arch/x86/boot/edd.c

   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;
 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