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