Maximum bootable kernel size in current ARM linux

[Nicolas Pitre]

On Tue, 14 Sep 2010, Bruce M. Penrod wrote:

> 
> 
> Nicolas Pitre wrote:
> > On Mon, 13 Sep 2010, Bruce M. Penrod wrote:
> > 
> > > 
> > > Russell King - ARM Linux wrote:
> > > > On Mon, Sep 13, 2010 at 12:40:56AM -0700, Bruce M. Penrod wrote:
> > > > > This seems like a pretty straightforward question, but extensive web
> > > > > searching hasn't shown a really clear, up-to-date answer.  The most
> > > > > recent info is circa 2004 and states that 4MB is the largest
> > > > > uncompressed
> > > > > ARM kernel that may be loaded.  Not being an ARM assembly  guru
> > > > > (head.S
> > > > > baffles me), I'd like to know if that is still true in  2010, and if
> > > > > it
> > > > > is, why?
> > > > It is no longer true; the only limit now is the size of contiguous RAM
> > > > to fit the kernel image into.
> > > > 
> > > Interesting.  I finally was able to get an uncompressed kernel a little
> > > below
> > > 4MB, and now it boots.  I'm working with 2.6.35rc6 on an OpenRD Ultimate
> > > (Marvell Kirkwood) with Slackware, doing native compiles.  I'm wondering
> > > if
> > > there could be any problem with U-Boot for larger kernels than 4MB, but it
> > > doesn't complain and says that it is copying the image.  The symptom I had
> > > with a much larger kernel (~15MB) is a total hang, not even "Uncompressing
> > > linux".
> > > 
> > > I'll add some innocuous stuff back in until I get above 4MB again and see
> > > if
> > > it breaks again.
> > 
> > When it breaks, do you still see the "Uncompressing Linux... done, booting
> > the kernel." message?
> > 
> > 
> > Nicolas
> > 
> 
> I think it depended upon how "too big" the kernel was.  With one only slightly
> larger than 4 MB, I did see "Uncompressing Linux...", but not "done, booting
> the kernel."  With a very large kernel (15MB), nothing printed at all.
> 
> I have not retested since successfully booting one slightly smaller than 4096
> * 1024.  When I do, I will post the results.  Should happen today.

OK.  Also please provide the size of your arch/arm/boot/zImage as well 
as arch/arm/boot/Image.  Also, at what address do you load your kernel 
in memory?


Nicolas