pxe_call.c

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00001 /*
00002  * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
00003  *
00004  * This program is free software; you can redistribute it and/or
00005  * modify it under the terms of the GNU General Public License as
00006  * published by the Free Software Foundation; either version 2 of the
00007  * License, or any later version.
00008  *
00009  * This program is distributed in the hope that it will be useful, but
00010  * WITHOUT ANY WARRANTY; without even the implied warranty of
00011  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012  * General Public License for more details.
00013  *
00014  * You should have received a copy of the GNU General Public License
00015  * along with this program; if not, write to the Free Software
00016  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00017  */
00018 
00019 FILE_LICENCE ( GPL2_OR_LATER );
00020 
00021 #include <gpxe/uaccess.h>
00022 #include <gpxe/init.h>
00023 #include <registers.h>
00024 #include <biosint.h>
00025 #include <pxe.h>
00026 #include <pxe_call.h>
00027 
00028 /** @file
00029  *
00030  * PXE API entry point
00031  */
00032 
00033 /** Vector for chaining INT 1A */
00034 extern struct segoff __text16 ( pxe_int_1a_vector );
00035 #define pxe_int_1a_vector __use_text16 ( pxe_int_1a_vector )
00036 
00037 /** INT 1A handler */
00038 extern void pxe_int_1a ( void );
00039 
00040 /** INT 1A hooked flag */
00041 static int int_1a_hooked = 0;
00042 
00043 /** A function pointer to hold any PXE API call
00044  *
00045  * Used by pxe_api_call() to avoid large swathes of duplicated code.
00046  */
00047 union pxenv_call {
00048         PXENV_EXIT_t ( * any ) ( union u_PXENV_ANY * );
00049         PXENV_EXIT_t ( * unknown ) ( struct s_PXENV_UNKNOWN * );
00050         PXENV_EXIT_t ( * unload_stack ) ( struct s_PXENV_UNLOAD_STACK * );
00051         PXENV_EXIT_t ( * get_cached_info )
00052                         ( struct s_PXENV_GET_CACHED_INFO * );
00053         PXENV_EXIT_t ( * restart_tftp ) ( struct s_PXENV_TFTP_READ_FILE * );
00054         PXENV_EXIT_t ( * start_undi ) ( struct s_PXENV_START_UNDI * );
00055         PXENV_EXIT_t ( * stop_undi ) ( struct s_PXENV_STOP_UNDI * );
00056         PXENV_EXIT_t ( * start_base ) ( struct s_PXENV_START_BASE * );
00057         PXENV_EXIT_t ( * stop_base ) ( struct s_PXENV_STOP_BASE * );
00058         PXENV_EXIT_t ( * tftp_open ) ( struct s_PXENV_TFTP_OPEN * );
00059         PXENV_EXIT_t ( * tftp_close ) ( struct s_PXENV_TFTP_CLOSE * );
00060         PXENV_EXIT_t ( * tftp_read ) ( struct s_PXENV_TFTP_READ * );
00061         PXENV_EXIT_t ( * tftp_read_file ) ( struct s_PXENV_TFTP_READ_FILE * );
00062         PXENV_EXIT_t ( * tftp_get_fsize ) ( struct s_PXENV_TFTP_GET_FSIZE * );
00063         PXENV_EXIT_t ( * udp_open ) ( struct s_PXENV_UDP_OPEN * );
00064         PXENV_EXIT_t ( * udp_close ) ( struct s_PXENV_UDP_CLOSE * );
00065         PXENV_EXIT_t ( * udp_write ) ( struct s_PXENV_UDP_WRITE * );
00066         PXENV_EXIT_t ( * udp_read ) ( struct s_PXENV_UDP_READ * );
00067         PXENV_EXIT_t ( * undi_startup ) ( struct s_PXENV_UNDI_STARTUP * );
00068         PXENV_EXIT_t ( * undi_cleanup ) ( struct s_PXENV_UNDI_CLEANUP * );
00069         PXENV_EXIT_t ( * undi_initialize )
00070                         ( struct s_PXENV_UNDI_INITIALIZE * );
00071         PXENV_EXIT_t ( * undi_reset_adapter ) ( struct s_PXENV_UNDI_RESET * );
00072         PXENV_EXIT_t ( * undi_shutdown ) ( struct s_PXENV_UNDI_SHUTDOWN * );
00073         PXENV_EXIT_t ( * undi_open ) ( struct s_PXENV_UNDI_OPEN * );
00074         PXENV_EXIT_t ( * undi_close ) ( struct s_PXENV_UNDI_CLOSE * );
00075         PXENV_EXIT_t ( * undi_transmit ) ( struct s_PXENV_UNDI_TRANSMIT * );
00076         PXENV_EXIT_t ( * undi_set_mcast_address )
00077                         ( struct s_PXENV_UNDI_SET_MCAST_ADDRESS * );
00078         PXENV_EXIT_t ( * undi_set_station_address )
