epan/dissectors/packet-gdb.c

   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
  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
  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
 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(tvb, 0, -1, (void *)gdb_tree, NULL);
 137
 138     while(tvbparse_get(tt, want)) {
 139         ;
 140     }
 141 }
 142
 143
 144 static int
 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
 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
 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  -  http://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  */