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