Merge remote-tracking branch 'stefanha/tracing' into staging

* stefanha/tracing:
  Update simpletrace.py for new log format
  Simpletrace v2: Support multiple arguments, strings.
  monitor: remove unused do_info_trace
  trace: added ability to comment out events in the list

6 files changed, 340 insertions, 196 deletions

diff --git a/monitor.c b/monitor.c
index 09aa3cdf52..49dccfe854 100644
--- a/monitor.c
+++ b/monitor.c
@@ -941,13 +941,6 @@ static void do_info_cpu_stats(Monitor *mon)
 }
 #endif
 
-#if defined(CONFIG_TRACE_SIMPLE)
-static void do_info_trace(Monitor *mon)
-{
-    st_print_trace((FILE *)mon, &monitor_fprintf);
-}
-#endif
-
 static void do_trace_print_events(Monitor *mon)
 {
     trace_print_events((FILE *)mon, &monitor_fprintf);
@@ -2689,15 +2682,6 @@ static mon_cmd_t info_cmds[] = {
         .help       = "show roms",
         .mhandler.info = do_info_roms,
     },
-#if defined(CONFIG_TRACE_SIMPLE)
-    {
-        .name       = "trace",
-        .args_type  = "",
-        .params     = "",
-        .help       = "show current contents of trace buffer",
-        .mhandler.info = do_info_trace,
-    },
-#endif
     {
         .name       = "trace-events",
         .args_type  = "",
diff --git a/scripts/simpletrace.py b/scripts/simpletrace.py
index f55e5e63f9..9b4419f7c3 100755
--- a/scripts/simpletrace.py
+++ b/scripts/simpletrace.py
@@ -12,53 +12,69 @@
 import struct
 import re
 import inspect
+from tracetool import _read_events, Event
+from tracetool.backend.simple import is_string
 
 header_event_id = 0xffffffffffffffff
 header_magic    = 0xf2b177cb0aa429b4
-header_version  = 0
 dropped_event_id = 0xfffffffffffffffe
 
-trace_fmt = '=QQQQQQQQ'
-trace_len = struct.calcsize(trace_fmt)
-event_re  = re.compile(r'(disable\s+)?([a-zA-Z0-9_]+)\(([^)]*)\).*')
+log_header_fmt = '=QQQ'
+rec_header_fmt = '=QQII'
 
-def parse_events(fobj):
-    """Parse a trace-events file into {event_num: (name, arg1, ...)}."""
-
-    def get_argnames(args):
-        """Extract argument names from a parameter list."""
-        return tuple(arg.split()[-1].lstrip('*') for arg in args.split(','))
-
-    events = {dropped_event_id: ('dropped', 'count')}
-    event_num = 0
-    for line in fobj:
-        m = event_re.match(line.strip())
-        if m is None:
-            continue
-
-        disable, name, args = m.groups()
-        events[event_num] = (name,) + get_argnames(args)
-        event_num += 1
-    return events
+def read_header(fobj, hfmt):
+    '''Read a trace record header'''
+    hlen = struct.calcsize(hfmt)
+    hdr = fobj.read(hlen)
+    if len(hdr) != hlen:
+        return None
+    return struct.unpack(hfmt, hdr)
 
-def read_record(fobj):
+def get_record(edict, rechdr, fobj):
     """Deserialize a trace record from a file into a tuple (event_num, timestamp, arg1, ..., arg6)."""
-    s = fobj.read(trace_len)
-    if len(s) != trace_len:
+    if rechdr is None:
         return None
-    return struct.unpack(trace_fmt, s)
+    rec = (rechdr[0], rechdr[1])
+    if rechdr[0] != dropped_event_id:
+        event_id = rechdr[0]
+        event = edict[event_id]
+        for type, name in event.args:
+            if is_string(type):
+                l = fobj.read(4)
+                (len,) = struct.unpack('=L', l)
+                s = fobj.read(len)
+                rec = rec + (s,)
+            else:
+                (value,) = struct.unpack('=Q', fobj.read(8))
+                rec = rec + (value,)
+    else:
+        (value,) = struct.unpack('=Q', fobj.read(8))
+        rec = rec + (value,)
+    return rec
+
+
+def read_record(edict, fobj):
+    """Deserialize a trace record from a file into a tuple (event_num, timestamp, arg1, ..., arg6)."""
+    rechdr = read_header(fobj, rec_header_fmt)
+    return get_record(edict, rechdr, fobj) # return tuple of record elements
 