00079                         ( struct s_PXENV_UNDI_SET_STATION_ADDRESS * );
00080         PXENV_EXIT_t ( * undi_set_packet_filter )
00081                         ( struct s_PXENV_UNDI_SET_PACKET_FILTER * );
00082         PXENV_EXIT_t ( * undi_get_information )
00083                         ( struct s_PXENV_UNDI_GET_INFORMATION * );
00084         PXENV_EXIT_t ( * undi_get_statistics )
00085                         ( struct s_PXENV_UNDI_GET_STATISTICS * );
00086         PXENV_EXIT_t ( * undi_clear_statistics )
00087                         ( struct s_PXENV_UNDI_CLEAR_STATISTICS * );
00088         PXENV_EXIT_t ( * undi_initiate_diags )
00089                         ( struct s_PXENV_UNDI_INITIATE_DIAGS * );
00090         PXENV_EXIT_t ( * undi_force_interrupt )
00091                         ( struct s_PXENV_UNDI_FORCE_INTERRUPT * );
00092         PXENV_EXIT_t ( * undi_get_mcast_address )
00093                         ( struct s_PXENV_UNDI_GET_MCAST_ADDRESS * );
00094         PXENV_EXIT_t ( * undi_get_nic_type )
00095                         ( struct s_PXENV_UNDI_GET_NIC_TYPE * );
00096         PXENV_EXIT_t ( * undi_get_iface_info )
00097                         ( struct s_PXENV_UNDI_GET_IFACE_INFO * );
00098         PXENV_EXIT_t ( * undi_get_state ) ( struct s_PXENV_UNDI_GET_STATE * );
00099         PXENV_EXIT_t ( * undi_isr ) ( struct s_PXENV_UNDI_ISR * );
00100         PXENV_EXIT_t ( * file_open ) ( struct s_PXENV_FILE_OPEN * );
00101         PXENV_EXIT_t ( * file_close ) ( struct s_PXENV_FILE_CLOSE * );
00102         PXENV_EXIT_t ( * file_select ) ( struct s_PXENV_FILE_SELECT * );
00103         PXENV_EXIT_t ( * file_read ) ( struct s_PXENV_FILE_READ * );
00104         PXENV_EXIT_t ( * get_file_size ) ( struct s_PXENV_GET_FILE_SIZE * );
00105         PXENV_EXIT_t ( * file_exec ) ( struct s_PXENV_FILE_EXEC * );
00106         PXENV_EXIT_t ( * file_api_check ) ( struct s_PXENV_FILE_API_CHECK * );
00107         PXENV_EXIT_t ( * file_exit_hook ) ( struct s_PXENV_FILE_EXIT_HOOK * );
00108 };
00109 
00110 /**
00111  * Handle an unknown PXE API call
00112  *
00113  * @v pxenv_unknown                     Pointer to a struct s_PXENV_UNKNOWN
00114  * @ret #PXENV_EXIT_FAILURE             Always
00115  * @err #PXENV_STATUS_UNSUPPORTED       Always
00116  */
00117 static PXENV_EXIT_t pxenv_unknown ( struct s_PXENV_UNKNOWN *pxenv_unknown ) {
00118         pxenv_unknown->Status = PXENV_STATUS_UNSUPPORTED;
00119         return PXENV_EXIT_FAILURE;
00120 }
00121 
00122 /**
00123  * Dispatch PXE API call
00124  *
00125  * @v bx                PXE opcode
00126  * @v es:di             Address of PXE parameter block
00127  * @ret ax              PXE exit code
00128  */
00129 __asmcall void pxe_api_call ( struct i386_all_regs *ix86 ) {
00130         int opcode = ix86->regs.bx;
00131         userptr_t parameters = real_to_user ( ix86->segs.es, ix86->regs.di );
00132         size_t param_len;
00133         union u_PXENV_ANY pxenv_any;
00134         union pxenv_call pxenv_call;
00135         PXENV_EXIT_t ret;
00136 
00137         switch ( opcode ) {
00138         case PXENV_UNLOAD_STACK:
00139                 pxenv_call.unload_stack = pxenv_unload_stack;
00140                 param_len = sizeof ( pxenv_any.unload_stack );
00141                 break;
00142         case PXENV_GET_CACHED_INFO:
00143                 pxenv_call.get_cached_info = pxenv_get_cached_info;
00144                 param_len = sizeof ( pxenv_any.get_cached_info );
00145                 break;
00146         case PXENV_RESTART_TFTP:
00147                 pxenv_call.restart_tftp = pxenv_restart_tftp;
00148                 param_len = sizeof ( pxenv_any.restart_tftp );
00149                 break;
00150         case PXENV_START_UNDI:
00151                 pxenv_call.start_undi = pxenv_start_undi;
00152                 param_len = sizeof ( pxenv_any.start_undi );
00153                 break;
