[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 uint64_t 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 */
    uint8_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;
    uint64_t dropped_count;
    size_t unused __attribute__ ((unused));

    for (;;) {
        wait_for_trace_records_available();

        if (dropped_events) {
            dropped.rec.event = DROPPED_EVENT_ID,
            dropped.rec.timestamp_ns = get_clock();
            dropped.rec.length = sizeof(TraceRecord) + sizeof(dropped_events),
            dropped.rec.reserved = 0;
            while (1) {
                dropped_count = dropped_events;
                if (g_atomic_int_compare_and_exchange((gint *)&dropped_events,
                                                      dropped_count, 0)) {
                    break;
                }
            }
            memcpy(dropped.rec.arguments, &dropped_count, sizeof(uint64_t));
            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();

    while (1) {
        old_idx = 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((gint *)&dropped_events);
            return -ENOSPC;
        }

        if (g_atomic_int_compare_and_exchange((gint *)&trace_idx,
                                              old_idx, new_idx)) {
            break;
        }
    }

    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 ((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
26f7227b SH	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>
85aff158	15	#ifndef _WIN32
0b5538c3 SH	16	#include <signal.h>
0b5538c3 SH	17	#include <pthread.h>
85aff158	18	#endif
1de7afc9	19	#include "qemu/timer.h"
26f7227b	20	#include "trace.h"
e4858974	21	#include "trace/control.h"
26f7227b SH	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 */
62bab732	30	#define HEADER_VERSION 2
26f7227b	31
0b5538c3 SH	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
0b5538c3 SH	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	*/
85aff158 SH	42	static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
	43	static GCond *trace_available_cond;
	44	static GCond *trace_empty_cond;
0b5538c3 SH	45	static bool trace_available;
	46	static bool trace_writeout_enabled;
	47
62bab732 HPB	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];
26f7227b	54	static unsigned int trace_idx;
62bab732 HPB	55	static unsigned int writeout_idx;
62bab732 HPB	56	static uint64_t dropped_events;
26f7227b	57	static FILE *trace_fp;
4552e410	58	static char *trace_file_name;
26f7227b	59
62bab732 HPB	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	uint8_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 */
8ae601e8	73	} TraceLogHeader;
62bab732 HPB	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	}
c5ceb523	90	/**
0b5538c3 SH	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.
c5ceb523	97	*/
62bab732	98	static bool get_trace_record(unsigned int idx, TraceRecord **recordptr)
9410b56c	99	{
62bab732 HPB	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)) {
0b5538c3	106	return false;
9410b56c PS	107	}
9410b56c PS	108
62bab732 HPB	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);
c5ceb523	122	return true;
9410b56c PS	123	}
9410b56c PS	124
0b5538c3 SH	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)
26f7227b	131	{
85aff158	132	g_static_mutex_lock(&trace_lock);
0b5538c3	133	trace_available = true;