-def read_trace_file(fobj):
+def read_trace_file(edict, fobj):
     """Deserialize trace records from a file, yielding record tuples (event_num, timestamp, arg1, ..., arg6)."""
-    header = read_record(fobj)
+    header = read_header(fobj, log_header_fmt)
     if header is None or \
        header[0] != header_event_id or \
-       header[1] != header_magic or \
-       header[2] != header_version:
-        raise ValueError('not a trace file or incompatible version')
+       header[1] != header_magic:
+        raise ValueError('Not a valid trace file!')
+    if header[2] != 0 and \
+       header[2] != 2:
+        raise ValueError('Unknown version of tracelog format!')
+
+    log_version = header[2]
+    if log_version == 0:
+        raise ValueError('Older log format, not supported with this Qemu release!')
 
     while True:
-        rec = read_record(fobj)
+        rec = read_record(edict, fobj)
         if rec is None:
             break
 
@@ -89,16 +105,29 @@ class Analyzer(object):
 def process(events, log, analyzer):
     """Invoke an analyzer on each event in a log."""
     if isinstance(events, str):
-        events = parse_events(open(events, 'r'))
+        events = _read_events(open(events, 'r'))
     if isinstance(log, str):
         log = open(log, 'rb')
 
+    enabled_events = []
+    dropped_event = Event.build("Dropped_Event(uint64_t num_events_dropped)")
+    edict = {dropped_event_id: dropped_event}
+
+    for e in events:
+        if 'disable' not in e.properties:
+            enabled_events.append(e)
+    for num, event in enumerate(enabled_events):
+        edict[num] = event
+
     def build_fn(analyzer, event):
-        fn = getattr(analyzer, event[0], None)
+        if isinstance(event, str):
+            return analyzer.catchall
+
+        fn = getattr(analyzer, event.name, None)
         if fn is None:
             return analyzer.catchall
 
-        event_argcount = len(event) - 1
+        event_argcount = len(event.args)
         fn_argcount = len(inspect.getargspec(fn)[0]) - 1
         if fn_argcount == event_argcount + 1:
             # Include timestamp as first argument
@@ -109,9 +138,9 @@ def process(events, log, analyzer):
 
     analyzer.begin()
     fn_cache = {}
-    for rec in read_trace_file(log):
+    for rec in read_trace_file(edict, log):
         event_num = rec[0]
-        event = events[event_num]
+        event = edict[event_num]
         if event_num not in fn_cache:
             fn_cache[event_num] = build_fn(analyzer, event)
         fn_cache[event_num](event, rec)
@@ -128,7 +157,7 @@ def run(analyzer):
         sys.stderr.write('usage: %s <trace-events> <trace-file>\n' % sys.argv[0])
         sys.exit(1)
 
-    events = parse_events(open(sys.argv[1], 'r'))
+    events = _read_events(open(sys.argv[1], 'r'))
     process(events, sys.argv[2], analyzer)
 
 if __name__ == '__main__':
@@ -137,15 +166,20 @@ if __name__ == '__main__':
             self.last_timestamp = None
 
         def catchall(self, event, rec):
+            i = 1
             timestamp = rec[1]
             if self.last_timestamp is None:
                 self.last_timestamp = timestamp
             delta_ns = timestamp - self.last_timestamp
             self.last_timestamp = timestamp
 
