1/*-
2 * Copyright 2015 Toomas Soome <tsoome@me.com>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27/*
28 * Chain loader to load BIOS boot block either from MBR or PBR.
29 *
30 * Note the boot block location 0000:7c000 conflicts with loader, so we need to
31 * read in to temporary space and relocate on exec, when btx is stopped.
32 */
33
34#include <sys/cdefs.h>
35__FBSDID("$FreeBSD: stable/11/stand/i386/loader/chain.c 346476 2019-04-21 03:36:05Z kevans $");
36
37#include <stand.h>
38#include <sys/param.h>
39#include <sys/linker.h>
40#include <sys/diskmbr.h>
41
42#include "bootstrap.h"
43#include "libi386/libi386.h"
44#include "btxv86.h"
45
46/*
47 * The MBR/VBR is located in first sector of disk/partition.
48 * Read 512B to temporary location and set up relocation. Then
49 * exec relocator.
50 */
51#define	SECTOR_SIZE	(512)
52
53COMMAND_SET(chain, "chain", "chain load boot block from device", command_chain);
54
55static int
56command_chain(int argc, char *argv[])
57{
58	int fd, len, size = SECTOR_SIZE;
59	struct stat st;
60	vm_offset_t mem = 0x100000;
61	struct i386_devdesc *rootdev;
62
63	if (argc == 1) {
64		command_errmsg = "no device or file name specified";
65		return (CMD_ERROR);
66	}
67	if (argc != 2) {
68		command_errmsg = "invalid trailing arguments";
69		return (CMD_ERROR);
70	}
71
72	fd = open(argv[1], O_RDONLY);
73	if (fd == -1) {
74		command_errmsg = "open failed";
75		return (CMD_ERROR);
76	}
77
78	len = strlen(argv[1]);
79	if (argv[1][len-1] != ':') {
80		if (fstat(fd, &st) == -1) {
81			command_errmsg = "stat failed";
82			close(fd);
83			return (CMD_ERROR);
84		}
85		size = st.st_size;
86	} else if (strncmp(argv[1], "disk", 4) != 0) {
87		command_errmsg = "can only use disk device";
88		close(fd);
89		return (CMD_ERROR);
90	}
91
92	i386_getdev((void **)(&rootdev), argv[1], NULL);
93	if (rootdev == NULL) {
94		command_errmsg = "can't determine root device";
95		close(fd);
96		return (CMD_ERROR);
97	}
98
99	if (archsw.arch_readin(fd, mem, size) != size) {
100		command_errmsg = "failed to read disk";
101		close(fd);
102		return (CMD_ERROR);
103	}
104	close(fd);
105
106	if (argv[1][len-1] == ':' &&
107	    *((uint16_t *)PTOV(mem + DOSMAGICOFFSET)) != DOSMAGIC) {
108		command_errmsg = "wrong magic";
109		return (CMD_ERROR);
110	}
111
112	relocater_data[0].src = mem;
113	relocater_data[0].dest = 0x7C00;
114	relocater_data[0].size = size;
115
116	relocator_edx = bd_unit2bios(rootdev);
117	relocator_esi = relocater_size;
118	relocator_ds = 0;
119	relocator_es = 0;
120	relocator_fs = 0;
121	relocator_gs = 0;
122	relocator_ss = 0;
123	relocator_cs = 0;
124	relocator_sp = 0x7C00;
125	relocator_ip = 0x7C00;
126	relocator_a20_enabled = 0;
127
128	i386_copyin(relocater, 0x600, relocater_size);
129
130	dev_cleanup();
131
132	__exec((void *)0x600);
133
134	panic("exec returned");
135	return (CMD_ERROR);		/* not reached */
136}
137