[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;

/* g_cond_new() was deprecated in glib 2.31 but we still need to support it */
#if GLIB_CHECK_VERSION(2, 31, 0)
static GCond the_trace_available_cond;
static GCond the_trace_empty_cond;
static GCond *trace_available_cond = &the_trace_available_cond;
static GCond *trace_empty_cond = &the_trace_empty_cond;
#else
static GCond *trace_available_cond;
static GCond *trace_empty_cond;
#endif

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 volatile gint trace_idx;
static unsigned int writeout_idx;
static volatile gint 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 (((unsigned int)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

#if GLIB_CHECK_VERSION(2, 31, 0)
    thread = g_thread_new("trace-thread", fn, NULL);
#else
    thread = g_thread_create(fn, NULL, FALSE, NULL);
#endif

#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
    }

#if !GLIB_CHECK_VERSION(2, 31, 0)
    trace_available_cond = g_cond_new();
    trace_empty_cond = g_cond_new();
#endif

    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	42	static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
4a0e6714 SH	43
	44	/* g_cond_new() was deprecated in glib 2.31 but we still need to support it */
	45	#if GLIB_CHECK_VERSION(2, 31, 0)
	46	static GCond the_trace_available_cond;
	47	static GCond the_trace_empty_cond;
	48	static GCond *trace_available_cond = &the_trace_available_cond;
	49	static GCond *trace_empty_cond = &the_trace_empty_cond;
	50	#else
85aff158 SH	51	static GCond *trace_available_cond;
85aff158 SH	52	static GCond *trace_empty_cond;
4a0e6714 SH	53	#endif
4a0e6714 SH	54
0b5538c3 SH	55	static bool trace_available;
	56	static bool trace_writeout_enabled;
	57
62bab732 HPB	58	enum {
	59	TRACE_BUF_LEN = 4096 * 64,
	60	TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
	61	};
	62
	63	uint8_t trace_buf[TRACE_BUF_LEN];
30d94087	64	static volatile gint trace_idx;
62bab732	65	static unsigned int writeout_idx;
30d94087	66	static volatile gint dropped_events;
26f7227b	67	static FILE *trace_fp;
4552e410	68	static char *trace_file_name;
26f7227b	69
62bab732 HPB	70	/* * Trace buffer entry */
	71	typedef struct {
	72	uint64_t event; /* TraceEventID */
	73	uint64_t timestamp_ns;
	74	uint32_t length; /* in bytes */
	75	uint32_t reserved; /* unused */
fb3a5085	76	uint64_t arguments[];
62bab732 HPB	77	} TraceRecord;
	78
	79	typedef struct {
	80	uint64_t header_event_id; /* HEADER_EVENT_ID */
	81	uint64_t header_magic; /* HEADER_MAGIC */
	82	uint64_t header_version; /* HEADER_VERSION */
8ae601e8	83	} TraceLogHeader;
62bab732 HPB	84
	85
	86	static void read_from_buffer(unsigned int idx, void *dataptr, size_t size);
	87	static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size);
	88
	89	static void clear_buffer_range(unsigned int idx, size_t len)
	90	{
	91	uint32_t num = 0;
	92	while (num < len) {
	93	if (idx >= TRACE_BUF_LEN) {
	94	idx = idx % TRACE_BUF_LEN;
	95	}
	96	trace_buf[idx++] = 0;
	97	num++;
	98	}
	99	}
c5ceb523	100	/**
0b5538c3 SH	101	* Read a trace record from the trace buffer
	102	*
	103	* @idx Trace buffer index
	104	* @record Trace record to fill
	105	*
	106	* Returns false if the record is not valid.
c5ceb523	107	*/
62bab732	108	static bool get_trace_record(unsigned int idx, TraceRecord **recordptr)
9410b56c	109	{
62bab732 HPB	110	uint64_t event_flag = 0;
	111	TraceRecord record;
	112	/* read the event flag to see if its a valid record */
	113	read_from_buffer(idx, &record, sizeof(event_flag));
	114
	115	if (!(record.event & TRACE_RECORD_VALID)) {
0b5538c3	116	return false;
9410b56c PS	117	}
9410b56c PS	118
62bab732 HPB	119	smp_rmb(); /* read memory barrier before accessing record */
	120	/* read the record header to know record length */
	121	read_from_buffer(idx, &record, sizeof(TraceRecord));
	122	recordptr = malloc(record.length); / dont use g_malloc, can deadlock when traced */
	123	/* make a copy of record to avoid being overwritten */
	124	read_from_buffer(idx, *recordptr, record.length);
	125	smp_rmb(); /* memory barrier before clearing valid flag */
	126	(*recordptr)->event &= ~TRACE_RECORD_VALID;
	127	/* clear the trace buffer range for consumed record otherwise any byte
	128	* with its MSB set may be considered as a valid event id when the writer
	129	* thread crosses this range of buffer again.