00154         case PXENV_STOP_UNDI:
00155                 pxenv_call.stop_undi = pxenv_stop_undi;
00156                 param_len = sizeof ( pxenv_any.stop_undi );
00157                 break;
00158         case PXENV_START_BASE:
00159                 pxenv_call.start_base = pxenv_start_base;
00160                 param_len = sizeof ( pxenv_any.start_base );
00161                 break;
00162         case PXENV_STOP_BASE:
00163                 pxenv_call.stop_base = pxenv_stop_base;
00164                 param_len = sizeof ( pxenv_any.stop_base );
00165                 break;
00166         case PXENV_TFTP_OPEN:
00167                 pxenv_call.tftp_open = pxenv_tftp_open;
00168                 param_len = sizeof ( pxenv_any.tftp_open );
00169                 break;
00170         case PXENV_TFTP_CLOSE:
00171                 pxenv_call.tftp_close = pxenv_tftp_close;
00172                 param_len = sizeof ( pxenv_any.tftp_close );
00173                 break;
00174         case PXENV_TFTP_READ:
00175                 pxenv_call.tftp_read = pxenv_tftp_read;
00176                 param_len = sizeof ( pxenv_any.tftp_read );
00177                 break;
00178         case PXENV_TFTP_READ_FILE:
00179                 pxenv_call.tftp_read_file = pxenv_tftp_read_file;
00180                 param_len = sizeof ( pxenv_any.tftp_read_file );
00181                 break;
00182         case PXENV_TFTP_GET_FSIZE:
00183                 pxenv_call.tftp_get_fsize = pxenv_tftp_get_fsize;
00184                 param_len = sizeof ( pxenv_any.tftp_get_fsize );
00185                 break;
00186         case PXENV_UDP_OPEN:
00187                 pxenv_call.udp_open = pxenv_udp_open;
00188                 param_len = sizeof ( pxenv_any.udp_open );
00189                 break;
00190         case PXENV_UDP_CLOSE:
00191                 pxenv_call.udp_close = pxenv_udp_close;
00192                 param_len = sizeof ( pxenv_any.udp_close );
00193                 break;
00194         case PXENV_UDP_WRITE:
00195                 pxenv_call.udp_write = pxenv_udp_write;
00196                 param_len = sizeof ( pxenv_any.udp_write );
00197                 break;
00198         case PXENV_UDP_READ:
00199                 pxenv_call.udp_read = pxenv_udp_read;
00200                 param_len = sizeof ( pxenv_any.udp_read );
00201                 break;
00202         case PXENV_UNDI_STARTUP:
00203                 pxenv_call.undi_startup = pxenv_undi_startup;
00204                 param_len = sizeof ( pxenv_any.undi_startup );
00205                 break;
00206         case PXENV_UNDI_CLEANUP:
00207                 pxenv_call.undi_cleanup = pxenv_undi_cleanup;
00208                 param_len = sizeof ( pxenv_any.undi_cleanup );
00209                 break;
00210         case PXENV_UNDI_INITIALIZE:
00211                 pxenv_call.undi_initialize = pxenv_undi_initialize;
00212                 param_len = sizeof ( pxenv_any.undi_initialize );
00213                 break;
00214         case PXENV_UNDI_RESET_ADAPTER:
00215                 pxenv_call.undi_reset_adapter = pxenv_undi_reset_adapter;
00216                 param_len = sizeof ( pxenv_any.undi_reset_adapter );
00217                 break;
00218         case PXENV_UNDI_SHUTDOWN:
00219                 pxenv_call.undi_shutdown = pxenv_undi_shutdown;
00220                 param_len = sizeof ( pxenv_any.undi_shutdown );
00221                 break;
00222         case PXENV_UNDI_OPEN:
00223                 pxenv_call.undi_open = pxenv_undi_open;
00224                 param_len = sizeof ( pxenv_any.undi_open );
00225                 break;
00226         case PXENV_UNDI_CLOSE:
00227                 pxenv_call.undi_close = pxenv_undi_close;
00228                 param_len = sizeof ( pxenv_any.undi_close );
00229                 break;
00230         case PXENV_UNDI_TRANSMIT:
00231                 pxenv_call.undi_transmit = pxenv_undi_transmit;
00232                 param_len = sizeof ( pxenv_any.undi_transmit );
