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 #include <asm/nospec-branch.h> 21 22 asm ( 23 " .pushsection .text, \"ax\", @progbits\n" 24 " .type my_tramp, @function\n" 25 " .globl my_tramp\n" 26 " my_tramp:" 27 ASM_ENDBR 28 " pushq %rbp\n" 29 " movq %rsp, %rbp\n" 30 CALL_DEPTH_ACCOUNT 31 " pushq %rdi\n" 32 " call my_direct_func\n" 33 " popq %rdi\n" 34 " leave\n" 35 ASM_RET 36 " .size my_tramp, .-my_tramp\n" 37 " .popsection\n" 38 ); 39 40 #endif /* CONFIG_X86_64 */ 41 42 #ifdef CONFIG_S390 43 44 asm ( 45 " .pushsection .text, \"ax\", @progbits\n" 46 " .type my_tramp, @function\n" 47 " .globl my_tramp\n" 48 " my_tramp:" 49 " lgr %r1,%r15\n" 50 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 51 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 52 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 53 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 54 " brasl %r14,my_direct_func\n" 55 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 56 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 57 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 58 " lgr %r1,%r0\n" 59 " br %r1\n" 60 " .size my_tramp, .-my_tramp\n" 61 " .popsection\n" 62 ); 63 64 #endif /* CONFIG_S390 */ 65 66 static int __init ftrace_direct_init(void) 67 { 68 return register_ftrace_direct((unsigned long)wake_up_process, 69 (unsigned long)my_tramp); 70 } 71 72 static void __exit ftrace_direct_exit(void) 73 { 74 unregister_ftrace_direct((unsigned long)wake_up_process, 75 (unsigned long)my_tramp); 76 } 77 78 module_init(ftrace_direct_init); 79 module_exit(ftrace_direct_exit); 80 81 MODULE_AUTHOR("Steven Rostedt"); 82 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()"); 83 MODULE_LICENSE("GPL"); 84