[Linaro-dev] Introducing kexecboot software

[Yuri Bushmelev]

Hello!

I wish to introduce kexecboot software here. It would be great to see 
kexecboot in list of Linaro supported projects.

Feel free to contact me about this software by email or on irc.freenode.net,  
#kexecboot channel. My nickname is Jay7.

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Kexecboot is a C program able to scan the partitions on available devices, 
offering a graphical framebuffer menu and allowing user to select from which 
one to boot. Specifically, kexecboot creates the command line for kexec.

Typically kexecboot resides together with kexec in a small initramfs, 
embedded in a custom-tailored kernel compiled with support for initramfs and 
kexec system call. Both binaries are built static, linked against klibc to 
optimize size.

Flashed on NAND and launched as first kernel by the original bootloader, 
this solution gives following advantages:

 * multi machine support: we build for many architectures using OpenEmbedded 
(tested on arm and x86/x86_64)
 * zImage and uImage support
 * easy customization: just add machine-specific workarounds (see Zaurus raw 
read of bootparams from NAND)
 * small size: complete linux-kexecboot_2.6.x image (initramfs + kernel) is 
about 1Mb (less with lzma patches)
 * easy boot choice: boot from SD/CF/NAND/... even if bootloader doesn't 
support it
 * multiple fs detection: we support many filesystems e.g. ext2/3/4, jffs2, 
reiserfs, vfat and more (ubifs is work in progress)
 * kernel upgrade: no need to flash the device (kernel is in /boot of 
removable media)
 * rapid testing: different distributions can live in separate partitions on 
the same device 

Thus, kexecboot is an interesting solution for embedded linux distributions, 
which can just rely on kexecboot whithout having to consider what the real 
bootloader can and cannot do.

About customization, initially the program has been developed for Sharp 
Zaurus PDA (armv5te). For the machines of that family there is specific code 
reading bootparams directly from NAND, circumventing the obsolete bootloader 
which is incompatible with modern 2.6.x kernels. 
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We are sponsored by CELF in this year to do following work:
1.Write user's and developer's guides.
2.Extend architecture and filesystems support. MIPS arch support and UBIFS 
support will be added.
3.Improve debugging ability. We should allow users to have ability to look 
for debugging information without special hardware (serial cable e.g.).
4.Implement text-mode UI. We have already patches against one of old 
releases. This can be used later to use kexecboot UI over serial line or 
telnet/ssh connection.
5.Improve GUI. Make GUI more clean and eye-candy (fonts and icons).
6.Add ability to use multiple kernels on same partition. Current 
implementation allows only one kernel per partition.

List of accessible hardware:
- Sharp Zaurus'es: C860, C1000, C3200, SL-5500, SL-6000;
- TouchBook (waiting for order, donated by CELF for this device support 
work).
- Ben NanoNote (waiting for delivery, donated by CELF for MIPS support 
work);

Links:
 * Current project home (down at this moment, we are looking for hosting): 
http://projects.linuxtogo.org/projects/kexecboot
 * Project git tree: 
http://git.linuxtogo.org/?p=groups/kexecboot/kexecboot.git
 * OpenEmbedded recipes: 
http://cgit.openembedded.org/cgit.cgi/openembedded/tree/recipes/kexecboot

-- 
Yuri Bushmelev