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