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Tom Zanussirostedt
Tom Zanussi
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rostedt
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tracing: Add kprobe event command generation test module
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. Link: http://lkml.kernel.org/r/97e502b204f9dba948e3fa3a4315448298218787.1580323897.git.zanussi@kernel.org Acked-by: Masami Hiramatsu <[email protected]> Signed-off-by: Tom Zanussi <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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‎kernel/trace/Kconfig

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@@ -787,6 +787,18 @@ config SYNTH_EVENT_GEN_TEST
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If unsure, say N.
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config KPROBE_EVENT_GEN_TEST
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tristate "Test module for in-kernel kprobe event generation"
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depends on KPROBE_EVENTS
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help
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This option creates a test module to check the base
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functionality of in-kernel kprobe event definition.
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To test, insert the module, and then check the trace buffer
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for the generated kprobe events.
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If unsure, say N.
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config TRACE_EVAL_MAP_FILE
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bool "Show eval mappings for trace events"
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depends on TRACING

‎kernel/trace/Makefile

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@@ -45,6 +45,7 @@ obj-$(CONFIG_TRACING) += trace_printk.o
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obj-$(CONFIG_TRACING_MAP) += tracing_map.o
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obj-$(CONFIG_PREEMPTIRQ_DELAY_TEST) += preemptirq_delay_test.o
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obj-$(CONFIG_SYNTH_EVENT_GEN_TEST) += synth_event_gen_test.o
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obj-$(CONFIG_KPROBE_EVENT_GEN_TEST) += kprobe_event_gen_test.o
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obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
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obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o
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obj-$(CONFIG_PREEMPTIRQ_TRACEPOINTS) += trace_preemptirq.o

