iBoce

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Cabinet

Windows Installer

Synopsis

Configuration

Internals

Support

License

Todo

iBoce v0.3 for PocketPC 2002 is available both as installer or cabinet.

iBoce is a small program that allows to to boot Linux (or some other O.S.) directly from Windows CE ^tm, without the need for flashing your iPAQ. It does so by preloading the required data (kernel image, root image, ...) into RAM before preparing the hardware and jumping to the kernel entry point.

You may find this program particulary useful if :

• you want to try Linux on your iPAQ, but don't feel confident enough to erase your current flash content, taking the risk to transform your handheld into a brick
• you have a Compact Flash sleeve, and want to enjoy the opportunity to switch from one Linux distribution to another by just plugging in the adequate Compact Flash card
• you often have to test new Linux configurations, and want to enjoy the possibility to transfer very fast your new kernel or ramdisk using USB or Ethernet.

iBoce is part of the Evoles project, a new declinaison of Linux for embedded device, based on highly portable tools (Tcl, JAVA) and standards (XML, HTML). More information on the Evoles platform can be found at http://www.evoles.com or http://www.evolane.com/evoles.

When iBoce is started, it reads its configuration from a file called 'iboce.txt' in the same directory than the main executable. Each time a file name is not absolute, it is considered relative to the directory of the executable.

Global options

timeout=integer

This gives the delay (in seconds) before the default boot session is started. If value=0, the session will be booted immediatly, without displaying any interface. If value<0, the countdown will be disabled.

default=sessionname

Name of the default option, i.e. the one that will be booted automatically when a timeout is defined. If this option is not present, the default session is the first one defined in the configuration file.

Sessions

A session describe a special boot process. It is declared as :

[session_name]
option=value
option=value
...

where name is the name of the session.

Standard options

image=filename[,addr[,mirror]]

Name of the file containing the kernel image.

ramdisk=filename[,addr[,mirror]]

Name of the file containing the ramdisk image.

loader=filename

Name of the file containing the external bootloader code.

cmdline=arg1 ... argn

Set the command line passed to the Linux kernel.

append=arg1 ... argn

Append additional arguments to the command line passed to the Linux kernel.

serial=baudrate

Define the default configuration for the serial console. Set baudrate to a negative value to disable the initialization of the console.

include=sessionname

Import all the configuration from the given session name into current session. All options not explicitely defined into the source session are left unchanged into current session.

bootable=bool

This decides if the current session is a bootable one (default is true). A non bootable session is useful when used in conjonction with the include statement, to define a partial configuration common to several bootable sessions.

Advanced options

Those options allow the user to setup precisely the memory layout that will be used during the boot process. Each address can be given either as a decimal number or, more logically, as an hexadecimal one (for example 0xc0008000).

imageaddr=addr

Set the physical address where the kernel data will be copied. This default to 0xc0008000 when using the internal boot loader, or to 0xc0400000 if an external boot loader as been specified.

tagsaddr=addr

Set the physical address where the Linux tags will be copied. Linux tags are the translation of the parameters (command line, ramdisk size, etc...) to pass to the Linux kernel. This default to 0xc0000100 if no external boot loader is loaded, or to none (i.e. addr=0) otherwise. This cluster will always be less than 0xf00 bytes large.

ramdiskaddr=addr

Set the physical address where the ramdisk data will be copied. This default to 0xc0800000.

loaderaddr=addr

Set the physical address where the boot loader will be copied. For compatibility with the OSLoader program, this default to 0xc0022000.

entry=addr

Define the physical address to jump at for booting. If none provided, this default to the address of the loader if defined, or to the address of the kernel otherwise.

This section briefly presents the principles used internally by the iBoce boot loader. iBoce has been designed to keep algorithms as concise and explicit as possible. The bot process has been divided into 4 stages :

Initial memory layout (from WinCE)
Compute the required number of pages (npages=sum(data)+3) and allocated them. Last three pages are respectively for Boot code2, Boot code 3 and Boot code 1 (see below).
Compute upper bound for the memory region that will get occupied by data (upper=max(max(target[i]+size[i], i=0..n-1))).
reserved=max(upper,start of RAM+npages*pagesize)
Boot3_target=reserved
LCD_target=reserved+pagesize
Allocated pages are spread into RAM, so locate them, and order them according to their physical address.
Call Exec, which is the interface between the Windows CE world and the assembler one. It will disable MMU and interrupts and jump to boot code 1

Boot stage 1 :
compact all the npages-1 pages as a contiguous block starting at the beginning of RAM.
Jump to new location of boot code 2 (=start of RAM+(npages-3)*pagesize)

Boot stage 2 :
Compute reserved address = max(current adress of Boot stage 3,
Copy code for 'Boot stage 3' to the previously computed Boot3_Target, and jump to this address.

Boot stage 3 :
Translate each cluster to its final location (for i=n-1 to i=0). This is necessarily a forward translation, so since we start by translation the last file, no overlap can occur.
Prepare hardware (LCD, Serial, MMU, etc...). This is highly platform specific.
Jump to kernel entry point

More informations (FAQ, mailing list, documentation,...) and latest revision can be found at http://www.evolane.com.

For now, iBoce is distributed only in binary format. It is free of use for individuals. If you wish to use it in a commercial project, please contact our commercial team at sales@evolane.com for getting a licence.

Evolane actually does not have the required (human and hardware) ressources for extensive developpement on iBoce, since most of its activities are focused on the Evoles embedded system, and derived works for customers. However, we plan to use some functionnalites that may be of general interest :

• test and adapt for booting several operating systems (NetBSD, etc...).
• support for "on the fly" decompression of data. This consist in adding the free "libz" library into the code.
• support for flashing, and/or better collaboration with the genuine CRL boot loader to propose a fully automatic installation procedure by preloading all the data in RAM, without the need for XMODEM or TFTP transfers. This appear to be a relatively straight-forward task. The reason we did not already integrated such a functionnality into current version is that the very few iPaq we own are all crucial to some other actual projects, so we definitaly could not take the risk to transform one of them into a brick and wait too long for CRL to fix it. However, if someone (CRL ?) accepts to provide us with some kind of support that could prevent us from this risk (JTAG cable with related technical ressources to restore FLASH, additional iPAQ handheld for testing, financial support, etc...), please contact us (evolane@evolane.com) so that we could go further in this direction.