1 /* packet-gdb.c
2 * Routines for dissection of GDB's Remote Serial Protocol
3 *
4 * Copyright 2014, Martin Kaiser <martin@kaiser.cx>
5 *
6 * Wireshark - Network traffic analyzer
7 * By Gerald Combs <gerald@wireshark.org>
8 * Copyright 1998 Gerald Combs
9 *
10 * SPDX-License-Identifier: GPL-2.0-or-later
11 */
12
13 /*
14 * The GDB Remote Serial Protocol is used between an instance of the
15 * GNU Debugger and a remote target such as an embedded system.
16 * It can be run over TCP/IP or a serial line, we support only TCP/IP.
17 *
18 * The protocol specification is in Annex E of the GDB user manual
19 * http://www.gnu.org/software/gdb/documentation/
20 *
21 */
22
23 #include "config.h"
24
25 #include <epan/packet.h>
26 #include <epan/tvbparse.h>
27
28 enum {
29 GDB_TOK_ACK,
30 GDB_TOK_START,
31 GDB_TOK_PAYLOAD,
32 GDB_TOK_END,
33 GDB_TOK_CHKSUM
34 };
35
36 static const value_string gdb_ack[] = {
37 { '+', "Transmission successful" },
38 { '-', "Transmission failed" },
39 { 0, NULL }
40 };
41
42
43 void proto_register_gdb(void);
44 void proto_reg_handoff_gdb(void);
45
46 static int proto_gdb = -1;
47
48 static gint ett_gdb = -1;
49
50 static int hf_gdb_ack = -1;
51 static int hf_gdb_start = -1;
52 static int hf_gdb_payload = -1;
53 static int hf_gdb_end = -1;
54 static int hf_gdb_chksum = -1;
55
56 static tvbparse_wanted_t *want;
57
58 static void
dissect_gdb_token(void * tvbparse_data,const void * wanted_data,tvbparse_elem_t * tok)59 dissect_gdb_token(void *tvbparse_data, const void *wanted_data, tvbparse_elem_t *tok)
60 {
61 proto_tree *tree;
62 guint token;
63
64 if (!tok) /* XXX - is this check necessary? */
65 return;
66
67 tree = (proto_tree *)tvbparse_data;
68 token = GPOINTER_TO_UINT(wanted_data);
69
70 /* XXX - check that tok->len is what we expect? */
71 switch (token) {
72 case GDB_TOK_ACK:
73 proto_tree_add_item(tree, hf_gdb_ack,
74 tok->tvb, tok->offset, tok->len, ENC_ASCII|ENC_NA);
75 break;
76 case GDB_TOK_START:
77 proto_tree_add_item(tree, hf_gdb_start,
78 tok->tvb, tok->offset, tok->len, ENC_ASCII|ENC_NA);
79 break;
80 case GDB_TOK_PAYLOAD:
81 proto_tree_add_item(tree, hf_gdb_payload,
82 tok->tvb, tok->offset, tok->len, ENC_NA);
83 break;
84 case GDB_TOK_END:
85 proto_tree_add_item(tree, hf_gdb_end,
86 tok->tvb, tok->offset, tok->len, ENC_ASCII|ENC_NA);
87 break;
88 case GDB_TOK_CHKSUM:
89 proto_tree_add_item(tree, hf_gdb_chksum,
90 tok->tvb, tok->offset, tok->len, ENC_ASCII|ENC_NA);
91 break;
92 default:
93 break;
94 }
95 }
96
init_gdb_parser(void)97 static void init_gdb_parser(void) {
98 tvbparse_wanted_t *want_ack;
99 tvbparse_wanted_t *want_start;
100 tvbparse_wanted_t *want_payload;
101 tvbparse_wanted_t *want_end;
102 tvbparse_wanted_t *want_chksum;
103
104 want_ack = tvbparse_chars(-1, 1, 1, "+-",
105 GUINT_TO_POINTER(GDB_TOK_ACK), NULL, dissect_gdb_token);
106 want_start = tvbparse_chars(-1, 1, 1, "$",
107 GUINT_TO_POINTER(GDB_TOK_START), NULL, dissect_gdb_token);
108 want_payload = tvbparse_not_chars(-1, 1, 0, "$#",
109 GUINT_TO_POINTER(GDB_TOK_PAYLOAD), NULL, dissect_gdb_token);
110 want_end = tvbparse_chars(-1, 1, 1, "#",
111 GUINT_TO_POINTER(GDB_TOK_END), NULL, dissect_gdb_token);
112 want_chksum = tvbparse_chars(-1, 2, 2, "0123456789abcdefABCDEF",
113 GUINT_TO_POINTER(GDB_TOK_CHKSUM), NULL, dissect_gdb_token);
114
115 want = tvbparse_set_seq(-1, NULL, NULL, NULL,
116 tvbparse_some(-1, 0, 1, NULL, NULL, NULL, want_ack),
