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    revision 1132 by niro, Sat Sep 1 22:45:15 2007 UTC revision 1133 by niro, Thu Aug 19 09:50:43 2010 UTC
    # Line 1  Line 1 
     ; $Id: layout.inc,v 1.1 2007-09-01 22:44:05 niro Exp $  
    1  ; -----------------------------------------------------------------------  ; -----------------------------------------------------------------------
    2  ;    ;
    3  ;   Copyright 1994-2004 H. Peter Anvin - All Rights Reserved  ;   Copyright 1994-2009 H. Peter Anvin - All Rights Reserved
    4    ;   Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
    5  ;  ;
    6  ;   This program is free software; you can redistribute it and/or modify  ;   This program is free software; you can redistribute it and/or modify
    7  ;   it under the terms of the GNU General Public License as published by  ;   it under the terms of the GNU General Public License as published by
    # Line 17  Line 17 
    17  ; Memory layout of segments  ; Memory layout of segments
    18  ;  ;
    19    
    20     ; Default to 16-bit code
    21     bits 16
    22    
    23  ; Memory below 0800h is reserved for the BIOS and the MBR.  ; Memory below 0800h is reserved for the BIOS and the MBR.
    24  BSS_START equ 0800h  BSS_START equ 0800h
    # Line 24  BSS_START equ 0800h Line 26  BSS_START equ 0800h
    26  ; Text starts at the load address of 07C00h.  ; Text starts at the load address of 07C00h.
    27  TEXT_START equ 7C00h  TEXT_START equ 7C00h
    28    
    29    ;
    30    ; Stack layout
    31    ;
    32    ; PXELINUX: There are apparently some AMI BIOSes in the field which
    33    ; put their BEV stack somewhere below 7C00h (and therefore don't
    34    ; handle localboot properly), so avoid that immediate memory region.
    35    ; The range that is known to be bad is approximately 75E8..7C00; the
    36    ; lower bound is tight.
    37    ;
    38     global STACK_LEN, STACK_TOP, STACK_BASE
    39    STACK_LEN equ 4096
    40    %if IS_PXELINUX
    41    STACK_TOP equ 7000h
    42    %else
    43    STACK_TOP equ 7c00h
    44    %endif
    45    STACK_BASE equ STACK_TOP - STACK_LEN
    46    
    47  ; The secondary BSS section, above the text; we really wish we could  ; The secondary BSS section, above the text; we really wish we could
    48  ; just make it follow .bcopy32 or hang off the end,  ; just make it follow .bcopy32 or hang off the end,
    49  ; but it doesn't seem to work that way.  ; but it doesn't seem to work that way.
    50  LATEBSS_START equ 0B000h  LATEBSS_START equ 0B800h
       
     ; Reserve memory for the stack.  This causes checkov to abort the  
     ; compile if we violate this space.  
     STACK_SIZE equ 4096  
     STACK_START equ TEXT_START-STACK_SIZE  
    51    
    52  %ifdef MAP  ;
    53   [map all MAP]  ; The various sections and their relationship
    54    ;
    55     ; Use .earlybss for things that MUST be in low memory.
    56     section .earlybss nobits
    57     section .config write progbits align=4
    58     section .replacestub exec write progbits align=16
    59    
    60     ; Use .bss for things that doesn't have to be in low memory;
    61     ; with .bss1 and .bss2 to offload.  .earlybss should be used
    62     ; for things that absolutely have to be below 0x7c00.
    63     section .bss write nobits align=16
    64    
    65    %if 0 ; IS_PXELINUX
    66     ; Warning here: RBFG build 22 randomly overwrites
    67     ; memory location [0x5680,0x576c), possibly more.  It
    68     ; seems that it gets confused and screws up the
    69     ; pointer to its own internal packet buffer and starts
    70     ; writing a received ARP packet into low memory.
    71     section .rbfg write nobits
    72    RBFG_brainfuck: resb 2048 ; Bigger than an Ethernet packet...
    73  %endif  %endif
    74    
    75     section .bss2 write nobits align=16
    76    
    77     section .text exec write progbits align=16
    78     section .bcopyxx exec write progbits align=16
    79     section .data write progbits align=16
    80    
    81     section .adv write nobits align=512
    82    
    83     ; .uibss contains bss data which is guaranteed to be
    84     ; safe to clobber during the loading of the image.  This
    85     ; is because while loading the primary image we will clobber
    86     ; the spillover from the last fractional sector load.
    87     section .uibss write nobits align=16
    88    
    89     ; Normal bss...
    90     section .bss1 write nobits align=16
    91    
    92     ; Symbols from linker script
    93    %macro SECINFO 1
    94     extern __%1_start, __%1_lma, __%1_end
    95     extern __%1_len, __%1_dwords
    96    %endmacro
    97     SECINFO config
    98     SECINFO replacestub
    99    
    100     global _start
    101    
    102     section .text
    103    
    104  ;  ;
    105  ; The various sections and their relationship  ; Segment assignments in the bottom 640K
    106    ; Keep the low-memory footprint as small as possible... overrun is a hard
    107    ; failure!
    108    ;
    109    ; 0000h - main code/data segment (and BIOS segment)
    110    
    111    xfer_buf_seg equ 1000h
    112    aux_seg equ 2000h
    113    
    114    serial_buf_size equ 4096 ; Should be a power of 2
    115    
    116    ;
    117    ; Contents of aux_seg
    118  ;  ;
    119   org TEXT_START   struc aux
    120    .fontbuf resb 8192
    121    .serial resb serial_buf_size
    122    
    123   ; NASM BUG: refers to hacks to handle NASM 0.98.38 bugs; might need   alignb 4096 ; Align the next segment to 4K
    124   ; conditional compilation   endstruc
    125    
    126   section .earlybss nobits start=BSS_START  aux_seg_end equ aux_seg + (aux_size >> 4)
    127   section .bcopy32  align=4 valign=16 follows=.data vfollows=.earlybss  
    128   ; NASM BUG: follows= here should be vfollows=  ;
    129   section .bss      nobits align=256 follows=.bcopy32  ; Bounce buffer for I/O to high mem
    130    ; Note: we keep all the segments page-aligned, even if that probably
    131   section .text  start=TEXT_START  ; is somewhat excessive.  Sector alignment is obligatory, however.
    132   ; NASM BUG: follows=.text not accepted here  ;
    133   section .data  align=16 ; follows=.text  
    134    %if IS_ISOLINUX
    135   ; NASM BUG: We would like to do follows=.bcopy32  ; ISOLINUX doesn't have a block cache yet
    136   section .latebss  nobits align=16 start=LATEBSS_START  real_mode_seg equ aux_seg_end
    137    %else
    138   ; Reserve space for stack  cache_seg equ aux_seg_end ; 64K area for metadata cache
    139   section .stack  nobits align=16 start=STACK_START  real_mode_seg equ cache_seg + 1000h
    140  Stack resb STACK_SIZE  
    141    pktbuf_seg equ cache_seg ; PXELINUX packet buffers
    142    %endif
    143    
    144    comboot_seg equ real_mode_seg ; COMBOOT image loading zone
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