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; -----------------------------------------------------------------------
;
; Copyright 1994-2009 H. Peter Anvin - All Rights Reserved
; Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, Inc., 53 Temple Place Ste 330,
; Bostom MA 02111-1307, USA; either version 2 of the License, or
; (at your option) any later version; incorporated herein by reference.
;
; -----------------------------------------------------------------------
;
; layout.inc
;
; Memory layout of segments
;
; Default to 16-bit code
bits 16
; Memory below 0800h is reserved for the BIOS and the MBR.
BSS_START equ 0800h
; Text starts at the load address of 07C00h.
TEXT_START equ 7C00h
;
; Stack layout
;
; PXELINUX: There are apparently some AMI BIOSes in the field which
; put their BEV stack somewhere below 7C00h (and therefore don't
; handle localboot properly), so avoid that immediate memory region.
; The range that is known to be bad is approximately 75E8..7C00; the
; lower bound is tight.
;
global STACK_LEN, STACK_TOP, STACK_BASE
STACK_LEN equ 4096
%if IS_PXELINUX
STACK_TOP equ 7000h
%else
STACK_TOP equ 7c00h
%endif
STACK_BASE equ STACK_TOP - STACK_LEN
; The secondary BSS section, above the text; we really wish we could
; just make it follow .bcopy32 or hang off the end,
; but it doesn't seem to work that way.
LATEBSS_START equ 0B800h
;
; The various sections and their relationship
;
; Use .earlybss for things that MUST be in low memory.
section .earlybss nobits
section .config write progbits align=4
section .replacestub exec write progbits align=16
section .gentextnr exec write nobits align=16
; Use .bss16 for things that doesn't have to be in low memory;
; .earlybss should be used for things that absolutely have
; to be below 0x7c00.
section .bss16 write nobits align=16
%if 0 ; IS_PXELINUX
; Warning here: RBFG build 22 randomly overwrites
; memory location [0x5680,0x576c), possibly more. It
; seems that it gets confused and screws up the
; pointer to its own internal packet buffer and starts
; writing a received ARP packet into low memory.
section .rbfg write nobits
RBFG_brainfuck: resb 2048 ; Bigger than an Ethernet packet...
%endif
section .init exec write progbits align=1
section .text16 exec write progbits align=1
section .textnr exec nowrite progbits align=1
section .bcopyxx exec write progbits align=16
section .data16 write progbits align=16
section .adv write nobits align=512
; .uibss contains bss data which is guaranteed to be
; safe to clobber during the loading of the image. This
; is because while loading the primary image we will clobber
; the spillover from the last fractional sector load.
section .uibss write nobits align=16
; Symbols from linker script
%macro SECINFO 1
extern __%1_start, __%1_lma, __%1_end
extern __%1_len, __%1_dwords
%endmacro
SECINFO bss16
SECINFO uibss
SECINFO config
SECINFO replacestub
SECINFO pm_code
SECINFO high_clear
SECINFO bss
extern free_high_memory
global _start
section .text16
;
; Segment assignments in the bottom 640K
; Keep the low-memory footprint as small as possible... overrun is a hard
; failure!
;
; 0000h - main code/data segment (and BIOS segment)
;
; This stuff really should come from the linker...
;
global xfer_buf_seg, core_xfer_buf
xfer_buf_seg equ 3000h
core_xfer_buf equ xfer_buf_seg << 4
serial_buf_size equ 4096 ; Should be a power of 2
;
; Contents of aux_seg
;
extern aux_seg ; Actual segment assigned by linker
struc aux
.fontbuf resb 8192
.serial resb serial_buf_size
alignb 4096 ; Align the next segment to 4K
endstruc
section .auxseg write nobits align=16
auxseg resb aux_size
;
; Bounce buffer for I/O to high mem
; Note: we keep all the segments page-aligned, even if that probably
; is somewhat excessive. Sector alignment is obligatory, however.
;
global cache_seg, core_cache_buf
cache_seg equ 4000h ; 64K area for metadata cache
core_cache_buf equ cache_seg << 4
real_mode_seg equ 5000h
pktbuf_seg equ cache_seg ; PXELINUX packet buffers
comboot_seg equ real_mode_seg ; COMBOOT image loading zone
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