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 "vmlinux.h"
8#include "syscall_nrs.h"
9#include <linux/version.h>
10#include <uapi/linux/unistd.h>
11#include <bpf/bpf_helpers.h>
12#include <bpf/bpf_tracing.h>
13#include <bpf/bpf_core_read.h>
14
15#define __stringify(x) #x
16#define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
17
18struct {
19	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
20	__uint(key_size, sizeof(u32));
21	__uint(value_size, sizeof(u32));
22#ifdef __mips__
23	__uint(max_entries, 6000); /* MIPS n64 syscalls start at 5000 */
24#else
25	__uint(max_entries, 1024);
26#endif
27} progs SEC(".maps");
28
29SEC("kprobe/__seccomp_filter")
30int bpf_prog1(struct pt_regs *ctx)
31{
32	int sc_nr = (int)PT_REGS_PARM1(ctx);
33
34	/* dispatch into next BPF program depending on syscall number */
35	bpf_tail_call(ctx, &progs, sc_nr);
36
37	/* fall through -> unknown syscall */
38	if (sc_nr >= __NR_getuid && sc_nr <= __NR_getsid) {
39		char fmt[] = "syscall=%d (one of get/set uid/pid/gid)\n";
40		bpf_trace_printk(fmt, sizeof(fmt), sc_nr);
41	}
42	return 0;
43}
44
45/* we jump here when syscall number == __NR_write */
46PROG(SYS__NR_write)(struct pt_regs *ctx)
47{
48	struct seccomp_data sd;
49
50	bpf_core_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
51	if (sd.args[2] == 512) {
52		char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
53		bpf_trace_printk(fmt, sizeof(fmt),
54				 sd.args[0], sd.args[1], sd.args[2]);
55	}
56	return 0;
57}
58
59PROG(SYS__NR_read)(struct pt_regs *ctx)
60{
61	struct seccomp_data sd;
62
63	bpf_core_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
64	if (sd.args[2] > 128 && sd.args[2] <= 1024) {
65		char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
66		bpf_trace_printk(fmt, sizeof(fmt),
67				 sd.args[0], sd.args[1], sd.args[2]);
68	}
69	return 0;
70}
71
72#ifdef __NR_mmap2
73PROG(SYS__NR_mmap2)(struct pt_regs *ctx)
74{
75	char fmt[] = "mmap2\n";
76
77	bpf_trace_printk(fmt, sizeof(fmt));
78	return 0;
79}
80#endif
81
82#ifdef __NR_mmap
83PROG(SYS__NR_mmap)(struct pt_regs *ctx)
84{
85	char fmt[] = "mmap\n";
86
87	bpf_trace_printk(fmt, sizeof(fmt));
88	return 0;
89}
90#endif
91
92char _license[] SEC("license") = "GPL";
93u32 _version SEC("version") = LINUX_VERSION_CODE;
94