1/*
2 * Copyright (C) 2008 Daniel Verkamp <daniel@drv.nu>.
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 SYSLINUX COMBOOT API
21 *
22 */
23
24FILE_LICENCE ( GPL2_OR_LATER );
25
26#include <errno.h>
27#include <realmode.h>
28#include <biosint.h>
29#include <console.h>
30#include <stdlib.h>
31#include <comboot.h>
32#include <bzimage.h>
33#include <pxe_call.h>
34#include <setjmp.h>
35#include <string.h>
36#include <gpxe/posix_io.h>
37#include <gpxe/process.h>
38#include <gpxe/serial.h>
39#include <gpxe/init.h>
40#include <gpxe/image.h>
41#include <usr/imgmgmt.h>
42#include "config/console.h"
43#include "config/serial.h"
44
45/** The "SYSLINUX" version string */
46static char __data16_array ( syslinux_version, [] ) = "gPXE " VERSION;
47#define syslinux_version __use_data16 ( syslinux_version )
48
49/** The "SYSLINUX" copyright string */
50static char __data16_array ( syslinux_copyright, [] ) = "http://etherboot.org";
51#define syslinux_copyright __use_data16 ( syslinux_copyright )
52
53static char __data16_array ( syslinux_configuration_file, [] ) = "";
54#define syslinux_configuration_file __use_data16 ( syslinux_configuration_file )
55
56/** Feature flags */
57static uint8_t __data16 ( comboot_feature_flags ) = COMBOOT_FEATURE_IDLE_LOOP;
58#define comboot_feature_flags __use_data16 ( comboot_feature_flags )
59
60typedef union {
61	syslinux_pm_regs pm; syslinux_rm_regs rm;
62} syslinux_regs;
63
64/** Initial register values for INT 22h AX=1Ah and 1Bh */
65static syslinux_regs __text16 ( comboot_initial_regs );
66#define comboot_initial_regs __use_text16 ( comboot_initial_regs )
67
68static struct segoff __text16 ( int20_vector );
69#define int20_vector __use_text16 ( int20_vector )
70
71static struct segoff __text16 ( int21_vector );
72#define int21_vector __use_text16 ( int21_vector )
73
74static struct segoff __text16 ( int22_vector );
75#define int22_vector __use_text16 ( int22_vector )
76
77extern void int20_wrapper ( void );
78extern void int21_wrapper ( void );
79extern void int22_wrapper ( void );
80
81/* setjmp/longjmp context buffer used to return after loading an image */
82rmjmp_buf comboot_return;
83
84/* Replacement image when exiting with COMBOOT_EXIT_RUN_KERNEL */
85struct image *comboot_replacement_image;
86
87/* Mode flags set by INT 22h AX=0017h */
88static uint16_t comboot_graphics_mode = 0;
89
90
91/**
92 * Print a string with a particular terminator
93 */
94static void print_user_string ( unsigned int segment, unsigned int offset, char terminator ) {
95	int i = 0;
96	char c;
97	userptr_t str = real_to_user ( segment, offset );
98	for ( ; ; ) {
99		copy_from_user ( &c, str, i, 1 );
100		if ( c == terminator ) break;
101		putchar ( c );
102		i++;
103	}
104}
105
106
107/**
108 * Perform a series of memory copies from a list in low memory
109 */
110static void shuffle ( unsigned int list_segment, unsigned int list_offset, unsigned int count )
111{
112	comboot_shuffle_descriptor shuf[COMBOOT_MAX_SHUFFLE_DESCRIPTORS];
113	unsigned int i;
114
115	/* Copy shuffle descriptor list so it doesn't get overwritten */
116	copy_from_user ( shuf, real_to_user ( list_segment, list_offset ), 0,
117	                 count * sizeof( comboot_shuffle_descriptor ) );
118
119	/* Do the copies */
120	for ( i = 0; i < count; i++ ) {
121		userptr_t src_u = phys_to_user ( shuf[ i ].src );