00233                 break;
00234         case PXENV_UNDI_SET_MCAST_ADDRESS:
00235                 pxenv_call.undi_set_mcast_address =
00236                         pxenv_undi_set_mcast_address;
00237                 param_len = sizeof ( pxenv_any.undi_set_mcast_address );
00238                 break;
00239         case PXENV_UNDI_SET_STATION_ADDRESS:
00240                 pxenv_call.undi_set_station_address =
00241                         pxenv_undi_set_station_address;
00242                 param_len = sizeof ( pxenv_any.undi_set_station_address );
00243                 break;
00244         case PXENV_UNDI_SET_PACKET_FILTER:
00245                 pxenv_call.undi_set_packet_filter =
00246                         pxenv_undi_set_packet_filter;
00247                 param_len = sizeof ( pxenv_any.undi_set_packet_filter );
00248                 break;
00249         case PXENV_UNDI_GET_INFORMATION:
00250                 pxenv_call.undi_get_information = pxenv_undi_get_information;
00251                 param_len = sizeof ( pxenv_any.undi_get_information );
00252                 break;
00253         case PXENV_UNDI_GET_STATISTICS:
00254                 pxenv_call.undi_get_statistics = pxenv_undi_get_statistics;
00255                 param_len = sizeof ( pxenv_any.undi_get_statistics );
00256                 break;
00257         case PXENV_UNDI_CLEAR_STATISTICS:
00258                 pxenv_call.undi_clear_statistics = pxenv_undi_clear_statistics;
00259                 param_len = sizeof ( pxenv_any.undi_clear_statistics );
00260                 break;
00261         case PXENV_UNDI_INITIATE_DIAGS:
00262                 pxenv_call.undi_initiate_diags = pxenv_undi_initiate_diags;
00263                 param_len = sizeof ( pxenv_any.undi_initiate_diags );
00264                 break;
00265         case PXENV_UNDI_FORCE_INTERRUPT:
00266                 pxenv_call.undi_force_interrupt = pxenv_undi_force_interrupt;
00267                 param_len = sizeof ( pxenv_any.undi_force_interrupt );
00268                 break;
00269         case PXENV_UNDI_GET_MCAST_ADDRESS:
00270                 pxenv_call.undi_get_mcast_address =
00271                         pxenv_undi_get_mcast_address;
00272                 param_len = sizeof ( pxenv_any.undi_get_mcast_address );
00273                 break;
00274         case PXENV_UNDI_GET_NIC_TYPE:
00275                 pxenv_call.undi_get_nic_type = pxenv_undi_get_nic_type;
00276                 param_len = sizeof ( pxenv_any.undi_get_nic_type );
00277                 break;
00278         case PXENV_UNDI_GET_IFACE_INFO:
00279                 pxenv_call.undi_get_iface_info = pxenv_undi_get_iface_info;
00280                 param_len = sizeof ( pxenv_any.undi_get_iface_info );
00281                 break;
00282         case PXENV_UNDI_ISR:
00283                 pxenv_call.undi_isr = pxenv_undi_isr;
00284                 param_len = sizeof ( pxenv_any.undi_isr );
00285                 break;
00286         case PXENV_FILE_OPEN:
00287                 pxenv_call.file_open = pxenv_file_open;
00288                 param_len = sizeof ( pxenv_any.file_open );
00289                 break;
00290         case PXENV_FILE_CLOSE:
00291                 pxenv_call.file_close = pxenv_file_close;
00292                 param_len = sizeof ( pxenv_any.file_close );
00293                 break;
00294         case PXENV_FILE_SELECT:
00295                 pxenv_call.file_select = pxenv_file_select;
00296                 param_len = sizeof ( pxenv_any.file_select );
00297                 break;
00298         case PXENV_FILE_READ:
00299                 pxenv_call.file_read = pxenv_file_read;
00300                 param_len = sizeof ( pxenv_any.file_read );
00301                 break;
00302         case PXENV_GET_FILE_SIZE:
00303                 pxenv_call.get_file_size = pxenv_get_file_size;
00304                 param_len = sizeof ( pxenv_any.get_file_size );