‎kernel/trace/kprobe_event_gen_test.c

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// SPDX-License-Identifier: GPL-2.0
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/*
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* Test module for in-kernel kprobe event creation and generation.
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*
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* Copyright (C) 2019 Tom Zanussi <[email protected]>
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*/
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#include <linux/module.h>
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#include <linux/trace_events.h>
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/*
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* This module is a simple test of basic functionality for in-kernel
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* kprobe/kretprobe event creation. The first test uses
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* kprobe_event_gen_cmd_start(), kprobe_event_add_fields() and
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* kprobe_event_gen_cmd_end() to create a kprobe event, which is then
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* enabled in order to generate trace output. The second creates a
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* kretprobe event using kretprobe_event_gen_cmd_start() and
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* kretprobe_event_gen_cmd_end(), and is also then enabled.
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*
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* To test, select CONFIG_KPROBE_EVENT_GEN_TEST and build the module.
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* Then:
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*
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* # insmod kernel/trace/kprobe_event_gen_test.ko
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* # cat /sys/kernel/debug/tracing/trace
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*
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* You should see many instances of the "gen_kprobe_test" and
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* "gen_kretprobe_test" events in the trace buffer.
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*
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* To remove the events, remove the module:
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*
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* # rmmod kprobe_event_gen_test
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*
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*/
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static struct trace_event_file *gen_kprobe_test;
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static struct trace_event_file *gen_kretprobe_test;
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/*
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* Test to make sure we can create a kprobe event, then add more
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* fields.
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*/
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static int __init test_gen_kprobe_cmd(void)
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{
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struct dynevent_cmd cmd;
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char *buf;
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int ret;
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/* Create a buffer to hold the generated command */
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buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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/* Before generating the command, initialize the cmd object */
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kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
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/*
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* Define the gen_kprobe_test event with the first 2 kprobe
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* fields.
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*/
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ret = kprobe_event_gen_cmd_start(&cmd, "gen_kprobe_test",
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"do_sys_open",
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"dfd=%ax", "filename=%dx");
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if (ret)
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goto free;
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/* Use kprobe_event_add_fields to add the rest of the fields */
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ret = kprobe_event_add_fields(&cmd, "flags=%cx", "mode=+4($stack)");
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if (ret)
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goto free;
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/*
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* This actually creates the event.
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*/
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ret = kprobe_event_gen_cmd_end(&cmd);
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if (ret)
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goto free;
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/*
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* Now get the gen_kprobe_test event file. We need to prevent
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* the instance and event from disappearing from underneath
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* us, which trace_get_event_file() does (though in this case
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* we're using the top-level instance which never goes away).
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*/
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gen_kprobe_test = trace_get_event_file(NULL, "kprobes",
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"gen_kprobe_test");
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if (IS_ERR(gen_kprobe_test)) {
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ret = PTR_ERR(gen_kprobe_test);
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goto delete;
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}
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/* Enable the event or you won't see anything */
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ret = trace_array_set_clr_event(gen_kprobe_test->tr,
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"kprobes", "gen_kprobe_test", true);
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if (ret) {
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trace_put_event_file(gen_kprobe_test);
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goto delete;
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}
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out:
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return ret;
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delete:
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/* We got an error after creating the event, delete it */
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ret = kprobe_event_delete("gen_kprobe_test");
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free:
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kfree(buf);
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goto out;
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}
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/*
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* Test to make sure we can create a kretprobe event.
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*/
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static int __init test_gen_kretprobe_cmd(void)
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{
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struct dynevent_cmd cmd;
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char *buf;
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int ret;
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/* Create a buffer to hold the generated command */
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buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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/* Before generating the command, initialize the cmd object */
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kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
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/*
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* Define the kretprobe event.
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*/
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ret = kretprobe_event_gen_cmd_start(&cmd, "gen_kretprobe_test",
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"do_sys_open",
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"$retval");
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if (ret)
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goto free;
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/*
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* This actually creates the event.
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*/
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ret = kretprobe_event_gen_cmd_end(&cmd);
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if (ret)
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goto free;
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/*
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* Now get the gen_kretprobe_test event file. We need to
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* prevent the instance and event from disappearing from
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* underneath us, which trace_get_event_file() does (though in
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* this case we're using the top-level instance which never
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* goes away).
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*/
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gen_kretprobe_test = trace_get_event_file(NULL, "kprobes",
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"gen_kretprobe_test");
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if (IS_ERR(gen_kretprobe_test)) {
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ret = PTR_ERR(gen_kretprobe_test);
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goto delete;
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}
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/* Enable the event or you won't see anything */
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ret = trace_array_set_clr_event(gen_kretprobe_test->tr,
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"kprobes", "gen_kretprobe_test", true);
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if (ret) {
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trace_put_event_file(gen_kretprobe_test);
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goto delete;
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}
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out:
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return ret;
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delete:
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/* We got an error after creating the event, delete it */
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ret = kprobe_event_delete("gen_kretprobe_test");
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free:
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kfree(buf);
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goto out;
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}
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static int __init kprobe_event_gen_test_init(void)
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{
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int ret;
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ret = test_gen_kprobe_cmd();
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if (ret)
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return ret;
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ret = test_gen_kretprobe_cmd();
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if (ret) {
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WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
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"kprobes",
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"gen_kretprobe_test", false));
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trace_put_event_file(gen_kretprobe_test);
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WARN_ON(kprobe_event_delete("gen_kretprobe_test"));
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}
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return ret;
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}
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static void __exit kprobe_event_gen_test_exit(void)
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{
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/* Disable the event or you can't remove it */
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WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
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"kprobes",
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"gen_kprobe_test", false));
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/* Now give the file and instance back */
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trace_put_event_file(gen_kprobe_test);
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/* Now unregister and free the event */
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WARN_ON(kprobe_event_delete("gen_kprobe_test"));
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/* Disable the event or you can't remove it */
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WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
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"kprobes",
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"gen_kretprobe_test", false));
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/* Now give the file and instance back */
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trace_put_event_file(gen_kretprobe_test);
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/* Now unregister and free the event */
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WARN_ON(kprobe_event_delete("gen_kretprobe_test"));
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}
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module_init(kprobe_event_gen_test_init)
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module_exit(kprobe_event_gen_test_exit)
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MODULE_AUTHOR("Tom Zanussi");
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MODULE_DESCRIPTION("kprobe event generation test");
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MODULE_LICENSE("GPL v2");

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