122		userptr_t dest_u = phys_to_user ( shuf[ i ].dest );
123
124		if ( shuf[ i ].src == 0xFFFFFFFF ) {
125			/* Fill with 0 instead of copying */
126			memset_user ( dest_u, 0, 0, shuf[ i ].len );
127		} else if ( shuf[ i ].dest == 0xFFFFFFFF ) {
128			/* Copy new list of descriptors */
129			count = shuf[ i ].len / sizeof( comboot_shuffle_descriptor );
130			assert ( count <= COMBOOT_MAX_SHUFFLE_DESCRIPTORS );
131			copy_from_user ( shuf, src_u, 0, shuf[ i ].len );
132			i = -1;
133		} else {
134			/* Regular copy */
135			memmove_user ( dest_u, 0, src_u, 0, shuf[ i ].len );
136		}
137	}
138}
139
140
141/**
142 * Set default text mode
143 */
144void comboot_force_text_mode ( void ) {
145	if ( comboot_graphics_mode & COMBOOT_VIDEO_VESA ) {
146		/* Set VGA mode 3 via VESA VBE mode set */
147		__asm__ __volatile__ (
148			REAL_CODE (
149				"mov $0x4F02, %%ax\n\t"
150				"mov $0x03, %%bx\n\t"
151				"int $0x10\n\t"
152			)
153		: : );
154	} else if ( comboot_graphics_mode & COMBOOT_VIDEO_GRAPHICS ) {
155		/* Set VGA mode 3 via standard VGA mode set */
156		__asm__ __volatile__ (
157			REAL_CODE (
158				"mov $0x03, %%ax\n\t"
159				"int $0x10\n\t"
160			)
161		: : );
162	}
163
164	comboot_graphics_mode = 0;
165}
166
167
168/**
169 * Fetch kernel and optional initrd
170 */
171static int comboot_fetch_kernel ( char *kernel_file, char *cmdline ) {
172	struct image *kernel = NULL;
173	struct image *initrd = NULL;
174	char *initrd_file;
175	int rc;
176
177	/* Find initrd= parameter, if any */
178	if ( ( initrd_file = strstr ( cmdline, "initrd=" ) ) != NULL ) {
179		char *initrd_end;
180
181		/* skip "initrd=" */
182		initrd_file += 7;
183
184		/* Find terminating space, if any, and replace with NUL */
185		initrd_end = strchr ( initrd_file, ' ' );
186		if ( initrd_end )
187			*initrd_end = '\0';
188
189		DBG ( "COMBOOT: fetching initrd '%s'\n", initrd_file );
190
191		/* Allocate and fetch initrd */
192		initrd = alloc_image();
193		if ( ! initrd ) {
194			DBG ( "COMBOOT: could not allocate initrd\n" );
195			rc = -ENOMEM;
196			goto out;
197		}
198		if ( ( rc = imgfetch ( initrd, initrd_file,
199				       register_image ) ) != 0 ) {
200			DBG ( "COMBOOT: could not fetch initrd: %s\n",
201			      strerror ( rc ) );
202			goto out;
203		}
204
205		/* Restore space after initrd name, if applicable */
206		if ( initrd_end )
207			*initrd_end = ' ';
208	}
209
210	DBG ( "COMBOOT: fetching kernel '%s'\n", kernel_file );
211
212	/* Allocate and fetch kernel */
213	kernel = alloc_image();
214	if ( ! kernel ) {
215		DBG ( "COMBOOT: could not allocate kernel\n" );
216		rc = -ENOMEM;
217		goto out;
218	}
219	if ( ( rc = imgfetch ( kernel, kernel_file,
220			       register_image ) ) != 0 ) {
221		DBG ( "COMBOOT: could not fetch kernel: %s\n",
222		      strerror ( rc ) );
223		goto out;
224	}
225	if ( ( rc = image_set_cmdline ( kernel, cmdline ) ) != 0 ) {
226		DBG ( "COMBOOT: could not set kernel command line: %s\n",
227		      strerror ( rc ) );
228		goto out;
229	}
230
231	/* Store kernel as replacement image */
232	assert ( comboot_replacement_image == NULL );
233	comboot_replacement_image = image_get ( kernel );
234
235 out:
236	/* Drop image references unconditionally; either we want to
237	 * discard them, or they have been registered and we should
238	 * drop out local reference.
