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 #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  */
  25 static 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
  40 static 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
  75 static 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
 122 void 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