diff mbox series

[v2,3/7] libtracefs: New APIs for enable / disable tracing

Message ID 20210112092024.605705-4-tz.stoyanov@gmail.com (mailing list archive)
State Accepted
Headers show
Series New libtracefs APIs | expand

Commit Message

Tzvetomir Stoyanov (VMware) Jan. 12, 2021, 9:20 a.m. UTC 
These new APIs can be used to enable / disable tracing in given ftrace
instance:
  tracefs_trace_is_on();
  tracefs_trace_on();
  tracefs_trace_off();
  tracefs_trace_on_get_fd();
  tracefs_trace_on_fd();
  tracefs_trace_off_fd();

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/tracefs.h   |  18 ++++++++
 src/Makefile        |   1 +
 src/tracefs-tools.c | 109 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 128 insertions(+)
 create mode 100644 src/tracefs-tools.c

Comments

Steven Rostedt Feb. 19, 2021, 3:07 a.m. UTC | #1 
On Tue, 12 Jan 2021 11:20:20 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:

> These new APIs can be used to enable / disable tracing in given ftrace
> instance:
>   tracefs_trace_is_on();
>   tracefs_trace_on();
>   tracefs_trace_off();
>   tracefs_trace_on_get_fd();
>   tracefs_trace_on_fd();
>   tracefs_trace_off_fd();
> 

I just realized we don't have:

tracefs_trace_marker_get_fd();

Which we should, as it's one of the files we want to have the file
descriptor for to write directly without having to open it each time.

(I could have used it right now)

-- Steve
diff mbox series

Patch

diff --git a/include/tracefs.h b/include/tracefs.h
index bec8369..85a776e 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -40,6 +40,24 @@  bool tracefs_instance_exists(const char *name);
 bool tracefs_file_exists(struct tracefs_instance *instance, char *name);
 bool tracefs_dir_exists(struct tracefs_instance *instance, char *name);
 
+int tracefs_trace_is_on(struct tracefs_instance *instance);
+int tracefs_trace_on(struct tracefs_instance *instance);
+int tracefs_trace_off(struct tracefs_instance *instance);
+int tracefs_trace_on_fd(int fd);
+int tracefs_trace_off_fd(int fd);
+
+/**
+ * tracefs_trace_on_get_fd - Get a file descriptor of "tracing_on" in given instance
+ * @instance: ftrace instance, can be NULL for the top instance
+ *
+ * Returns -1 in case of an error, or a valid file descriptor to "tracing_on"
+ * file for reading and writing.The returned FD must be closed with close().
+ */
+static inline int tracefs_trace_on_get_fd(struct tracefs_instance *instance)
+{
+	return tracefs_instance_file_open(instance, "tracing_on", O_RDWR);
+}
+
 /* events */
 void tracefs_list_free(char **list);
 char **tracefs_event_systems(const char *tracing_dir);
diff --git a/src/Makefile b/src/Makefile
index 3f64905..dabdbb4 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -6,6 +6,7 @@  OBJS =
 OBJS += tracefs-utils.o
 OBJS += tracefs-instance.o
 OBJS += tracefs-events.o
+OBJS += tracefs-tools.o
 
 OBJS := $(OBJS:%.o=$(bdir)/%.o)
 DEPS := $(OBJS:$(bdir)/%.o=$(bdir)/.%.d)
diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
new file mode 100644
index 0000000..101f389
--- /dev/null
+++ b/src/tracefs-tools.c
@@ -0,0 +1,109 @@ 
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Copyright (C) 2008, 2009, 2010 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
+ *
+ * Updates:
+ * Copyright (C) 2021, VMware, Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
+ *
+ */
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "tracefs.h"
+#include "tracefs-local.h"
+
+#define TRACE_CTRL	"tracing_on"
+
+static int trace_on_off(int fd, bool on)
+{
+	const char *val = on ? "1" : "0";
+	int ret;
+
+	ret = write(fd, val, 1);
+	if (ret == 1)
+		return 0;
+
+	return -1;
+}
+
+static int trace_on_off_file(struct tracefs_instance *instance, bool on)
+{
+	int ret;
+	int fd;
+
+	fd = tracefs_instance_file_open(instance, TRACE_CTRL, O_WRONLY);
+	if (fd < 0)
+		return -1;
+	ret = trace_on_off(fd, on);
+	close(fd);
+
+	return ret;
+}
+
+/**
+ * tracefs_trace_is_on - Check if writing traces to the ring buffer is enabled
+ * @instance: ftrace instance, can be NULL for the top instance
+ *
+ * Returns -1 in case of an error, 0 if tracing is disable or 1 if tracing
+ * is enabled.
+ */
+int tracefs_trace_is_on(struct tracefs_instance *instance)
+{
+	long long res;
+
+	if (tracefs_instance_file_read_number(instance, TRACE_CTRL, &res) == 0)
+		return (int)res;
+
+	return -1;
+}
+
+/**
+ * tracefs_trace_on - Enable writing traces to the ring buffer of the given instance
+ * @instance: ftrace instance, can be NULL for the top instance
+ *
+ * Returns -1 in case of an error or 0 otherwise
+ */
+int tracefs_trace_on(struct tracefs_instance *instance)
+{
+	return trace_on_off_file(instance, true);
+}
+
+/**
+ * tracefs_trace_off - Disable writing traces to the ring buffer of the given instance
+ * @instance: ftrace instance, can be NULL for the top instance
+ *
+ * Returns -1 in case of an error or 0 otherwise
+ */
+int tracefs_trace_off(struct tracefs_instance *instance)
+{
+	return trace_on_off_file(instance, false);
+}
+
+/**
+ * tracefs_trace_on_fd - Enable writing traces to the ring buffer
+ * @fd: File descriptor to ftrace tracing_on file, previously opened
+ *	with tracefs_trace_on_get_fd()
+ *
+ * Returns -1 in case of an error or 0 otherwise
+ */
+int tracefs_trace_on_fd(int fd)
+{
+	if (fd < 0)
+		return -1;
+	return trace_on_off(fd, true);
+}
+
+/**
+ * tracefs_trace_off_fd - Disable writing traces to the ring buffer
+ * @fd: File descriptor to ftrace tracing_on file, previously opened
+ *	with tracefs_trace_on_get_fd()
+ *
+ * Returns -1 in case of an error or 0 otherwise
+ */
+int tracefs_trace_off_fd(int fd)
+{
+	if (fd < 0)
+		return -1;
+	return trace_on_off(fd, false);
+}