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/bpf_helpers.h>
14 #include <bpf/bpf_tracing.h>
15 
16 #define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
17 
18 struct {
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 
29 SEC("kprobe/__seccomp_filter")
bpf_prog1(struct pt_regs * ctx)30 int 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 */
PROG(SYS__NR_write)46 PROG(SYS__NR_write)(struct pt_regs *ctx)
47 {
48 	struct seccomp_data sd;
49 
50 	bpf_probe_read_kernel(&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 
PROG(SYS__NR_read)59 PROG(SYS__NR_read)(struct pt_regs *ctx)
60 {
61 	struct seccomp_data sd;
62 
63 	bpf_probe_read_kernel(&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
PROG(SYS__NR_mmap2)73 PROG(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
PROG(SYS__NR_mmap)83 PROG(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 
92 char _license[] SEC("license") = "GPL";
93 u32 _version SEC("version") = LINUX_VERSION_CODE;
94