Archipelago » qemu

/*

 * 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 0

/** 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 buffer entry */

typedef struct {

    uint64_t event;

    uint64_t timestamp_ns;

    uint64_t x1;

    uint64_t x2;

    uint64_t x3;

    uint64_t x4;

    uint64_t x5;

    uint64_t x6;

} TraceRecord;

enum {

    TRACE_BUF_LEN = 4096,

    TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,

};

/*

 * 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;

static TraceRecord trace_buf[TRACE_BUF_LEN];

static unsigned int trace_idx;

static FILE *trace_fp;

static char *trace_file_name = NULL;

/**

 * 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 *record)

{

    if (!(trace_buf[idx].event & TRACE_RECORD_VALID)) {

        return false;

    }

    __sync_synchronize(); /* read memory barrier before accessing record */

    *record = trace_buf[idx];

    record->event &= ~TRACE_RECORD_VALID;

    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 record;

    unsigned int writeout_idx = 0;

    unsigned int num_available, idx;

    size_t unused __attribute__ ((unused));

    for (;;) {

        wait_for_trace_records_available();

        num_available = trace_idx - writeout_idx;

        if (num_available > TRACE_BUF_LEN) {

            record = (TraceRecord){

                .event = DROPPED_EVENT_ID,

                .x1 = num_available,

            };

            unused = fwrite(&record, sizeof(record), 1, trace_fp);

            writeout_idx += num_available;

        }

        idx = writeout_idx % TRACE_BUF_LEN;

        while (get_trace_record(idx, &record)) {

            trace_buf[idx].event = 0; /* clear valid bit */

            unused = fwrite(&record, sizeof(record), 1, trace_fp);

            idx = ++writeout_idx % TRACE_BUF_LEN;

        }

        fflush(trace_fp);

    }

    return NULL;

}

static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,

                  uint64_t x4, uint64_t x5, uint64_t x6)

{

    unsigned int idx;

    uint64_t timestamp;

    if (!trace_list[event].state) {

        return;

    }

    timestamp = get_clock();

    idx = g_atomic_int_exchange_and_add((gint *)&trace_idx, 1) % TRACE_BUF_LEN;

    trace_buf[idx] = (TraceRecord){

        .event = event,

        .timestamp_ns = timestamp,

        .x1 = x1,

        .x2 = x2,

        .x3 = x3,

        .x4 = x4,

        .x5 = x5,

        .x6 = x6,

    };

    __sync_synchronize(); /* write barrier before marking as valid */

    trace_buf[idx].event |= TRACE_RECORD_VALID;

    if ((idx + 1) % TRACE_BUF_FLUSH_THRESHOLD == 0) {

        flush_trace_file(false);

    }

}

void trace0(TraceEventID event)

{

    trace(event, 0, 0, 0, 0, 0, 0);

}

void trace1(TraceEventID event, uint64_t x1)

{

    trace(event, x1, 0, 0, 0, 0, 0);

}

void trace2(TraceEventID event, uint64_t x1, uint64_t x2)

{

    trace(event, x1, x2, 0, 0, 0, 0);

}

void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3)

{

    trace(event, x1, x2, x3, 0, 0, 0);

}

void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4)

{

    trace(event, x1, x2, x3, x4, 0, 0);

}

void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5)

{

    trace(event, x1, x2, x3, x4, x5, 0);

}

void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6)

{

    trace(event, x1, x2, x3, x4, x5, x6);

}

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 TraceRecord header = {

            .event = HEADER_EVENT_ID,

            .timestamp_ns = HEADER_MAGIC,

            .x1 = 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);

    free(trace_file_name);

    if (!file) {

        if (asprintf(&trace_file_name, CONFIG_TRACE_FILE, getpid()) < 0) {

            trace_file_name = NULL;

            return false;

        }

    } else {

        if (asprintf(&trace_file_name, "%s", file) < 0) {

            trace_file_name = NULL;

            return false;

        }

    }

    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_print_trace(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))

{

    unsigned int i;

    for (i = 0; i < TRACE_BUF_LEN; i++) {

        TraceRecord record;

        if (!get_trace_record(i, &record)) {

            continue;

        }

        stream_printf(stream, "Event %" PRIu64 " : %" PRIx64 " %" PRIx64

                      " %" PRIx64 " %" PRIx64 " %" PRIx64 " %" PRIx64 "\n",

                      record.event, record.x1, record.x2,

                      record.x3, record.x4, record.x5,

                      record.x6);

    }

}

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(writeout_thread, 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()) {

        g_thread_init(NULL);

    }

    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;

}