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 *   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 */
  24static 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
  39static 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
  74static 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
 121void 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
 182