239	 */
240	image_put ( kernel );
241	image_put ( initrd );
242	return rc;
243}
244
245
246/**
247 * Terminate program interrupt handler
248 */
249static __asmcall void int20 ( struct i386_all_regs *ix86 __unused ) {
250	rmlongjmp ( comboot_return, COMBOOT_EXIT );
251}
252
253
254/**
255 * DOS-compatible API
256 */
257static __asmcall void int21 ( struct i386_all_regs *ix86 ) {
258	ix86->flags |= CF;
259
260	switch ( ix86->regs.ah ) {
261	case 0x00:
262	case 0x4C: /* Terminate program */
263		rmlongjmp ( comboot_return, COMBOOT_EXIT );
264		break;
265
266	case 0x01: /* Get Key with Echo */
267	case 0x08: /* Get Key without Echo */
268		/* TODO: handle extended characters? */
269		ix86->regs.al = getchar( );
270
271		/* Enter */
272		if ( ix86->regs.al == 0x0A )
273			ix86->regs.al = 0x0D;
274
275		if ( ix86->regs.ah == 0x01 )
276			putchar ( ix86->regs.al );
277
278		ix86->flags &= ~CF;
279		break;
280
281	case 0x02: /* Write Character */
282		putchar ( ix86->regs.dl );
283		ix86->flags &= ~CF;
284		break;
285
286	case 0x04: /* Write Character to Serial Port */
287		serial_putc ( ix86->regs.dl );
288		ix86->flags &= ~CF;
289		break;
290
291	case 0x09: /* Write DOS String to Console */
292		print_user_string ( ix86->segs.ds, ix86->regs.dx, '$' );
293		ix86->flags &= ~CF;
294		break;
295
296	case 0x0B: /* Check Keyboard */
297		if ( iskey() )
298			ix86->regs.al = 0xFF;
299		else
300			ix86->regs.al = 0x00;
301
302		ix86->flags &= ~CF;
303		break;
304
305	case 0x30: /* Check DOS Version */
306		/* Bottom halves all 0; top halves spell "SYSLINUX" */
307		ix86->regs.eax = 0x59530000;
308		ix86->regs.ebx = 0x4C530000;
309		ix86->regs.ecx = 0x4E490000;
310		ix86->regs.edx = 0x58550000;
311		ix86->flags &= ~CF;
312		break;
313
314	default:
315		DBG ( "COMBOOT unknown int21 function %02x\n", ix86->regs.ah );
316		break;
317	}
318}
319
320
321/**
322 * SYSLINUX API
323 */
324static __asmcall void int22 ( struct i386_all_regs *ix86 ) {
325	ix86->flags |= CF;
326
327	switch ( ix86->regs.ax ) {
328	case 0x0001: /* Get Version */
329
330		/* Number of INT 22h API functions available */
331		ix86->regs.ax = 0x001D;
332
333		/* SYSLINUX version number */
334		ix86->regs.ch = 0; /* major */
335		ix86->regs.cl = 0; /* minor */
336
337		/* SYSLINUX derivative ID */
338		ix86->regs.dl = BZI_LOADER_TYPE_GPXE;
339
340		/* SYSLINUX version and copyright strings */
341		ix86->segs.es = rm_ds;
342		ix86->regs.si = ( ( unsigned ) __from_data16 ( syslinux_version ) );
343		ix86->regs.di = ( ( unsigned ) __from_data16 ( syslinux_copyright ) );
344
345		ix86->flags &= ~CF;
346		break;
347
348	case 0x0002: /* Write String */
349		print_user_string ( ix86->segs.es, ix86->regs.bx, '\0' );
350		ix86->flags &= ~CF;
351		break;
352
353	case 0x0003: /* Run command */
354		{
355			userptr_t cmd_u = real_to_user ( ix86->segs.es, ix86->regs.bx );
356			int len = strlen_user ( cmd_u, 0 );
357			char cmd[len + 1];
358			copy_from_user ( cmd, cmd_u, 0, len + 1 );
359			DBG ( "COMBOOT: executing command '%s'\n", cmd );
360			system ( cmd );
361			DBG ( "COMBOOT: exiting after executing command...\n" );
362			rmlongjmp ( comboot_return, COMBOOT_EXIT_COMMAND );
363		}
364		break;
365
366	case 0x0004: /* Run default command */
367		/* FIXME: just exit for now */
368		rmlongjmp ( comboot_return, COMBOOT_EXIT_COMMAND );
369		break;
370
371	case 0x0005: /* Force text mode */
372		comboot_force_text_mode ( );
373		ix86->flags &= ~CF;
374		break;
375
376	case 0x0006: /* Open file */
377		{
378			int fd;
379			userptr_t file_u = real_to_user ( ix86->segs.es, ix86->regs.si );
380			int len = strlen_user ( file_u, 0 );
381			char file[len + 1];
382
383			copy_from_user ( file, file_u, 0, len + 1 );
384
385			if ( file[0] == '\0' ) {
386				DBG ( "COMBOOT: attempted open with empty file name\n" );
387				break;
388			}
389
390			DBG ( "COMBOOT: opening file '%s'\n", file );
391
392			fd = open ( file );
393
394			if ( fd < 0 ) {
395				DBG ( "COMBOOT: error opening file %s\n", file );
396				break;
397			}
398
399			/* This relies on the fact that a gPXE POSIX fd will
400			 * always fit in 16 bits.
