1 // SPDX-License-Identifier: GPL-2.0-only 2 #include <linux/module.h> 3 4 #include <linux/sched.h> /* for wake_up_process() */ 5 #include <linux/ftrace.h> 6 #include <asm/asm-offsets.h> 7 8 extern void my_direct_func(struct task_struct *p); 9 10 void my_direct_func(struct task_struct *p) 11 { 12 trace_printk("waking up %s-%d\n", p->comm, p->pid); 13 } 14 15 extern void my_tramp(void *); 16 17 #ifdef CONFIG_X86_64 18 19 #include <asm/ibt.h> 20 21 asm ( 22 " .pushsection .text, \"ax\", @progbits\n" 23 " .type my_tramp, @function\n" 24 " .globl my_tramp\n" 25 " my_tramp:" 26 ASM_ENDBR 27 " pushq %rbp\n" 28 " movq %rsp, %rbp\n" 29 " pushq %rdi\n" 30 " call my_direct_func\n" 31 " popq %rdi\n" 32 " leave\n" 33 ASM_RET 34 " .size my_tramp, .-my_tramp\n" 35 " .popsection\n" 36 ); 37 38 #endif /* CONFIG_X86_64 */ 39 40 #ifdef CONFIG_S390 41 42 asm ( 43 " .pushsection .text, \"ax\", @progbits\n" 44 " .type my_tramp, @function\n" 45 " .globl my_tramp\n" 46 " my_tramp:" 47 " lgr %r1,%r15\n" 48 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 49 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 50 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 51 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 52 " brasl %r14,my_direct_func\n" 53 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 54 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 55 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 56 " lgr %r1,%r0\n" 57 " br %r1\n" 58 " .size my_tramp, .-my_tramp\n" 59 " .popsection\n" 60 ); 61 62 #endif /* CONFIG_S390 */ 63 64 static int __init ftrace_direct_init(void) 65 { 66 return register_ftrace_direct((unsigned long)wake_up_process, 67 (unsigned long)my_tramp); 68 } 69 70 static void __exit ftrace_direct_exit(void) 71 { 72 unregister_ftrace_direct((unsigned long)wake_up_process, 73 (unsigned long)my_tramp); 74 } 75 76 module_init(ftrace_direct_init); 77 module_exit(ftrace_direct_exit); 78 79 MODULE_AUTHOR("Steven Rostedt"); 80 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()"); 81 MODULE_LICENSE("GPL"); 82