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Re: grub_dl_unload_all()

From: Robert Millan
Subject: Re: grub_dl_unload_all()
Date: Thu, 24 Jan 2008 12:47:03 +0100
User-agent: Mutt/1.5.13 (2006-08-11)

On Thu, Jan 24, 2008 at 09:57:45AM +0100, Yoshinori K. Okuji wrote:
> > How important is it to unload all modules?  What do you suggest?  Do we fix
> > everything to unload all modules (is that even possible?)?  Do we unload
> > all modules on i386-pc "because we can" and not do this on ieee1275
> > platforms?
> It is important so that we can make sure that all cleanups are executed 
> before 
> transferring control. For example, if serial settings have been tweaked by 
> GRUB, they should be reverted to the original state. At least, this is 
> considered to be a good manner. Another example is video settings. Let's say, 
> GRUB changes video mode to show a fancy menu. Some operating systems may not 
> work well in graphical mode, then GRUB must turn it back to text mode.

I remember about the video mode issue, but IIRC it only affects i386-pc.  Also,
I don't think anyone will assume serial port to be in a particular state during
boot.  Do we have similar concerns on ieee1275 ?

Anyway, any suggestions on how we can archieve this?  Unless I missed
something, the ieee1275/multiboot2 loader puts the OS image at its link
address, whatever it may be, which leaves us with no provisions in case it
overwrote something.

It's unlikely that it overwrites our boot routine, but when we try to unload
all modules, things break.

Makes it sound like we'll have to:

  - add a relocator in our final jump routine
  - put OS image in dynamic memory
  - put the relocator/final routine in dynamic memory
  - unload all modules
  - jump to the relocator/final routine, passing it the parameters indicating
    it has to copy OS image from dynamic memory to the target area, whichever
    it may be.

(in both cases of dynamic alloc, ensuring they won't overlap with target OS
load area)

Is this _really_ the only way to solve this problem?

Robert Millan

<GPLv2> I know my rights; I want my phone call!
<DRM> What use is a phone call… if you are unable to speak?
(as seen on /.)

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