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  *
   6  *   This file is part of the Linux kernel, and is made available under
   7  *   the terms of the GNU General Public License version 2.
   8  *
   9  * ----------------------------------------------------------------------- */
  10
  11 /*
  12  * Get EDD BIOS disk information
  13  */
  14
  15 #include "boot.h"
  16 #include <linux/edd.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         u16 ax, bx, cx, dx;
  26
  27         ax = 0x0201;            /* Legacy Read, one sector */
  28         cx = 0x0001;            /* Sector 0-0-1 */
  29         dx = devno;
  30         bx = (size_t)buf;
  31         asm volatile("pushfl; stc; int $0x13; setc %%al; popfl"
  32                      : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx)
  33                      : : "esi", "edi", "memory");
  34
  35         return -(u8)ax;         /* 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
  45         sector_size = ei->params.bytes_per_sector;
  46         if (!sector_size)
  47                 sector_size = 512; /* Best available guess */
  48
  49         /* Produce a naturally aligned buffer on the heap */
  50         buf_base = (ds() << 4) + (u32)&_end;
  51         mbr_base = (buf_base+sector_size-1) & ~(sector_size-1);
  52         mbrbuf_ptr = _end + (mbr_base-buf_base);
  53         mbrbuf_end = mbrbuf_ptr + sector_size;
  54
  55         /* Make sure we actually have space on the heap... */
  56         if (!(boot_params.hdr.loadflags & CAN_USE_HEAP))
  57                 return -1;
  58         if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
  59                 return -1;
  60
  61         if (read_mbr(devno, mbrbuf_ptr))
  62                 return -1;
  63
  64         *mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
  65         return 0;
  66 }
  67
  68 static int get_edd_info(u8 devno, struct edd_info *ei)
  69 {
  70         u16 ax, bx, cx, dx, di;
  71
  72         memset(ei, 0, sizeof *ei);
  73
  74         /* Check Extensions Present */
  75
  76         ax = 0x4100;
  77         bx = EDDMAGIC1;
  78         dx = devno;
  79         asm("pushfl; stc; int $0x13; setc %%al; popfl"
  80             : "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx)
  81             : : "esi", "edi");
  82
  83         if ((u8)ax)
  84                 return -1;      /* No extended information */
  85
  86         if (bx != EDDMAGIC2)
  87                 return -1;
  88
  89         ei->device  = devno;
  90         ei->version = ax >> 8;  /* EDD version number */
  91         ei->interface_support = cx; /* EDD functionality subsets */
  92
  93         /* Extended Get Device Parameters */
  94
  95         ei->params.length = sizeof(ei->params);
  96         ax = 0x4800;
  97         dx = devno;
  98         asm("pushfl; int $0x13; popfl"
  99             : "+a" (ax), "+d" (dx), "=m" (ei->params)
 100             : "S" (&ei->params)
 101             : "ebx", "ecx", "edi");
 102
 103         /* Get legacy CHS parameters */
 104
 105         /* Ralf Brown recommends setting ES:DI to 0:0 */
 106         ax = 0x0800;
 107         dx = devno;
 108         di = 0;
 109         asm("pushw %%es; "
 110             "movw %%di,%%es; "
 111             "pushfl; stc; int $0x13; setc %%al; popfl; "
 112             "popw %%es"
 113             : "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di)
 114             : : "esi");
 115
 116         if ((u8)ax == 0) {
 117                 ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2);
 118                 ei->legacy_max_head = dx >> 8;
 119                 ei->legacy_sectors_per_track = cx & 0x3f;
 120         }
 121
 122         return 0;
 123 }
 124
 125 void query_edd(void)
 126 {
 127         char eddarg[8];
 128         int do_mbr = 1;
 129 #ifdef CONFIG_EDD_OFF
 130         int do_edd = 0;
 131 #else
 132         int do_edd = 1;
 133 #endif
 134         int be_quiet;
 135         int devno;
 136         struct edd_info ei, *edp;
 137         u32 *mbrptr;
 138
 139         if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) {
 140                 if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) {
 141                         do_edd = 1;
 142                         do_mbr = 0;
 143                 }
 144                 else if (!strcmp(eddarg, "off"))
 145                         do_edd = 0;
 146                 else if (!strcmp(eddarg, "on"))
 147                         do_edd = 1;
 148         }
 149
 150         be_quiet = cmdline_find_option_bool("quiet");
 151
 152         edp    = boot_params.eddbuf;
 153         mbrptr = boot_params.edd_mbr_sig_buffer;
 154
 155         if (!do_edd)
 156                 return;
 157
 158         /* Bugs in OnBoard or AddOnCards Bios may hang the EDD probe,
 159          * so give a hint if this happens.
 160          */
 161
 162         if (!be_quiet)
 163                 printf("Probing EDD (edd=off to disable)... ");
 164
 165         for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {
 166                 /*
 167                  * Scan the BIOS-supported hard disks and query EDD
 168                  * information...
 169                  */
 170                 if (!get_edd_info(devno, &ei)
 171                     && boot_params.eddbuf_entries < EDDMAXNR) {
 172                         memcpy(edp, &ei, sizeof ei);
 173                         edp++;
 174                         boot_params.eddbuf_entries++;
 175                 }
 176
 177                 if (do_mbr && !read_mbr_sig(devno, &ei, mbrptr++))
 178                         boot_params.edd_mbr_sig_buf_entries = devno-0x80+1;
 179         }
 180
 181         if (!be_quiet)
 182                 printf("ok\n");
 183 }
 184
 185 #endif