232 lines
5.6 KiB
Plaintext
232 lines
5.6 KiB
Plaintext
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==========================================
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$Id: README,v 1.1 2002/11/25 02:07:53 rminnich Exp $
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==========================================
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ADLO
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A project to combine LinuxBIOS and BOCHS BIOS to add support
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for booting legacy applications, such as Microsoft Windows.
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==========================================
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Boot Overvew:
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ADLO requires an boot loader with ELF support.
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In our case it is either LinuxBIOS or EtherBOOT.
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Sample execution paths:
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LinuxBIOS -> ADLO -> LILO -> LINUX
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LinuxBIOS -> EtherBOOT -> ADLO -> LILO -> LINUX
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Then it can start any real mode application.
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In our case it could be LILO or GRUB, but
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choices are not limited to this.
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==========================================
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ADLO overview:
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-Elf header
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-mainteance routines
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-bochs bios
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-vga bios
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------------------------------------------
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Elf header
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hand crafted binary. Currently there are 3 diff binaries
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for three different sizes of payload (65kb,113kb,129kb).
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they are catted at beginning of file
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------------------------------------------
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mainteance routines
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this is the loader.s file which gets compiled into loader.o binary
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it is catted 2nd right after elf header and it is where
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control is being transfered when the elf is executed.
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it consist of :
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-tuneups:
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select device to boot
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set memory for Int15/EAX=E820
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enable LBA
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copy LinuxBIOS table [TODO]
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-shadow :
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enable/write/read
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-copy:
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bochs @ 0xF00000
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video bios (binary only) @ 0xC00000
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-switch
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from Real to Protected Mode
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-jump
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jmp to the bios at 0xFFFF:0x0000
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we must have bios payload always at 1kb
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offset from start of ELF payload so loader.o
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must be always 1024 bytes.
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------------------------------------------
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BOCHS BIOS
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we have taken the boch's project and just extracted
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its bios from it only. it took us (so far) only
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minor modifications in order to make it work.
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basically it is the following directory in the
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bochs sources
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bochs-cvs/bochs/bios
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of all files there the rombios.c is the key file.
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Most of the times our patches are against current
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version of the rombios.c file. We try to feed back
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the patches to bochs maintainers so that's possible
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to use the bochs bios as is.
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the boch's related stuff are in bochs subdirectory.
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building boch's bios is as simple as
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cd bochs/bochs-cvs/bochs/bios
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make
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the resulting file rombios.bin is our bios image.
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-----
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At present time, it is recommended to use
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dev86-0.16.3 + my patch in order to compile
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bochs' bios. The dev86 package can be found
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at:
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http://www.cix.co.uk/~mayday/
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prepatched sources at:
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http://www.missl.cs.umd.edu/~adam/dev86-0.16.3-MSR.tgz
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------------------------------------------
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Video BIOS
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Video BIOS we use is binary only, so far.
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At the present time we are using the original
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Video BIOS as supplied from the system.
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To get the image simply type:
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make makevideobios
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The right thing will happen. For refernece the
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magic line in the Makefile is:
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videobios:
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dd if=/proc/kcore \
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of=./video.bios.bin \
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bs=1 count=65536 skip=790528
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---------------
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We assume it is located at 0xC00000-0xE00000
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and we use 'dd and /proc/kcore to extract it
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(obviously it works as root only).
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Obviously it needs to be done with original
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(as shipped by manufactuer bios) so it should
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be done as the first step of the ADLO setup.
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---------------
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The /proc/kcore is in ELF format (linux kernel
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2.4.x and later) so if we want to get accurate
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image of ram we must skip the ELF header.
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The magic command is :
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readelf -a /proc/kcore
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Program Headers:
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Type Offset VirtAddr PhysAddr FileSiz MemSiz
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NOTE 0x0007d4 0x00000000 0x00000000 0x005b0 0x00000
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LOAD 0x001000 0xc0000000 0x00000000 0xff60000 0xff60000
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^^^^^^^^
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There we look for the first LOAD section, and see what
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is its offset (for us it is 0x1000)
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---------------
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64KiB = 65536
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0x0C 00 00 + 0x10 00 = 790528
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---------------
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On technical note in our case video bios
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is just 48kb, but for paranoia sake we copy
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64kb.
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==========================================
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Environment overview
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ADLO is an ELF file and thus can be loaded either directly from 1)
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LinuxBIOS, or 2) via EtherBOOT, or 3) via EtherBOOT+ AA patch for FS
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support.
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1)
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Both LinuxBIOS and ADLO are on the same EEPROM chip. From end-user
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viewpoint it is probably the most similar to the bios classic.
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(computer boots up and just loads whatever is in MBR).
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2)
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Set it up in /tftpboot directory on dhcp/tftp server and have it served
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from there. (this is how we did the development)
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3)
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Use AA patch and put it as /kernel file and it will be then loaded by
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etherboot from local hard disk.
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------------------------------------------
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Before ADLO starts.
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ADLO requires an boot loader with ELF support.
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In our case it is:
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-LinuxBIOS
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-LinuxBIOS and EtherBOOT
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-LinuxBIOS and EtherBOOT + AA polled I/O patch (w/ FS support).
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As little as LinuxBIOS only is required to get ADLO
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up and running.
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For development purposes it is recommended full set of
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LinuxBIOS + EtherBOOT and boot via DHCP/TFTP.
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------------------------------------------
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After ADLO finish.
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ADLO will attempt to locate the first hard disk
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and read MBR from it and execute.
|
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Then it can start any real mode application.
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In our case it could be LILO or GRUB
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but choices are not limited to this.
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In our case it would cause LILO to load
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(fully usable) and from there it was able to
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execute simple programs. so far the list
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of the program is limited to linux which
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runs somewhat. More to come in future.
|
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==========================================
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