401			 */
402#if (POSIX_FD_MAX > 65535)
403#error POSIX_FD_MAX too large
404#endif
405			ix86->regs.si = (uint16_t) fd;
406
407			ix86->regs.cx = COMBOOT_FILE_BLOCKSZ;
408			ix86->regs.eax = fsize ( fd );
409			ix86->flags &= ~CF;
410		}
411		break;
412
413	case 0x0007: /* Read file */
414		{
415			int fd = ix86->regs.si;
416			int len = ix86->regs.cx * COMBOOT_FILE_BLOCKSZ;
417			int rc;
418			fd_set fds;
419			userptr_t buf = real_to_user ( ix86->segs.es, ix86->regs.bx );
420
421			/* Wait for data ready to read */
422			FD_ZERO ( &fds );
423			FD_SET ( fd, &fds );
424
425			select ( &fds, 1 );
426
427			rc = read_user ( fd, buf, 0, len );
428			if ( rc < 0 ) {
429				DBG ( "COMBOOT: read failed\n" );
430				ix86->regs.si = 0;
431				break;
432			}
433
434			ix86->regs.ecx = rc;
435			ix86->flags &= ~CF;
436		}
437		break;
438
439	case 0x0008: /* Close file */
440		{
441			int fd = ix86->regs.si;
442			close ( fd );
443			ix86->flags &= ~CF;
444		}
445		break;
446
447	case 0x0009: /* Call PXE Stack */
448		if ( pxe_api_call_weak ( ix86 ) != 0 )
449			ix86->flags |= CF;
450		else
451			ix86->flags &= ~CF;
452		break;
453
454	case 0x000A: /* Get Derivative-Specific Information */
455
456		/* gPXE has its own derivative ID, so there is no defined
457		 * output here; just return AL for now */
458		ix86->regs.al = BZI_LOADER_TYPE_GPXE;
459		ix86->flags &= ~CF;
460		break;
461
462	case 0x000B: /* Get Serial Console Configuration */
463#if defined(CONSOLE_SERIAL) && !defined(COMPRESERVE)
464		ix86->regs.dx = COMCONSOLE;
465		ix86->regs.cx = 115200 / COMSPEED;
466		ix86->regs.bx = 0;
467#else
468		ix86->regs.dx = 0;
469#endif
470
471		ix86->flags &= ~CF;
472		break;
473
474	case 0x000E: /* Get configuration file name */
475		/* FIXME: stub */
476		ix86->segs.es = rm_ds;
477		ix86->regs.bx = ( ( unsigned ) __from_data16 ( syslinux_configuration_file ) );
478		ix86->flags &= ~CF;
479		break;
480
481	case 0x000F: /* Get IPAPPEND strings */
482		/* FIXME: stub */
483		ix86->regs.cx = 0;
484		ix86->segs.es = 0;
485		ix86->regs.bx = 0;
486		ix86->flags &= ~CF;
487		break;
488
489	case 0x0010: /* Resolve hostname */
490		{
491			userptr_t hostname_u = real_to_user ( ix86->segs.es, ix86->regs.bx );
492			int len = strlen_user ( hostname_u, 0 );
493			char hostname[len];
494			struct in_addr addr;
495
496			copy_from_user ( hostname, hostname_u, 0, len + 1 );
497
498			/* TODO:
499			 * "If the hostname does not contain a dot (.), the
500			 * local domain name is automatically appended."
