src/core/gdbstub.c

   1 /*
   2  * Copyright (C) 2008 Stefan Hajnoczi <stefanha@gmail.com>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 /**
  20  * @file
  21  *
  22  * GDB stub for remote debugging
  23  *
  24  */
  25
  26 #include <stdlib.h>
  27 #include <stdio.h>
  28 #include <string.h>
  29 #include <ctype.h>
  30 #include <byteswap.h>
  31 #include <gpxe/gdbstub.h>
  32 #include "gdbmach.h"
  33
  34 enum {
  35         POSIX_EINVAL = 0x1c,  /* used to report bad arguments to GDB */
  36         SIZEOF_PAYLOAD = 256, /* buffer size of GDB payload data */
  37 };
  38
  39 struct gdbstub {
  40         struct gdb_transport *trans;
  41         int exit_handler; /* leave interrupt handler */
  42
  43         int signo;
  44         gdbreg_t *regs;
  45
  46         void ( * parse ) ( struct gdbstub *stub, char ch );
  47         uint8_t cksum1;
  48
  49         /* Buffer for payload data when parsing a packet.  Once the
  50          * packet has been received, this buffer is used to hold
  51          * the reply payload. */
  52         char buf [ SIZEOF_PAYLOAD + 4 ]; /* $...PAYLOAD...#XX */
  53         char *payload;                   /* start of payload */
  54         int len;                         /* length of payload */
  55 };
  56
  57 /* Packet parser states */
  58 static void gdbstub_state_new ( struct gdbstub *stub, char ch );
  59 static void gdbstub_state_data ( struct gdbstub *stub, char ch );
  60 static void gdbstub_state_cksum1 ( struct gdbstub *stub, char ch );
  61 static void gdbstub_state_cksum2 ( struct gdbstub *stub, char ch );
  62 static void gdbstub_state_wait_ack ( struct gdbstub *stub, char ch );
  63
  64 static uint8_t gdbstub_from_hex_digit ( char ch ) {
  65         return ( isdigit ( ch ) ? ch - '0' : tolower ( ch ) - 'a' + 0xa ) & 0xf;
  66 }
  67
  68 static uint8_t gdbstub_to_hex_digit ( uint8_t b ) {
  69         b &= 0xf;
  70         return ( b < 0xa ? '0' : 'a' - 0xa ) + b;
  71 }
  72
  73 /*
  74  * To make reading/writing device memory atomic, we check for
  75  * 2- or 4-byte aligned operations and handle them specially.
  76  */
  77
  78 static void gdbstub_from_hex_buf ( char *dst, char *src, int lenbytes ) {
  79         if ( lenbytes == 2 && ( ( unsigned long ) dst & 0x1 ) == 0 ) {
  80                 uint16_t i = gdbstub_from_hex_digit ( src [ 2 ] ) << 12 |
  81                         gdbstub_from_hex_digit ( src [ 3 ] ) << 8 |
  82                         gdbstub_from_hex_digit ( src [ 0 ] ) << 4 |
  83                         gdbstub_from_hex_digit ( src [ 1 ] );
  84                 * ( uint16_t * ) dst = cpu_to_le16 ( i );
  85         } else if ( lenbytes == 4 && ( ( unsigned long ) dst & 0x3 ) == 0 ) {
  86                 uint32_t i = gdbstub_from_hex_digit ( src [ 6 ] ) << 28 |
  87                         gdbstub_from_hex_digit ( src [ 7 ] ) << 24 |
  88                         gdbstub_from_hex_digit ( src [ 4 ] ) << 20 |
  89                         gdbstub_from_hex_digit ( src [ 5 ] ) << 16 |
  90                         gdbstub_from_hex_digit ( src [ 2 ] ) << 12 |
  91                         gdbstub_from_hex_digit ( src [ 3 ] ) << 8 |
  92                         gdbstub_from_hex_digit ( src [ 0 ] ) << 4 |
  93                         gdbstub_from_hex_digit ( src [ 1 ] );
  94                 * ( uint32_t * ) dst = cpu_to_le32 ( i );
  95         } else {
  96                 while ( lenbytes-- > 0 ) {
  97                         *dst++ = gdbstub_from_hex_digit ( src [ 0 ] ) << 4 |
  98                                 gdbstub_from_hex_digit ( src [ 1 ] );
  99                         src += 2;
 100                 }
 101         }
 102 }
 103
 104 static void gdbstub_to_hex_buf ( char *dst, char *src, int lenbytes ) {
 105         if ( lenbytes == 2 && ( ( unsigned long ) src & 0x1 ) == 0 ) {
 106                 uint16_t i = cpu_to_le16 ( * ( uint16_t * ) src );
 107                 dst [ 0 ] = gdbstub_to_hex_digit ( i >> 4 );
