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 dissector_handle_t gdb_handle;
  47
  48 static int proto_gdb;
  49
  50 static int ett_gdb;
  51
  52 static int hf_gdb_ack;
  53 static int hf_gdb_start;
  54 static int hf_gdb_payload;
  55 static int hf_gdb_end;
  56 static int hf_gdb_chksum;
  57
  58 static tvbparse_wanted_t *want;
  59
  60 static void
  61 dissect_gdb_token(void *tvbparse_data, const void *wanted_data, tvbparse_elem_t *tok)
  62 {
  63     proto_tree *tree;
  64     unsigned    token;
  65
  66     if (!tok)   /* XXX - is this check necessary? */
  67         return;
  68
  69     tree = (proto_tree *)tvbparse_data;
  70     token = GPOINTER_TO_UINT(wanted_data);
  71
  72     /* XXX - check that tok->len is what we expect? */
  73     switch (token) {
  74         case GDB_TOK_ACK:
  75             proto_tree_add_item(tree, hf_gdb_ack,
  76                     tok->tvb, tok->offset, tok->len, ENC_ASCII|ENC_NA);
  77             break;
  78         case GDB_TOK_START:
  79             proto_tree_add_item(tree, hf_gdb_start,
  80                     tok->tvb, tok->offset, tok->len, ENC_ASCII);
  81             break;
  82         case GDB_TOK_PAYLOAD:
  83             proto_tree_add_item(tree, hf_gdb_payload,
  84                     tok->tvb, tok->offset, tok->len, ENC_NA);
  85             break;
  86         case GDB_TOK_END:
  87             proto_tree_add_item(tree, hf_gdb_end,
  88                     tok->tvb, tok->offset, tok->len, ENC_ASCII);
  89             break;
  90         case GDB_TOK_CHKSUM:
  91             proto_tree_add_item(tree, hf_gdb_chksum,
  92                     tok->tvb, tok->offset, tok->len, ENC_ASCII);
  93             break;
  94         default:
  95             break;
  96     }
  97 }
  98
  99 static void init_gdb_parser(void) {
 100     tvbparse_wanted_t *want_ack;
 101     tvbparse_wanted_t *want_start;
 102     tvbparse_wanted_t *want_payload;
 103     tvbparse_wanted_t *want_end;
 104     tvbparse_wanted_t *want_chksum;
 105
 106     want_ack = tvbparse_chars(-1, 1, 1, "+-",
 107             GUINT_TO_POINTER(GDB_TOK_ACK), NULL, dissect_gdb_token);
 108     want_start = tvbparse_chars(-1, 1, 1, "$",
 109             GUINT_TO_POINTER(GDB_TOK_START), NULL, dissect_gdb_token);
 110     want_payload = tvbparse_not_chars(-1, 1, 0, "$#",
 111             GUINT_TO_POINTER(GDB_TOK_PAYLOAD), NULL, dissect_gdb_token);
 112     want_end = tvbparse_chars(-1, 1, 1, "#",
 113             GUINT_TO_POINTER(GDB_TOK_END), NULL, dissect_gdb_token);
 114     want_chksum = tvbparse_chars(-1, 2, 2, "0123456789abcdefABCDEF",
 115             GUINT_TO_POINTER(GDB_TOK_CHKSUM), NULL, dissect_gdb_token);
 116
 117     want = tvbparse_set_seq(-1, NULL, NULL, NULL,
 118             tvbparse_some(-1, 0, 1, NULL, NULL, NULL, want_ack),
 119             want_start, want_payload, want_end, want_chksum, NULL);
 120 }
 121
 122
 123 static void
 124 dissect_gdb_packet(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 125 {
 126     proto_item  *ti;
 127     proto_tree  *gdb_tree;
 128     tvbparse_t  *tt;
 129
 130     col_set_str(pinfo->cinfo, COL_PROTOCOL, "GDB");
 131     col_clear(pinfo->cinfo, COL_INFO);
 132
 133     ti = proto_tree_add_protocol_format(tree, proto_gdb,
 134             tvb, 0, tvb_reported_length(tvb), "GDB Remote Serial Protocol");