85aff158	134	g_cond_signal(trace_available_cond);
c5ceb523	135
0b5538c3	136	if (wait) {
85aff158	137	g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(&trace_lock));
26f7227b	138	}
0b5538c3	139
85aff158	140	g_static_mutex_unlock(&trace_lock);
c5ceb523 SH	141	}
c5ceb523 SH	142
0b5538c3	143	static void wait_for_trace_records_available(void)
c5ceb523	144	{
85aff158	145	g_static_mutex_lock(&trace_lock);
0b5538c3	146	while (!(trace_available && trace_writeout_enabled)) {
85aff158 SH	147	g_cond_signal(trace_empty_cond);
	148	g_cond_wait(trace_available_cond,
	149	g_static_mutex_get_mutex(&trace_lock));
c5ceb523	150	}
0b5538c3	151	trace_available = false;
85aff158	152	g_static_mutex_unlock(&trace_lock);
26f7227b SH	153	}
26f7227b SH	154
85aff158	155	static gpointer writeout_thread(gpointer opaque)
26f7227b	156	{
62bab732 HPB	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	uint64_t dropped_count;
0caf448b	164	size_t unused __attribute__ ((unused));
0b5538c3 SH	165
	166	for (;;) {
	167	wait_for_trace_records_available();
	168
62bab732 HPB	169	if (dropped_events) {
	170	dropped.rec.event = DROPPED_EVENT_ID,
	171	dropped.rec.timestamp_ns = get_clock();
	172	dropped.rec.length = sizeof(TraceRecord) + sizeof(dropped_events),
	173	dropped.rec.reserved = 0;
	174	while (1) {
	175	dropped_count = dropped_events;
	176	if (g_atomic_int_compare_and_exchange((gint *)&dropped_events,
	177	dropped_count, 0)) {
	178	break;
	179	}
	180	}
	181	memcpy(dropped.rec.arguments, &dropped_count, sizeof(uint64_t));
	182	unused = fwrite(&dropped.rec, dropped.rec.length, 1, trace_fp);
0b5538c3	183	}
26f7227b	184
62bab732 HPB	185	while (get_trace_record(idx, &recordptr)) {
	186	unused = fwrite(recordptr, recordptr->length, 1, trace_fp);
	187	writeout_idx += recordptr->length;
	188	free(recordptr); /* dont use g_free, can deadlock when traced */
	189	idx = writeout_idx % TRACE_BUF_LEN;
0b5538c3	190	}
26f7227b	191
0b5538c3	192	fflush(trace_fp);
26f7227b	193	}
0b5538c3	194	return NULL;
26f7227b SH	195	}
26f7227b SH	196
62bab732	197	void trace_record_write_u64(TraceBufferRecord *rec, uint64_t val)
26f7227b	198	{
62bab732	199	rec->rec_off = write_to_buffer(rec->rec_off, &val, sizeof(uint64_t));
26f7227b SH	200	}
26f7227b SH	201
62bab732	202	void trace_record_write_str(TraceBufferRecord rec, const char s, uint32_t slen)
26f7227b	203	{
62bab732 HPB	204	/* Write string length first */
	205	rec->rec_off = write_to_buffer(rec->rec_off, &slen, sizeof(slen));
	206	/* Write actual string now */
	207	rec->rec_off = write_to_buffer(rec->rec_off, (void*)s, slen);
26f7227b SH	208	}
26f7227b SH	209
62bab732	210	int trace_record_start(TraceBufferRecord *rec, TraceEventID event, size_t datasize)
26f7227b	211	{
62bab732 HPB	212	unsigned int idx, rec_off, old_idx, new_idx;
	213	uint32_t rec_len = sizeof(TraceRecord) + datasize;
	214	uint64_t timestamp_ns = get_clock();
	215
	216	while (1) {
	217	old_idx = 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((gint *)&dropped_events);
	224	return -ENOSPC;
	225	}
26f7227b	226
62bab732 HPB	227	if (g_atomic_int_compare_and_exchange((gint *)&trace_idx,
	228	old_idx, new_idx)) {
	229	break;
	230	}
	231	}
26f7227b	232
62bab732	233	idx = old_idx % TRACE_BUF_LEN;
62bab732 HPB	234
62bab732 HPB	235	rec_off = idx;
83d35d3e HPB	236	rec_off = write_to_buffer(rec_off, &event, sizeof(event));
