aboutsummaryrefslogtreecommitdiff
path: root/arch/x86/boot/edd.c
blob: 1fb4bc70cee932361d6dff50bdff7f3b5b6aaad7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
// SPDX-License-Identifier: GPL-2.0-only
/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
 *
 * ----------------------------------------------------------------------- */

/*
 * Get EDD BIOS disk information
 */

#include "boot.h"
#include <linux/edd.h>
#include "string.h"

#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)

/*
 * Read the MBR (first sector) from a specific device.
 */
static int read_mbr(u8 devno, void *buf)
{
	struct biosregs ireg, oreg;

	initregs(&ireg);
	ireg.ax = 0x0201;		/* Legacy Read, one sector */
	ireg.cx = 0x0001;		/* Sector 0-0-1 */
	ireg.dl = devno;
	ireg.bx = (size_t)buf;

	intcall(0x13, &ireg, &oreg);

	return -(oreg.eflags & X86_EFLAGS_CF); /* 0 or -1 */
}

static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig)
{
	int sector_size;
	char *mbrbuf_ptr, *mbrbuf_end;
	u32 buf_base, mbr_base;
	extern char _end[];
	u16 mbr_magic;

	sector_size = ei->params.bytes_per_sector;
	if (!sector_size)
		sector_size = 512; /* Best available guess */

	/* Produce a naturally aligned buffer on the heap */
	buf_base = (ds() << 4) + (u32)&_end;
	mbr_base = (buf_base+sector_size-1) & ~(sector_size-1);
	mbrbuf_ptr = _end + (mbr_base-buf_base);
	mbrbuf_end = mbrbuf_ptr + sector_size;

	/* Make sure we actually have space on the heap... */
	if (!(boot_params.hdr.loadflags & CAN_USE_HEAP))
		return -1;
	if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
		return -1;

	memset(mbrbuf_ptr, 0, sector_size);
	if (read_mbr(devno, mbrbuf_ptr))
		return -1;

	*mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
	mbr_magic = *(u16 *)&mbrbuf_ptr[510];

	/* check for valid MBR magic */
	return mbr_magic == 0xAA55 ? 0 : -1;
}

static int get_edd_info(u8 devno, struct edd_info *ei)
{
	struct biosregs ireg, oreg;

	memset(ei, 0, sizeof(*ei));

	/* Check Extensions Present */

	initregs(&ireg);
	ireg.ah = 0x41;
	ireg.bx = EDDMAGIC1;
	ireg.dl = devno;
	intcall(0x13, &ireg, &oreg);

	if (oreg.eflags & X86_EFLAGS_CF)
		return -1;	/* No extended information */

	if (oreg.bx != EDDMAGIC2)
		return -1;

	ei->device  = devno;
	ei->version = oreg.ah;		 /* EDD version number */
	ei->interface_support = oreg.cx; /* EDD functionality subsets */

	/* Extended Get Device Parameters */

	ei->params.length = sizeof(ei->params);
	ireg.ah = 0x48;
	ireg.si = (size_t)&ei->params;
	intcall(0x13, &ireg, &oreg);

	/* Get legacy CHS parameters */

	/* Ralf Brown recommends setting ES:DI to 0:0 */
	ireg.ah = 0x08;
	ireg.es = 0;
	intcall(0x13, &ireg, &oreg);

	if (!(oreg.eflags & X86_EFLAGS_CF)) {
		ei->legacy_max_cylinder = oreg.ch + ((oreg.cl & 0xc0) << 2);
		ei->legacy_max_head = oreg.dh;
		ei->legacy_sectors_per_track = oreg.cl & 0x3f;
	}

	return 0;
}

void query_edd(void)
{
	char eddarg[8];
	int do_mbr = 1;
#ifdef CONFIG_EDD_OFF
	int do_edd = 0;
#else
	int do_edd = 1;
#endif
	int be_quiet;
	int devno;
	struct edd_info ei, *edp;
	u32 *mbrptr;

	if (cmdline_find_option("edd", eddarg, sizeof(eddarg)) > 0) {
		if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) {
			do_edd = 1;
			do_mbr = 0;
		}
		else if (!strcmp(eddarg, "off"))
			do_edd = 0;
		else if (!strcmp(eddarg, "on"))
			do_edd = 1;
	}

	be_quiet = cmdline_find_option_bool("quiet");

	edp    = boot_params.eddbuf;
	mbrptr = boot_params.edd_mbr_sig_buffer;

	if (!do_edd)
		return;

	/* Bugs in OnBoard or AddOnCards Bios may hang the EDD probe,
	 * so give a hint if this happens.
	 */

	if (!be_quiet)
		printf("Probing EDD (edd=off to disable)... ");

	for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {
		/*
		 * Scan the BIOS-supported hard disks and query EDD
		 * information...
		 */
		if (!get_edd_info(devno, &ei)
		    && boot_params.eddbuf_entries < EDDMAXNR) {
			memcpy(edp, &ei, sizeof(ei));
			edp++;
			boot_params.eddbuf_entries++;
		}

		if (do_mbr && !read_mbr_sig(devno, &ei, mbrptr++))
			boot_params.edd_mbr_sig_buf_entries = devno-0x80+1;
	}

	if (!be_quiet)
		printf("ok\n");
}

#endif