-            fields = [event[0], '%0.3f' % (delta_ns / 1000.0)]
-            for i in xrange(1, len(event)):
-                fields.append('%s=0x%x' % (event[i], rec[i + 1]))
+            fields = [event.name, '%0.3f' % (delta_ns / 1000.0)]
+            for type, name in event.args:
+                if is_string(type):
+                    fields.append('%s=%s' % (name, rec[i + 1]))
+                else:
+                    fields.append('%s=0x%x' % (name, rec[i + 1]))
+                i += 1
             print ' '.join(fields)
 
     run(Formatter())
diff --git a/scripts/tracetool/backend/simple.py b/scripts/tracetool/backend/simple.py
index fbb5717c66..c7e47d6d72 100644
--- a/scripts/tracetool/backend/simple.py
+++ b/scripts/tracetool/backend/simple.py
@@ -15,9 +15,16 @@ __email__      = "stefanha@linux.vnet.ibm.com"
 
 from tracetool import out
 
+def is_string(arg):
+    strtype = ('const char*', 'char*', 'const char *', 'char *')
+    if arg.lstrip().startswith(strtype):
+        return True
+    else:
+        return False
 
 def c(events):
     out('#include "trace.h"',
+        '#include "trace/simple.h"',
         '',
         'TraceEvent trace_list[] = {')
 
@@ -26,30 +33,75 @@ def c(events):
             name = e.name,
             )
 
-    out('};')
+    out('};',
+        '')
+
+    for num, event in enumerate(events):
+        out('void trace_%(name)s(%(args)s)',
+            '{',
+            '    TraceBufferRecord rec;',
+            name = event.name,
+            args = event.args,
+            )
+        sizes = []
+        for type_, name in event.args:
+            if is_string(type_):
+                out('    size_t arg%(name)s_len = %(name)s ? MIN(strlen(%(name)s), MAX_TRACE_STRLEN) : 0;',
+                    name = name,
+                   )
+                strsizeinfo = "4 + arg%s_len" % name
+                sizes.append(strsizeinfo)
+            else:
+                sizes.append("8")
+        sizestr = " + ".join(sizes)
+        if len(event.args) == 0:
+            sizestr = '0'
+
+
+        out('',
+            '    if (!trace_list[%(event_id)s].state) {',
+            '        return;',
+            '    }',
+            '',
+            '    if (trace_record_start(&rec, %(event_id)s, %(size_str)s)) {',
+            '        return; /* Trace Buffer Full, Event Dropped ! */',
+            '    }',
+            event_id = num,
+            size_str = sizestr,
+            )
+
+        if len(event.args) > 0:
+            for type_, name in event.args:
+                # string
+                if is_string(type_):
+                    out('    trace_record_write_str(&rec, %(name)s, arg%(name)s_len);',
+                        name = name,
+                       )
+                # pointer var (not string)
+                elif type_.endswith('*'):
+                    out('    trace_record_write_u64(&rec, (uint64_t)(uint64_t *)%(name)s);',
+                        name = name,
+                       )
+                # primitive data type
+                else:
+                    out('    trace_record_write_u64(&rec, (uint64_t)%(name)s);',
+                       name = name,
+                       )
+
+        out('    trace_record_finish(&rec);',
+            '}',
+            '')
+
 
 def h(events):
     out('#include "trace/simple.h"',
         '')
 
-    for num, e in enumerate(events):
-        if len(e.args):
-            argstr = e.args.names()
-            arg_prefix = ', (uint64_t)(uintptr_t)'
-            cast_args = arg_prefix + arg_prefix.join(argstr)
-            simple_args = (str(num) + cast_args)
-        else:
-            simple_args = str(num)
-
-        out('static inline void trace_%(name)s(%(args)s)',
-            '{',
-            '    trace%(argc)d(%(trace_args)s);',
-            '}',
-            name = e.name,
-            args = e.args,
-            argc = len(e.args),
-            trace_args = simple_args,
+    for event in events:
+        out('void trace_%(name)s(%(args)s);',
+            name = event.name,
+            args = event.args,
             )
-
+    out('')
     out('#define NR_TRACE_EVENTS %d' % len(events))
     out('extern TraceEvent trace_list[NR_TRACE_EVENTS];')
diff --git a/trace/control.c b/trace/control.c
index 4c5527d20a..22d5863eeb 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -27,6 +27,9 @@ void trace_backend_init_events(const char *fname)
         size_t len = strlen(line_buf);
         if (len > 1) {              /* skip empty lines */
             line_buf[len - 1] = '\0';
+            if ('#' == line_buf[0]) { /* skip commented lines */
+                continue;
+            }
             if (!trace_event_set_state(line_buf, true)) {
                 fprintf(stderr,
                         "error: trace event '%s' does not exist\n", line_buf);
diff --git a/trace/simple.c b/trace/simple.c
index b4a3c6e950..b700ea317c 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -27,7 +27,7 @@
 #define HEADER_MAGIC 0xf2b177cb0aa429b4ULL
 
