Re: [Qemu-devel] [PATCH] x86 Multiboot support (extended)

[Alexander Graf]

On Jan 31, 2008, at 10:58 AM, Kevin Wolf wrote:

> Hi,
>
> I like this idea. When I just tried to load my multiboot kernel it
> failed, though, because of the following piece of code:
>
> > +    // XXX: multiboot header may be within the first 8192 bytes,  
> > but header
> > +    //      is only the first 1024
> > +
> > +    // Ok, let's see if it is a multiboot image
> > +    for(i=0; i<(256 - 12); i+=4) { // the header is 12x32bit long
> > +        if(ldl_p(header+i) == 0x1BADB002) {
>
> I wonder if there is any reason why you didn't just replace the 1024  
> by
> 8192 in load_linux but added an XXX. Would this cause any problems I
> missed? With this change and replacing 256 by 8192 in the above code  
> it
> works for my kernel, too.
>
> Anyway, I think the for condition should be i < 4 * (256 - 12), even
> without changing the 1024.

This version should fix the long header issue. I made the linux loader  
fetch the first 8kb as header, so multiboot can search through all  
necessary data.

I also implemented module parameters. Kevin needed this to boot a  
homebrew kernel. You can now pass commandline parameters to the  
multiboot modules by adding them after the filename, seperated through  
a space. This is the very same approach grub takes.

To boot a xen kernel you would give a command line like this:

qemu -hda image -kernel xen -initrd "vmlinux-xen root=/dev/hda,initrd- 
xen"

This way the vmlinux module gets the command line parameter "root=/dev/ 
hda".

Regards,

Alex

multiboot.new.patch
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