[PATCH v3] libtracefs: Add new API for open trace marker file

["Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>]

Added new APIs for working with trace marker files of given instance.
Write strings in the trace_marker file:
 tracefs_print_init();
 tracefs_printf();
 tracefs_vprintf();
 tracefs_print_close();
Write binary data in trace_marker_raw file:
 tracefs_binary_init();
 tracefs_binary_write();
 tracefs_binary_close();

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
v3 changes:
 - Split the APIs in two groups - printing formated strings and writing binary data
v2 changes:
 - Added set of new APIs, instead of the previously proposed API for just
   opening the file.

 include/tracefs-local.h |   2 +
 include/tracefs.h       |  11 +++
 src/Makefile            |   1 +
 src/tracefs-instance.c  |   6 ++
 src/tracefs-marker.c    | 175 ++++++++++++++++++++++++++++++++++++++++
 5 files changed, 195 insertions(+)
 create mode 100644 src/tracefs-marker.c

diff --git a/include/tracefs-local.h b/include/tracefs-local.h
index 5a69ef7..d9bbf6e 100644
--- a/include/tracefs-local.h
+++ b/include/tracefs-local.h
@@ -20,6 +20,8 @@ struct tracefs_instance {
 	char	*name;
 	int	flags;
 	int	ftrace_filter_fd;
+	int	ftrace_marker_fd;
+	int	ftrace_marker_raw_fd;
 };
 
 /* Can be overridden */
diff --git a/include/tracefs.h b/include/tracefs.h
index befcc48..7181b75 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -63,6 +63,17 @@ static inline int tracefs_trace_on_get_fd(struct tracefs_instance *instance)
 	return tracefs_instance_file_open(instance, "tracing_on", O_RDWR);
 }
 
+/* trace print string*/
+int tracefs_print_init(struct tracefs_instance *instance);
+int tracefs_printf(struct tracefs_instance *instance, const char *fmt, ...);
+int tracefs_vprintf(struct tracefs_instance *instance, const char *fmt, va_list ap);
+void tracefs_print_close(struct tracefs_instance *instance);
+
+/* trace write binary data*/
+int tracefs_binary_init(struct tracefs_instance *instance);
+int tracefs_binary_write(struct tracefs_instance *instance, void *data, int len);
+void tracefs_binary_close(struct tracefs_instance *instance);
+
 /* events */
 void tracefs_list_free(char **list);
 char **tracefs_event_systems(const char *tracing_dir);
diff --git a/src/Makefile b/src/Makefile
index dabdbb4..b4cff07 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -7,6 +7,7 @@ OBJS += tracefs-utils.o
 OBJS += tracefs-instance.o
 OBJS += tracefs-events.o
 OBJS += tracefs-tools.o
+OBJS += tracefs-marker.o
 
 OBJS := $(OBJS:%.o=$(bdir)/%.o)
 DEPS := $(OBJS:$(bdir)/%.o=$(bdir)/.%.d)
diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index e87b360..bedf000 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -44,6 +44,8 @@ static struct tracefs_instance *instance_alloc(const char *trace_dir, const char
 	}
 
 	instance->ftrace_filter_fd = -1;
+	instance->ftrace_marker_fd = -1;
+	instance->ftrace_marker_raw_fd = -1;
 
 	return instance;
 
@@ -68,6 +70,10 @@ void tracefs_instance_free(struct tracefs_instance *instance)
 		return;
 	free(instance->trace_dir);
 	free(instance->name);
+	if (instance->ftrace_marker_fd >= 0)
+		close(instance->ftrace_marker_fd);
+	if (instance->ftrace_marker_raw_fd >= 0)
+		close(instance->ftrace_marker_raw_fd);
 	free(instance);
 }
 
