Commit b06457c8 authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

ftrace: Add sample module that uses register_ftrace_direct() 



Add a sample module that shows a simple use case for
regsiter_ftrace_direct(), and how to use it.

Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 013bf0da

samples/Kconfig

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@@ -19,6 +19,14 @@ config SAMPLE_TRACE_PRINTK 
	 This builds a module that calls trace_printk() and can be used to

	 test various trace_printk() calls from a module.



config SAMPLE_FTRACE_DIRECT

	tristate "Build register_ftrace_direct() example"

	depends on DYNAMIC_FTRACE_WITH_DIRECT_CALLS && m

	depends on X86_64 # has x86_64 inlined asm

	help

	  This builds an ftrace direct function example

	  that hooks to wake_up_process and prints the parameters.



config SAMPLE_KOBJECT

	tristate "Build kobject examples"

	help

samples/Makefile

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@@ -17,6 +17,7 @@ obj-$(CONFIG_SAMPLE_RPMSG_CLIENT) += rpmsg/ 
subdir-$(CONFIG_SAMPLE_SECCOMP)		+= seccomp

obj-$(CONFIG_SAMPLE_TRACE_EVENTS)	+= trace_events/

obj-$(CONFIG_SAMPLE_TRACE_PRINTK)	+= trace_printk/

obj-$(CONFIG_SAMPLE_FTRACE_DIRECT)	+= ftrace/

obj-$(CONFIG_VIDEO_PCI_SKELETON)	+= v4l/

obj-y					+= vfio-mdev/

subdir-$(CONFIG_SAMPLE_VFS)		+= vfs

samples/ftrace/Makefile

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# SPDX-License-Identifier: GPL-2.0-only



obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct.o

samples/ftrace/ftrace-direct.c

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// SPDX-License-Identifier: GPL-2.0-only

#include <linux/module.h>



#include <linux/sched.h> /* for wake_up_process() */

#include <linux/ftrace.h>



void my_direct_func(struct task_struct *p)

{

	trace_printk("wakeing up %s-%d\n", p->comm, p->pid);

}



extern void my_tramp(void *);



asm (

"	.pushsection    .text, \"ax\", @progbits\n"

"   my_tramp:"

"	pushq %rbp\n"

"	movq %rsp, %rbp\n"

"	pushq %rdi\n"

"	call my_direct_func\n"

"	popq %rdi\n"

"	leave\n"

"	ret\n"

"	.popsection\n"

);





static int __init ftrace_direct_init(void)

{

	return register_ftrace_direct((unsigned long)wake_up_process,

				     (unsigned long)my_tramp);

}



static void __exit ftrace_direct_exit(void)

{

	unregister_ftrace_direct((unsigned long)wake_up_process,

				 (unsigned long)my_tramp);

}



module_init(ftrace_direct_init);

module_exit(ftrace_direct_exit);



MODULE_AUTHOR("Steven Rostedt");

MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");

MODULE_LICENSE("GPL");