[qemu.git] / trace / simple.c

/*
 * Simple trace backend
 *
 * Copyright IBM, Corp. 2010
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 */

#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <time.h>
#ifndef _WIN32
#include <signal.h>
#include <pthread.h>
#endif
#include "qemu/timer.h"
#include "trace.h"
#include "trace/control.h"

/** Trace file header event ID */
#define HEADER_EVENT_ID (~(uint64_t)0) /* avoids conflicting with TraceEventIDs */

/** Trace file magic number */
#define HEADER_MAGIC 0xf2b177cb0aa429b4ULL

/** Trace file version number, bump if format changes */
#define HEADER_VERSION 2

/** Records were dropped event ID */
#define DROPPED_EVENT_ID (~(uint64_t)0 - 1)

/** Trace record is valid */
#define TRACE_RECORD_VALID ((uint64_t)1 << 63)

/*
 * Trace records are written out by a dedicated thread.  The thread waits for
 * records to become available, writes them out, and then waits again.
 */
static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
static GCond *trace_available_cond;
static GCond *trace_empty_cond;
static bool trace_available;
static bool trace_writeout_enabled;

enum {
    TRACE_BUF_LEN = 4096 * 64,
    TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
};

uint8_t trace_buf[TRACE_BUF_LEN];
static unsigned int trace_idx;
static unsigned int writeout_idx;
static int dropped_events;
static FILE *trace_fp;
static char *trace_file_name;

/* * Trace buffer entry */
typedef struct {
    uint64_t event; /*   TraceEventID */
    uint64_t timestamp_ns;
    uint32_t length;   /*    in bytes */
    uint32_t reserved; /*    unused */
    uint64_t arguments[];
} TraceRecord;

typedef struct {
    uint64_t header_event_id; /* HEADER_EVENT_ID */
    uint64_t header_magic;    /* HEADER_MAGIC    */
    uint64_t header_version;  /* HEADER_VERSION  */
} TraceLogHeader;


static void read_from_buffer(unsigned int idx, void *dataptr, size_t size);
static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size);

static void clear_buffer_range(unsigned int idx, size_t len)
{
    uint32_t num = 0;
    while (num < len) {
        if (idx >= TRACE_BUF_LEN) {
            idx = idx % TRACE_BUF_LEN;
        }
        trace_buf[idx++] = 0;
        num++;
    }
}
/**
 * Read a trace record from the trace buffer
 *
 * @idx         Trace buffer index
 * @record      Trace record to fill
 *
 * Returns false if the record is not valid.
 */
static bool get_trace_record(unsigned int idx, TraceRecord **recordptr)
{
    uint64_t event_flag = 0;
    TraceRecord record;
    /* read the event flag to see if its a valid record */
    read_from_buffer(idx, &record, sizeof(event_flag));

    if (!(record.event & TRACE_RECORD_VALID)) {
        return false;
    }

    smp_rmb(); /* read memory barrier before accessing record */
    /* read the record header to know record length */
    read_from_buffer(idx, &record, sizeof(TraceRecord));
    *recordptr = malloc(record.length); /* dont use g_malloc, can deadlock when traced */
    /* make a copy of record to avoid being overwritten */
    read_from_buffer(idx, *recordptr, record.length);
    smp_rmb(); /* memory barrier before clearing valid flag */
    (*recordptr)->event &= ~TRACE_RECORD_VALID;
    /* clear the trace buffer range for consumed record otherwise any byte
     * with its MSB set may be considered as a valid event id when the writer
     * thread crosses this range of buffer again.
     */
    clear_buffer_range(idx, record.length);
    return true;
}