501			 */
502
503			comboot_resolv ( hostname, &addr );
504
505			ix86->regs.eax = addr.s_addr;
506			ix86->flags &= ~CF;
507		}
508		break;
509
510	case 0x0011: /* Maximum number of shuffle descriptors */
511		ix86->regs.cx = COMBOOT_MAX_SHUFFLE_DESCRIPTORS;
512		ix86->flags &= ~CF;
513		break;
514
515	case 0x0012: /* Cleanup, shuffle and boot */
516		if ( ix86->regs.cx > COMBOOT_MAX_SHUFFLE_DESCRIPTORS )
517			break;
518
519		/* Perform final cleanup */
520		shutdown ( SHUTDOWN_BOOT );
521
522		/* Perform sequence of copies */
523		shuffle ( ix86->segs.es, ix86->regs.di, ix86->regs.cx );
524
525		/* Jump to real-mode entry point */
526		__asm__ __volatile__ (
527			REAL_CODE (
528				"pushw %0\n\t"
529				"popw %%ds\n\t"
530				"pushl %1\n\t"
531				"lret\n\t"
532			)
533			:
534			: "r" ( ix86->segs.ds ),
535			  "r" ( ix86->regs.ebp ),
536			  "d" ( ix86->regs.ebx ),
537			  "S" ( ix86->regs.esi ) );
538
539		assert ( 0 ); /* Execution should never reach this point */
540
541		break;
542
543	case 0x0013: /* Idle loop call */
544		step ( );
545		ix86->flags &= ~CF;
546		break;
547
548	case 0x0015: /* Get feature flags */
549		ix86->segs.es = rm_ds;
550		ix86->regs.bx = ( ( unsigned ) __from_data16 ( &comboot_feature_flags ) );
551		ix86->regs.cx = 1; /* Number of feature flag bytes */
552		ix86->flags &= ~CF;
553		break;
554
555	case 0x0016: /* Run kernel image */
556		{
557			userptr_t file_u = real_to_user ( ix86->segs.ds, ix86->regs.si );
558			userptr_t cmd_u = real_to_user ( ix86->segs.es, ix86->regs.bx );
559			int file_len = strlen_user ( file_u, 0 );
560			int cmd_len = strlen_user ( cmd_u, 0 );
561			char file[file_len + 1];
562			char cmd[cmd_len + 1];
563
564			copy_from_user ( file, file_u, 0, file_len + 1 );
565			copy_from_user ( cmd, cmd_u, 0, cmd_len + 1 );
566
567			DBG ( "COMBOOT: run kernel %s %s\n", file, cmd );
568			comboot_fetch_kernel ( file, cmd );
569			/* Technically, we should return if we
570			 * couldn't load the kernel, but it's not safe
571			 * to do that since we have just overwritten
572			 * part of the COMBOOT program's memory space.
