1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* -*- linux-c -*- ------------------------------------------------------- * |
3 | * |
4 | * Copyright (C) 1991, 1992 Linus Torvalds |
5 | * Copyright 2007 rPath, Inc. - All Rights Reserved |
6 | * Copyright 2009 Intel Corporation; author H. Peter Anvin |
7 | * |
8 | * ----------------------------------------------------------------------- */ |
9 | |
10 | /* |
11 | * Get EDD BIOS disk information |
12 | */ |
13 | |
14 | #include "boot.h" |
15 | #include <linux/edd.h> |
16 | #include "string.h" |
17 | |
18 | #if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE) |
19 | |
20 | /* |
21 | * Read the MBR (first sector) from a specific device. |
22 | */ |
23 | static int read_mbr(u8 devno, void *buf) |
24 | { |
25 | struct biosregs ireg, oreg; |
26 | |
27 | initregs(regs: &ireg); |
28 | ireg.ax = 0x0201; /* Legacy Read, one sector */ |
29 | ireg.cx = 0x0001; /* Sector 0-0-1 */ |
30 | ireg.dl = devno; |
31 | ireg.bx = (size_t)buf; |
32 | |
33 | intcall(int_no: 0x13, ireg: &ireg, oreg: &oreg); |
34 | |
35 | return -(oreg.eflags & X86_EFLAGS_CF); /* 0 or -1 */ |
36 | } |
37 | |
38 | static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig) |
39 | { |
40 | int sector_size; |
41 | char *mbrbuf_ptr, *mbrbuf_end; |
42 | u32 buf_base, mbr_base; |
43 | extern char _end[]; |
44 | u16 mbr_magic; |
45 | |
46 | sector_size = ei->params.bytes_per_sector; |
47 | if (!sector_size) |
48 | sector_size = 512; /* Best available guess */ |
49 | |
50 | /* Produce a naturally aligned buffer on the heap */ |
51 | buf_base = (ds() << 4) + (u32)&_end; |
52 | mbr_base = (buf_base+sector_size-1) & ~(sector_size-1); |
53 | mbrbuf_ptr = _end + (mbr_base-buf_base); |
54 | mbrbuf_end = mbrbuf_ptr + sector_size; |
55 | |
56 | /* Make sure we actually have space on the heap... */ |
57 | if (!(boot_params.hdr.loadflags & CAN_USE_HEAP)) |
58 | return -1; |
59 | if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr) |
60 | return -1; |
61 | |
62 | memset(mbrbuf_ptr, 0, sector_size); |
63 | if (read_mbr(devno, buf: mbrbuf_ptr)) |
64 | return -1; |
65 | |
66 | *mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET]; |
67 | mbr_magic = *(u16 *)&mbrbuf_ptr[510]; |
68 | |
69 | /* check for valid MBR magic */ |
70 | return mbr_magic == 0xAA55 ? 0 : -1; |
71 | } |
72 | |
73 | static int get_edd_info(u8 devno, struct edd_info *ei) |
74 | { |
75 | struct biosregs ireg, oreg; |
76 | |
77 | memset(ei, 0, sizeof(*ei)); |
78 | |
79 | /* Check Extensions Present */ |
80 | |
81 | initregs(regs: &ireg); |
82 | ireg.ah = 0x41; |
83 | ireg.bx = EDDMAGIC1; |
84 | ireg.dl = devno; |
85 | intcall(int_no: 0x13, ireg: &ireg, oreg: &oreg); |
86 | |
87 | if (oreg.eflags & X86_EFLAGS_CF) |
88 | return -1; /* No extended information */ |
89 | |
90 | if (oreg.bx != EDDMAGIC2) |
91 | return -1; |
92 | |
93 | ei->device = devno; |
94 | ei->version = oreg.ah; /* EDD version number */ |
95 | ei->interface_support = oreg.cx; /* EDD functionality subsets */ |
96 | |
97 | /* Extended Get Device Parameters */ |
98 | |
99 | ei->params.length = sizeof(ei->params); |
100 | ireg.ah = 0x48; |
101 | ireg.si = (size_t)&ei->params; |
102 | intcall(int_no: 0x13, ireg: &ireg, oreg: &oreg); |
103 | |
104 | /* Get legacy CHS parameters */ |
105 | |
106 | /* Ralf Brown recommends setting ES:DI to 0:0 */ |
107 | ireg.ah = 0x08; |
108 | ireg.es = 0; |
109 | intcall(int_no: 0x13, ireg: &ireg, oreg: &oreg); |
110 | |
111 | if (!(oreg.eflags & X86_EFLAGS_CF)) { |
112 | ei->legacy_max_cylinder = oreg.ch + ((oreg.cl & 0xc0) << 2); |
113 | ei->legacy_max_head = oreg.dh; |
114 | ei->legacy_sectors_per_track = oreg.cl & 0x3f; |
115 | } |
116 | |
117 | return 0; |
118 | } |
119 | |
120 | void query_edd(void) |
121 | { |
122 | char eddarg[8]; |
123 | int do_mbr = 1; |
124 | #ifdef CONFIG_EDD_OFF |
125 | int do_edd = 0; |
126 | #else |
127 | int do_edd = 1; |
128 | #endif |
129 | int be_quiet; |
130 | int devno; |
131 | struct edd_info ei, *edp; |
132 | u32 *mbrptr; |
133 | |
134 | if (cmdline_find_option(option: "edd" , buffer: eddarg, bufsize: sizeof(eddarg)) > 0) { |
135 | if (!strcmp(str1: eddarg, str2: "skipmbr" ) || !strcmp(str1: eddarg, str2: "skip" )) { |
136 | do_edd = 1; |
137 | do_mbr = 0; |
138 | } |
139 | else if (!strcmp(str1: eddarg, str2: "off" )) |
140 | do_edd = 0; |
141 | else if (!strcmp(str1: eddarg, str2: "on" )) |
142 | do_edd = 1; |
143 | } |
144 | |
145 | be_quiet = cmdline_find_option_bool(option: "quiet" ); |
146 | |
147 | edp = boot_params.eddbuf; |
148 | mbrptr = boot_params.edd_mbr_sig_buffer; |
149 | |
150 | if (!do_edd) |
151 | return; |
152 | |
153 | /* Bugs in OnBoard or AddOnCards Bios may hang the EDD probe, |
154 | * so give a hint if this happens. |
155 | */ |
156 | |
157 | if (!be_quiet) |
158 | printf(fmt: "Probing EDD (edd=off to disable)... " ); |
159 | |
160 | for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) { |
161 | /* |
162 | * Scan the BIOS-supported hard disks and query EDD |
163 | * information... |
164 | */ |
165 | if (!get_edd_info(devno, ei: &ei) |
166 | && boot_params.eddbuf_entries < EDDMAXNR) { |
167 | memcpy(edp, &ei, sizeof(ei)); |
168 | edp++; |
169 | boot_params.eddbuf_entries++; |
170 | } |
171 | |
172 | if (do_mbr && !read_mbr_sig(devno, ei: &ei, mbrsig: mbrptr++)) |
173 | boot_params.edd_mbr_sig_buf_entries = devno-0x80+1; |
174 | } |
175 | |
176 | if (!be_quiet) |
177 | printf(fmt: "ok\n" ); |
178 | } |
179 | |
180 | #endif |
181 | |