cxl: add a helper to parse trace events into a json object

Add a helper function that parses a trace event captured by libtraceevent
in a tep handle. All the parsed fields are added to a json object. The
json object is added to the provided list in the input parameter.

Tested-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/166803885399.145141.7371810852032502111.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

cxl/event_trace.c

@@ -0,0 +1,193 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2022, Intel Corp. All rights reserved.
+#include <stdio.h>
+#include <errno.h>
+#include <json-c/json.h>
+#include <util/json.h>
+#include <util/util.h>
+#include <util/strbuf.h>
+#include <ccan/list/list.h>
+#include <uuid/uuid.h>
+#include <traceevent/event-parse.h>
+#include "event_trace.h"
+
+#define _GNU_SOURCE
+#include <string.h>
+
+static struct json_object *num_to_json(void *num, int elem_size, unsigned long flags)
+{
+	bool sign = flags & TEP_FIELD_IS_SIGNED;
+	int64_t val = 0;
+
+	/* special case 64 bit as the call depends on sign */
+	if (elem_size == 8) {
+		if (sign)
+			return json_object_new_int64(*(int64_t *)num);
+		else
+			return json_object_new_uint64(*(uint64_t *)num);
+	}
+
+	/* All others fit in a signed 64 bit */
+	switch (elem_size) {
+	case 1:
+		if (sign)
+			val = *(int8_t *)num;
+		else
+			val = *(uint8_t *)num;
+		break;
+	case 2:
+		if (sign)
+			val = *(int16_t *)num;
+		else
+			val = *(uint16_t *)num;
+		break;
+	case 4:
+		if (sign)
+			val = *(int32_t *)num;
+		else
+			val = *(uint32_t *)num;
+		break;
+	default:
+		/*
+		 * Odd sizes are converted in the kernel to one of the above.
+		 * It is an error to see them here.
+		 */
+		return NULL;
+	}
+
+	return json_object_new_int64(val);
+}
+
+static int cxl_event_to_json(struct tep_event *event, struct tep_record *record,
+			     struct list_head *jlist_head)
+{
+	struct json_object *jevent, *jobj, *jarray;
+	struct tep_format_field **fields;
+	struct jlist_node *jnode;
+	int i, j, rc = 0;
+
+	jnode = malloc(sizeof(*jnode));
+	if (!jnode)
+		return -ENOMEM;
+
+	jevent = json_object_new_object();
+	if (!jevent) {
+		rc = -ENOMEM;
+		goto err_jnode;
+	}
+	jnode->jobj = jevent;
+
+	fields = tep_event_fields(event);
+	if (!fields) {
+		rc = -ENOENT;
+		goto err_jevent;
+	}
+
+	jobj = json_object_new_string(event->system);
+	if (!jobj) {
+		rc = -ENOMEM;
+		goto err_jevent;
+	}
+	json_object_object_add(jevent, "system", jobj);
+
+	jobj = json_object_new_string(event->name);
+	if (!jobj) {
+		rc = -ENOMEM;
+		goto err_jevent;
+	}
+	json_object_object_add(jevent, "event", jobj);
+
+	jobj = json_object_new_uint64(record->ts);
+	if (!jobj) {
+		rc = -ENOMEM;
+		goto err_jevent;
+	}
+	json_object_object_add(jevent, "timestamp", jobj);
+
+	for (i = 0; fields[i]; i++) {
+		struct tep_format_field *f = fields[i];
+		int len;
+
+		if (f->flags & TEP_FIELD_IS_STRING) {
+			char *str;
+
+			str = tep_get_field_raw(NULL, event, f->name, record, &len, 0);
+			if (!str)
+				continue;
+
+			jobj = json_object_new_string(str);
+			if (!jobj) {
+				rc = -ENOMEM;
+				goto err_jevent;
+			}
+
+			json_object_object_add(jevent, f->name, jobj);
+		} else if (f->flags & TEP_FIELD_IS_ARRAY) {
+			unsigned char *data;
+			int chunks;
+
+			data = tep_get_field_raw(NULL, event, f->name, record, &len, 0);
+			if (!data)
+				continue;
+
+			jarray = json_object_new_array();
+			if (!jarray) {
+				rc = -ENOMEM;
+				goto err_jevent;
+			}
+
+			chunks = f->size / f->elementsize;
+			for (j = 0; j < chunks; j++) {
+				jobj = num_to_json(data, f->elementsize, f->flags);
+				if (!jobj) {
+					json_object_put(jarray);
+					return -ENOMEM;
+				}
+				json_object_array_add(jarray, jobj);
+				data += f->elementsize;
+			}
+
+			json_object_object_add(jevent, f->name, jarray);
+		} else { /* single number */
+			unsigned char *data;
+			char *tmp;
+
+			data = tep_get_field_raw(NULL, event, f->name, record, &len, 0);
+			if (!data)
+				continue;
+
+			/* check to see if we have a UUID */
+			tmp = strcasestr(f->type, "uuid_t");
+			if (tmp) {
+				char uuid[40];
+
+				uuid_unparse(data, uuid);
+				jobj = json_object_new_string(uuid);
+				if (!jobj) {
+					rc = -ENOMEM;
+					goto err_jevent;
+				}
+
+				json_object_object_add(jevent, f->name, jobj);
+				continue;
+			}
+
+			jobj = num_to_json(data, f->elementsize, f->flags);
+			if (!jobj) {
+				rc = -ENOMEM;
+				goto err_jevent;
+			}
+
+			json_object_object_add(jevent, f->name, jobj);
+		}
+	}
+
+	list_add_tail(jlist_head, &jnode->list);
+	return 0;
+
+err_jevent:
+	json_object_put(jevent);
+err_jnode:
+	free(jnode);
+	return rc;
+}

cxl/event_trace.h

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2022 Intel Corporation. All rights reserved. */
+#ifndef __CXL_EVENT_TRACE_H__
+#define __CXL_EVENT_TRACE_H__
+
+#include <json-c/json.h>
+#include <ccan/list/list.h>
+
+struct jlist_node {
+	struct json_object *jobj;
+	struct list_node list;
+};
+
+#endif

cxl/meson.build

@@ -7,6 +7,7 @@ cxl_src = [
   'memdev.c',
   'json.c',
   'filter.c',
+  'event_trace.c',
 ]
 
 cxl_tool = executable('cxl',
@@ -19,6 +20,7 @@ cxl_tool = executable('cxl',
     kmod,
     json,
     versiondep,
+    traceevent,
   ],
   install : true,
   install_dir : rootbindir,

meson.build

@@ -143,6 +143,7 @@ kmod = dependency('libkmod')
 libudev = dependency('libudev')
 uuid = dependency('uuid')
 json = dependency('json-c')
+traceevent = dependency('libtraceevent')
 if get_option('docs').enabled()
   if get_option('asciidoctor').enabled()
     asciidoc = find_program('asciidoctor', required : true)