/*
* 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(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;
}