diff --git a/src/tracefs-marker.c b/src/tracefs-marker.c
new file mode 100644
index 0000000..0dc72f6
--- /dev/null
+++ b/src/tracefs-marker.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Copyright (C) 2021, VMware, Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
+ *
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+
+#include "tracefs.h"
+#include "tracefs-local.h"
+
+/* File descriptors for Top level trace markers */
+static int ftrace_marker_fd = -1;
+static int ftrace_marker_raw_fd = -1;
+
+static inline int *get_marker_fd(struct tracefs_instance *instance, bool raw)
+{
+	if (raw)
+		return instance ? &instance->ftrace_marker_raw_fd : &ftrace_marker_raw_fd;
+	return instance ? &instance->ftrace_marker_fd : &ftrace_marker_fd;
+}
+
+static int marker_init(struct tracefs_instance *instance, bool raw)
+{
+	int *fd = get_marker_fd(instance, raw);
+
+	if (*fd >= 0)
+		return 0;
+	if (raw)
+		*fd = tracefs_instance_file_open(instance, "trace_marker_raw", O_WRONLY | O_CLOEXEC);
+	else
+		*fd = tracefs_instance_file_open(instance, "trace_marker", O_WRONLY | O_CLOEXEC);
+
+	return *fd < 0 ? -1 : 0;
+}
+
+static void marker_close(struct tracefs_instance *instance, bool raw)
+{
+	int *fd = get_marker_fd(instance, raw);
+
+	if (*fd < 0)
+		return;
+	close(*fd);
+	*fd = -1;
+}
+
+static int marker_write(struct tracefs_instance *instance, bool raw, void *data, int len)
+{
+	int *fd = get_marker_fd(instance, raw);
+	int ret;
+
+	if (!data || len < 1)
+		return -1;
+	if (*fd < 0) {
+		ret = marker_init(instance, raw);
+		if (ret < 0)
+			return ret;
+	}
+
+	ret = write(*fd, data, len);
+
+	return ret == len ? 0 : -1;
+}
+
+/**
+ * tracefs_print_init - Open trace marker of selected instance for writing
+ * @instance: ftrace instance, can be NULL for top tracing instance.
+ *
+ * Returns 0 if the trace marker is opened successfully, or -1 in case of an error
+ */
+int tracefs_print_init(struct tracefs_instance *instance)
+{
+	return marker_init(instance, false);
+}
+
+/**
+ * tracefs_vprintf - Write a formatted string in the trace marker
+ * @instance: ftrace instance, can be NULL for top tracing instance.
+ * @fmt: pritnf formatted string
+ * @ap: list of arguments for the formatted string
+ *
+ * If the trace marker of the desired instance is not open already,
+ * this API will open it for writing. It will stay open until
+ * tracefs_print_close() is called.
+ *
+ * Returns 0 if the string is written correctly, or -1 in case of an error
+ */
+int tracefs_vprintf(struct tracefs_instance *instance, const char *fmt, va_list ap)
+{
+	char *str = NULL;
+	int ret;
+
+	ret = vasprintf(&str, fmt, ap);
+	if (ret < 0)
+		return ret;
+	ret = marker_write(instance, false, str, strlen(str) + 1);
+	free(str);
+
+	return ret;
+}
+
+/**
+ * tracefs_printf - Write a formatted string in the trace marker
+ * @instance: ftrace instance, can be NULL for top tracing instance.
+ * @fmt: pritnf formatted string with variable arguments ...
+ *
+ * If the trace marker of the desired instance is not open already,
+ * this API will open it for writing. It will stay open until
+ * tracefs_print_close() is called.
+ *
+ * Returns 0 if the string is written correctly, or -1 in case of an error
+ */
+int tracefs_printf(struct tracefs_instance *instance, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap, fmt);
+	ret = tracefs_vprintf(instance, fmt, ap);
+	va_end(ap);
+
+	return ret;
+}
+
+/**
+ * tracefs_print_close - Close trace marker of selected instance
+ * @instance: ftrace instance, can be NULL for top tracing instance.
+ *
+ * Closes the trace marker, previously opened with any of the other tracefs_print APIs
+ */
+void tracefs_print_close(struct tracefs_instance *instance)
+{
+	marker_close(instance, false);
+}
+
+/**
+ * tracefs_binary_init - Open raw trace marker of selected instance for writing
+ * @instance: ftrace instance, can be NULL for top tracing instance.
+ *
+ * Returns 0 if the raw trace marker is opened successfully, or -1 in case of an error
+ */
+int tracefs_binary_init(struct tracefs_instance *instance)
+{
+	return marker_init(instance, true);
+}
+
+/**
+ * tracefs_binary_write - Write binary data in the raw trace marker
+ * @instance: ftrace instance, can be NULL for top tracing instance.
+ * @data: binary data, that is going to be written in the trace marker
+ * @len: length of the @data
+ *
+ * If the raw trace marker of the desired instance is not open already,
+ * this API will open it for writing. It will stay open until
+ * tracefs_binary_close() is called.
+ *
+ * Returns 0 if the data is written correctly, or -1 in case of an error
+ */
+int tracefs_binary_write(struct tracefs_instance *instance, void *data, int len)
+{
+	return marker_write(instance, true, data, len);
+}
+
+/**
+ * tracefs_binary_close - Close raw trace marker of selected instance
+ * @instance: ftrace instance, can be NULL for top tracing instance.
+ *
+ * Closes the raw trace marker, previously opened with any of the other tracefs_binary APIs
+ */
+void tracefs_binary_close(struct tracefs_instance *instance)
+{
+	marker_close(instance, true);
+}
-- 
2.30.2