 /** Trace file version number, bump if format changes */
-#define HEADER_VERSION 0
+#define HEADER_VERSION 2
 
 /** Records were dropped event ID */
 #define DROPPED_EVENT_ID (~(uint64_t)0 - 1)
@@ -35,23 +35,6 @@
 /** 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.
@@ -62,11 +45,48 @@ static GCond *trace_empty_cond;
 static bool trace_available;
 static bool trace_writeout_enabled;
 
-static TraceRecord trace_buf[TRACE_BUF_LEN];
+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 = NULL;
 
+/* * 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  */
+} TraceRecordHeader;
+
+
+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
  *
@@ -75,16 +95,30 @@ static char *trace_file_name = NULL;
  *
  * Returns false if the record is not valid.
  */
-static bool get_trace_record(unsigned int idx, TraceRecord *record)
+static bool get_trace_record(unsigned int idx, TraceRecord **recordptr)
 {
-    if (!(trace_buf[idx].event & TRACE_RECORD_VALID)) {
+    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;
     }
 
-    __sync_synchronize(); /* read memory barrier before accessing record */
-
-    *record = trace_buf[idx];
-    record->event &= ~TRACE_RECORD_VALID;
+    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;
 }
 
@@ -120,29 +154,39 @@ static void wait_for_trace_records_available(void)
 
 static gpointer writeout_thread(gpointer opaque)
 {
-    TraceRecord record;
-    unsigned int writeout_idx = 0;
-    unsigned int num_available, idx;
+    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();
 
-        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;
+        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);
         }
 
-        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;
+        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);
@@ -150,73 +194,93 @@ static gpointer writeout_thread(gpointer opaque)
     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)
+void trace_record_write_u64(TraceBufferRecord *rec, uint64_t val)
 {
-    unsigned int idx;
-    uint64_t timestamp;
-
-    if (!trace_list[event].state) {
-        return;
-    }
-
-    timestamp = get_clock();
-#if GLIB_CHECK_VERSION(2, 30, 0)
-    idx = g_atomic_int_add((gint *)&trace_idx, 1) % TRACE_BUF_LEN;
-#else
-    idx = g_atomic_int_exchange_and_add((gint *)&trace_idx, 1) % TRACE_BUF_LEN;
-#endif
-    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);
-    }
+    rec->rec_off = write_to_buffer(rec->rec_off, &val, sizeof(uint64_t));
 }
 
-void trace0(TraceEventID event)
+void trace_record_write_str(TraceBufferRecord *rec, const char *s, uint32_t slen)
 {
-    trace(event, 0, 0, 0, 0, 0, 0);
+    /* 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);
 }
 
-void trace1(TraceEventID event, uint64_t x1)
+int trace_record_start(TraceBufferRecord *rec, TraceEventID event, size_t datasize)
 {
-    trace(event, x1, 0, 0, 0, 0, 0);
-}
+    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;
+        }
 
-void trace2(TraceEventID event, uint64_t x1, uint64_t x2)
-{
-    trace(event, x1, x2, 0, 0, 0, 0);
-}
+        if (g_atomic_int_compare_and_exchange((gint *)&trace_idx,
+                                              old_idx, new_idx)) {
+            break;
+        }
+    }
 
