Linux Kernel  3.7.1
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edd.c
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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  */
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 
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 
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 
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;
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)
168  memcpy(edp, &ei, sizeof ei);
169  edp++;
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