00305                 break;
00306         case PXENV_FILE_EXEC:
00307                 pxenv_call.file_exec = pxenv_file_exec;
00308                 param_len = sizeof ( pxenv_any.file_exec );
00309                 break;
00310         case PXENV_FILE_API_CHECK:
00311                 pxenv_call.file_api_check = pxenv_file_api_check;
00312                 param_len = sizeof ( pxenv_any.file_api_check );
00313                 break;
00314         case PXENV_FILE_EXIT_HOOK:
00315                 pxenv_call.file_exit_hook = pxenv_file_exit_hook;
00316                 param_len = sizeof ( pxenv_any.file_exit_hook );
00317                 break;
00318         default:
00319                 DBG ( "PXENV_UNKNOWN_%hx", opcode );
00320                 pxenv_call.unknown = pxenv_unknown;
00321                 param_len = sizeof ( pxenv_any.unknown );
00322                 break;
00323         }
00324 
00325         /* Copy parameter block from caller */
00326         copy_from_user ( &pxenv_any, parameters, 0, param_len );
00327 
00328         /* Set default status in case child routine fails to do so */
00329         pxenv_any.Status = PXENV_STATUS_FAILURE;
00330 
00331         /* Hand off to relevant API routine */
00332         DBG ( "[" );
00333         ret = pxenv_call.any ( &pxenv_any );
00334         if ( pxenv_any.Status != PXENV_STATUS_SUCCESS ) {
00335                 DBG ( " %02x", pxenv_any.Status );
00336         }
00337         if ( ret != PXENV_EXIT_SUCCESS ) {
00338                 DBG ( ret == PXENV_EXIT_FAILURE ? " err" : " ??" );
00339         }
00340         DBG ( "]" );
00341         
00342         /* Copy modified parameter block back to caller and return */
00343         copy_to_user ( parameters, 0, &pxenv_any, param_len );
00344         ix86->regs.ax = ret;
00345 }
00346 
00347 /**
00348  * Dispatch weak PXE API call with PXE stack available
00349  *
00350  * @v ix86              Registers for PXE call
00351  * @ret present         Zero (PXE stack present)
00352  */
00353 int _pxe_api_call_weak ( struct i386_all_regs *ix86 )
00354 {
00355         pxe_api_call ( ix86 );
00356         return 0;
00357 }
00358 
00359 /**
00360  * Dispatch PXE loader call
00361  *
00362  * @v es:di             Address of PXE parameter block
00363  * @ret ax              PXE exit code
00364  */
00365 __asmcall void pxe_loader_call ( struct i386_all_regs *ix86 ) {
00366         userptr_t uparams = real_to_user ( ix86->segs.es, ix86->regs.di );
00367         struct s_UNDI_LOADER params;
00368         PXENV_EXIT_t ret;
00369 
00370         /* Copy parameter block from caller */
00371         copy_from_user ( &params, uparams, 0, sizeof ( params ) );
00372 
00373         /* Fill in ROM segment address */
00374         ppxe.UNDIROMID.segment = ix86->segs.ds;
00375 
00376         /* Set default status in case child routine fails to do so */
00377         params.Status = PXENV_STATUS_FAILURE;
00378 
00379         /* Call UNDI loader */
00380         ret = undi_loader ( &params );
00381 
00382         /* Copy modified parameter block back to caller and return */
00383         copy_to_user ( uparams, 0, &params, sizeof ( params ) );
00384         ix86->regs.ax = ret;
00385 }
00386 
00387 /**
00388  * Calculate byte checksum as used by PXE
00389  *
00390  * @v data              Data
00391  * @v size              Length of data
00392  * @ret sum             Checksum
00393  */
00394 static uint8_t pxe_checksum ( void *data, size_t size ) {
00395         uint8_t *bytes = data;
00396         uint8_t sum = 0;
00397 
00398         while ( size-- ) {
00399                 sum += *bytes++;
00400         }
00401         return sum;
00402 }
00403 
00404 /**
00405  * Initialise !PXE and PXENV+ structures
00406  *
00407  */
00408 static void pxe_init_structures ( void ) {
00409         uint32_t rm_cs_phys = ( rm_cs << 4 );
00410         uint32_t rm_ds_phys = ( rm_ds << 4 );