117 want_start, want_payload, want_end, want_chksum, NULL);
118 }
119
120
121 static void
dissect_gdb_packet(tvbuff_t * tvb,packet_info * pinfo,proto_tree * tree)122 dissect_gdb_packet(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
123 {
124 proto_item *ti;
125 proto_tree *gdb_tree;
126 tvbparse_t *tt;
127
128 col_set_str(pinfo->cinfo, COL_PROTOCOL, "GDB");
129 col_clear(pinfo->cinfo, COL_INFO);
130
131 ti = proto_tree_add_protocol_format(tree, proto_gdb,
132 tvb, 0, tvb_reported_length(tvb), "GDB Remote Serial Protocol");
133 gdb_tree = proto_item_add_subtree(ti, ett_gdb);
134
135 /* XXX support multiple sub-trees */
136 tt = tvbparse_init(pinfo->pool, tvb, 0, -1, (void *)gdb_tree, NULL);
137
138 while(tvbparse_get(tt, want)) {
139 ;
140 }
141 }
142
143
144 static int
dissect_gdb_tcp(tvbuff_t * tvb,packet_info * pinfo,proto_tree * tree,void * data _U_)145 dissect_gdb_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
146 {
147 gint offset=0, offset_start;
148 gint pos;
149 guint packet_len;
150 tvbuff_t *packet_tvb;
151
152 while (tvb_captured_length_remaining(tvb, offset) > 0) {
153 packet_tvb = NULL;
154 offset_start = offset;
155 pos = tvb_find_guint8(tvb, offset, -1, '#');
156 if (pos != -1) {
157 offset += pos;
158 offset++; /* skip the hash sign */
159 /* to have a complete packet, we need another two bytes
160 for the checksum */
161 if (tvb_bytes_exist(tvb, offset, 2)) {
162 offset += 2;
163 packet_len = offset-offset_start;
164 packet_tvb = tvb_new_subset_length(tvb, offset_start,
165 packet_len);
166 }
167 }
168
169 if (packet_tvb)
170 dissect_gdb_packet(tvb, pinfo, tree);
171 else {
172 pinfo->desegment_offset = offset;
173 pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
174 return tvb_captured_length(tvb);
175 }
176 }
177 return tvb_captured_length(tvb);
178 }
179
180
181 void
proto_register_gdb(void)182 proto_register_gdb(void)
183 {
184 static hf_register_info hf[] = {
185 { &hf_gdb_ack,
186 { "Acknowledge", "gdb.ack", FT_CHAR, BASE_HEX,
187 VALS(gdb_ack), 0, NULL, HFILL } },
188 { &hf_gdb_start,
189 { "Start character", "gdb.start", FT_STRING, BASE_NONE,
190 NULL, 0, NULL, HFILL } },
191 { &hf_gdb_payload,
192 { "Payload", "gdb.payload", FT_BYTES, BASE_NONE,
193 NULL, 0, NULL, HFILL } },
194 { &hf_gdb_end,
195 { "Terminating character", "gdb.end", FT_STRING, BASE_NONE,
196 NULL, 0, NULL, HFILL } },
197 { &hf_gdb_chksum,
198 { "Checksum", "gdb.chksum", FT_STRING, BASE_NONE,
199 NULL, 0, NULL, HFILL } }
200 };
201
202 static gint *ett[] = {
203 &ett_gdb
204 };
205
206
207 proto_gdb = proto_register_protocol("GDB Remote Serial Protocol", "GDB remote", "gdb");
208
209 proto_register_field_array(proto_gdb, hf, array_length(hf));
210 proto_register_subtree_array(ett, array_length(ett));
211
212 init_gdb_parser();
213 }
214
215
216 void
proto_reg_handoff_gdb(void)217 proto_reg_handoff_gdb(void)
218 {
219 dissector_handle_t gdb_handle;
220
221 gdb_handle = create_dissector_handle(dissect_gdb_tcp, proto_gdb);
222
223 dissector_add_for_decode_as_with_preference("tcp.port", gdb_handle);
224 }
225
226 /*
227 * Editor modelines - https://www.wireshark.org/tools/modelines.html
228 *
229 * Local variables:
230 * c-basic-offset: 4
231 * tab-width: 8
232 * indent-tabs-mode: nil
233 * End:
234 *
235 * vi: set shiftwidth=4 tabstop=8 expandtab:
236 * :indentSize=4:tabSize=8:noTabs=true:
237 */
238