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 #include <asm/ibt.h> 26 27 asm ( 28 " .pushsection .text, \"ax\", @progbits\n" 29 " .type my_tramp1, @function\n" 30 " .globl my_tramp1\n" 31 " my_tramp1:" 32 ASM_ENDBR 33 " pushq %rbp\n" 34 " movq %rsp, %rbp\n" 35 " pushq %rdi\n" 36 " movq 8(%rbp), %rdi\n" 37 " call my_direct_func1\n" 38 " popq %rdi\n" 39 " leave\n" 40 ASM_RET 41 " .size my_tramp1, .-my_tramp1\n" 42 43 " .type my_tramp2, @function\n" 44 " .globl my_tramp2\n" 45 " my_tramp2:" 46 ASM_ENDBR 47 " pushq %rbp\n" 48 " movq %rsp, %rbp\n" 49 " pushq %rdi\n" 50 " movq 8(%rbp), %rdi\n" 51 " call my_direct_func2\n" 52 " popq %rdi\n" 53 " leave\n" 54 ASM_RET 55 " .size my_tramp2, .-my_tramp2\n" 56 " .popsection\n" 57 ); 58 59 #endif /* CONFIG_X86_64 */ 60 61 #ifdef CONFIG_S390 62 63 asm ( 64 " .pushsection .text, \"ax\", @progbits\n" 65 " .type my_tramp1, @function\n" 66 " .globl my_tramp1\n" 67 " my_tramp1:" 68 " lgr %r1,%r15\n" 69 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 70 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 71 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 72 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 73 " lgr %r2,%r0\n" 74 " brasl %r14,my_direct_func1\n" 75 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 76 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 77 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 78 " lgr %r1,%r0\n" 79 " br %r1\n" 80 " .size my_tramp1, .-my_tramp1\n" 81 "\n" 82 " .type my_tramp2, @function\n" 83 " .globl my_tramp2\n" 84 " my_tramp2:" 85 " lgr %r1,%r15\n" 86 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 87 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 88 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 89 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 90 " lgr %r2,%r0\n" 91 " brasl %r14,my_direct_func2\n" 92 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 93 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 94 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 95 " lgr %r1,%r0\n" 96 " br %r1\n" 97 " .size my_tramp2, .-my_tramp2\n" 98 " .popsection\n" 99 ); 100 101 #endif /* CONFIG_S390 */ 102 103 static unsigned long my_tramp = (unsigned long)my_tramp1; 104 static unsigned long tramps[2] = { 105 (unsigned long)my_tramp1, 106 (unsigned long)my_tramp2, 107 }; 108 109 static struct ftrace_ops direct; 110 111 static int simple_thread(void *arg) 112 { 113 static int t; 114 int ret = 0; 115 116 while (!kthread_should_stop()) { 117 set_current_state(TASK_INTERRUPTIBLE); 118 schedule_timeout(2 * HZ); 119 120 if (ret) 121 continue; 122 t ^= 1; 123 ret = modify_ftrace_direct_multi(&direct, tramps[t]); 124 if (!ret) 125 my_tramp = tramps[t]; 126 WARN_ON_ONCE(ret); 127 } 128 129 return 0; 130 } 131 132 static struct task_struct *simple_tsk; 133 134 static int __init ftrace_direct_multi_init(void) 135 { 136 int ret; 137 138 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0); 139 ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0); 140 141 ret = register_ftrace_direct_multi(&direct, my_tramp); 142 143 if (!ret) 144 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); 145 return ret; 146 } 147 148 static void __exit ftrace_direct_multi_exit(void) 149 { 150 kthread_stop(simple_tsk); 151 unregister_ftrace_direct_multi(&direct, my_tramp); 152 } 153 154 module_init(ftrace_direct_multi_init); 155 module_exit(ftrace_direct_multi_exit); 156 157 MODULE_AUTHOR("Jiri Olsa"); 158 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()"); 159 MODULE_LICENSE("GPL"); 160