1// SPDX-License-Identifier: GPL-2.0-only
  2#include <linux/module.h>
  3
  4#include <linux/mm.h> /* for handle_mm_fault() */
  5#include <linux/ftrace.h>
  6#ifndef CONFIG_ARM64
  7#include <asm/asm-offsets.h>
  8#endif
  9
 10extern void my_direct_func(struct vm_area_struct *vma, unsigned long address,
 11			   unsigned int flags, struct pt_regs *regs);
 12
 13void my_direct_func(struct vm_area_struct *vma, unsigned long address,
 14		    unsigned int flags, struct pt_regs *regs)
 15{
 16	trace_printk("handle mm fault vma=%p address=%lx flags=%x regs=%p\n",
 17		     vma, address, flags, regs);
 18}
 19
 20extern void my_tramp(void *);
 21
 22#ifdef CONFIG_RISCV
 23#include <asm/asm.h>
 24
 25asm (
 26"       .pushsection    .text, \"ax\", @progbits\n"
 27"       .type           my_tramp, @function\n"
 28"       .globl          my_tramp\n"
 29"   my_tramp:\n"
 30"       addi	sp,sp,-5*"SZREG"\n"
 31"       "REG_S"	a0,0*"SZREG"(sp)\n"
 32"       "REG_S"	a1,1*"SZREG"(sp)\n"
 33"       "REG_S"	a2,2*"SZREG"(sp)\n"
 34"       "REG_S"	t0,3*"SZREG"(sp)\n"
 35"       "REG_S"	ra,4*"SZREG"(sp)\n"
 36"       call	my_direct_func\n"
 37"       "REG_L"	a0,0*"SZREG"(sp)\n"
 38"       "REG_L"	a1,1*"SZREG"(sp)\n"
 39"       "REG_L"	a2,2*"SZREG"(sp)\n"
 40"       "REG_L"	t0,3*"SZREG"(sp)\n"
 41"       "REG_L"	ra,4*"SZREG"(sp)\n"
 42"       addi	sp,sp,5*"SZREG"\n"
 43"       jr	t0\n"
 44"       .size           my_tramp, .-my_tramp\n"
 45"       .popsection\n"
 46);
 47
 48#endif /* CONFIG_RISCV */
 49
 50#ifdef CONFIG_X86_64
 51
 52#include <asm/ibt.h>
 53#include <asm/nospec-branch.h>
 54
 55asm (
 56"	.pushsection    .text, \"ax\", @progbits\n"
 57"	.type		my_tramp, @function\n"
 58"	.globl		my_tramp\n"
 59"   my_tramp:"
 60	ASM_ENDBR
 61"	pushq %rbp\n"
 62"	movq %rsp, %rbp\n"
 63	CALL_DEPTH_ACCOUNT
 64"	pushq %rdi\n"
 65"	pushq %rsi\n"
 66"	pushq %rdx\n"
 67"	pushq %rcx\n"
 68"	call my_direct_func\n"
 69"	popq %rcx\n"
 70"	popq %rdx\n"
 71"	popq %rsi\n"
 72"	popq %rdi\n"
 73"	leave\n"
 74	ASM_RET
 75"	.size		my_tramp, .-my_tramp\n"
 76"	.popsection\n"
 77);
 78
 79#endif /* CONFIG_X86_64 */
 80
 81#ifdef CONFIG_S390
 82
 83asm (
 84"	.pushsection	.text, \"ax\", @progbits\n"
 85"	.type		my_tramp, @function\n"
 86"	.globl		my_tramp\n"
 87"   my_tramp:"
 88"	lgr		%r1,%r15\n"
 89"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
 90"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
 91"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
 92"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
 93"	brasl		%r14,my_direct_func\n"
 94"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
 95"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
 96"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
 97"	lgr		%r1,%r0\n"
 98"	br		%r1\n"
 99"	.size		my_tramp, .-my_tramp\n"
100"	.popsection\n"
101);
102
103#endif /* CONFIG_S390 */
104
105#ifdef CONFIG_ARM64
106
107asm (
108"	.pushsection	.text, \"ax\", @progbits\n"
109"	.type		my_tramp, @function\n"
110"	.globl		my_tramp\n"
111"   my_tramp:"
112"	hint	34\n" // bti	c
113"	sub	sp, sp, #48\n"
114"	stp	x9, x30, [sp]\n"
115"	stp	x0, x1, [sp, #16]\n"
116"	stp	x2, x3, [sp, #32]\n"
117"	bl	my_direct_func\n"
118"	ldp	x30, x9, [sp]\n"
119"	ldp	x0, x1, [sp, #16]\n"
120"	ldp	x2, x3, [sp, #32]\n"
121"	add	sp, sp, #48\n"
122"	ret	x9\n"
123"	.size		my_tramp, .-my_tramp\n"
124"	.popsection\n"
125);
126
127#endif /* CONFIG_ARM64 */
128
129#ifdef CONFIG_LOONGARCH
130
131asm (
132"	.pushsection	.text, \"ax\", @progbits\n"
133"	.type		my_tramp, @function\n"
134"	.globl		my_tramp\n"
135"   my_tramp:\n"
136"	addi.d	$sp, $sp, -48\n"
137"	st.d	$a0, $sp, 0\n"
138"	st.d	$a1, $sp, 8\n"
139"	st.d	$a2, $sp, 16\n"
140"	st.d	$t0, $sp, 24\n"
141"	st.d	$ra, $sp, 32\n"
142"	bl	my_direct_func\n"
143"	ld.d	$a0, $sp, 0\n"
144"	ld.d	$a1, $sp, 8\n"
145"	ld.d	$a2, $sp, 16\n"
146"	ld.d	$t0, $sp, 24\n"
147"	ld.d	$ra, $sp, 32\n"
148"	addi.d	$sp, $sp, 48\n"
149"	jr	$t0\n"
150"	.size		my_tramp, .-my_tramp\n"
151"	.popsection\n"
152);
153
154#endif /* CONFIG_LOONGARCH */
155
156static struct ftrace_ops direct;
157
158static int __init ftrace_direct_init(void)
159{
160	ftrace_set_filter_ip(&direct, (unsigned long) handle_mm_fault, 0, 0);
161
162	return register_ftrace_direct(&direct, (unsigned long) my_tramp);
163}
164
165static void __exit ftrace_direct_exit(void)
166{
167	unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
168}
169
170module_init(ftrace_direct_init);
171module_exit(ftrace_direct_exit);
172
173MODULE_AUTHOR("Steven Rostedt");
174MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
175MODULE_LICENSE("GPL");