00411 
00412         /* Fill in missing segment fields */
00413         ppxe.EntryPointSP.segment = rm_cs;
00414         ppxe.EntryPointESP.segment = rm_cs;
00415         ppxe.Stack.segment_address = rm_ds;
00416         ppxe.Stack.Physical_address = rm_ds_phys;
00417         ppxe.UNDIData.segment_address = rm_ds;
00418         ppxe.UNDIData.Physical_address = rm_ds_phys;
00419         ppxe.UNDICode.segment_address = rm_cs;
00420         ppxe.UNDICode.Physical_address = rm_cs_phys;
00421         ppxe.UNDICodeWrite.segment_address = rm_cs;
00422         ppxe.UNDICodeWrite.Physical_address = rm_cs_phys;
00423         pxenv.RMEntry.segment = rm_cs;
00424         pxenv.StackSeg = rm_ds;
00425         pxenv.UNDIDataSeg = rm_ds;
00426         pxenv.UNDICodeSeg = rm_cs;
00427         pxenv.PXEPtr.segment = rm_cs;
00428 
00429         /* Update checksums */
00430         ppxe.StructCksum -= pxe_checksum ( &ppxe, sizeof ( ppxe ) );
00431         pxenv.Checksum -= pxe_checksum ( &pxenv, sizeof ( pxenv ) );
00432 }
00433 
00434 /** PXE structure initialiser */
00435 struct init_fn pxe_init_fn __init_fn ( INIT_NORMAL ) = {
00436         .initialise = pxe_init_structures,
00437 };
00438 
00439 /**
00440  * Activate PXE stack
00441  *
00442  * @v netdev            Net device to use as PXE net device
00443  */
00444 void pxe_activate ( struct net_device *netdev ) {
00445 
00446         /* Ensure INT 1A is hooked */
00447         if ( ! int_1a_hooked ) {
00448                 hook_bios_interrupt ( 0x1a, ( unsigned int ) pxe_int_1a,
00449                                       &pxe_int_1a_vector );
00450                 int_1a_hooked = 1;
00451         }
00452 
00453         /* Set PXE network device */
00454         pxe_set_netdev ( netdev );
00455 }
00456 
00457 /**
00458  * Deactivate PXE stack
00459  *
00460  * @ret rc              Return status code
00461  */
00462 int pxe_deactivate ( void ) {
00463         int rc;
00464 
00465         /* Clear PXE network device */
00466         pxe_set_netdev ( NULL );
00467 
00468         /* Ensure INT 1A is unhooked, if possible */
00469         if ( int_1a_hooked ) {
00470                 if ( ( rc = unhook_bios_interrupt ( 0x1a,
00471                                                     (unsigned int) pxe_int_1a,
00472                                                     &pxe_int_1a_vector ))!= 0){
00473                         DBG ( "Could not unhook INT 1A: %s\n",
00474                               strerror ( rc ) );
00475                         return rc;
00476                 }
00477                 int_1a_hooked = 0;
00478         }
00479 
00480         return 0;
00481 }
00482 
00483 /**
00484  * Start PXE NBP at 0000:7c00
00485  *
00486  * @ret rc              Return status code
00487  */
00488 int pxe_start_nbp ( void ) {
00489         int discard_b, discard_c, discard_d, discard_D;
00490         uint16_t rc;
00491 
00492         /* Far call to PXE NBP */
00493         __asm__ __volatile__ ( REAL_CODE ( "movw %%cx, %%es\n\t"
00494                                            "pushw %%es\n\t"
00495                                            "pushw %%di\n\t"
00496                                            "sti\n\t"
00497                                            "lcall $0, $0x7c00\n\t"
00498                                            "addw $4, %%sp\n\t" )
00499                                : "=a" ( rc ), "=b" ( discard_b ),
00500                                  "=c" ( discard_c ), "=d" ( discard_d ),
00501                                  "=D" ( discard_D )
00502                                : "a" ( 0 ), "b" ( __from_text16 ( &pxenv ) ),
00503                                  "c" ( rm_cs ),
00504                                  "d" ( virt_to_phys ( &pxenv ) ),
00505                                  "D" ( __from_text16 ( &ppxe ) )
00506                                : "esi", "ebp", "memory" );
00507 
00508         return rc;
00509 }