Simpletrace v2: Support multiple arguments, strings.

Existing simpletrace backend allows to trace at max 6 args and does not
support strings. This newer tracelog format gets rid of fixed size records
and therefore allows to trace variable number of args including strings.

Sample trace with strings:
v9fs_version 0.000 tag=0xffff id=0x64 msize=0x2000 version=9P2000.L
v9fs_version_return 6.705 tag=0xffff id=0x64 msize=0x2000 version=9P2000.L

Signed-off-by: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

1 files changed, 32 insertions, 7 deletions

diff --git a/trace/simple.h b/trace/simple.h
index 6b5358c9f2..7e521c1e1f 100644
--- a/trace/simple.h
+++ b/trace/simple.h
@@ -22,16 +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_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 */