LXR linux/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 * arch/i386/boot/edd.c
  13 *
  14 * Get EDD BIOS disk information
  15 */
  16
  17#include "boot.h"
  18#include <linux/edd.h>
  19
  20#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
  21
  22/*
  23 * Read the MBR (first sector) from a specific device.
  24 */
  25static int read_mbr(u8 devno, void *buf)
  26{
  27        u16 ax, bx, cx, dx;
  28
  29        ax = 0x0201;            /* Legacy Read, one sector */
  30        cx = 0x0001;            /* Sector 0-0-1 */
  31        dx = devno;
  32        bx = (size_t)buf;
  33        asm volatile("pushfl; stc; int $0x13; setc %%al; popfl"
  34                     : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx)
  35                     : : "esi", "edi", "memory");
  36
  37        return -(u8)ax;         /* 0 or -1 */
  38}
  39
  40static 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
  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        if (read_mbr(devno, mbrbuf_ptr))
  64                return -1;
  65
  66        *mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
  67        return 0;
  68}
  69
  70static int get_edd_info(u8 devno, struct edd_info *ei)
  71{
  72        u16 ax, bx, cx, dx, di;
  73
  74        memset(ei, 0, sizeof *ei);
  75
  76        /* Check Extensions Present */
  77
  78        ax = 0x4100;
  79        bx = EDDMAGIC1;
  80        dx = devno;
  81        asm("pushfl; stc; int $0x13; setc %%al; popfl"
  82            : "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx)
  83            : : "esi", "edi");
  84
  85        if ((u8)ax)
  86                return -1;      /* No extended information */
  87
  88        if (bx != EDDMAGIC2)
  89                return -1;
  90
  91        ei->device  = devno;
  92        ei->version = ax >> 8;  /* EDD version number */
  93        ei->interface_support = cx; /* EDD functionality subsets */
  94
  95        /* Extended Get Device Parameters */
  96
  97        ei->params.length = sizeof(ei->params);
  98        ax = 0x4800;
  99        dx = devno;
 100        asm("pushfl; int $0x13; popfl"
 101            : "+a" (ax), "+d" (dx), "=m" (ei->params)
 102            : "S" (&ei->params)
 103            : "ebx", "ecx", "edi");
 104
 105        /* Get legacy CHS parameters */
 106
 107        /* Ralf Brown recommends setting ES:DI to 0:0 */
 108        ax = 0x0800;
 109        dx = devno;
 110        di = 0;
 111        asm("pushw %%es; "
 112            "movw %%di,%%es; "
 113            "pushfl; stc; int $0x13; setc %%al; popfl; "
 114            "popw %%es"
 115            : "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di)
 116            : : "esi");
 117
 118        if ((u8)ax == 0) {
 119                ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2);
 120                ei->legacy_max_head = dx >> 8;
 121                ei->legacy_sectors_per_track = cx & 0x3f;
 122        }
 123
 124        return 0;
 125}
 126
 127void query_edd(void)
 128{
 129        char eddarg[8];
 130        int do_mbr = 1;
 131        int do_edd = 1;
 132        int be_quiet;
 133        int devno;
 134        struct edd_info ei, *edp;
 135        u32 *mbrptr;
 136
 137        if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) {
 138                if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip"))
 139                        do_mbr = 0;
 140                else if (!strcmp(eddarg, "off"))
 141                        do_edd = 0;
 142        }
 143
 144        be_quiet = cmdline_find_option_bool("quiet");
 145
 146        edp    = boot_params.eddbuf;
 147        mbrptr = boot_params.edd_mbr_sig_buffer;
 148
 149        if (!do_edd)
 150                return;
 151
 152        /* Bugs in OnBoard or AddOnCards Bios may hang the EDD probe,
 153         * so give a hint if this happens.
 154         */
 155
 156        if (!be_quiet)
 157                printf("Probing EDD (edd=off to disable)... ");
 158
 159        for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {
 160                /*
 161                 * Scan the BIOS-supported hard disks and query EDD
 162                 * information...
 163                 */
 164                get_edd_info(devno, &ei);
 165
 166                if (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, mbrptr++))
 173                        boot_params.edd_mbr_sig_buf_entries = devno-0x80+1;
 174        }
 175
 176        if (!be_quiet)
 177                printf("ok\n");
 178}
 179
 180#endif
 181