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