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Subject[PATCH v2 11/12] tracing: Add kprobe event command generation test module
Date
Add a test module that checks the basic functionality of the in-kernel
kprobe event command generation API by creating kprobe events from a
module.

Signed-off-by: Tom Zanussi <zanussi@kernel.org>
---
kernel/trace/Kconfig | 12 ++
kernel/trace/Makefile | 1 +
kernel/trace/kprobe_event_gen_test.c | 223 +++++++++++++++++++++++++++++++++++
3 files changed, 236 insertions(+)
create mode 100644 kernel/trace/kprobe_event_gen_test.c

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 0597d60158b4..3e1b34ada52a 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -788,6 +788,18 @@ config SYNTH_EVENT_GEN_TEST

If unsure, say N.

+config KPROBE_EVENT_GEN_TEST
+ tristate "Test module for in-kernel kprobe event generation"
+ depends on KPROBE_EVENTS
+ help
+ This option creates a test module to check the base
+ functionality of in-kernel kprobe event definition.
+
+ To test, insert the module, and then check the trace buffer
+ for the generated kprobe events.
+
+ If unsure, say N.
+
config TRACE_EVAL_MAP_FILE
bool "Show eval mappings for trace events"
depends on TRACING
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 99de699c6062..0da59827babd 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -45,6 +45,7 @@ obj-$(CONFIG_TRACING) += trace_printk.o
obj-$(CONFIG_TRACING_MAP) += tracing_map.o
obj-$(CONFIG_PREEMPTIRQ_DELAY_TEST) += preemptirq_delay_test.o
obj-$(CONFIG_SYNTH_EVENT_GEN_TEST) += synth_event_gen_test.o
+obj-$(CONFIG_KPROBE_EVENT_GEN_TEST) += kprobe_event_gen_test.o
obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o
obj-$(CONFIG_PREEMPTIRQ_TRACEPOINTS) += trace_preemptirq.o
diff --git a/kernel/trace/kprobe_event_gen_test.c b/kernel/trace/kprobe_event_gen_test.c
new file mode 100644
index 000000000000..06d99c62b29b
--- /dev/null
+++ b/kernel/trace/kprobe_event_gen_test.c
@@ -0,0 +1,223 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test module for in-kernel kprobe event creation and generation.
+ *
+ * Copyright (C) 2019 Tom Zanussi <zanussi@kernel.org>
+ */
+
+#include <linux/module.h>
+#include <linux/trace_events.h>
+#include "trace.h"
+
+/*
+ * This module is a simple test of basic functionality for in-kernel
+ * kprobe/kretprobe event creation. The first test uses
+ * gen_kprobe_event(), add_probe_fields() and create_dynevent() to
+ * create a kprobe event, which is then enabled in order to generate
+ * trace output. The second creates a kretprobe event using
+ * gen_kretprobe_event() and create_dynevent, and is also then
+ * enabled.
+ *
+ * To test, select CONFIG_KPROBE_EVENT_GEN_TEST and build the module.
+ * Then:
+ *
+ * # insmod kernel/trace/kprobe_event_gen_test.ko
+ * # cat /sys/kernel/debug/tracing/trace
+ *
+ * You should see many instances of the "gen_kprobe_test" and
+ * "gen_kretprobe_test" events in the trace buffer.
+ *
+ * To remove the events, remove the module:
+ *
+ * # rmmod kprobe_event_gen_test
+ *
+ */
+
+static struct trace_event_file *gen_kprobe_test;
+static struct trace_event_file *gen_kretprobe_test;
+
+/*
+ * Test to make sure we can create a kprobe event, then add more
+ * fields.
+ */
+static int __init test_gen_kprobe_cmd(void)
+{
+ struct dynevent_cmd cmd;
+ char *buf;
+ int ret;
+
+ /* Create a buffer to hold the generated command */
+ buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ /* Before generating the command, initialize the cmd object */
+ kprobe_dynevent_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
+
+ /*
+ * Define the gen_kprobe_test event with the first 2 kprobe
+ * fields.
+ */
+ ret = gen_kprobe_cmd(&cmd, "gen_kprobe_test", "do_sys_open",
+ "dfd=%ax", "filename=%dx");
+ if (ret)
+ goto free;
+
+ /* Use add_probe_fields to add the rest of the fields */
+