	130	*/
	131	clear_buffer_range(idx, record.length);
c5ceb523	132	return true;
9410b56c PS	133	}
9410b56c PS	134
0b5538c3 SH	135	/**
	136	* Kick writeout thread
	137	*
	138	* @wait Whether to wait for writeout thread to complete
	139	*/
	140	static void flush_trace_file(bool wait)
26f7227b	141	{
85aff158	142	g_static_mutex_lock(&trace_lock);
0b5538c3	143	trace_available = true;
85aff158	144	g_cond_signal(trace_available_cond);
c5ceb523	145
0b5538c3	146	if (wait) {
85aff158	147	g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(&trace_lock));
26f7227b	148	}
0b5538c3	149
85aff158	150	g_static_mutex_unlock(&trace_lock);
c5ceb523 SH	151	}
c5ceb523 SH	152
0b5538c3	153	static void wait_for_trace_records_available(void)
c5ceb523	154	{
85aff158	155	g_static_mutex_lock(&trace_lock);
0b5538c3	156	while (!(trace_available && trace_writeout_enabled)) {
85aff158 SH	157	g_cond_signal(trace_empty_cond);
	158	g_cond_wait(trace_available_cond,
	159	g_static_mutex_get_mutex(&trace_lock));
c5ceb523	160	}
0b5538c3	161	trace_available = false;
85aff158	162	g_static_mutex_unlock(&trace_lock);
26f7227b SH	163	}
26f7227b SH	164
85aff158	165	static gpointer writeout_thread(gpointer opaque)
26f7227b	166	{
62bab732 HPB	167	TraceRecord *recordptr;
	168	union {
	169	TraceRecord rec;
	170	uint8_t bytes[sizeof(TraceRecord) + sizeof(uint64_t)];
	171	} dropped;
	172	unsigned int idx = 0;
fb3a5085	173	int dropped_count;
0caf448b	174	size_t unused __attribute__ ((unused));
0b5538c3 SH	175
	176	for (;;) {
	177	wait_for_trace_records_available();
	178
e722d705	179	if (g_atomic_int_get(&dropped_events)) {
62bab732 HPB	180	dropped.rec.event = DROPPED_EVENT_ID,
62bab732 HPB	181	dropped.rec.timestamp_ns = get_clock();
fb3a5085	182	dropped.rec.length = sizeof(TraceRecord) + sizeof(uint64_t),
62bab732	183	dropped.rec.reserved = 0;
b6b2c962	184	do {
e722d705	185	dropped_count = g_atomic_int_get(&dropped_events);
b6b2c962 MA	186	} while (!g_atomic_int_compare_and_exchange(&dropped_events,
b6b2c962 MA	187	dropped_count, 0));
fb3a5085	188	dropped.rec.arguments[0] = dropped_count;
62bab732	189	unused = fwrite(&dropped.rec, dropped.rec.length, 1, trace_fp);
0b5538c3	190	}
26f7227b	191
62bab732 HPB	192	while (get_trace_record(idx, &recordptr)) {
	193	unused = fwrite(recordptr, recordptr->length, 1, trace_fp);
	194	writeout_idx += recordptr->length;
	195	free(recordptr); /* dont use g_free, can deadlock when traced */
	196	idx = writeout_idx % TRACE_BUF_LEN;
0b5538c3	197	}
26f7227b	198
0b5538c3	199	fflush(trace_fp);
26f7227b	200	}
0b5538c3	201	return NULL;
26f7227b SH	202	}
26f7227b SH	203
62bab732	204	void trace_record_write_u64(TraceBufferRecord *rec, uint64_t val)
26f7227b	205	{
62bab732	206	rec->rec_off = write_to_buffer(rec->rec_off, &val, sizeof(uint64_t));
26f7227b SH	207	}
26f7227b SH	208
62bab732	209	void trace_record_write_str(TraceBufferRecord rec, const char s, uint32_t slen)
26f7227b	210	{
62bab732 HPB	211	/* Write string length first */
	212	rec->rec_off = write_to_buffer(rec->rec_off, &slen, sizeof(slen));
	213	/* Write actual string now */
	214	rec->rec_off = write_to_buffer(rec->rec_off, (void*)s, slen);
26f7227b SH	215	}
26f7227b SH	216
62bab732	217	int trace_record_start(TraceBufferRecord *rec, TraceEventID event, size_t datasize)
26f7227b	218	{
62bab732 HPB	219	unsigned int idx, rec_off, old_idx, new_idx;
	220	uint32_t rec_len = sizeof(TraceRecord) + datasize;
	221	uint64_t timestamp_ns = get_clock();
	222
b6b2c962	223	do {
e722d705	224	old_idx = g_atomic_int_get(&trace_idx);
62bab732 HPB	225	smp_rmb();
	226	new_idx = old_idx + rec_len;
	227
	228	if (new_idx - writeout_idx > TRACE_BUF_LEN) {
	229	/* Trace Buffer Full, Event dropped ! */
fb3a5085	230	g_atomic_int_inc(&dropped_events);
