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 | |