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 extern void my_direct_func1(unsigned long ip); 8 extern void my_direct_func2(unsigned long ip); 9 10 void my_direct_func1(unsigned long ip) 11 { 12 trace_printk("my direct func1 ip %lx\n", ip); 13 } 14 15 void my_direct_func2(unsigned long ip) 16 { 17 trace_printk("my direct func2 ip %lx\n", ip); 18 } 19 20 extern void my_tramp1(void *); 21 extern void my_tramp2(void *); 22 23 #ifdef CONFIG_X86_64 24 25 asm ( 26 " .pushsection .text, \"ax\", @progbits\n" 27 " .type my_tramp1, @function\n" 28 " .globl my_tramp1\n" 29 " my_tramp1:" 30 " pushq %rbp\n" 31 " movq %rsp, %rbp\n" 32 " pushq %rdi\n" 33 " movq 8(%rbp), %rdi\n" 34 " call my_direct_func1\n" 35 " popq %rdi\n" 36 " leave\n" 37 " ret\n" 38 " .size my_tramp1, .-my_tramp1\n" 39 " .type my_tramp2, @function\n" 40 "\n" 41 " .globl my_tramp2\n" 42 " my_tramp2:" 43 " pushq %rbp\n" 44 " movq %rsp, %rbp\n" 45 " pushq %rdi\n" 46 " movq 8(%rbp), %rdi\n" 47 " call my_direct_func2\n" 48 " popq %rdi\n" 49 " leave\n" 50 " ret\n" 51 " .size my_tramp2, .-my_tramp2\n" 52 " .popsection\n" 53 ); 54 55 #endif /* CONFIG_X86_64 */ 56 57 #ifdef CONFIG_S390 58 59 asm ( 60 " .pushsection .text, \"ax\", @progbits\n" 61 " .type my_tramp1, @function\n" 62 " .globl my_tramp1\n" 63 " my_tramp1:" 64 " lgr %r1,%r15\n" 65 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 66 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 67 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 68 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 69 " lgr %r2,%r0\n" 70 " brasl %r14,my_direct_func1\n" 71 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 72 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 73 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 74 " lgr %r1,%r0\n" 75 " br %r1\n" 76 " .size my_tramp1, .-my_tramp1\n" 77 "\n" 78 " .type my_tramp2, @function\n" 79 " .globl my_tramp2\n" 80 " my_tramp2:" 81 " lgr %r1,%r15\n" 82 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 83 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 84 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 85 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 86 " lgr %r2,%r0\n" 87 " brasl %r14,my_direct_func2\n" 88 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 89 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 90 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 91 " lgr %r1,%r0\n" 92 " br %r1\n" 93 " .size my_tramp2, .-my_tramp2\n" 94 " .popsection\n" 95 ); 96 97 #endif /* CONFIG_S390 */ 98 99 static unsigned long my_tramp = (unsigned long)my_tramp1; 100 static unsigned long tramps[2] = { 101 (unsigned long)my_tramp1, 102 (unsigned long)my_tramp2, 103 }; 104 105 static struct ftrace_ops direct; 106 107 static int simple_thread(void *arg) 108 { 109 static int t; 110 int ret = 0; 111 112 while (!kthread_should_stop()) { 113 set_current_state(TASK_INTERRUPTIBLE); 114 schedule_timeout(2 * HZ); 115 116 if (ret) 117 continue; 118 t ^= 1; 119 ret = modify_ftrace_direct_multi(&direct, tramps[t]); 120 if (!ret) 121 my_tramp = tramps[t]; 122 WARN_ON_ONCE(ret); 123 } 124 125 return 0; 126 } 127 128 static struct task_struct *simple_tsk; 129 130 static int __init ftrace_direct_multi_init(void) 131 { 132 int ret; 133 134 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0); 135 ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0); 136 137 ret = register_ftrace_direct_multi(&direct, my_tramp); 138 139 if (!ret) 140 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); 141 return ret; 142 } 143 144 static void __exit ftrace_direct_multi_exit(void) 145 { 146 kthread_stop(simple_tsk); 147 unregister_ftrace_direct_multi(&direct, my_tramp); 148 } 149 150 module_init(ftrace_direct_multi_init); 151 module_exit(ftrace_direct_multi_exit); 152 153 MODULE_AUTHOR("Jiri Olsa"); 154 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()"); 155 MODULE_LICENSE("GPL"); 156