1/*
2 * Copyright (c) 2015 Dmitry V. Levin <ldv@altlinux.org>
3 * Copyright (c) 2015-2017 The strace developers.
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. The name of the author may not be used to endorse or promote products
15 *    derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include "defs.h"
30
31#ifdef HAVE_LINUX_SECCOMP_H
32# include <linux/seccomp.h>
33#endif
34#include "xlat/seccomp_ops.h"
35#include "xlat/seccomp_filter_flags.h"
36
37#ifdef HAVE_LINUX_FILTER_H
38# include <linux/filter.h>
39# include "xlat/bpf_class.h"
40# include "xlat/bpf_miscop.h"
41# include "xlat/bpf_mode.h"
42# include "xlat/bpf_op_alu.h"
43# include "xlat/bpf_op_jmp.h"
44# include "xlat/bpf_rval.h"
45# include "xlat/bpf_size.h"
46# include "xlat/bpf_src.h"
47
48# ifndef SECCOMP_RET_ACTION
49#  define SECCOMP_RET_ACTION 0x7fff0000U
50# endif
51# include "xlat/seccomp_ret_action.h"
52#endif
53
54struct bpf_filter {
55	uint16_t code;
56	uint8_t jt;
57	uint8_t jf;
58	uint32_t k;
59};
60
61#ifdef HAVE_LINUX_FILTER_H
62
63static void
64decode_bpf_code(uint16_t code)
65{
66	uint16_t i = code & ~BPF_CLASS(code);
67
68	printxval(bpf_class, BPF_CLASS(code), "BPF_???");
69	switch (BPF_CLASS(code)) {
70		case BPF_LD:
71		case BPF_LDX:
72			tprints("|");
73			printxval(bpf_size, BPF_SIZE(code), "BPF_???");
74			tprints("|");
75			printxval(bpf_mode, BPF_MODE(code), "BPF_???");
76			break;
77		case BPF_ST:
78		case BPF_STX:
79			if (i) {
80				tprintf("|%#x", i);
81				tprints_comment("BPF_???");
82			}
83			break;
84		case BPF_ALU:
85			tprints("|");
86			printxval(bpf_src, BPF_SRC(code), "BPF_???");
87			tprints("|");
88			printxval(bpf_op_alu, BPF_OP(code), "BPF_???");
89			break;
90		case BPF_JMP:
91			tprints("|");
92			printxval(bpf_src, BPF_SRC(code), "BPF_???");
93			tprints("|");
94			printxval(bpf_op_jmp, BPF_OP(code), "BPF_???");
95			break;
96		case BPF_RET:
97			tprints("|");
98			printxval(bpf_rval, BPF_RVAL(code), "BPF_???");
99			i &= ~BPF_RVAL(code);
100			if (i) {
101				tprintf("|%#x", i);
102				tprints_comment("BPF_???");
103			}
104			break;
105		case BPF_MISC:
106			tprints("|");
107			printxval(bpf_miscop, BPF_MISCOP(code), "BPF_???");
108			i &= ~BPF_MISCOP(code);
109			if (i) {
110				tprintf("|%#x", i);
111				tprints_comment("BPF_???");
112			}
113			break;
114	}
115
116}
117
118#endif /* HAVE_LINUX_FILTER_H */
119
120static void
121decode_bpf_stmt(const struct bpf_filter *filter)
122{
123#ifdef HAVE_LINUX_FILTER_H
124	tprints("BPF_STMT(");
125	decode_bpf_code(filter->code);
126	tprints(", ");
127	if (BPF_CLASS(filter->code) == BPF_RET) {
128		unsigned int action = SECCOMP_RET_ACTION & filter->k;
129		unsigned int data = filter->k & ~action;
130
131		printxval(seccomp_ret_action, action, "SECCOMP_RET_???");
132		if (data)
133			tprintf("|%#x)", data);
134		else
135			tprints(")");
136	} else {
137		tprintf("%#x)", filter->k);
138	}
139#else
140	tprintf("BPF_STMT(%#x, %#x)", filter->code, filter->k);
141#endif /* HAVE_LINUX_FILTER_H */
142}
143
144static void
145decode_bpf_jump(const struct bpf_filter *filter)
146{
147#ifdef HAVE_LINUX_FILTER_H
148	tprints("BPF_JUMP(");
149	decode_bpf_code(filter->code);
150	tprintf(", %#x, %#x, %#x)",
151		filter->k, filter->jt, filter->jf);
152#else
153	tprintf("BPF_JUMP(%#x, %#x, %#x, %#x)",
154		filter->code, filter->k, filter->jt, filter->jf);
155#endif /* HAVE_LINUX_FILTER_H */
156}
157
158#ifndef BPF_MAXINSNS
159# define BPF_MAXINSNS 4096
160#endif
161
162static bool
163print_bpf_filter(struct tcb *tcp, void *elem_buf, size_t elem_size, void *data)
164{
165	const struct bpf_filter *filter = elem_buf;
166	unsigned int *pn = data;
167
168	if ((*pn)++ >= BPF_MAXINSNS) {
169		tprints("...");
170		return false;
171	}
172
173	if (filter->jt || filter->jf)
174		decode_bpf_jump(filter);
175	else
176		decode_bpf_stmt(filter);
177
178	return true;
179}
180
181void
182print_seccomp_fprog(struct tcb *const tcp, const kernel_ulong_t addr,
183		    const unsigned short len)
184{
185	if (abbrev(tcp)) {
186		printaddr(addr);
187	} else {
188		unsigned int insns = 0;
189		struct bpf_filter filter;
190
191		print_array(tcp, addr, len, &filter, sizeof(filter),
192			    umoven_or_printaddr, print_bpf_filter, &insns);
193	}
194}
195
196#include "seccomp_fprog.h"
197
198void
199print_seccomp_filter(struct tcb *const tcp, const kernel_ulong_t addr)
200{
201	struct seccomp_fprog fprog;
202
203	if (fetch_seccomp_fprog(tcp, addr, &fprog)) {
204		tprintf("{len=%hu, filter=", fprog.len);
205		print_seccomp_fprog(tcp, fprog.filter, fprog.len);
206		tprints("}");
207	}
208}
209
210static void
211decode_seccomp_set_mode_strict(const unsigned int flags,
212			       const kernel_ulong_t addr)
213{
214	tprintf("%u, ", flags);
215	printaddr(addr);
216}
217
218SYS_FUNC(seccomp)
219{
220	unsigned int op = tcp->u_arg[0];
221
222	printxval(seccomp_ops, op, "SECCOMP_SET_MODE_???");
223	tprints(", ");
224
225	if (op == SECCOMP_SET_MODE_FILTER) {
226		printflags(seccomp_filter_flags, tcp->u_arg[1],
227			   "SECCOMP_FILTER_FLAG_???");
228		tprints(", ");
229		print_seccomp_filter(tcp, tcp->u_arg[2]);
230	} else {
231		decode_seccomp_set_mode_strict(tcp->u_arg[1],
232					       tcp->u_arg[2]);
233	}
234
235	return RVAL_DECODED;
236}
237