/* -----------------------------------------------------------------------
*
*   Copyright 2007-2009 H. Peter Anvin - All Rights Reserved
*   Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
*
*   Permission is hereby granted, free of charge, to any person
*   obtaining a copy of this software and associated documentation
*   files (the "Software"), to deal in the Software without
*   restriction, including without limitation the rights to use,
*   copy, modify, merge, publish, distribute, sublicense, and/or
*   sell copies of the Software, and to permit persons to whom
*   the Software is furnished to do so, subject to the following
*   conditions:
*
*   The above copyright notice and this permission notice shall
*   be included in all copies or substantial portions of the Software.
*
*   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
*   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
*   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
*   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
*   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
*   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
*   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
*   OTHER DEALINGS IN THE SOFTWARE.
*
* ----------------------------------------------------------------------- */

#include <machine/asm.h>
#include <sys/bootblock.h>

#ifdef CTRL_80
       .macro ADJUST_DRIVE
       testb   $0x04, BIOS_kbdflags
       jz      1f
       movb    $0x80, %dl
1:
       .endm
#elif defined(FORCE_80)
       .macro ADJUST_DRIVE
       movb    $0x80, %dl
       .endm
#else
       .macro ADJUST_DRIVE
       .endm
#endif

       .code16
       .text

       .globl  bootsec
stack           = 0x7c00

/* Partition table header here */
phdr            = stack         /* Above the stack, overwritten by bootsect */
/* Partition table sector here */
/* To handle > 32K we need to play segment tricks... */
psec            = _phdr + 512

/* Where we put DS:SI */
dssi_out        = start + 0x1be

BIOS_kbdflags   = 0x417
BIOS_page       = 0x462

       /* gas/ld has issues with doing this as absolute addresses... */
       .section ".bootsec", "a", @nobits
       .globl  bootsec
bootsec:
       .space  512

       .text
       .globl  start
start:
       cli
       xorw    %ax, %ax
       movw    %ax, %ds
       movw    %ax, %ss
       movw    $stack, %sp
       movw    %sp, %si
       pushw   %es             /* 4(%bp) es:di -> $PnP header */
       pushw   %di             /* 2(%bp) */
       movw    %ax, %es
       sti
       cld

       /* Copy down to 0:0x600 */
       movw    $start, %di
       movw    $(512/2), %cx
       rep; movsw

       ljmpw   $0, $next
next:

       ADJUST_DRIVE
       pushw   %dx             /* 0(%bp) = %dl -> drive number */

       /* Check to see if we have EBIOS */
       pushw   %dx             /* drive number */
       movb    $0x41, %ah      /* %al == 0 already */
       movw    $0x55aa, %bx
       xorw    %cx, %cx
       xorb    %dh, %dh
       stc
       int     $0x13
       jc      1f
       cmpw    $0xaa55, %bx
       jne     1f
       shrw    %cx             /* Bit 0 = fixed disk subset */
       jnc     1f

       /* We have EBIOS; patch in the following code at
          read_sector_cbios: movb $0x42, %ah ;  jmp read_common */
       movl    $0xeb42b4+((read_common-read_sector_cbios-4) << 24), \
               (read_sector_cbios)

1:
       popw    %dx

       /* Get (C)HS geometry */
       movb    $0x08, %ah
       int     $0x13
       andw    $0x3f, %cx      /* Sector count */
       movw    %sp, %bp        /* %bp -> frame pointer: LEAVE UNCHANGED */
       pushw   %cx             /* -2(%bp) Save sectors on the stack */
       movzbw  %dh, %ax        /* dh = max head */
       incw    %ax             /* From 0-based max to count */
       mulw    %cx             /* Heads*sectors -> sectors per cylinder */

       /* Save sectors/cylinder on the stack */
       pushw   %dx             /* -4(%bp) High word */
       pushw   %ax             /* -6(%bp) Low word */

       /* Load partition table header */
       xorl    %eax,%eax
       cltd
       incw    %ax             /* %edx:%eax = 1 */
       movw    $phdr, %bx
       pushw   %bx             /* -8(%bp) phdr == bootsect */
       call    read_sector

       /* Number of partition sectors */
       /* We assume the partition table is 32K or less, and that
          the sector size is 512. */
       /* Note: phdr == 6(%bp) */
       movw    (80+6)(%bp),%cx         /* NumberOfPartitionEntries */
       movw    (84+6)(%bp),%ax         /* SizeOfPartitionEntry */
       pushw   %ax
       pushw   %cx
       mulw    %cx
       shrw    $9,%ax
       xchgw   %ax,%cx
       incw    %cx

       /* Starting LBA of partition array */
       movl    (72+6)(%bp),%eax
       movl    (76+6)(%bp),%edx

       pushw   %bx
get_ptab:
       call    read_sector
       call    inc64
       loop    get_ptab

