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 #include <asm/nospec-branch.h> 7 8 extern void my_direct_func1(unsigned long ip); 9 extern void my_direct_func2(unsigned long ip); 10 11 void my_direct_func1(unsigned long ip) 12 { 13 trace_printk("my direct func1 ip %lx\n", ip); 14 } 15 16 void my_direct_func2(unsigned long ip) 17 { 18 trace_printk("my direct func2 ip %lx\n", ip); 19 } 20 21 extern void my_tramp1(void *); 22 extern void my_tramp2(void *); 23 24 #ifdef CONFIG_X86_64 25 26 #include <asm/ibt.h> 27 28 asm ( 29 " .pushsection .text, \"ax\", @progbits\n" 30 " .type my_tramp1, @function\n" 31 " .globl my_tramp1\n" 32 " my_tramp1:" 33 ASM_ENDBR 34 " pushq %rbp\n" 35 " movq %rsp, %rbp\n" 36 CALL_DEPTH_ACCOUNT 37 " pushq %rdi\n" 38 " movq 8(%rbp), %rdi\n" 39 " call my_direct_func1\n" 40 " popq %rdi\n" 41 " leave\n" 42 ASM_RET 43 " .size my_tramp1, .-my_tramp1\n" 44 45 " .type my_tramp2, @function\n" 46 " .globl my_tramp2\n" 47 " my_tramp2:" 48 ASM_ENDBR 49 " pushq %rbp\n" 50 " movq %rsp, %rbp\n" 51 CALL_DEPTH_ACCOUNT 52 " pushq %rdi\n" 53 " movq 8(%rbp), %rdi\n" 54 " call my_direct_func2\n" 55 " popq %rdi\n" 56 " leave\n" 57 ASM_RET 58 " .size my_tramp2, .-my_tramp2\n" 59 " .popsection\n" 60 ); 61 62 #endif /* CONFIG_X86_64 */ 63 64 #ifdef CONFIG_S390 65 66 asm ( 67 " .pushsection .text, \"ax\", @progbits\n" 68 " .type my_tramp1, @function\n" 69 " .globl my_tramp1\n" 70 " my_tramp1:" 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 " lgr %r2,%r0\n" 77 " brasl %r14,my_direct_func1\n" 78 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 79 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 80 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 81 " lgr %r1,%r0\n" 82 " br %r1\n" 83 " .size my_tramp1, .-my_tramp1\n" 84 "\n" 85 " .type my_tramp2, @function\n" 86 " .globl my_tramp2\n" 87 " my_tramp2:" 88 " lgr %r1,%r15\n" 89 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 90 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 91 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 92 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 93 " lgr %r2,%r0\n" 94 " brasl %r14,my_direct_func2\n" 95 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 96 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 97 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 98 " lgr %r1,%r0\n" 99 " br %r1\n" 100 " .size my_tramp2, .-my_tramp2\n" 101 " .popsection\n" 102 ); 103 104 #endif /* CONFIG_S390 */ 105 106 static unsigned long my_tramp = (unsigned long)my_tramp1; 107 static unsigned long tramps[2] = { 108 (unsigned long)my_tramp1, 109 (unsigned long)my_tramp2, 110 }; 111 112 static struct ftrace_ops direct; 113 114 static int simple_thread(void *arg) 115 { 116 static int t; 117 int ret = 0; 118 119 while (!kthread_should_stop()) { 120 set_current_state(TASK_INTERRUPTIBLE); 121 schedule_timeout(2 * HZ); 122 123 if (ret) 124 continue; 125 t ^= 1; 126 ret = modify_ftrace_direct_multi(&direct, tramps[t]); 127 if (!ret) 128 my_tramp = tramps[t]; 129 WARN_ON_ONCE(ret); 130 } 131 132 return 0; 133 } 134 135 static struct task_struct *simple_tsk; 136 137 static int __init ftrace_direct_multi_init(void) 138 { 139 int ret; 140 141 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0); 142 ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0); 143 144 ret = register_ftrace_direct_multi(&direct, my_tramp); 145 146 if (!ret) 147 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); 148 return ret; 149 } 150 151 static void __exit ftrace_direct_multi_exit(void) 152 { 153 kthread_stop(simple_tsk); 154 unregister_ftrace_direct_multi(&direct, my_tramp); 155 } 156 157 module_init(ftrace_direct_multi_init); 158 module_exit(ftrace_direct_multi_exit); 159 160 MODULE_AUTHOR("Jiri Olsa"); 161 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()"); 162 MODULE_LICENSE("GPL"); 163