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(unsigned long ip) 8 { 9 trace_printk("my direct func1 ip %lx\n", ip); 10 } 11 12 void my_direct_func2(unsigned long ip) 13 { 14 trace_printk("my direct func2 ip %lx\n", ip); 15 } 16 17 extern void my_tramp1(void *); 18 extern void my_tramp2(void *); 19 20 #ifdef CONFIG_X86_64 21 22 asm ( 23 " .pushsection .text, \"ax\", @progbits\n" 24 " .type my_tramp1, @function\n" 25 " .globl my_tramp1\n" 26 " my_tramp1:" 27 " pushq %rbp\n" 28 " movq %rsp, %rbp\n" 29 " pushq %rdi\n" 30 " movq 8(%rbp), %rdi\n" 31 " call my_direct_func1\n" 32 " popq %rdi\n" 33 " leave\n" 34 " ret\n" 35 " .size my_tramp1, .-my_tramp1\n" 36 " .type my_tramp2, @function\n" 37 "\n" 38 " .globl my_tramp2\n" 39 " my_tramp2:" 40 " pushq %rbp\n" 41 " movq %rsp, %rbp\n" 42 " pushq %rdi\n" 43 " movq 8(%rbp), %rdi\n" 44 " call my_direct_func2\n" 45 " popq %rdi\n" 46 " leave\n" 47 " ret\n" 48 " .size my_tramp2, .-my_tramp2\n" 49 " .popsection\n" 50 ); 51 52 #endif /* CONFIG_X86_64 */ 53 54 #ifdef CONFIG_S390 55 56 asm ( 57 " .pushsection .text, \"ax\", @progbits\n" 58 " .type my_tramp1, @function\n" 59 " .globl my_tramp1\n" 60 " my_tramp1:" 61 " lgr %r1,%r15\n" 62 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 63 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 64 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 65 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 66 " lgr %r2,%r0\n" 67 " brasl %r14,my_direct_func1\n" 68 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 69 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 70 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 71 " lgr %r1,%r0\n" 72 " br %r1\n" 73 " .size my_tramp1, .-my_tramp1\n" 74 "\n" 75 " .type my_tramp2, @function\n" 76 " .globl my_tramp2\n" 77 " my_tramp2:" 78 " lgr %r1,%r15\n" 79 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 80 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 81 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 82 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 83 " lgr %r2,%r0\n" 84 " brasl %r14,my_direct_func2\n" 85 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 86 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 87 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 88 " lgr %r1,%r0\n" 89 " br %r1\n" 90 " .size my_tramp2, .-my_tramp2\n" 91 " .popsection\n" 92 ); 93 94 #endif /* CONFIG_S390 */ 95 96 static unsigned long my_tramp = (unsigned long)my_tramp1; 97 static unsigned long tramps[2] = { 98 (unsigned long)my_tramp1, 99 (unsigned long)my_tramp2, 100 }; 101 102 static struct ftrace_ops direct; 103 104 static int simple_thread(void *arg) 105 { 106 static int t; 107 int ret = 0; 108 109 while (!kthread_should_stop()) { 110 set_current_state(TASK_INTERRUPTIBLE); 111 schedule_timeout(2 * HZ); 112 113 if (ret) 114 continue; 115 t ^= 1; 116 ret = modify_ftrace_direct_multi(&direct, tramps[t]); 117 if (!ret) 118 my_tramp = tramps[t]; 119 WARN_ON_ONCE(ret); 120 } 121 122 return 0; 123 } 124 125 static struct task_struct *simple_tsk; 126 127 static int __init ftrace_direct_multi_init(void) 128 { 129 int ret; 130 131 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0); 132 ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0); 133 134 ret = register_ftrace_direct_multi(&direct, my_tramp); 135 136 if (!ret) 137 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); 138 return ret; 139 } 140 141 static void __exit ftrace_direct_multi_exit(void) 142 { 143 kthread_stop(simple_tsk); 144 unregister_ftrace_direct_multi(&direct, my_tramp); 145 } 146 147 module_init(ftrace_direct_multi_init); 148 module_exit(ftrace_direct_multi_exit); 149 150 MODULE_AUTHOR("Jiri Olsa"); 151 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()"); 152 MODULE_LICENSE("GPL"); 153