[PATCH 7/8] trace-cruncher: Check kernel support in the eprobe constructor

From: "Yordan Karadzhov (VMware)" <y.karadz@gmail.com>
To: linux-trace-devel@vger.kernel.org
Cc: "Yordan Karadzhov (VMware)" <y.karadz@gmail.com>
Subject: [PATCH 7/8] trace-cruncher: Check kernel support in the eprobe constructor
Date: Thu, 10 Feb 2022 17:23:38 +0200	[thread overview]
Message-ID: <20220210152339.363943-8-y.karadz@gmail.com> (raw)
In-Reply-To: <20220210152339.363943-1-y.karadz@gmail.com>

'eprobes' have been introduced in kernel version 5.15. Before trying to
create eprobe, we have to check if suport is avaiable. In the case of
using an older version of the kernel, an apropriate error message is
provided.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 src/ftracepy-utils.c | 48 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)

diff --git a/src/ftracepy-utils.c b/src/ftracepy-utils.c
index 20f0cd9..85f5bbc 100644
--- a/src/ftracepy-utils.c
+++ b/src/ftracepy-utils.c
@@ -12,6 +12,7 @@
 // C
 #include <search.h>
 #include <string.h>
+#include <sys/utsname.h>
 #include <sys/wait.h>
 #include <signal.h>
 #include <time.h>
@@ -23,6 +24,47 @@ PyObject *TFS_ERROR;
 PyObject *TEP_ERROR;
 PyObject *TRACECRUNCHER_ERROR;
 
+static char *kernel_version()
+{
+	struct utsname uts;
+
+	if (uname(&uts) != 0) {
+		PyErr_SetString(TFS_ERROR, "Failed to get kernel version.");
+		return NULL;
+	}
+
+	return strdup(uts.release);
+}
+
+static bool check_kernel_support(const char *api, int major, int minor)
+{
+	char *buff, *this_kernel = kernel_version();
+	const char *dlm = ".";
+	bool ret = false;
+	int mj, mn;
+
+        buff = strtok(this_kernel, dlm);
+	mj = atoi(buff);
+	if (mj > major)
+		ret = true;
+
+	if (mj == major) {
+		buff = strtok(NULL, dlm);
+		mn = atoi(buff);
+		if (mn >= minor)
+			ret = true;
+	}
+
+	free(this_kernel);
+	if (!ret) {
+		PyErr_Format(TFS_ERROR,
+			     "Using \'%s()\' requires kernel versions >= %i.%i",
+			     api, major, minor);
+	}
+
+	return ret;
+}
+
 static const char *get_instance_name(struct tracefs_instance *instance);
 
 static char *tfs_error_log(struct tracefs_instance *instance, bool *ok)
@@ -2382,6 +2424,10 @@ PyObject *PyFtrace_eprobe(PyObject *self, PyObject *args, PyObject *kwargs)
 		return NULL;
 	}
 
+	/* 'eprobes' are introduced in kernel version 5.15. */
+	if (!check_kernel_support("eprobe", 5, 15))
+		return NULL;
+
 	eprobe = tracefs_eprobe_alloc(TC_SYS, event, target_system, target_event, fetchargs);
 	if (!eprobe) {
 		MEM_ERROR;
@@ -2395,7 +2441,7 @@ PyObject *PyFtrace_eprobe(PyObject *self, PyObject *args, PyObject *kwargs)
 	 * there is no need to 'destroy' this event at exit.
 	 */
 	set_destroy_flag(py_dyn, false);
-	return py_dyn;;
+	return py_dyn;
 }
 
 static PyObject *set_filter(PyObject *args, PyObject *kwargs,
-- 
2.32.0

