1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2019 Facebook
3
4 #include <linux/ptrace.h>
5 #include <linux/bpf.h>
6 #include <bpf/bpf_helpers.h>
7
8 const struct {
9 unsigned a[4];
10 /*
11 * if the struct's size is multiple of 16, compiler will put it into
12 * .rodata.cst16 section, which is not recognized by libbpf; work
13 * around this by ensuring we don't have 16-aligned struct
14 */
15 char _y;
16 } rdonly_values = { .a = {2, 3, 4, 5} };
17
18 struct {
19 unsigned did_run;
20 unsigned iters;
21 unsigned sum;
22 } res = {};
23
24 SEC("raw_tracepoint/sys_enter:skip_loop")
25 int skip_loop(struct pt_regs *ctx)
26 {
27 /* prevent compiler to optimize everything out */
28 unsigned * volatile p = (void *)&rdonly_values.a;
29 unsigned iters = 0, sum = 0;
30
31 /* we should never enter this loop */
32 while (*p & 1) {
33 iters++;
34 sum += *p;
35 p++;
36 }
37 res.did_run = 1;
38 res.iters = iters;
39 res.sum = sum;
40 return 0;
41 }
42
43 SEC("raw_tracepoint/sys_enter:part_loop")
44 int part_loop(struct pt_regs *ctx)
45 {
46 /* prevent compiler to optimize everything out */
47 unsigned * volatile p = (void *)&rdonly_values.a;
48 unsigned iters = 0, sum = 0;
49
50 /* validate verifier can derive loop termination */
51 while (*p < 5) {
52 iters++;
53 sum += *p;
54 p++;
55 }
56 res.did_run = 1;
57 res.iters = iters;
58 res.sum = sum;
59 return 0;
60 }
61
62 SEC("raw_tracepoint/sys_enter:full_loop")
63 int full_loop(struct pt_regs *ctx)
64 {
65 /* prevent compiler to optimize everything out */
66 unsigned * volatile p = (void *)&rdonly_values.a;
67 int i = sizeof(rdonly_values.a) / sizeof(rdonly_values.a[0]);
68 unsigned iters = 0, sum = 0;
69
70 /* validate verifier can allow full loop as well */
71 while (i > 0 ) {
72 iters++;
73 sum += *p;
74 p++;
75 i--;
76 }
77 res.did_run = 1;
78 res.iters = iters;
79 res.sum = sum;
80 return 0;
81 }
82
83 char _license[] SEC("license") = "GPL";
84
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