samples/ftrace/ftrace-direct-too.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 #include <linux/module.h>
0003
0004 #include <linux/mm.h> /* for handle_mm_fault() */
0005 #include <linux/ftrace.h>
0006 #include <asm/asm-offsets.h>
0007
0008 extern void my_direct_func(struct vm_area_struct *vma,
0009                unsigned long address, unsigned int flags);
0010
0011 void my_direct_func(struct vm_area_struct *vma,
0012             unsigned long address, unsigned int flags)
0013 {
0014     trace_printk("handle mm fault vma=%p address=%lx flags=%x\n",
0015              vma, address, flags);
0016 }
0017
0018 extern void my_tramp(void *);
0019
0020 #ifdef CONFIG_X86_64
0021
0022 #include <asm/ibt.h>
0023
0024 asm (
0025 "   .pushsection    .text, \"ax\", @progbits\n"
0026 "   .type       my_tramp, @function\n"
0027 "   .globl      my_tramp\n"
0028 "   my_tramp:"
0029     ASM_ENDBR
0030 "   pushq %rbp\n"
0031 "   movq %rsp, %rbp\n"
0032 "   pushq %rdi\n"
0033 "   pushq %rsi\n"
0034 "   pushq %rdx\n"
0035 "   call my_direct_func\n"
0036 "   popq %rdx\n"
0037 "   popq %rsi\n"
0038 "   popq %rdi\n"
0039 "   leave\n"
0040     ASM_RET
0041 "   .size       my_tramp, .-my_tramp\n"
0042 "   .popsection\n"
0043 );
0044
0045 #endif /* CONFIG_X86_64 */
0046
0047 #ifdef CONFIG_S390
0048
0049 asm (
0050 "   .pushsection    .text, \"ax\", @progbits\n"
0051 "   .type       my_tramp, @function\n"
0052 "   .globl      my_tramp\n"
0053 "   my_tramp:"
0054 "   lgr     %r1,%r15\n"
0055 "   stmg        %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
0056 "   stg     %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
0057 "   aghi        %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
0058 "   stg     %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
0059 "   brasl       %r14,my_direct_func\n"
0060 "   aghi        %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
0061 "   lmg     %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
0062 "   lg      %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
0063 "   lgr     %r1,%r0\n"
0064 "   br      %r1\n"
0065 "   .size       my_tramp, .-my_tramp\n"
0066 "   .popsection\n"
0067 );
0068
0069 #endif /* CONFIG_S390 */
0070
0071 static int __init ftrace_direct_init(void)
0072 {
0073     return register_ftrace_direct((unsigned long)handle_mm_fault,
0074                      (unsigned long)my_tramp);
0075 }
0076
0077 static void __exit ftrace_direct_exit(void)
0078 {
0079     unregister_ftrace_direct((unsigned long)handle_mm_fault,
0080                  (unsigned long)my_tramp);
0081 }
0082
0083 module_init(ftrace_direct_init);
0084 module_exit(ftrace_direct_exit);
0085
0086 MODULE_AUTHOR("Steven Rostedt");
0087 MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
0088 MODULE_LICENSE("GPL");