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Annotation of qemu/roms/ipxe/src/arch/i386/prefix/exeprefix.S, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (C) 2011 Michael Brown <[email protected]>.
        !             3:  *
        !             4:  * This program is free software; you can redistribute it and/or
        !             5:  * modify it under the terms of the GNU General Public License as
        !             6:  * published by the Free Software Foundation; either version 2 of the
        !             7:  * License, or any later version.
        !             8:  *
        !             9:  * This program is distributed in the hope that it will be useful, but
        !            10:  * WITHOUT ANY WARRANTY; without even the implied warranty of
        !            11:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        !            12:  * General Public License for more details.
        !            13:  *
        !            14:  * You should have received a copy of the GNU General Public License
        !            15:  * along with this program; if not, write to the Free Software
        !            16:  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
        !            17:  *
        !            18:  */
        !            19: 
        !            20: FILE_LICENCE ( GPL2_OR_LATER )
        !            21: 
        !            22: /* Initial temporary stack size */
        !            23: #define EXE_STACK_SIZE 0x400
        !            24: 
        !            25: /* Temporary decompression area (avoid DOS high memory area) */
        !            26: #define EXE_DECOMPRESS_ADDRESS 0x110000
        !            27: 
        !            28: /* Fields within the Program Segment Prefix */
        !            29: #define PSP_CMDLINE_LEN 0x80
        !            30: #define PSP_CMDLINE_START 0x81
        !            31: 
        !            32:        .text
        !            33:        .arch i386
        !            34:        .org 0
        !            35:        .code16
        !            36:        .section ".prefix", "awx", @progbits
        !            37: 
        !            38: signature:
        !            39:        /* "MZ" signature */
        !            40:        .ascii  "MZ"
        !            41: 
        !            42: last_block:
        !            43:        /* Number of bytes in last block that are really used */
        !            44:        .word   0
        !            45: 
        !            46: blocks:
        !            47:        /* Number of 512-byte blocks */
        !            48:        .word   0
        !            49:        .section ".zinfo.fixup", "a", @progbits /* Compressor fixups */
        !            50:        .ascii  "ADDW"
        !            51:        .long   blocks
        !            52:        .long   512
        !            53:        .long   0
        !            54:        .previous
        !            55: 
        !            56: num_reloc:
        !            57:        /* Number of relocation entries stored after the header */
        !            58:        .word   0
        !            59: 
        !            60: header_pgh:
        !            61:        /* Number of paragraphs in the header */
        !            62:        .word   ( ( _exe_start - signature ) / 16 )
        !            63: 
        !            64: min_bss_pgh:
        !            65:        /* Minimum number of paragraphs of additional (BSS) memory */
        !            66:        .word   ( EXE_STACK_SIZE / 16 )
        !            67: 
        !            68: max_bss_pgh:
        !            69:        /* Maximum number of paragraphs of additional (BSS) memory */
        !            70:        .word   ( EXE_STACK_SIZE / 16 )
        !            71: 
        !            72: init_ss:
        !            73:        /* Initial stack segment (relative to start of executable) */
        !            74:        .word   -( ( _exe_start - signature ) / 16 )
        !            75:        .section ".zinfo.fixup", "a", @progbits /* Compressor fixups */
        !            76:        .ascii  "ADDW"
        !            77:        .long   init_ss
        !            78:        .long   16
        !            79:        .long   0
        !            80:        .previous
        !            81: 
        !            82: init_sp:
        !            83:        /* Initial stack pointer */
        !            84:        .word   EXE_STACK_SIZE
        !            85: 
        !            86: checksum:
        !            87:        /* Checksum (ignored) */
        !            88:        .word   0
        !            89: 
        !            90: init_ip:
        !            91:        /* Initial instruction pointer */
        !            92:        .word   _exe_start
        !            93: 
        !            94: init_cs:
        !            95:        /* Initial code segment (relative to start of executable) */
        !            96:        .word   -( ( _exe_start - signature ) / 16 )
        !            97: 
        !            98: reloc_table:
        !            99:        /* Relocation table offset */
        !           100:        .word   0
        !           101: 
        !           102: overlay:
        !           103:        /* Overlay number */
        !           104:        .word   0
        !           105: 
        !           106:        .align 16, 0
        !           107: 
        !           108:        .globl  _exe_start
        !           109: _exe_start:
        !           110:        /* Install iPXE.  Use a fixed temporary decompression area to
        !           111:         * avoid trashing the DOS high memory area.
        !           112:         */
        !           113:        call    alloc_basemem
        !           114:        xorl    %esi, %esi
        !           115:        movl    $EXE_DECOMPRESS_ADDRESS, %edi
        !           116:        clc
        !           117:        call    install_prealloc
        !           118: 
        !           119:        /* Set up real-mode stack */
        !           120:        movw    %bx, %ss
        !           121:        movw    $_estack16, %sp
        !           122: 
        !           123:        /* Jump to .text16 segment */
        !           124:        pushw   %ax
        !           125:        pushw   $1f
        !           126:        lret
        !           127:        .section ".text16", "awx", @progbits
        !           128: 1:
        !           129:        /* Terminate command line with a NUL */
        !           130:        movzbw  PSP_CMDLINE_LEN, %si
        !           131:        movb    $0, PSP_CMDLINE_START(%si)
        !           132: 
        !           133:        /* Calculate command line physical address */
        !           134:        xorl    %esi, %esi
        !           135:        movw    %ds, %si
        !           136:        shll    $4, %esi
        !           137:        addl    $PSP_CMDLINE_START, %esi
        !           138: 
        !           139:        /* Set up %ds for access to .data16 */
        !           140:        movw    %bx, %ds
        !           141: 
        !           142:        /* Record command line address */
        !           143:        movl    %esi, cmdline_phys
        !           144: 
        !           145:        /* Run iPXE */
        !           146:        pushl   $main
        !           147:        pushw   %cs
        !           148:        call    prot_call
        !           149:        popl    %ecx /* discard */
        !           150: 
        !           151:        /* Uninstall iPXE */
        !           152:        call    uninstall
        !           153: 
        !           154:        /* Exit back to DOS.  This is very unlikely to work */
        !           155:        movw    $0x4c00, %ax
        !           156:        int     $0x21

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