	237	rec_off = write_to_buffer(rec_off, &timestamp_ns, sizeof(timestamp_ns));
	238	rec_off = write_to_buffer(rec_off, &rec_len, sizeof(rec_len));
62bab732 HPB	239
	240	rec->tbuf_idx = idx;
	241	rec->rec_off = (idx + sizeof(TraceRecord)) % TRACE_BUF_LEN;
	242	return 0;
26f7227b SH	243	}
26f7227b SH	244
62bab732	245	static void read_from_buffer(unsigned int idx, void *dataptr, size_t size)
26f7227b	246	{
62bab732 HPB	247	uint8_t *data_ptr = dataptr;
	248	uint32_t x = 0;
	249	while (x < size) {
	250	if (idx >= TRACE_BUF_LEN) {
	251	idx = idx % TRACE_BUF_LEN;
	252	}
	253	data_ptr[x++] = trace_buf[idx++];
	254	}
26f7227b SH	255	}
26f7227b SH	256
62bab732	257	static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size)
26f7227b	258	{
62bab732 HPB	259	uint8_t *data_ptr = dataptr;
	260	uint32_t x = 0;
	261	while (x < size) {
	262	if (idx >= TRACE_BUF_LEN) {
	263	idx = idx % TRACE_BUF_LEN;
	264	}
	265	trace_buf[idx++] = data_ptr[x++];
	266	}
	267	return idx; /* most callers wants to know where to write next */
26f7227b SH	268	}
26f7227b SH	269
62bab732	270	void trace_record_finish(TraceBufferRecord *rec)
26f7227b	271	{
db8894f2 HPB	272	TraceRecord record;
db8894f2 HPB	273	read_from_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
62bab732	274	smp_wmb(); /* write barrier before marking as valid */
db8894f2 HPB	275	record.event \|= TRACE_RECORD_VALID;
db8894f2 HPB	276	write_to_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
62bab732 HPB	277
	278	if ((trace_idx - writeout_idx) > TRACE_BUF_FLUSH_THRESHOLD) {
	279	flush_trace_file(false);
	280	}
26f7227b SH	281	}
26f7227b SH	282
0b5538c3 SH	283	void st_set_trace_file_enabled(bool enable)
	284	{
	285	if (enable == !!trace_fp) {
	286	return; /* no change */
	287	}
	288
	289	/* Halt trace writeout */
	290	flush_trace_file(true);
	291	trace_writeout_enabled = false;
	292	flush_trace_file(true);
	293
	294	if (enable) {
8ae601e8	295	static const TraceLogHeader header = {
62bab732 HPB	296	.header_event_id = HEADER_EVENT_ID,
	297	.header_magic = HEADER_MAGIC,
	298	/* Older log readers will check for version at next location */
	299	.header_version = HEADER_VERSION,
0b5538c3 SH	300	};
0b5538c3 SH	301
6c2a4074	302	trace_fp = fopen(trace_file_name, "wb");
0b5538c3 SH	303	if (!trace_fp) {
	304	return;
	305	}
	306
	307	if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
	308	fclose(trace_fp);
	309	trace_fp = NULL;
	310	return;
	311	}
	312
	313	/* Resume trace writeout */
	314	trace_writeout_enabled = true;
	315	flush_trace_file(false);
	316	} else {
	317	fclose(trace_fp);
	318	trace_fp = NULL;
	319	}
	320	}
	321
26f7227b	322	/**
0b5538c3 SH	323	* Set the name of a trace file
	324	*
	325	* @file The trace file name or NULL for the default name-<pid> set at
	326	* config time
26f7227b	327	*/
0b5538c3	328	bool st_set_trace_file(const char *file)
26f7227b	329	{
0b5538c3 SH	330	st_set_trace_file_enabled(false);
0b5538c3 SH	331
4552e410	332	g_free(trace_file_name);
0b5538c3 SH	333
0b5538c3 SH	334	if (!file) {
4552e410	335	trace_file_name = g_strdup_printf(CONFIG_TRACE_FILE, getpid());
0b5538c3	336	} else {
4552e410	337	trace_file_name = g_strdup_printf("%s", file);
0b5538c3 SH	338	}
	339
	340	st_set_trace_file_enabled(true);
	341	return true;
	342	}
	343
	344	void st_print_trace_file_status(FILE stream, int (stream_printf)(FILE stream, const char fmt, ...))
