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 asm ( 20 " .pushsection .text, \"ax\", @progbits\n" 21 " .type my_tramp, @function\n" 22 " .globl my_tramp\n" 23 " my_tramp:" 24 " pushq %rbp\n" 25 " movq %rsp, %rbp\n" 26 " pushq %rdi\n" 27 " call my_direct_func\n" 28 " popq %rdi\n" 29 " leave\n" 30 ASM_RET 31 " .size my_tramp, .-my_tramp\n" 32 " .popsection\n" 33 ); 34 35 #endif /* CONFIG_X86_64 */ 36 37 #ifdef CONFIG_S390 38 39 asm ( 40 " .pushsection .text, \"ax\", @progbits\n" 41 " .type my_tramp, @function\n" 42 " .globl my_tramp\n" 43 " my_tramp:" 44 " lgr %r1,%r15\n" 45 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 46 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 47 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 48 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 49 " brasl %r14,my_direct_func\n" 50 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 51 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 52 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 53 " lgr %r1,%r0\n" 54 " br %r1\n" 55 " .size my_tramp, .-my_tramp\n" 56 " .popsection\n" 57 ); 58 59 #endif /* CONFIG_S390 */ 60 61 static int __init ftrace_direct_init(void) 62 { 63 return register_ftrace_direct((unsigned long)wake_up_process, 64 (unsigned long)my_tramp); 65 } 66 67 static void __exit ftrace_direct_exit(void) 68 { 69 unregister_ftrace_direct((unsigned long)wake_up_process, 70 (unsigned long)my_tramp); 71 } 72 73 module_init(ftrace_direct_init); 74 module_exit(ftrace_direct_exit); 75 76 MODULE_AUTHOR("Steven Rostedt"); 77 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()"); 78 MODULE_LICENSE("GPL"); 79