/**
 * Kick writeout thread
 *
 * @wait        Whether to wait for writeout thread to complete
 */
static void flush_trace_file(bool wait)
{
    g_static_mutex_lock(&trace_lock);
    trace_available = true;
    g_cond_signal(trace_available_cond);

    if (wait) {
        g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(&trace_lock));
    }

    g_static_mutex_unlock(&trace_lock);
}

static void wait_for_trace_records_available(void)
{
    g_static_mutex_lock(&trace_lock);
    while (!(trace_available && trace_writeout_enabled)) {
        g_cond_signal(trace_empty_cond);
        g_cond_wait(trace_available_cond,
                    g_static_mutex_get_mutex(&trace_lock));
    }
    trace_available = false;
    g_static_mutex_unlock(&trace_lock);
}

static gpointer writeout_thread(gpointer opaque)
{
    TraceRecord *recordptr;
    union {
        TraceRecord rec;
        uint8_t bytes[sizeof(TraceRecord) + sizeof(uint64_t)];
    } dropped;
    unsigned int idx = 0;
    int dropped_count;
    size_t unused __attribute__ ((unused));

    for (;;) {
        wait_for_trace_records_available();

        if (g_atomic_int_get(&dropped_events)) {
            dropped.rec.event = DROPPED_EVENT_ID,
            dropped.rec.timestamp_ns = get_clock();
            dropped.rec.length = sizeof(TraceRecord) + sizeof(uint64_t),
            dropped.rec.reserved = 0;
            do {
                dropped_count = g_atomic_int_get(&dropped_events);
            } while (!g_atomic_int_compare_and_exchange(&dropped_events,
                                                        dropped_count, 0));
            dropped.rec.arguments[0] = dropped_count;
            unused = fwrite(&dropped.rec, dropped.rec.length, 1, trace_fp);
        }

        while (get_trace_record(idx, &recordptr)) {
            unused = fwrite(recordptr, recordptr->length, 1, trace_fp);
            writeout_idx += recordptr->length;
            free(recordptr); /* dont use g_free, can deadlock when traced */
            idx = writeout_idx % TRACE_BUF_LEN;
        }

        fflush(trace_fp);
    }
    return NULL;
}

void trace_record_write_u64(TraceBufferRecord *rec, uint64_t val)
{
    rec->rec_off = write_to_buffer(rec->rec_off, &val, sizeof(uint64_t));
}

void trace_record_write_str(TraceBufferRecord *rec, const char *s, uint32_t slen)
{
    /* Write string length first */
    rec->rec_off = write_to_buffer(rec->rec_off, &slen, sizeof(slen));
    /* Write actual string now */
    rec->rec_off = write_to_buffer(rec->rec_off, (void*)s, slen);
}

int trace_record_start(TraceBufferRecord *rec, TraceEventID event, size_t datasize)
{
    unsigned int idx, rec_off, old_idx, new_idx;
    uint32_t rec_len = sizeof(TraceRecord) + datasize;
    uint64_t timestamp_ns = get_clock();

    do {
        old_idx = g_atomic_int_get(&trace_idx);
        smp_rmb();
        new_idx = old_idx + rec_len;

        if (new_idx - writeout_idx > TRACE_BUF_LEN) {
            /* Trace Buffer Full, Event dropped ! */
            g_atomic_int_inc(&dropped_events);
            return -ENOSPC;
        }
    } while (!g_atomic_int_compare_and_exchange(&trace_idx, old_idx, new_idx));

    idx = old_idx % TRACE_BUF_LEN;

    rec_off = idx;
    rec_off = write_to_buffer(rec_off, &event, sizeof(event));
    rec_off = write_to_buffer(rec_off, &timestamp_ns, sizeof(timestamp_ns));
    rec_off = write_to_buffer(rec_off, &rec_len, sizeof(rec_len));

    rec->tbuf_idx = idx;
    rec->rec_off  = (idx + sizeof(TraceRecord)) % TRACE_BUF_LEN;
    return 0;
}

static void read_from_buffer(unsigned int idx, void *dataptr, size_t size)
{
    uint8_t *data_ptr = dataptr;
    uint32_t x = 0;
    while (x < size) {
        if (idx >= TRACE_BUF_LEN) {
            idx = idx % TRACE_BUF_LEN;
        }
        data_ptr[x++] = trace_buf[idx++];
    }
}

static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size)
{
    uint8_t *data_ptr = dataptr;
    uint32_t x = 0;
    while (x < size) {
        if (idx >= TRACE_BUF_LEN) {
            idx = idx % TRACE_BUF_LEN;
        }
        trace_buf[idx++] = data_ptr[x++];
    }
    return idx; /* most callers wants to know where to write next */
}

void trace_record_finish(TraceBufferRecord *rec)
{
    TraceRecord record;
    read_from_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
    smp_wmb(); /* write barrier before marking as valid */
    record.event |= TRACE_RECORD_VALID;
    write_to_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));

    if ((g_atomic_int_get(&trace_idx) - writeout_idx)
        > TRACE_BUF_FLUSH_THRESHOLD) {
        flush_trace_file(false);
    }
}

void st_set_trace_file_enabled(bool enable)
{
    if (enable == !!trace_fp) {
        return; /* no change */
    }

