Re: [RFC] x86 ELF bootable kernels/Linux booting Linux/LinuxBIOS

[ebiederm@xmission.com (Eric W. Biederman)]

"H. Peter Anvin" <hpa@zytor.com> writes:

> Eric W. Biederman wrote:
> 
> > What is magic about interactivity?  What makes this a different
> > problem?  We approach booting from totally different perspectives,
> > which makes communicating clearly hard.  If you spell out individual problems
> > I will show you how I would solve
> > them.
> >
> 
> 
> It makes it a very different problem because YOU DON'T KNOW WHAT YOU'RE BOOTING
> UNTIL THE USER TELLS YOU.
> 
> In fact, depending on just exactly what you're doing, you might not even know
> what you're booting until you have already gotten several items downloaded
> (consider, for example, a device-probing bootloader.)
> 
> Therefore, the bootloader must be able to obtain boot medium services not just
> once and for all, but on a back-and-forth basis.  There needs to be an API
> between the boot loader and the firmware, and just "stuffing it into memory"
> doesn't count.

If you are correct, then there a fundamental design problem with my
Linux Booting Linux code.  Because that is exactly what I do.  I stuff
the kernel in memory and jump to it.  Once the new kernel starts there is
no back and forth.  _Please_ help me understand why this back and
forth is needed.  

Here is my experience.  Non-interactive etherboot, doesn't know what
it is booting, or where it is booting from until the DHCP server tells
it.  Then it gets a file from a TFTP server and boots that.

When booting the Linux kernel it never attempts to do a back and forth
via the firmware to the boot medium.  Instead someone has a clue about
what the boot medium was and it mounts that medium using it's own
drivers.  Booting a rescue cd is a good example.

_Please_ help me find the flaw in my understanding.