1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2021 Facebook */
3 
4 #include "vmlinux.h"
5 #include <bpf/bpf_helpers.h>
6 #include "bpf_misc.h"
7 
8 char _license[] SEC("license") = "GPL";
9 
10 struct callback_ctx {
11 	int output;
12 };
13 
14 struct {
15 	__uint(type, BPF_MAP_TYPE_HASH);
16 	__uint(max_entries, 32);
17 	__type(key, int);
18 	__type(value, int);
19 } map1 SEC(".maps");
20 
21 /* These should be set by the user program */
22 u32 nested_callback_nr_loops;
23 u32 stop_index = -1;
24 u32 nr_loops;
25 int pid;
26 int callback_selector;
27 
28 /* Making these global variables so that the userspace program
29  * can verify the output through the skeleton
30  */
31 int nr_loops_returned;
32 int g_output;
33 int err;
34 
35 static int callback(__u32 index, void *data)
36 {
37 	struct callback_ctx *ctx = data;
38 
39 	if (index >= stop_index)
40 		return 1;
41 
42 	ctx->output += index;
43 
44 	return 0;
45 }
46 
47 static int empty_callback(__u32 index, void *data)
48 {
49 	return 0;
50 }
51 
52 static int nested_callback2(__u32 index, void *data)
53 {
54 	nr_loops_returned += bpf_loop(nested_callback_nr_loops, callback, data, 0);
55 
56 	return 0;
57 }
58 
59 static int nested_callback1(__u32 index, void *data)
60 {
61 	bpf_loop(nested_callback_nr_loops, nested_callback2, data, 0);
62 	return 0;
63 }
64 
65 SEC("fentry/" SYS_PREFIX "sys_nanosleep")
66 int test_prog(void *ctx)
67 {
68 	struct callback_ctx data = {};
69 
70 	if (bpf_get_current_pid_tgid() >> 32 != pid)
71 		return 0;
72 
73 	nr_loops_returned = bpf_loop(nr_loops, callback, &data, 0);
74 
75 	if (nr_loops_returned < 0)
76 		err = nr_loops_returned;
77 	else
78 		g_output = data.output;
79 
80 	return 0;
81 }
82 
83 SEC("fentry/" SYS_PREFIX "sys_nanosleep")
84 int prog_null_ctx(void *ctx)
85 {
86 	if (bpf_get_current_pid_tgid() >> 32 != pid)
87 		return 0;
88 
89 	nr_loops_returned = bpf_loop(nr_loops, empty_callback, NULL, 0);
90 
91 	return 0;
92 }
93 
94 SEC("fentry/" SYS_PREFIX "sys_nanosleep")
95 int prog_invalid_flags(void *ctx)
96 {
97 	struct callback_ctx data = {};
98 
99 	if (bpf_get_current_pid_tgid() >> 32 != pid)
100 		return 0;
101 
102 	err = bpf_loop(nr_loops, callback, &data, 1);
103 
104 	return 0;
105 }
106 
107 SEC("fentry/" SYS_PREFIX "sys_nanosleep")
108 int prog_nested_calls(void *ctx)
109 {
110 	struct callback_ctx data = {};
111 
112 	if (bpf_get_current_pid_tgid() >> 32 != pid)
113 		return 0;
114 
115 	nr_loops_returned = 0;
116 	bpf_loop(nr_loops, nested_callback1, &data, 0);
117 
118 	g_output = data.output;
119 
120 	return 0;
121 }
122 
123 static int callback_set_f0(int i, void *ctx)
124 {
125 	g_output = 0xF0;
126 	return 0;
127 }
128 
129 static int callback_set_0f(int i, void *ctx)
130 {
131 	g_output = 0x0F;
132 	return 0;
133 }
134 
135 /*
136  * non-constant callback is a corner case for bpf_loop inline logic
137  */
138 SEC("fentry/" SYS_PREFIX "sys_nanosleep")
139 int prog_non_constant_callback(void *ctx)
140 {
141 	if (bpf_get_current_pid_tgid() >> 32 != pid)
142 		return 0;
143 
144 	int (*callback)(int i, void *ctx);
145 
146 	g_output = 0;
147 
148 	if (callback_selector == 0x0F)
149 		callback = callback_set_0f;
150 	else
151 		callback = callback_set_f0;
152 
153 	bpf_loop(1, callback, NULL, 0);
154 
155 	return 0;
156 }
157 
158 static int stack_check_inner_callback(void *ctx)
159 {
160 	return 0;
161 }
162 
163 static int map1_lookup_elem(int key)
164 {
165 	int *val = bpf_map_lookup_elem(&map1, &key);
166 
167 	return val ? *val : -1;
168 }
169 
170 static void map1_update_elem(int key, int val)
171 {
172 	bpf_map_update_elem(&map1, &key, &val, BPF_ANY);
173 }
174 
175 static int stack_check_outer_callback(void *ctx)
176 {
177 	int a = map1_lookup_elem(1);
178 	int b = map1_lookup_elem(2);
179 	int c = map1_lookup_elem(3);
180 	int d = map1_lookup_elem(4);
181 	int e = map1_lookup_elem(5);
182 	int f = map1_lookup_elem(6);
183 
184 	bpf_loop(1, stack_check_inner_callback, NULL, 0);
185 
186 	map1_update_elem(1, a + 1);
187 	map1_update_elem(2, b + 1);
188 	map1_update_elem(3, c + 1);
189 	map1_update_elem(4, d + 1);
190 	map1_update_elem(5, e + 1);
191 	map1_update_elem(6, f + 1);
192 
193 	return 0;
194 }
195 
196 /* Some of the local variables in stack_check and
197  * stack_check_outer_callback would be allocated on stack by
198  * compiler. This test should verify that stack content for these
199  * variables is preserved between calls to bpf_loop (might be an issue
200  * if loop inlining allocates stack slots incorrectly).
201  */
202 SEC("fentry/" SYS_PREFIX "sys_nanosleep")
203 int stack_check(void *ctx)
204 {
205 	if (bpf_get_current_pid_tgid() >> 32 != pid)
206 		return 0;
207 
208 	int a = map1_lookup_elem(7);
209 	int b = map1_lookup_elem(8);
210 	int c = map1_lookup_elem(9);
211 	int d = map1_lookup_elem(10);
212 	int e = map1_lookup_elem(11);
213 	int f = map1_lookup_elem(12);
214 
215 	bpf_loop(1, stack_check_outer_callback, NULL, 0);
216 
217 	map1_update_elem(7,  a + 1);
218 	map1_update_elem(8, b + 1);
219 	map1_update_elem(9, c + 1);
220 	map1_update_elem(10, d + 1);
221 	map1_update_elem(11, e + 1);
222 	map1_update_elem(12, f + 1);
223 
224 	return 0;
225 }
226