 135     gdb_tree = proto_item_add_subtree(ti, ett_gdb);
 136
 137     /* XXX support multiple sub-trees */
 138     tt = tvbparse_init(pinfo->pool, tvb, 0, -1, (void *)gdb_tree, NULL);
 139
 140     while(tvbparse_get(tt, want)) {
 141         ;
 142     }
 143 }
 144
 145
 146 static int
 147 dissect_gdb_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
 148 {
 149     int       offset=0, offset_start;
 150     int       pos;
 151     unsigned  packet_len;
 152     tvbuff_t *packet_tvb;
 153
 154     while (tvb_captured_length_remaining(tvb, offset) > 0) {
 155         packet_tvb = NULL;
 156         offset_start = offset;
 157         pos = tvb_find_uint8(tvb, offset, -1, '#');
 158         if (pos != -1) {
 159             offset += pos;
 160             offset++; /* skip the hash sign */
 161             /* to have a complete packet, we need another two bytes
 162                for the checksum */
 163             if (tvb_bytes_exist(tvb, offset, 2)) {
 164                 offset += 2;
 165                 packet_len = offset-offset_start;
 166                 packet_tvb = tvb_new_subset_length(tvb, offset_start,
 167                         packet_len);
 168             }
 169         }
 170
 171         if (packet_tvb)
 172             dissect_gdb_packet(tvb, pinfo, tree);
 173         else {
 174             pinfo->desegment_offset = offset;
 175             pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
 176             return tvb_captured_length(tvb);
 177         }
 178     }
 179     return tvb_captured_length(tvb);
 180 }
 181
 182
 183 void
 184 proto_register_gdb(void)
 185 {
 186     static hf_register_info hf[] = {
 187         { &hf_gdb_ack,
 188           { "Acknowledge", "gdb.ack", FT_CHAR, BASE_HEX,
 189               VALS(gdb_ack), 0, NULL, HFILL } },
 190         { &hf_gdb_start,
 191           { "Start character", "gdb.start", FT_STRING, BASE_NONE,
 192               NULL, 0, NULL, HFILL } },
 193         { &hf_gdb_payload,
 194           { "Payload", "gdb.payload", FT_BYTES, BASE_NONE,
 195               NULL, 0, NULL, HFILL } },
 196         { &hf_gdb_end,
 197           { "Terminating character", "gdb.end", FT_STRING, BASE_NONE,
 198               NULL, 0, NULL, HFILL } },
 199         { &hf_gdb_chksum,
 200           { "Checksum", "gdb.chksum", FT_STRING, BASE_NONE,
 201               NULL, 0, NULL, HFILL } }
 202     };
 203
 204     static int *ett[] = {
 205         &ett_gdb
 206     };
 207
 208
 209     proto_gdb = proto_register_protocol("GDB Remote Serial Protocol", "GDB remote", "gdb");
 210     gdb_handle = register_dissector("gdb", dissect_gdb_tcp, proto_gdb);
 211
 212     proto_register_field_array(proto_gdb, hf, array_length(hf));
 213     proto_register_subtree_array(ett, array_length(ett));
 214
 215     init_gdb_parser();
 216 }
 217
 218
 219 void
 220 proto_reg_handoff_gdb(void)
 221 {
 222     dissector_add_for_decode_as_with_preference("tcp.port", gdb_handle);
 223 }
 224
 225 /*
 226  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 227  *
 228  * Local variables:
 229  * c-basic-offset: 4
 230  * tab-width: 8
 231  * indent-tabs-mode: nil
 232  * End:
 233  *
 234  * vi: set shiftwidth=4 tabstop=8 expandtab:
 235  * :indentSize=4:tabSize=8:noTabs=true:
 236  */