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