-void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3)
-{
-    trace(event, x1, x2, x3, 0, 0, 0);
+    idx = old_idx % TRACE_BUF_LEN;
+    /*  To check later if threshold crossed */
+    rec->next_tbuf_idx = new_idx % TRACE_BUF_LEN;
+
+    rec_off = idx;
+    rec_off = write_to_buffer(rec_off, (uint8_t*)&event, sizeof(event));
+    rec_off = write_to_buffer(rec_off, (uint8_t*)&timestamp_ns, sizeof(timestamp_ns));
+    rec_off = write_to_buffer(rec_off, (uint8_t*)&rec_len, sizeof(rec_len));
+
+    rec->tbuf_idx = idx;
+    rec->rec_off  = (idx + sizeof(TraceRecord)) % TRACE_BUF_LEN;
+    return 0;
 }
 
-void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4)
+static void read_from_buffer(unsigned int idx, void *dataptr, size_t size)
 {
-    trace(event, x1, x2, x3, x4, 0, 0);
+    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++];
+    }
 }
 
-void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5)
+static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size)
 {
-    trace(event, x1, x2, x3, x4, x5, 0);
+    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 trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6)
+void trace_record_finish(TraceBufferRecord *rec)
 {
-    trace(event, x1, x2, x3, x4, x5, x6);
+    uint8_t temp_rec[sizeof(TraceRecord)];
+    TraceRecord *record = (TraceRecord *) temp_rec;
+    read_from_buffer(rec->tbuf_idx, temp_rec, sizeof(TraceRecord));
+    smp_wmb(); /* write barrier before marking as valid */
+    record->event |= TRACE_RECORD_VALID;
+    write_to_buffer(rec->tbuf_idx, temp_rec, sizeof(TraceRecord));
+
+    if ((trace_idx - writeout_idx) > TRACE_BUF_FLUSH_THRESHOLD) {
+        flush_trace_file(false);
+    }
 }
 
 void st_set_trace_file_enabled(bool enable)
@@ -231,10 +295,11 @@ void st_set_trace_file_enabled(bool enable)
     flush_trace_file(true);
 
     if (enable) {
-        static const TraceRecord header = {
-            .event = HEADER_EVENT_ID,
-            .timestamp_ns = HEADER_MAGIC,
-            .x1 = HEADER_VERSION,
+        static const TraceRecordHeader 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");
@@ -291,24 +356,6 @@ void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream,
                   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);
diff --git a/trace/simple.h b/trace/simple.h
index 466e75b4ff..7e521c1e1f 100644
--- a/trace/simple.h
+++ b/trace/simple.h
@@ -22,17 +22,41 @@ typedef struct {
     bool state;
 } TraceEvent;
 
-void trace0(TraceEventID event);
-void trace1(TraceEventID event, uint64_t x1);
-void trace2(TraceEventID event, uint64_t x1, uint64_t x2);
-void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3);
-void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4);
-void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5);
-void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6);
-void st_print_trace(FILE *stream, fprintf_function stream_printf);
 void st_print_trace_file_status(FILE *stream, fprintf_function stream_printf);
 void st_set_trace_file_enabled(bool enable);
 bool st_set_trace_file(const char *file);
 void st_flush_trace_buffer(void);
 
+typedef struct {
+    unsigned int tbuf_idx;
+    unsigned int next_tbuf_idx;
+    unsigned int rec_off;
+} TraceBufferRecord;
+
+/* Note for hackers: Make sure MAX_TRACE_LEN < sizeof(uint32_t) */
+#define MAX_TRACE_STRLEN 512
+/**
+ * Initialize a trace record and claim space for it in the buffer
+ *
+ * @arglen  number of bytes required for arguments
+ */
+int trace_record_start(TraceBufferRecord *rec, TraceEventID id, size_t arglen);
+
+/**
+ * Append a 64-bit argument to a trace record
+ */
+void trace_record_write_u64(TraceBufferRecord *rec, uint64_t val);
+
+/**
+ * Append a string argument to a trace record
+ */
+void trace_record_write_str(TraceBufferRecord *rec, const char *s, uint32_t slen);
+
+/**
+ * Mark a trace record completed
+ *
+ * Don't append any more arguments to the trace record after calling this.
+ */
+void trace_record_finish(TraceBufferRecord *rec);
+
 #endif /* TRACE_SIMPLE_H */