summaryrefslogtreecommitdiff
path: root/samples/ftrace/ftrace-direct-modify.c
blob: 06d88914901266e248956d3809c982058168a66c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/ftrace.h>
#include <asm/asm-offsets.h>

extern void my_direct_func1(void);
extern void my_direct_func2(void);

void my_direct_func1(void)
{
	trace_printk("my direct func1\n");
}

void my_direct_func2(void)
{
	trace_printk("my direct func2\n");
}

extern void my_tramp1(void *);
extern void my_tramp2(void *);

static unsigned long my_ip = (unsigned long)schedule;

#ifdef CONFIG_X86_64

#include <asm/ibt.h>
#include <asm/nospec-branch.h>

asm (
"	.pushsection    .text, \"ax\", @progbits\n"
"	.type		my_tramp1, @function\n"
"	.globl		my_tramp1\n"
"   my_tramp1:"
	ASM_ENDBR
"	pushq %rbp\n"
"	movq %rsp, %rbp\n"
	CALL_DEPTH_ACCOUNT
"	call my_direct_func1\n"
"	leave\n"
"	.size		my_tramp1, .-my_tramp1\n"
	ASM_RET

"	.type		my_tramp2, @function\n"
"	.globl		my_tramp2\n"
"   my_tramp2:"
	ASM_ENDBR
"	pushq %rbp\n"
"	movq %rsp, %rbp\n"
	CALL_DEPTH_ACCOUNT
"	call my_direct_func2\n"
"	leave\n"
	ASM_RET
"	.size		my_tramp2, .-my_tramp2\n"
"	.popsection\n"
);

#endif /* CONFIG_X86_64 */

#ifdef CONFIG_S390

asm (
"	.pushsection	.text, \"ax\", @progbits\n"
"	.type		my_tramp1, @function\n"
"	.globl		my_tramp1\n"
"   my_tramp1:"
"	lgr		%r1,%r15\n"
"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
"	brasl		%r14,my_direct_func1\n"
"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
"	lgr		%r1,%r0\n"
"	br		%r1\n"
"	.size		my_tramp1, .-my_tramp1\n"
"	.type		my_tramp2, @function\n"
"	.globl		my_tramp2\n"
"   my_tramp2:"
"	lgr		%r1,%r15\n"
"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
"	brasl		%r14,my_direct_func2\n"
"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
"	lgr		%r1,%r0\n"
"	br		%r1\n"
"	.size		my_tramp2, .-my_tramp2\n"
"	.popsection\n"
);

#endif /* CONFIG_S390 */

#ifdef CONFIG_LOONGARCH

asm (
"	.pushsection    .text, \"ax\", @progbits\n"
"	.type		my_tramp1, @function\n"
"	.globl		my_tramp1\n"
"   my_tramp1:\n"
"	addi.d	$sp, $sp, -16\n"
"	st.d	$t0, $sp, 0\n"
"	st.d	$ra, $sp, 8\n"
"	bl	my_direct_func1\n"
"	ld.d	$t0, $sp, 0\n"
"	ld.d	$ra, $sp, 8\n"
"	addi.d	$sp, $sp, 16\n"
"	jr	$t0\n"
"	.size		my_tramp1, .-my_tramp1\n"

"	.type		my_tramp2, @function\n"
"	.globl		my_tramp2\n"
"   my_tramp2:\n"
"	addi.d	$sp, $sp, -16\n"
"	st.d	$t0, $sp, 0\n"
"	st.d	$ra, $sp, 8\n"
"	bl	my_direct_func2\n"
"	ld.d	$t0, $sp, 0\n"
"	ld.d	$ra, $sp, 8\n"
"	addi.d	$sp, $sp, 16\n"
"	jr	$t0\n"
"	.size		my_tramp2, .-my_tramp2\n"
"	.popsection\n"
);

#endif /* CONFIG_LOONGARCH */

static struct ftrace_ops direct;

static unsigned long my_tramp = (unsigned long)my_tramp1;
static unsigned long tramps[2] = {
	(unsigned long)my_tramp1,
	(unsigned long)my_tramp2,
};

static int simple_thread(void *arg)
{
	static int t;
	int ret = 0;

	while (!kthread_should_stop()) {
		set_current_state(TASK_INTERRUPTIBLE);
		schedule_timeout(2 * HZ);

		if (ret)
			continue;
		t ^= 1;
		ret = modify_ftrace_direct(&direct, tramps[t]);
		if (!ret)
			my_tramp = tramps[t];
		WARN_ON_ONCE(ret);
	}

	return 0;
}

static struct task_struct *simple_tsk;

static int __init ftrace_direct_init(void)
{
	int ret;

	ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
	ret = register_ftrace_direct(&direct, my_tramp);

	if (!ret)
		simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
	return ret;
}

static void __exit ftrace_direct_exit(void)
{
	kthread_stop(simple_tsk);
	unregister_ftrace_direct(&direct, my_tramp, true);
}

module_init(ftrace_direct_init);
module_exit(ftrace_direct_exit);

MODULE_AUTHOR("Steven Rostedt");
MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
MODULE_LICENSE("GPL");