linux/arch/x86/boot/edd.c
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   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 */
  23static 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
  38static 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
  68static 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
 125void 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
 186