 108                 dst [ 1 ] = gdbstub_to_hex_digit ( i );
 109                 dst [ 2 ] = gdbstub_to_hex_digit ( i >> 12 );
 110                 dst [ 3 ] = gdbstub_to_hex_digit ( i >> 8 );
 111         } else if ( lenbytes == 4 && ( ( unsigned long ) src & 0x3 ) == 0 ) {
 112                 uint32_t i = cpu_to_le32 ( * ( uint32_t * ) src );
 113                 dst [ 0 ] = gdbstub_to_hex_digit ( i >> 4 );
 114                 dst [ 1 ] = gdbstub_to_hex_digit ( i );
 115                 dst [ 2 ] = gdbstub_to_hex_digit ( i >> 12 );
 116                 dst [ 3 ] = gdbstub_to_hex_digit ( i >> 8 );
 117                 dst [ 4 ] = gdbstub_to_hex_digit ( i >> 20 );
 118                 dst [ 5 ] = gdbstub_to_hex_digit ( i >> 16);
 119                 dst [ 6 ] = gdbstub_to_hex_digit ( i >> 28 );
 120                 dst [ 7 ] = gdbstub_to_hex_digit ( i >> 24 );
 121         } else {
 122                 while ( lenbytes-- > 0 ) {
 123                         *dst++ = gdbstub_to_hex_digit ( *src >> 4 );
 124                         *dst++ = gdbstub_to_hex_digit ( *src );
 125                         src++;
 126                 }
 127         }
 128 }
 129
 130 static uint8_t gdbstub_cksum ( char *data, int len ) {
 131         uint8_t cksum = 0;
 132         while ( len-- > 0 ) {
 133                 cksum += ( uint8_t ) *data++;
 134         }
 135         return cksum;
 136 }
 137
 138 static void gdbstub_tx_packet ( struct gdbstub *stub ) {
 139         uint8_t cksum = gdbstub_cksum ( stub->payload, stub->len );
 140         stub->buf [ 0 ] = '$';
 141         stub->buf [ stub->len + 1 ] = '#';
 142         stub->buf [ stub->len + 2 ] = gdbstub_to_hex_digit ( cksum >> 4 );
 143         stub->buf [ stub->len + 3 ] = gdbstub_to_hex_digit ( cksum );
 144         stub->trans->send ( stub->buf, stub->len + 4 );
 145         stub->parse = gdbstub_state_wait_ack;
 146 }
 147
 148 /* GDB commands */
 149 static void gdbstub_send_ok ( struct gdbstub *stub ) {
 150         stub->payload [ 0 ] = 'O';
 151         stub->payload [ 1 ] = 'K';
 152         stub->len = 2;
 153         gdbstub_tx_packet ( stub );
 154 }
 155
 156 static void gdbstub_send_num_packet ( struct gdbstub *stub, char reply, int num ) {
 157         stub->payload [ 0 ] = reply;
 158         stub->payload [ 1 ] = gdbstub_to_hex_digit ( ( char ) num >> 4 );
 159         stub->payload [ 2 ] = gdbstub_to_hex_digit ( ( char ) num );
 160         stub->len = 3;
 161         gdbstub_tx_packet ( stub );
 162 }
 163
 164 /* Format is arg1,arg2,...,argn:data where argn are hex integers and data is not an argument */
 165 static int gdbstub_get_packet_args ( struct gdbstub *stub, unsigned long *args, int nargs, int *stop_idx ) {
 166         int i;
 167         char ch = 0;
 168         int argc = 0;
 169         unsigned long val = 0;
 170         for ( i = 1; i < stub->len && argc < nargs; i++ ) {
 171                 ch = stub->payload [ i ];
 172                 if ( ch == ':' ) {
 173                         break;
 174                 } else if ( ch == ',' ) {
 175                         args [ argc++ ] = val;
 176                         val = 0;
 177                 } else {
 178                         val = ( val << 4 ) | gdbstub_from_hex_digit ( ch );
 179                 }
 180         }
 181         if ( stop_idx ) {
 182                 *stop_idx = i;
 183         }
 184         if ( argc < nargs ) {
 185                 args [ argc++ ] = val;
 186         }
 187         return ( ( i == stub->len || ch == ':' ) && argc == nargs );
 188 }
 189
 190 static void gdbstub_send_errno ( struct gdbstub *stub, int errno ) {
 191         gdbstub_send_num_packet ( stub, 'E', errno );
 192 }
 193
 194 static void gdbstub_report_signal ( struct gdbstub *stub ) {
 195         gdbstub_send_num_packet ( stub, 'S', stub->signo );
 196 }
 197
 198 static void gdbstub_read_regs ( struct gdbstub *stub ) {
 199         gdbstub_to_hex_buf ( stub->payload, ( char * ) stub->regs, GDBMACH_SIZEOF_REGS );