+ ret = add_probe_fields(&cmd, "flags=%cx", "mode=+4($stack)");
+ if (ret)
+ goto free;
+
+ /*
+ * This actually creates the event.
+ */
+ ret = create_dynevent(&cmd);
+ if (ret)
+ goto free;
+
+ /*
+ * Now get the gen_kprobe_test event file. We need to prevent
+ * the instance and event from disappearing from underneath
+ * us, which get_event_file() does (though in this case we're
+ * using the top-level instance which never goes away).
+ */
+ gen_kprobe_test = get_event_file(NULL, "kprobes",
+ "gen_kprobe_test");
+ if (IS_ERR(gen_kprobe_test)) {
+ ret = PTR_ERR(gen_kprobe_test);
+ goto delete;
+ }
+
+ /* Enable the event or you won't see anything */
+ ret = trace_array_set_clr_event(gen_kprobe_test->tr,
+ "kprobes", "gen_kprobe_test", true);
+ if (ret) {
+ put_event_file(gen_kprobe_test);
+ goto delete;
+ }
+ out:
+ return ret;
+ delete:
+ /* We got an error after creating the event, delete it */
+ ret = delete_kprobe_event("gen_kprobe_test");
+ free:
+ kfree(buf);
+
+ goto out;
+}
+
+/*
+ * Test to make sure we can create a kretprobe event.
+ */
+static int __init test_gen_kretprobe_cmd(void)
+{
+ struct dynevent_cmd cmd;
+ char *buf;
+ int ret;
+
+ /* Create a buffer to hold the generated command */
+ buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ /* Before generating the command, initialize the cmd object */
+ kprobe_dynevent_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
+
+ /*
+ * Define the kretprobe event.
+ */
+ ret = gen_kretprobe_cmd(&cmd, "gen_kretprobe_test", "do_sys_open",
+ "$retval");
+ if (ret)
+ goto free;
+
+ /*
+ * This actually creates the event.
+ */
+ ret = create_dynevent(&cmd);
+ if (ret)
+ goto free;
+
+ /*
+ * Now get the gen_kretprobe_test event file. We need to prevent
+ * the instance and event from disappearing from underneath
+ * us, which get_event_file() does (though in this case we're
+ * using the top-level instance which never goes away).
+ */
+ gen_kretprobe_test = get_event_file(NULL, "kprobes",
+ "gen_kretprobe_test");
+ if (IS_ERR(gen_kretprobe_test)) {
+ ret = PTR_ERR(gen_kretprobe_test);
+ goto delete;
+ }
+
+ /* Enable the event or you won't see anything */
+ ret = trace_array_set_clr_event(gen_kretprobe_test->tr,
+ "kprobes", "gen_kretprobe_test", true);
+ if (ret) {
+ put_event_file(gen_kretprobe_test);
+ goto delete;
+ }
+ out:
+ return ret;
+ delete:
+ /* We got an error after creating the event, delete it */
+ ret = delete_kprobe_event("gen_kretprobe_test");
+ free:
+ kfree(buf);
+
+ goto out;
+}
+
+static int __init kprobe_event_gen_test_init(void)
+{
+ int ret;
+
+ ret = test_gen_kprobe_cmd();
+ if (ret)
+ return ret;
+
+ ret = test_gen_kretprobe_cmd();
+ if (ret) {
+ WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
+ "kprobes",
+ "gen_kretprobe_test", false));
+ put_event_file(gen_kretprobe_test);
+ WARN_ON(delete_kprobe_event("gen_kretprobe_test"));
+ }
+
+ return ret;
+}
+
+static void __exit kprobe_event_gen_test_exit(void)
+{
+ /* Disable the event or you can't remove it */
+ WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
+ "kprobes",
+ "gen_kprobe_test", false));
+
+ /* Now give the file and instance back */
+ put_event_file(gen_kprobe_test);
+
+ /* Now unregister and free the event */
+ WARN_ON(delete_kprobe_event("gen_kprobe_test"));
+
+ /* Disable the event or you can't remove it */
+ WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
+ "kprobes",
+ "gen_kretprobe_test", false));
+
+ /* Now give the file and instance back */
+ put_event_file(gen_kretprobe_test);
+
+ /* Now unregister and free the event */
+ WARN_ON(delete_kprobe_event("gen_kretprobe_test"));
+}
+
+module_init(kprobe_event_gen_test_init)
+module_exit(kprobe_event_gen_test_exit)
+
+MODULE_AUTHOR("Tom Zanussi");
+MODULE_DESCRIPTION("kprobe event generation test");
+MODULE_LICENSE("GPL v2");
--
2.14.1
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