1/* Copyright (c) 2015 PLUMgrid, http://plumgrid.com
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 */
7#include <linux/ptrace.h>
8#include <linux/version.h>
9#include <uapi/linux/bpf.h>
10#include <uapi/linux/seccomp.h>
11#include "bpf_helpers.h"
12
13#define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
14
15struct bpf_map_def SEC("maps") progs = {
16	.type = BPF_MAP_TYPE_PROG_ARRAY,
17	.key_size = sizeof(u32),
18	.value_size = sizeof(u32),
19	.max_entries = 1024,
20};
21
22SEC("kprobe/seccomp_phase1")
23int bpf_prog1(struct pt_regs *ctx)
24{
25	struct seccomp_data sd = {};
26
27	bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
28
29	/* dispatch into next BPF program depending on syscall number */
30	bpf_tail_call(ctx, &progs, sd.nr);
31
32	/* fall through -> unknown syscall */
33	if (sd.nr >= __NR_getuid && sd.nr <= __NR_getsid) {
34		char fmt[] = "syscall=%d (one of get/set uid/pid/gid)\n";
35		bpf_trace_printk(fmt, sizeof(fmt), sd.nr);
36	}
37	return 0;
38}
39
40/* we jump here when syscall number == __NR_write */
41PROG(__NR_write)(struct pt_regs *ctx)
42{
43	struct seccomp_data sd = {};
44
45	bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
46	if (sd.args[2] == 512) {
47		char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
48		bpf_trace_printk(fmt, sizeof(fmt),
49				 sd.args[0], sd.args[1], sd.args[2]);
50	}
51	return 0;
52}
53
54PROG(__NR_read)(struct pt_regs *ctx)
55{
56	struct seccomp_data sd = {};
57
58	bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
59	if (sd.args[2] > 128 && sd.args[2] <= 1024) {
60		char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
61		bpf_trace_printk(fmt, sizeof(fmt),
62				 sd.args[0], sd.args[1], sd.args[2]);
63	}
64	return 0;
65}
66
67PROG(__NR_mmap)(struct pt_regs *ctx)
68{
69	char fmt[] = "mmap\n";
70	bpf_trace_printk(fmt, sizeof(fmt));
71	return 0;
72}
73
74char _license[] SEC("license") = "GPL";
75u32 _version SEC("version") = LINUX_VERSION_CODE;
76