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Re: Contribution: a file loading module

From: Graeme Russ
Subject: Re: Contribution: a file loading module
Date: Sat, 25 Jun 2011 12:24:10 +1000
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On 24/06/11 01:42, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> On 17.06.2011 18:11, Pierre-Nicolas Clauss wrote:
>> Hi folks,
>> I subscribed to this list in order to share with you a humble
>> contribution of mine to grub.
>> As an OS developer enthusiastic, I needed to load a file to memory at
>> a given specific address.

I also have such a requirement - I am developing U-Boot for x86 systems and
I have real trouble getting documentation for the SDRAM initialisation
code. I figured I could leave that to BIOS for the time being and use GRUB
to load my U-Boot image into memory. This way, I do not have to flash the
BIOS chip until very late in the development cycle.

> While such a functionality would be a toy for loader developpers, it's
> completely useless for the end users. If the user has to know any single
> address or any single address figures in grub.cfg it's automatically a
> bad design. Also while it would be possible to write a loader in scripts
> using such kind of commands it's simply a wrong place for it. Loaders
> have to be written in C. Also people who really need such kind of
> functionality (devs) can quickly add such a kludge to the loader they
> are currently developping. As for the user the syntax has to be sth like
> loader_name <file> <args>

Well, I now have GRUB2 installed on a USB pen drive and have it run
memtestx86+. So from here I would like it to be a simple matter of copying
the U-Boot binary onto the USB pen drive and adding an entry in the
grub.cfg file - But I need the 'raw image loader' module to do this

> This allows for a much higher flexibility, portability and future-proof.
>> No command in grub 1.99 was fitting my needs (as my file as no
>> semantic known to grub: it's not a module, it's not an initrd, it's
>> not a multiboot kernel either), so I developed my own module.
> What is it then? I'm willing to consider adding new loading as long as
> they are sane and make sense.

I think a command like:

exec_file file load_address [execute_address]

would fit my needs perfectly. The U-Boot images are raw (not ELF) with a
32-bit entry point at the first byte of the file but this may change (I may
put the version string at the start of the file) so the optional
execute_address could come in handy.



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