blob: d83681b2270ddc4584ccad08f62dbdd301c117a5 [file] [log] [blame]
/*
* 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;
}