1 // SPDX-License-Identifier: GPL-2.0-only 2 #include <linux/module.h> 3 #include <linux/kthread.h> 4 #include <linux/ftrace.h> 5 #include <asm/asm-offsets.h> 6 7 void my_direct_func1(void) 8 { 9 trace_printk("my direct func1\n"); 10 } 11 12 void my_direct_func2(void) 13 { 14 trace_printk("my direct func2\n"); 15 } 16 17 extern void my_tramp1(void *); 18 extern void my_tramp2(void *); 19 20 static unsigned long my_ip = (unsigned long)schedule; 21 22 #ifdef CONFIG_X86_64 23 24 asm ( 25 " .pushsection .text, \"ax\", @progbits\n" 26 " .type my_tramp1, @function\n" 27 " .globl my_tramp1\n" 28 " my_tramp1:" 29 " pushq %rbp\n" 30 " movq %rsp, %rbp\n" 31 " call my_direct_func1\n" 32 " leave\n" 33 " .size my_tramp1, .-my_tramp1\n" 34 " ret\n" 35 " .type my_tramp2, @function\n" 36 " .globl my_tramp2\n" 37 " my_tramp2:" 38 " pushq %rbp\n" 39 " movq %rsp, %rbp\n" 40 " call my_direct_func2\n" 41 " leave\n" 42 " ret\n" 43 " .size my_tramp2, .-my_tramp2\n" 44 " .popsection\n" 45 ); 46 47 #endif /* CONFIG_X86_64 */ 48 49 #ifdef CONFIG_S390 50 51 asm ( 52 " .pushsection .text, \"ax\", @progbits\n" 53 " .type my_tramp1, @function\n" 54 " .globl my_tramp1\n" 55 " my_tramp1:" 56 " lgr %r1,%r15\n" 57 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 58 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 59 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 60 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 61 " brasl %r14,my_direct_func1\n" 62 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 63 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 64 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 65 " lgr %r1,%r0\n" 66 " br %r1\n" 67 " .size my_tramp1, .-my_tramp1\n" 68 " .type my_tramp2, @function\n" 69 " .globl my_tramp2\n" 70 " my_tramp2:" 71 " lgr %r1,%r15\n" 72 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 73 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 74 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 75 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 76 " brasl %r14,my_direct_func2\n" 77 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 78 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 79 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 80 " lgr %r1,%r0\n" 81 " br %r1\n" 82 " .size my_tramp2, .-my_tramp2\n" 83 " .popsection\n" 84 ); 85 86 #endif /* CONFIG_S390 */ 87 88 static unsigned long my_tramp = (unsigned long)my_tramp1; 89 static unsigned long tramps[2] = { 90 (unsigned long)my_tramp1, 91 (unsigned long)my_tramp2, 92 }; 93 94 static int simple_thread(void *arg) 95 { 96 static int t; 97 int ret = 0; 98 99 while (!kthread_should_stop()) { 100 set_current_state(TASK_INTERRUPTIBLE); 101 schedule_timeout(2 * HZ); 102 103 if (ret) 104 continue; 105 t ^= 1; 106 ret = modify_ftrace_direct(my_ip, my_tramp, tramps[t]); 107 if (!ret) 108 my_tramp = tramps[t]; 109 WARN_ON_ONCE(ret); 110 } 111 112 return 0; 113 } 114 115 static struct task_struct *simple_tsk; 116 117 static int __init ftrace_direct_init(void) 118 { 119 int ret; 120 121 ret = register_ftrace_direct(my_ip, my_tramp); 122 if (!ret) 123 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); 124 return ret; 125 } 126 127 static void __exit ftrace_direct_exit(void) 128 { 129 kthread_stop(simple_tsk); 130 unregister_ftrace_direct(my_ip, my_tramp); 131 } 132 133 module_init(ftrace_direct_init); 134 module_exit(ftrace_direct_exit); 135 136 MODULE_AUTHOR("Steven Rostedt"); 137 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()"); 138 MODULE_LICENSE("GPL"); 139