    /* Halt trace writeout */
    flush_trace_file(true);
    trace_writeout_enabled = false;
    flush_trace_file(true);

    if (enable) {
        static const TraceLogHeader header = {
            .header_event_id = HEADER_EVENT_ID,
            .header_magic = HEADER_MAGIC,
            /* Older log readers will check for version at next location */
            .header_version = HEADER_VERSION,
        };

        trace_fp = fopen(trace_file_name, "wb");
        if (!trace_fp) {
            return;
        }

        if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
            fclose(trace_fp);
            trace_fp = NULL;
            return;
        }

        /* Resume trace writeout */
        trace_writeout_enabled = true;
        flush_trace_file(false);
    } else {
        fclose(trace_fp);
        trace_fp = NULL;
    }
}

/**
 * Set the name of a trace file
 *
 * @file        The trace file name or NULL for the default name-<pid> set at
 *              config time
 */
bool st_set_trace_file(const char *file)
{
    st_set_trace_file_enabled(false);

    g_free(trace_file_name);

    if (!file) {
        trace_file_name = g_strdup_printf(CONFIG_TRACE_FILE, getpid());
    } else {
        trace_file_name = g_strdup_printf("%s", file);
    }

    st_set_trace_file_enabled(true);
    return true;
}

void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
{
    stream_printf(stream, "Trace file \"%s\" %s.\n",
                  trace_file_name, trace_fp ? "on" : "off");
}

void st_flush_trace_buffer(void)
{
    flush_trace_file(true);
}

void trace_print_events(FILE *stream, fprintf_function stream_printf)
{
    unsigned int i;

    for (i = 0; i < NR_TRACE_EVENTS; i++) {
        stream_printf(stream, "%s [Event ID %u] : state %u\n",
                      trace_list[i].tp_name, i, trace_list[i].state);
    }
}

bool trace_event_set_state(const char *name, bool state)
{
    unsigned int i;
    unsigned int len;
    bool wildcard = false;
    bool matched = false;

    len = strlen(name);
    if (len > 0 && name[len - 1] == '*') {
        wildcard = true;
        len -= 1;
    }
    for (i = 0; i < NR_TRACE_EVENTS; i++) {
        if (wildcard) {
            if (!strncmp(trace_list[i].tp_name, name, len)) {
                trace_list[i].state = state;
                matched = true;
            }
            continue;
        }
        if (!strcmp(trace_list[i].tp_name, name)) {
            trace_list[i].state = state;
            return true;
        }
    }
    return matched;
}

/* Helper function to create a thread with signals blocked.  Use glib's
 * portable threads since QEMU abstractions cannot be used due to reentrancy in
 * the tracer.  Also note the signal masking on POSIX hosts so that the thread
 * does not steal signals when the rest of the program wants them blocked.
 */
static GThread *trace_thread_create(GThreadFunc fn)
{
    GThread *thread;
#ifndef _WIN32
    sigset_t set, oldset;

    sigfillset(&set);
    pthread_sigmask(SIG_SETMASK, &set, &oldset);
#endif
    thread = g_thread_create(fn, NULL, FALSE, NULL);
#ifndef _WIN32
    pthread_sigmask(SIG_SETMASK, &oldset, NULL);
#endif

    return thread;
}

bool trace_backend_init(const char *events, const char *file)
{
    GThread *thread;

    if (!g_thread_supported()) {
#if !GLIB_CHECK_VERSION(2, 31, 0)
        g_thread_init(NULL);
#else
        fprintf(stderr, "glib threading failed to initialize.\n");
        exit(1);
#endif
    }

    trace_available_cond = g_cond_new();
    trace_empty_cond = g_cond_new();

    thread = trace_thread_create(writeout_thread);
    if (!thread) {
        fprintf(stderr, "warning: unable to initialize simple trace backend\n");
        return false;
    }

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