[PATCH 17/19] bootwrapper: compatibility layer for old U-Boots (a.k.a. cuImage, cuboot)

[Mark A. Greer]

On Thu, Mar 15, 2007 at 11:04:45AM +1100, David Gibson wrote:
> On Wed, Mar 14, 2007 at 04:23:39PM -0700, Mark A. Greer wrote:
> > On Wed, Mar 14, 2007 at 04:48:49PM -0500, Scott Wood wrote:
> > > Mark A. Greer wrote:
> > > >Are you sure that '_end' (which is the end of the zImage/cuImage)
> > > >is safe to use?  If the kernel is large enough (e.g., INITRAMFS)
> > > >it will overwrite your dtb when its decompressed and relocated to 0.
> > > >You need to grok the elfheader to figure out where the kernel will end
> > > >and take the max of that and _end.
> > > 
> > > Wouldn't it overwrite the bootwrapper itself before overwriting the heap?
> > 
> > Sure but that doesn't matter--the kernel is running so the bootwrapper's
> > life is over but the dtb's life isn't.
> 
> The bootloader now expands the kernel directly at 0, rather than
> allocating space for it, except on platforms that can't (OF).

Well, its not at 0 if you have a platform_ops.vmlinux_alloc()
defined which could be anyone.  But I get your point.

> So we
> *would* clobber the bootloader during the bootloader's life if the
> kernel was too large.  There's a check for a too-large kernel as we
> decompress it.

This seems like a problem to me.  Premably, INITRAMFS will be used
more & more often so this check is going to fail more & more often.
We'll end up havng to keep moving the addr it loads at further & further
back or define platform_ops.vmlinux_alloc() and have the issue I
mentioned.

Mark