
 235             .event = HEADER_EVENT_ID,
 236             .timestamp_ns = HEADER_MAGIC,
 237             .x1 = HEADER_VERSION,
 238         };
 239
 240         trace_fp = fopen(trace_file_name, "wb");
 241         if (!trace_fp) {
 242             return;
 243         }
 244
 245         if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
 246             fclose(trace_fp);
 247             trace_fp = NULL;
 248             return;
 249         }
 250
 251         /* Resume trace writeout */
 252         trace_writeout_enabled = true;
 253         flush_trace_file(false);
 254     } else {
 255         fclose(trace_fp);
 256         trace_fp = NULL;
 257     }
 258 }
 259
 260 /**
 261  * Set the name of a trace file
 262  *
 263  * @file        The trace file name or NULL for the default name-<pid> set at
 264  *              config time
 265  */
 266 bool st_set_trace_file(const char *file)
 267 {
 268     st_set_trace_file_enabled(false);
 269
 270     free(trace_file_name);
 271
 272     if (!file) {
 273         if (asprintf(&trace_file_name, CONFIG_TRACE_FILE, getpid()) < 0) {
 274             trace_file_name = NULL;
 275             return false;
 276         }
 277     } else {
 278         if (asprintf(&trace_file_name, "%s", file) < 0) {
 279             trace_file_name = NULL;
 280             return false;
 281         }
 282     }
 283
 284     st_set_trace_file_enabled(true);
 285     return true;
 286 }
 287
 288 void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
 289 {
 290     stream_printf(stream, "Trace file \"%s\" %s.\n",
 291                   trace_file_name, trace_fp ? "on" : "off");
 292 }
 293
 294 void st_print_trace(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
 295 {
 296     unsigned int i;
 297
 298     for (i = 0; i < TRACE_BUF_LEN; i++) {
 299         TraceRecord record;
 300
 301         if (!get_trace_record(i, &record)) {
 302             continue;
 303         }
 304         stream_printf(stream, "Event %" PRIu64 " : %" PRIx64 " %" PRIx64
 305                       " %" PRIx64 " %" PRIx64 " %" PRIx64 " %" PRIx64 "\n",
 306                       record.event, record.x1, record.x2,
 307                       record.x3, record.x4, record.x5,
 308                       record.x6);
 309     }
 310 }
 311
 312 void st_flush_trace_buffer(void)
 313 {
 314     flush_trace_file(true);
 315 }
 316
 317 void trace_print_events(FILE *stream, fprintf_function stream_printf)
 318 {
 319     unsigned int i;
 320
 321     for (i = 0; i < NR_TRACE_EVENTS; i++) {
 322         stream_printf(stream, "%s [Event ID %u] : state %u\n",
 323                       trace_list[i].tp_name, i, trace_list[i].state);
 324     }
 325 }
 326
 327 bool trace_event_set_state(const char *name, bool state)
 328 {
 329     unsigned int i;
 330     unsigned int len;
 331     bool wildcard = false;
 332     bool matched = false;
 333
 334     len = strlen(name);
 335     if (len > 0 && name[len - 1] == '*') {
 336         wildcard = true;
 337         len -= 1;
 338     }
 339     for (i = 0; i < NR_TRACE_EVENTS; i++) {
 340         if (wildcard) {
 341             if (!strncmp(trace_list[i].tp_name, name, len)) {
 342                 trace_list[i].state = state;
 343                 matched = true;
 344             }
 345             continue;
 346         }
 347         if (!strcmp(trace_list[i].tp_name, name)) {
 348             trace_list[i].state = state;
 349             return true;
 350         }
 351     }
 352     return matched;
 353 }
 354
 355 /* Helper function to create a thread with signals blocked.  Use glib's
 356  * portable threads since QEMU abstractions cannot be used due to reentrancy in
 357  * the tracer.  Also note the signal masking on POSIX hosts so that the thread
 358  * does not steal signals when the rest of the program wants them blocked.
 359  */
 360 static GThread *trace_thread_create(GThreadFunc fn)
 361 {
 362     GThread *thread;
 363 #ifndef _WIN32
 364     sigset_t set, oldset;
 365
 366     sigfillset(&set);
 367     pthread_sigmask(SIG_SETMASK, &set, &oldset);
 368 #endif
 369     thread = g_thread_create(fn, NULL, FALSE, NULL);
 370 #ifndef _WIN32
 371     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 372 #endif
 373
 374     return thread;
 375 }
 376
 377 bool trace_backend_init(const char *events, const char *file)
 378 {
 379     GThread *thread;
 380
 381     if (!g_thread_supported()) {
 382 #if !GLIB_CHECK_VERSION(2, 31, 0)
 383         g_thread_init(NULL);
 384 #else
 385         fprintf(stderr, "glib threading failed to initialize.\n");
 386         exit(1);
 387 #endif
 388     }
 389
 390     trace_available_cond = g_cond_new();
 391     trace_empty_cond = g_cond_new();
 392
 393     thread = trace_thread_create(writeout_thread);
 394     if (!thread) {
 395         fprintf(stderr, "warning: unable to initialize simple trace backend\n");
 396         return false;
 397     }
 398
 399     atexit(st_flush_trace_buffer);
 400     trace_backend_init_events(events);
 401     st_set_trace_file(file);
 402     return true;
 403 }