	345	{
	346	stream_printf(stream, "Trace file \"%s\" %s.\n",
	347	trace_file_name, trace_fp ? "on" : "off");
26f7227b	348	}
22890ab5	349
fc764105 L	350	void st_flush_trace_buffer(void)
	351	{
	352	flush_trace_file(true);
	353	}
	354
	355	void trace_print_events(FILE *stream, fprintf_function stream_printf)
22890ab5 PS	356	{
	357	unsigned int i;
	358
	359	for (i = 0; i < NR_TRACE_EVENTS; i++) {
	360	stream_printf(stream, "%s [Event ID %u] : state %u\n",
	361	trace_list[i].tp_name, i, trace_list[i].state);
	362	}
	363	}
	364
fc764105	365	bool trace_event_set_state(const char *name, bool state)
22890ab5 PS	366	{
22890ab5 PS	367	unsigned int i;
454e202d MW	368	unsigned int len;
	369	bool wildcard = false;
	370	bool matched = false;
	371
	372	len = strlen(name);
	373	if (len > 0 && name[len - 1] == '*') {
	374	wildcard = true;
	375	len -= 1;
	376	}
22890ab5	377	for (i = 0; i < NR_TRACE_EVENTS; i++) {
454e202d MW	378	if (wildcard) {
	379	if (!strncmp(trace_list[i].tp_name, name, len)) {
	380	trace_list[i].state = state;
	381	matched = true;
	382	}
	383	continue;
	384	}
0b5538c3	385	if (!strcmp(trace_list[i].tp_name, name)) {
fc764105	386	trace_list[i].state = state;
0b5538c3	387	return true;
22890ab5 PS	388	}
22890ab5 PS	389	}
454e202d	390	return matched;
0b5538c3 SH	391	}
0b5538c3 SH	392
85aff158 SH	393	/* Helper function to create a thread with signals blocked. Use glib's
	394	* portable threads since QEMU abstractions cannot be used due to reentrancy in
	395	* the tracer. Also note the signal masking on POSIX hosts so that the thread
	396	* does not steal signals when the rest of the program wants them blocked.
	397	*/
	398	static GThread *trace_thread_create(GThreadFunc fn)
22890ab5	399	{
85aff158 SH	400	GThread *thread;
85aff158 SH	401	#ifndef _WIN32
0b5538c3	402	sigset_t set, oldset;
22890ab5	403
0b5538c3 SH	404	sigfillset(&set);
0b5538c3 SH	405	pthread_sigmask(SIG_SETMASK, &set, &oldset);
85aff158	406	#endif
db3bf869	407	thread = g_thread_create(fn, NULL, FALSE, NULL);
85aff158	408	#ifndef _WIN32
0b5538c3	409	pthread_sigmask(SIG_SETMASK, &oldset, NULL);
85aff158	410	#endif
0b5538c3	411
85aff158 SH	412	return thread;
	413	}
	414
	415	bool trace_backend_init(const char events, const char file)
	416	{
	417	GThread *thread;
	418
	419	if (!g_thread_supported()) {
42ed3727	420	#if !GLIB_CHECK_VERSION(2, 31, 0)
85aff158	421	g_thread_init(NULL);
42ed3727 AL	422	#else
	423	fprintf(stderr, "glib threading failed to initialize.\n");
	424	exit(1);
	425	#endif
85aff158 SH	426	}
	427
	428	trace_available_cond = g_cond_new();
	429	trace_empty_cond = g_cond_new();
	430
	431	thread = trace_thread_create(writeout_thread);
	432	if (!thread) {
e4858974	433	fprintf(stderr, "warning: unable to initialize simple trace backend\n");
85aff158	434	return false;
22890ab5	435	}
0b5538c3	436
85aff158 SH	437	atexit(st_flush_trace_buffer);
	438	trace_backend_init_events(events);
	439	st_set_trace_file(file);
31d3c9b8	440	return true;
22890ab5	441	}