1/* -*- linux-c -*- ------------------------------------------------------- *
2 *
3 *   Copyright (C) 1991, 1992 Linus Torvalds
4 *   Copyright 2007 rPath, Inc. - All Rights Reserved
5 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
6 *
7 *   This file is part of the Linux kernel, and is made available under
8 *   the terms of the GNU General Public License version 2.
9 *
10 * ----------------------------------------------------------------------- */
11
12/*
13 * Get EDD BIOS disk information
14 */
15
16#include "boot.h"
17#include <linux/edd.h>
18#include "string.h"
19
20#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
21
22/*
23 * Read the MBR (first sector) from a specific device.
24 */
25static int read_mbr(u8 devno, void *buf)
26{
27	struct biosregs ireg, oreg;
28
29	initregs(&ireg);
30	ireg.ax = 0x0201;		/* Legacy Read, one sector */
31	ireg.cx = 0x0001;		/* Sector 0-0-1 */
32	ireg.dl = devno;
33	ireg.bx = (size_t)buf;
34
35	intcall(0x13, &ireg, &oreg);
36
37	return -(oreg.eflags & X86_EFLAGS_CF); /* 0 or -1 */
38}
39
40static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig)
41{
42	int sector_size;
43	char *mbrbuf_ptr, *mbrbuf_end;
44	u32 buf_base, mbr_base;
45	extern char _end[];
46	u16 mbr_magic;
47
48	sector_size = ei->params.bytes_per_sector;
49	if (!sector_size)
50		sector_size = 512; /* Best available guess */
51
52	/* Produce a naturally aligned buffer on the heap */
53	buf_base = (ds() << 4) + (u32)&_end;
54	mbr_base = (buf_base+sector_size-1) & ~(sector_size-1);
55	mbrbuf_ptr = _end + (mbr_base-buf_base);
56	mbrbuf_end = mbrbuf_ptr + sector_size;
57
58	/* Make sure we actually have space on the heap... */
59	if (!(boot_params.hdr.loadflags & CAN_USE_HEAP))
60		return -1;
61	if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
62		return -1;
63
64	memset(mbrbuf_ptr, 0, sector_size);
65	if (read_mbr(devno, mbrbuf_ptr))
66		return -1;
67
68	*mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
69	mbr_magic = *(u16 *)&mbrbuf_ptr[510];
70
71	/* check for valid MBR magic */
72	return mbr_magic == 0xAA55 ? 0 : -1;
73}
74
75static int get_edd_info(u8 devno, struct edd_info *ei)
76{
77	struct biosregs ireg, oreg;
78
79	memset(ei, 0, sizeof *ei);
80
81	/* Check Extensions Present */
82
83	initregs(&ireg);
84	ireg.ah = 0x41;
85	ireg.bx = EDDMAGIC1;
86	ireg.dl = devno;
87	intcall(0x13, &ireg, &oreg);
88
89	if (oreg.eflags & X86_EFLAGS_CF)
90		return -1;	/* No extended information */
91
92	if (oreg.bx != EDDMAGIC2)
93		return -1;
94
95	ei->device  = devno;
96	ei->version = oreg.ah;		 /* EDD version number */
97	ei->interface_support = oreg.cx; /* EDD functionality subsets */
98
99	/* Extended Get Device Parameters */
100
101	ei->params.length = sizeof(ei->params);
102	ireg.ah = 0x48;
103	ireg.si = (size_t)&ei->params;
104	intcall(0x13, &ireg, &oreg);
105
106	/* Get legacy CHS parameters */
107
108	/* Ralf Brown recommends setting ES:DI to 0:0 */
109	ireg.ah = 0x08;
110	ireg.es = 0;
111	intcall(0x13, &ireg, &oreg);
112
113	if (!(oreg.eflags & X86_EFLAGS_CF)) {
114		ei->legacy_max_cylinder = oreg.ch + ((oreg.cl & 0xc0) << 2);
115		ei->legacy_max_head = oreg.dh;
116		ei->legacy_sectors_per_track = oreg.cl & 0x3f;
117	}
118
119	return 0;
120}
121
122void query_edd(void)
123{
124	char eddarg[8];
125	int do_mbr = 1;
126#ifdef CONFIG_EDD_OFF
127	int do_edd = 0;
128#else
129	int do_edd = 1;
130#endif
131	int be_quiet;
132	int devno;
133	struct edd_info ei, *edp;
134	u32 *mbrptr;
135
136	if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) {
137		if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) {
138			do_edd = 1;
139			do_mbr = 0;
140		}
141		else if (!strcmp(eddarg, "off"))
142			do_edd = 0;
143		else if (!strcmp(eddarg, "on"))
144			do_edd = 1;
145	}
146
147	be_quiet = cmdline_find_option_bool("quiet");
148
149	edp    = boot_params.eddbuf;
150	mbrptr = boot_params.edd_mbr_sig_buffer;
151
152	if (!do_edd)
153		return;
154
155	/* Bugs in OnBoard or AddOnCards Bios may hang the EDD probe,
156	 * so give a hint if this happens.
157	 */
158
159	if (!be_quiet)
160		printf("Probing EDD (edd=off to disable)... ");
161
162	for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {
163		/*
164		 * Scan the BIOS-supported hard disks and query EDD
165		 * information...
166		 */
167		if (!get_edd_info(devno, &ei)
168		    && boot_params.eddbuf_entries < EDDMAXNR) {
169			memcpy(edp, &ei, sizeof ei);
170			edp++;
171			boot_params.eddbuf_entries++;
172		}
173
174		if (do_mbr && !read_mbr_sig(devno, &ei, mbrptr++))
175			boot_params.edd_mbr_sig_buf_entries = devno-0x80+1;
176	}
177
178	if (!be_quiet)
179		printf("ok\n");
180}
181
182#endif
183