       /* Find the boot partition */
       xorw    %si,%si                 /* Nothing found yet */
       popw    %di                     /* Partition table in memory */
       popw    %cx                     /* NumberOfPartitionEntries */
       popw    %ax                     /* SizeOfPartitionEntry */

find_part:
       /* If the PartitionTypeGUID is all zero, it's an empty slot */
       movl      (%di),%edx
       orl      4(%di),%edx
       orl      8(%di),%edx
       orl     12(%di),%edx
       jz      not_this
       testb   $0x04,48(%di)
       jz      not_this
       andw    %si,%si
       jnz     found_multiple
       movw    %di,%si
not_this:
       addw    %ax,%di
       loop    find_part

       andw    %si,%si
       jnz     found_part

missing_os:
       call    error
       .ascii  "Missing OS\r\n"

found_multiple:
       call    error
       .ascii  "Multiple active partitions\r\n"

found_part:
       xchgw   %ax,%cx         /* Set up %cx for rep movsb further down */

       movw    $dssi_out,%di
       pushw   %di

       /* 80 00 00 00 ee 00 00 00
          - bootable partition, type EFI (EE), no CHS information */
       xorl    %eax,%eax
       movb    $0x80,%al
       stosl
       movb    $0xed,%al
       stosl
       movl    32(%si),%eax
       movl    36(%si),%edx
       call    saturate_stosl          /* Partition start */

       movl    40(%si),%eax
       movl    44(%si),%edx
       subl    32(%si),%eax
       sbbl    36(%si),%edx
       call    inc64
       call    saturate_stosl          /* Partition length */

       movzwl  %cx,%eax                /* Length of GPT entry */
       stosl

       rep; movsb                      /* GPT entry follows MBR entry */
       popw    %si

/*
* boot: invoke the actual bootstrap. %ds:%si points to the
* partition information in memory.  The top word on the stack
* is phdr == 0x7c00 == the address of the boot sector.
*/
boot:
       movl    (32+20)(%si),%eax
       movl    (36+20)(%si),%edx
       popw    %bx
       call    read_sector
       cmpw    $0xaa55, -2(%bx)
       jne     missing_os      /* Not a valid boot sector */
       movw    %bp, %sp        /* driveno == bootsec-6 */
       popw    %dx             /* dl -> drive number */
       popw    %di             /* es:di -> $PnP vector */
       popw    %es
       movl    $0x54504721,%eax /* !GPT magic number */
       cli
       jmpw    *%sp            /* %sp == bootsec */

/*
* Store the value in %eax to %di iff %edx == 0, otherwise store -1.
* Returns the value that was actually written in %eax.
*/
saturate_stosl:
       andl    %edx,%edx
       jz 1f
       orl     $-1,%eax
1:      stosl
       ret

/*
* Increment %edx:%eax
*/
inc64:
       addl    $1,%eax
       adcl    $0,%edx
       ret

/*
* read_sector: read a single sector pointed to by %edx:%eax to
* %es:%bx.  CF is set on error.  All registers saved.
*/
read_sector:
       pushal
       pushl   %edx    /* MSW of LBA */
       pushl   %eax    /* LSW of LBA */
       pushw   %es     /* Buffer segment */
       pushw   %bx     /* Buffer offset */
       pushw   $1      /* Sector count */
       pushw   $16     /* Size of packet */
       movw    %sp, %si

       /* This chunk is skipped if we have ebios */
       /* Do not clobber %es:%bx or %edx:%eax before this chunk! */
read_sector_cbios:
       divl    -6(%bp) /* secpercyl */
       shlb    $6, %ah
       movb    %ah, %cl
       movb    %al, %ch
       xchgw   %dx, %ax
       divb    -2(%bp) /* sectors */
       movb    %al, %dh
       orb     %ah, %cl
       incw    %cx     /* Sectors are 1-based */
       movw    $0x0201, %ax

read_common:
       movb    (%bp), %dl /* driveno */
       int     $0x13
       leaw    16(%si), %sp    /* Drop DAPA */
       popal
       jc      disk_error
       addb    $2, %bh         /* bx += 512: point to the next buffer */
       ret

disk_error:
       call    error
       .ascii  "Disk error on boot\r\n"

/*
* Print error messages.  This is invoked with "call", with the
* error message at the return address.
*/
error:
       popw    %si
2:
       lodsb
       movb    $0x0e, %ah
       movb    (BIOS_page), %bh
       movb    $0x07, %bl
       int     $0x10           /* May destroy %bp */
       cmpb    $10, %al        /* Newline? */
       jne     2b

       int     $0x18           /* Boot failure */
die:
       hlt
       jmp     die

mbr_space = end - .
       . = MBR_DSN_OFFSET
end:

You are viewing proxied material from ftp.icm.edu.pl. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.