--- /dev/null
+/*
+ * 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"
+#include "trace/simple.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 3
+
+/** 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 CompatGMutex trace_lock;
+static CompatGCond trace_available_cond;
+static CompatGCond 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 volatile gint trace_idx;
+static unsigned int writeout_idx;
+static volatile gint dropped_events;
+static uint32_t trace_pid;
+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 pid;
+ 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_mutex_lock(&trace_lock);
+ trace_available = true;
+ g_cond_signal(&trace_available_cond);
+
+ if (wait) {
+ g_cond_wait(&trace_empty_cond, &trace_lock);
+ }
+
+ g_mutex_unlock(&trace_lock);
+}
+
+static void wait_for_trace_records_available(void)
+{
+ g_mutex_lock(&trace_lock);
+ while (!(trace_available && trace_writeout_enabled)) {
+ g_cond_signal(&trace_empty_cond);
+ g_cond_wait(&trace_available_cond, &trace_lock);
+ }
+ trace_available = false;
+ g_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.pid = trace_pid;
+ 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 event_u64 = event;
+ 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_u64, sizeof(event_u64));
+ rec_off = write_to_buffer(rec_off, ×tamp_ns, sizeof(timestamp_ns));
+ rec_off = write_to_buffer(rec_off, &rec_len, sizeof(rec_len));
+ rec_off = write_to_buffer(rec_off, &trace_pid, sizeof(trace_pid));
+
+ 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);
+}
+
+/* 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_new("trace-thread", fn, NULL);
+
+#ifndef _WIN32
+ pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+#endif
+
+ return thread;
+}
+
+bool st_init(const char *file)
+{
+ GThread *thread;
+
+ trace_pid = getpid();
+
+ 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);
+ st_set_trace_file(file);
+ return true;
+}
Code Review / kvmfornfv.git / blobdiff