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