[PATCH v4 2/7] libtracefs: Implement tracefs_kprobe_raw()

[Steven Rostedt <rostedt@goodmis.org>]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Add a function to facilitate creating a kprobe event. It has the "raw" in
its name because it still requires knowing the format of the kprobe. But
does handle the kprobe naming better and writing to the kprobe_event file.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/tracefs.h     |  4 +++
 src/Makefile          |  1 +
 src/tracefs-kprobes.c | 72 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+)
 create mode 100644 src/tracefs-kprobes.c

diff --git a/include/tracefs.h b/include/tracefs.h
index a21d2d2f22a6..bc504bcb0188 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -214,4 +214,8 @@ int tracefs_tracer_clear(struct tracefs_instance *instance);
 ssize_t tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, int flags);
 ssize_t tracefs_trace_pipe_print(struct tracefs_instance *instance, int flags);
 void tracefs_trace_pipe_stop(struct tracefs_instance *instance);
+
+int tracefs_kprobe_raw(const char *system, const char *event,
+		       const char *addr, const char *format);
+
 #endif /* _TRACE_FS_H */
diff --git a/src/Makefile b/src/Makefile
index b4cff07efc50..0697a047f4bc 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -8,6 +8,7 @@ OBJS += tracefs-instance.o
 OBJS += tracefs-events.o
 OBJS += tracefs-tools.o
 OBJS += tracefs-marker.o
+OBJS += tracefs-kprobes.o
 
 OBJS := $(OBJS:%.o=$(bdir)/%.o)
 DEPS := $(OBJS:$(bdir)/%.o=$(bdir)/.%.d)
diff --git a/src/tracefs-kprobes.c b/src/tracefs-kprobes.c
new file mode 100644
index 000000000000..d50191d55181
--- /dev/null
+++ b/src/tracefs-kprobes.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Copyright (C) 2021 VMware Inc, Steven Rostedt <rostedt@goodmis.org>
+ *
+ * Updates:
+ * Copyright (C) 2021, VMware, Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
+ *
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+
+#include "tracefs.h"
+#include "tracefs-local.h"
+
+#define KPROBE_EVENTS "kprobe_events"
+
+/**
+ * tracefs_kprobe_raw - Create a kprobe using raw format
+ * @system: The system name (NULL for the default kprobes)
+ * @event: The event to create (NULL to use @addr for the event)
+ * @addr: The function and offset (or address) to insert the probe
+ * @format: The raw format string to define the probe.
+ *
+ * Create a kprobe that will be in the @system group (or kprobes if
+ * @system is NULL). Have the name of @event (or @addr if @event is
+ * NULL). Will be inserted to @addr (function name, with or without
+ * offset, or a address). And the @format will define the raw format
+ * of the kprobe. See the Linux documentation file under:
+ * Documentation/trace/kprobetrace.rst
+ *
+ * Return 0 on success, or -1 on error.
+ *   If the syntex of @format was incorrect, running
+ *   tracefs_error_last(NULL) may show what went wrong.
+ *
+ * errno will be set to EBADMSG if addr or format is NULL.
+ */
+int tracefs_kprobe_raw(const char *system, const char *event,
+		       const char *addr, const char *format)
+{
+	char *str;
+	int ret;
+
+	if (!tracefs_file_exists(NULL, KPROBE_EVENTS))
+		return -1;
+
+	errno = EBADMSG;
+	if (!addr || !format)
+		return -1;
+
+	if (!event)
+		event = addr;
+
+	if (system)
+		ret = asprintf(&str, "p:%s/%s %s %s\n",
+			       system, event, addr, format);
+	else
+		ret = asprintf(&str, "p:%s %s %s\n",
+			       event, addr, format);
+
+	if (ret < 0)
+		return -1;
+
+	ret = tracefs_instance_file_append(NULL, KPROBE_EVENTS, str);
+	free(str);
+
+	return ret < 0 ? ret : 0;
+}
-- 
2.30.2