 200         stub->len = GDBMACH_SIZEOF_REGS * 2;
 201         gdbstub_tx_packet ( stub );
 202 }
 203
 204 static void gdbstub_write_regs ( struct gdbstub *stub ) {
 205         if ( stub->len != 1 + GDBMACH_SIZEOF_REGS * 2 ) {
 206                 gdbstub_send_errno ( stub, POSIX_EINVAL );
 207                 return;
 208         }
 209         gdbstub_from_hex_buf ( ( char * ) stub->regs, &stub->payload [ 1 ], GDBMACH_SIZEOF_REGS );
 210         gdbstub_send_ok ( stub );
 211 }
 212
 213 static void gdbstub_read_mem ( struct gdbstub *stub ) {
 214         unsigned long args [ 2 ];
 215         if ( !gdbstub_get_packet_args ( stub, args, sizeof args / sizeof args [ 0 ], NULL ) ) {
 216                 gdbstub_send_errno ( stub, POSIX_EINVAL );
 217                 return;
 218         }
 219         args [ 1 ] = ( args [ 1 ] < SIZEOF_PAYLOAD / 2 ) ? args [ 1 ] : SIZEOF_PAYLOAD / 2;
 220         gdbstub_to_hex_buf ( stub->payload, ( char * ) args [ 0 ], args [ 1 ] );
 221         stub->len = args [ 1 ] * 2;
 222         gdbstub_tx_packet ( stub );
 223 }
 224
 225 static void gdbstub_write_mem ( struct gdbstub *stub ) {
 226         unsigned long args [ 2 ];
 227         int colon;
 228         if ( !gdbstub_get_packet_args ( stub, args, sizeof args / sizeof args [ 0 ], &colon ) ||
 229                         colon >= stub->len || stub->payload [ colon ] != ':' ||
 230                         ( stub->len - colon - 1 ) % 2 != 0 ) {
 231                 gdbstub_send_errno ( stub, POSIX_EINVAL );
 232                 return;
 233         }
 234         gdbstub_from_hex_buf ( ( char * ) args [ 0 ], &stub->payload [ colon + 1 ], ( stub->len - colon - 1 ) / 2 );
 235         gdbstub_send_ok ( stub );
 236 }
 237
 238 static void gdbstub_continue ( struct gdbstub *stub, int single_step ) {
 239         gdbreg_t pc;
 240         if ( stub->len > 1 && gdbstub_get_packet_args ( stub, &pc, 1, NULL ) ) {
 241                 gdbmach_set_pc ( stub->regs, pc );
 242         }
 243         gdbmach_set_single_step ( stub->regs, single_step );
 244         stub->exit_handler = 1;
 245         /* Reply will be sent when we hit the next breakpoint or interrupt */
 246 }
 247
 248 static void gdbstub_breakpoint ( struct gdbstub *stub ) {
 249         unsigned long args [ 3 ];
 250         int enable = stub->payload [ 0 ] == 'Z' ? 1 : 0;
 251         if ( !gdbstub_get_packet_args ( stub, args, sizeof args / sizeof args [ 0 ], NULL ) ) {
 252                 gdbstub_send_errno ( stub, POSIX_EINVAL );
 253                 return;
 254         }
 255         if ( gdbmach_set_breakpoint ( args [ 0 ], args [ 1 ], args [ 2 ], enable ) ) {
 256                 gdbstub_send_ok ( stub );
 257         } else {
 258                 /* Not supported */
 259                 stub->len = 0;
 260                 gdbstub_tx_packet ( stub );
 261         }
 262 }
 263
 264 static void gdbstub_rx_packet ( struct gdbstub *stub ) {
 265         switch ( stub->payload [ 0 ] ) {
 266                 case '?':
 267                         gdbstub_report_signal ( stub );
 268                         break;
 269                 case 'g':
 270                         gdbstub_read_regs ( stub );
 271                         break;
 272                 case 'G':
 273                         gdbstub_write_regs ( stub );
 274                         break;
 275                 case 'm':
 276                         gdbstub_read_mem ( stub );
 277                         break;
 278                 case 'M':
 279                         gdbstub_write_mem ( stub );
 280                         break;
 281                 case 'c': /* Continue */
 282                 case 'k': /* Kill */
 283                 case 's': /* Step */
 284                 case 'D': /* Detach */
 285                         gdbstub_continue ( stub, stub->payload [ 0 ] == 's' );
 286                         if ( stub->payload [ 0 ] == 'D' ) {