573			 */
574			DBG ( "COMBOOT: exiting to run kernel...\n" );
575			rmlongjmp ( comboot_return, COMBOOT_EXIT_RUN_KERNEL );
576		}
577		break;
578
579	case 0x0017: /* Report video mode change */
580		comboot_graphics_mode = ix86->regs.bx;
581		ix86->flags &= ~CF;
582		break;
583
584	case 0x0018: /* Query custom font */
585		/* FIXME: stub */
586		ix86->regs.al = 0;
587		ix86->segs.es = 0;
588		ix86->regs.bx = 0;
589		ix86->flags &= ~CF;
590		break;
591
592	case 0x001B: /* Cleanup, shuffle and boot to real mode */
593		if ( ix86->regs.cx > COMBOOT_MAX_SHUFFLE_DESCRIPTORS )
594			break;
595
596		/* Perform final cleanup */
597		shutdown ( SHUTDOWN_BOOT );
598
599		/* Perform sequence of copies */
600		shuffle ( ix86->segs.es, ix86->regs.di, ix86->regs.cx );
601
602		/* Copy initial register values to .text16 */
603		memcpy_user ( real_to_user ( rm_cs, (unsigned) __from_text16 ( &comboot_initial_regs ) ), 0,
604		              real_to_user ( ix86->segs.ds, ix86->regs.si ), 0,
605		              sizeof(syslinux_rm_regs) );
606
607		/* Load initial register values */
608		__asm__ __volatile__ (
609			REAL_CODE (
610				/* Point SS:SP at the register value structure */
611				"pushw %%cs\n\t"
612				"popw %%ss\n\t"
613				"movw $comboot_initial_regs, %%sp\n\t"
614
615				/* Segment registers */
616				"popw %%es\n\t"
617				"popw %%ax\n\t" /* Skip CS */
618				"popw %%ds\n\t"
619				"popw %%ax\n\t" /* Skip SS for now */
620				"popw %%fs\n\t"
621				"popw %%gs\n\t"
622
623				/* GP registers */
624				"popl %%eax\n\t"
625				"popl %%ecx\n\t"
626				"popl %%edx\n\t"
627				"popl %%ebx\n\t"
628				"popl %%ebp\n\t" /* Skip ESP for now */
629				"popl %%ebp\n\t"
630				"popl %%esi\n\t"
631				"popl %%edi\n\t"
632
633				/* Load correct SS:ESP */
634				"movw $(comboot_initial_regs + 6), %%sp\n\t"
635				"popw %%ss\n\t"
636				"movl %%cs:(comboot_initial_regs + 28), %%esp\n\t"
637
638				"ljmp *%%cs:(comboot_initial_regs + 44)\n\t"
639			)
640			: : );
641
642		break;
643
644	case 0x001C: /* Get pointer to auxilliary data vector */
645		/* FIXME: stub */
646		ix86->regs.cx = 0; /* Size of the ADV */
647		ix86->flags &= ~CF;
648		break;
649
650	case 0x001D: /* Write auxilliary data vector */
651		/* FIXME: stub */
652		ix86->flags &= ~CF;
653		break;
654
655	default:
656		DBG ( "COMBOOT unknown int22 function %04x\n", ix86->regs.ax );
657		break;
658	}
659}
660
661/**
662 * Hook BIOS interrupts related to COMBOOT API (INT 20h, 21h, 22h)
663 */
664void hook_comboot_interrupts ( ) {
665
666	__asm__ __volatile__ (
667		TEXT16_CODE ( "\nint20_wrapper:\n\t"
668		              "pushl %0\n\t"
669		              "pushw %%cs\n\t"
670		              "call prot_call\n\t"
671		              "addw $4, %%sp\n\t"
672		              "iret\n\t" )
673		          : : "i" ( int20 ) );
674
675	hook_bios_interrupt ( 0x20, ( unsigned int ) int20_wrapper,
676		                      &int20_vector );
677
678	__asm__ __volatile__ (
679		TEXT16_CODE ( "\nint21_wrapper:\n\t"
680		              "pushl %0\n\t"
681		              "pushw %%cs\n\t"
682		              "call prot_call\n\t"
683		              "addw $4, %%sp\n\t"
684		              "iret\n\t" )
685		          : : "i" ( int21 ) );
686
687	hook_bios_interrupt ( 0x21, ( unsigned int ) int21_wrapper,
688	                      &int21_vector );
689
690	__asm__  __volatile__ (
691		TEXT16_CODE ( "\nint22_wrapper:\n\t"
692		              "pushl %0\n\t"
693		              "pushw %%cs\n\t"
694		              "call prot_call\n\t"
695		              "addw $4, %%sp\n\t"
696		              "iret\n\t" )
697		          : : "i" ( int22) );
698
699	hook_bios_interrupt ( 0x22, ( unsigned int ) int22_wrapper,
700	                      &int22_vector );
701}
702
703/**
704 * Unhook BIOS interrupts related to COMBOOT API (INT 20h, 21h, 22h)
705 */
706void unhook_comboot_interrupts ( ) {
707
708	unhook_bios_interrupt ( 0x20, ( unsigned int ) int20_wrapper,
709				&int20_vector );
710
711	unhook_bios_interrupt ( 0x21, ( unsigned int ) int21_wrapper,
712				&int21_vector );
713
714	unhook_bios_interrupt ( 0x22, ( unsigned int ) int22_wrapper,
715				&int22_vector );
716}
717