62bab732 HPB	231	return -ENOSPC;
62bab732 HPB	232	}
b6b2c962	233	} while (!g_atomic_int_compare_and_exchange(&trace_idx, old_idx, new_idx));
26f7227b	234
62bab732	235	idx = old_idx % TRACE_BUF_LEN;
62bab732 HPB	236
62bab732 HPB	237	rec_off = idx;
83d35d3e HPB	238	rec_off = write_to_buffer(rec_off, &event, sizeof(event));
	239	rec_off = write_to_buffer(rec_off, &timestamp_ns, sizeof(timestamp_ns));
	240	rec_off = write_to_buffer(rec_off, &rec_len, sizeof(rec_len));
62bab732 HPB	241
	242	rec->tbuf_idx = idx;
	243	rec->rec_off = (idx + sizeof(TraceRecord)) % TRACE_BUF_LEN;
	244	return 0;
26f7227b SH	245	}
26f7227b SH	246
62bab732	247	static void read_from_buffer(unsigned int idx, void *dataptr, size_t size)
26f7227b	248	{
62bab732 HPB	249	uint8_t *data_ptr = dataptr;
	250	uint32_t x = 0;
	251	while (x < size) {
	252	if (idx >= TRACE_BUF_LEN) {
	253	idx = idx % TRACE_BUF_LEN;
	254	}
	255	data_ptr[x++] = trace_buf[idx++];
	256	}
26f7227b SH	257	}
26f7227b SH	258
62bab732	259	static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size)
26f7227b	260	{
62bab732 HPB	261	uint8_t *data_ptr = dataptr;
	262	uint32_t x = 0;
	263	while (x < size) {
	264	if (idx >= TRACE_BUF_LEN) {
	265	idx = idx % TRACE_BUF_LEN;
	266	}
	267	trace_buf[idx++] = data_ptr[x++];
	268	}
	269	return idx; /* most callers wants to know where to write next */
26f7227b SH	270	}
26f7227b SH	271
62bab732	272	void trace_record_finish(TraceBufferRecord *rec)
26f7227b	273	{
db8894f2 HPB	274	TraceRecord record;
db8894f2 HPB	275	read_from_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
62bab732	276	smp_wmb(); /* write barrier before marking as valid */
db8894f2 HPB	277	record.event \|= TRACE_RECORD_VALID;
db8894f2 HPB	278	write_to_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
62bab732	279
30d94087	280	if (((unsigned int)g_atomic_int_get(&trace_idx) - writeout_idx)
e722d705	281	> TRACE_BUF_FLUSH_THRESHOLD) {
62bab732 HPB	282	flush_trace_file(false);
62bab732 HPB	283	}
26f7227b SH	284	}
26f7227b SH	285
0b5538c3 SH	286	void st_set_trace_file_enabled(bool enable)
	287	{
	288	if (enable == !!trace_fp) {
	289	return; /* no change */
	290	}
	291
	292	/* Halt trace writeout */
	293	flush_trace_file(true);
	294	trace_writeout_enabled = false;
	295	flush_trace_file(true);
	296
	297	if (enable) {
8ae601e8	298	static const TraceLogHeader header = {
62bab732 HPB	299	.header_event_id = HEADER_EVENT_ID,
	300	.header_magic = HEADER_MAGIC,
	301	/* Older log readers will check for version at next location */
	302	.header_version = HEADER_VERSION,
0b5538c3 SH	303	};
0b5538c3 SH	304
6c2a4074	305	trace_fp = fopen(trace_file_name, "wb");
0b5538c3 SH	306	if (!trace_fp) {
	307	return;
	308	}
	309
	310	if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
	311	fclose(trace_fp);
	312	trace_fp = NULL;
	313	return;
	314	}
	315
	316	/* Resume trace writeout */
	317	trace_writeout_enabled = true;
	318	flush_trace_file(false);
	319	} else {
	320	fclose(trace_fp);
	321	trace_fp = NULL;
	322	}
	323	}
	324
26f7227b	325	/**
0b5538c3 SH	326	* Set the name of a trace file
	327	*
	328	* @file The trace file name or NULL for the default name-<pid> set at
	329	* config time
26f7227b	330	*/
0b5538c3	331	bool st_set_trace_file(const char *file)
26f7227b	332	{
0b5538c3 SH	333	st_set_trace_file_enabled(false);
0b5538c3 SH	334
4552e410	335	g_free(trace_file_name);
0b5538c3 SH	336
0b5538c3 SH	337	if (!file) {
4552e410	338	trace_file_name = g_strdup_printf(CONFIG_TRACE_FILE, getpid());
0b5538c3	339	} else {
4552e410	340	trace_file_name = g_strdup_printf("%s", file);
0b5538c3 SH	341	}
	342
	343	st_set_trace_file_enabled(true);
	344	return true;
	345	}
	346
	347	void st_print_trace_file_status(FILE stream, int (stream_printf)(FILE stream, const char fmt, ...))