 287                                 gdbstub_send_ok ( stub );
 288                         }
 289                         break;
 290                 case 'Z': /* Insert breakpoint */
 291                 case 'z': /* Remove breakpoint */
 292                         gdbstub_breakpoint ( stub );
 293                         break;
 294                 default:
 295                         stub->len = 0;
 296                         gdbstub_tx_packet ( stub );
 297                         break;
 298         }
 299 }
 300
 301 /* GDB packet parser */
 302 static void gdbstub_state_new ( struct gdbstub *stub, char ch ) {
 303         if ( ch == '$' ) {
 304                 stub->len = 0;
 305                 stub->parse = gdbstub_state_data;
 306         }
 307 }
 308
 309 static void gdbstub_state_data ( struct gdbstub *stub, char ch ) {
 310         if ( ch == '#' ) {
 311                 stub->parse = gdbstub_state_cksum1;
 312         } else if ( ch == '$' ) {
 313                 stub->len = 0; /* retry new packet */
 314         } else {
 315                 /* If the length exceeds our buffer, let the checksum fail */
 316                 if ( stub->len < SIZEOF_PAYLOAD ) {
 317                         stub->payload [ stub->len++ ] = ch;
 318                 }
 319         }
 320 }
 321
 322 static void gdbstub_state_cksum1 ( struct gdbstub *stub, char ch ) {
 323         stub->cksum1 = gdbstub_from_hex_digit ( ch ) << 4;
 324         stub->parse = gdbstub_state_cksum2;
 325 }
 326
 327 static void gdbstub_state_cksum2 ( struct gdbstub *stub, char ch ) {
 328         uint8_t their_cksum;
 329         uint8_t our_cksum;
 330
 331         stub->parse = gdbstub_state_new;
 332         their_cksum = stub->cksum1 + gdbstub_from_hex_digit ( ch );
 333         our_cksum = gdbstub_cksum ( stub->payload, stub->len );
 334         if ( their_cksum == our_cksum ) {
 335                 stub->trans->send ( "+", 1 );
 336                 if ( stub->len > 0 ) {
 337                         gdbstub_rx_packet ( stub );
 338                 }
 339         } else {
 340                 stub->trans->send ( "-", 1 );
 341         }
 342 }
 343
 344 static void gdbstub_state_wait_ack ( struct gdbstub *stub, char ch ) {
 345         if ( ch == '+' ) {
 346                 stub->parse = gdbstub_state_new;
 347         } else {
 348                 /* This retransmit is very aggressive but necessary to keep
 349                  * in sync with GDB. */
 350                 gdbstub_tx_packet ( stub );
 351         }
 352 }
 353
 354 static void gdbstub_parse ( struct gdbstub *stub, char ch ) {
 355         stub->parse ( stub, ch );
 356 }
 357
 358 static struct gdbstub stub = {
 359         .parse = gdbstub_state_new
 360 };
 361
 362 void gdbstub_handler ( int signo, gdbreg_t *regs ) {
 363         char packet [ SIZEOF_PAYLOAD + 4 ];
 364         size_t len, i;
 365
 366         /* A transport must be set up */
 367         if ( !stub.trans ) {
 368                 return;
 369         }
 370
 371         stub.signo = signo;
 372         stub.regs = regs;
 373         stub.exit_handler = 0;
 374         gdbstub_report_signal ( &stub );
 375         while ( !stub.exit_handler && ( len = stub.trans->recv ( packet, sizeof ( packet ) ) ) > 0 ) {
 376                 for ( i = 0; i < len; i++ ) {
 377                         gdbstub_parse ( &stub, packet [ i ] );
 378                 }
 379         }
 380 }
 381
 382 struct gdb_transport *find_gdb_transport ( const char *name ) {
 383         struct gdb_transport *trans;
 384
 385         for_each_table_entry ( trans, GDB_TRANSPORTS ) {
 386                 if ( strcmp ( trans->name, name ) == 0 ) {
 387                         return trans;
 388                 }
 389         }
 390         return NULL;
 391 }
 392
 393 void gdbstub_start ( struct gdb_transport *trans ) {
 394         stub.trans = trans;
 395         stub.payload = &stub.buf [ 1 ];
 396         gdbmach_breakpoint();
 397 }