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#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 */
  25static 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
  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        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
  75static 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
 122void 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
 183