	348	{
	349	stream_printf(stream, "Trace file \"%s\" %s.\n",
	350	trace_file_name, trace_fp ? "on" : "off");
26f7227b	351	}
22890ab5	352
fc764105 LV	353	void st_flush_trace_buffer(void)
	354	{
	355	flush_trace_file(true);
	356	}
	357
	358	void trace_print_events(FILE *stream, fprintf_function stream_printf)
22890ab5 PS	359	{
	360	unsigned int i;
	361
	362	for (i = 0; i < NR_TRACE_EVENTS; i++) {
	363	stream_printf(stream, "%s [Event ID %u] : state %u\n",
	364	trace_list[i].tp_name, i, trace_list[i].state);
	365	}
	366	}
	367
fc764105	368	bool trace_event_set_state(const char *name, bool state)
22890ab5 PS	369	{
22890ab5 PS	370	unsigned int i;
454e202d MW	371	unsigned int len;
	372	bool wildcard = false;
	373	bool matched = false;
	374
	375	len = strlen(name);
	376	if (len > 0 && name[len - 1] == '*') {
	377	wildcard = true;
	378	len -= 1;
	379	}
22890ab5	380	for (i = 0; i < NR_TRACE_EVENTS; i++) {
454e202d MW	381	if (wildcard) {
	382	if (!strncmp(trace_list[i].tp_name, name, len)) {
	383	trace_list[i].state = state;
	384	matched = true;
	385	}
	386	continue;
	387	}
0b5538c3	388	if (!strcmp(trace_list[i].tp_name, name)) {
fc764105	389	trace_list[i].state = state;
0b5538c3	390	return true;
22890ab5 PS	391	}
22890ab5 PS	392	}
454e202d	393	return matched;
0b5538c3 SH	394	}
0b5538c3 SH	395
85aff158 SH	396	/* Helper function to create a thread with signals blocked. Use glib's
	397	* portable threads since QEMU abstractions cannot be used due to reentrancy in
	398	* the tracer. Also note the signal masking on POSIX hosts so that the thread
	399	* does not steal signals when the rest of the program wants them blocked.
	400	*/
	401	static GThread *trace_thread_create(GThreadFunc fn)
22890ab5	402	{
85aff158 SH	403	GThread *thread;
85aff158 SH	404	#ifndef _WIN32
0b5538c3	405	sigset_t set, oldset;
22890ab5	406
0b5538c3 SH	407	sigfillset(&set);
0b5538c3 SH	408	pthread_sigmask(SIG_SETMASK, &set, &oldset);
85aff158	409	#endif
4a0e6714 SH	410
	411	#if GLIB_CHECK_VERSION(2, 31, 0)
	412	thread = g_thread_new("trace-thread", fn, NULL);
	413	#else
db3bf869	414	thread = g_thread_create(fn, NULL, FALSE, NULL);
4a0e6714 SH	415	#endif
4a0e6714 SH	416
85aff158	417	#ifndef _WIN32
0b5538c3	418	pthread_sigmask(SIG_SETMASK, &oldset, NULL);
85aff158	419	#endif
0b5538c3	420
85aff158 SH	421	return thread;
	422	}
	423
	424	bool trace_backend_init(const char events, const char file)
	425	{
	426	GThread *thread;
	427
	428	if (!g_thread_supported()) {
42ed3727	429	#if !GLIB_CHECK_VERSION(2, 31, 0)
85aff158	430	g_thread_init(NULL);
42ed3727 AL	431	#else
	432	fprintf(stderr, "glib threading failed to initialize.\n");
	433	exit(1);
	434	#endif
85aff158 SH	435	}
85aff158 SH	436
4a0e6714	437	#if !GLIB_CHECK_VERSION(2, 31, 0)
85aff158 SH	438	trace_available_cond = g_cond_new();
85aff158 SH	439	trace_empty_cond = g_cond_new();
4a0e6714	440	#endif
85aff158 SH	441
	442	thread = trace_thread_create(writeout_thread);
	443	if (!thread) {
e4858974	444	fprintf(stderr, "warning: unable to initialize simple trace backend\n");
85aff158	445	return false;
22890ab5	446	}
0b5538c3	447
85aff158 SH	448	atexit(st_flush_trace_buffer);
	449	trace_backend_init_events(events);
	450	st_set_trace_file(file);
31d3c9b8	451	return true;
22890ab5	452	}