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@xxxxxxxxx>
---
include/tracefs.h | 18 ++++++++
src/Makefile | 1 +
src/tracefs-tools.c | 109 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 128 insertions(+)
create mode 100644 src/tracefs-tools.c
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@xxxxxxxxxx>
+ *
+ * Updates:
+ * Copyright (C) 2021, VMware, Tzvetomir Stoyanov <tz.stoyanov@xxxxxxxxx>
+ *
+ */
+#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);
+}
--
2.29.2
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