98 lines
1.9 KiB
C
98 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
#include <linux/module.h>
|
|
#include <linux/kthread.h>
|
|
#include <linux/ftrace.h>
|
|
|
|
extern void my_direct_func1(void);
|
|
extern void my_direct_func2(void);
|
|
|
|
void my_direct_func1(void)
|
|
{
|
|
trace_printk("my direct func1\n");
|
|
}
|
|
|
|
void my_direct_func2(void)
|
|
{
|
|
trace_printk("my direct func2\n");
|
|
}
|
|
|
|
extern void my_tramp1(void *);
|
|
extern void my_tramp2(void *);
|
|
|
|
static unsigned long my_ip = (unsigned long)schedule;
|
|
|
|
asm (
|
|
" .pushsection .text, \"ax\", @progbits\n"
|
|
" .type my_tramp1, @function\n"
|
|
" .globl my_tramp1\n"
|
|
" my_tramp1:"
|
|
" pushq %rbp\n"
|
|
" movq %rsp, %rbp\n"
|
|
" call my_direct_func1\n"
|
|
" leave\n"
|
|
" .size my_tramp1, .-my_tramp1\n"
|
|
ASM_RET
|
|
" .type my_tramp2, @function\n"
|
|
" .globl my_tramp2\n"
|
|
" my_tramp2:"
|
|
" pushq %rbp\n"
|
|
" movq %rsp, %rbp\n"
|
|
" call my_direct_func2\n"
|
|
" leave\n"
|
|
ASM_RET
|
|
" .size my_tramp2, .-my_tramp2\n"
|
|
" .popsection\n"
|
|
);
|
|
|
|
static unsigned long my_tramp = (unsigned long)my_tramp1;
|
|
static unsigned long tramps[2] = {
|
|
(unsigned long)my_tramp1,
|
|
(unsigned long)my_tramp2,
|
|
};
|
|
|
|
static int simple_thread(void *arg)
|
|
{
|
|
static int t;
|
|
int ret = 0;
|
|
|
|
while (!kthread_should_stop()) {
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
schedule_timeout(2 * HZ);
|
|
|
|
if (ret)
|
|
continue;
|
|
t ^= 1;
|
|
ret = modify_ftrace_direct(my_ip, my_tramp, tramps[t]);
|
|
if (!ret)
|
|
my_tramp = tramps[t];
|
|
WARN_ON_ONCE(ret);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static struct task_struct *simple_tsk;
|
|
|
|
static int __init ftrace_direct_init(void)
|
|
{
|
|
int ret;
|
|
|
|
ret = register_ftrace_direct(my_ip, my_tramp);
|
|
if (!ret)
|
|
simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
|
|
return ret;
|
|
}
|
|
|
|
static void __exit ftrace_direct_exit(void)
|
|
{
|
|
kthread_stop(simple_tsk);
|
|
unregister_ftrace_direct(my_ip, my_tramp);
|
|
}
|
|
|
|
module_init(ftrace_direct_init);
|
|
module_exit(ftrace_direct_exit);
|
|
|
|
MODULE_AUTHOR("Steven Rostedt");
|
|
MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
|
|
MODULE_LICENSE("GPL");
|