[U-Boot] U-Boot overlaps BSS and initrd on arm64

[Tom Rini]

On Tue, Nov 08, 2016 at 07:34:34PM +0000, Will Deacon wrote:
> On Tue, Nov 08, 2016 at 01:04:40PM -0500, Tom Rini wrote:
> > On Tue, Nov 08, 2016 at 06:01:42PM +0000, Will Deacon wrote:
> > > On Tue, Nov 08, 2016 at 12:51:44PM -0500, Tom Rini wrote:
> > > > On Tue, Nov 08, 2016 at 09:41:13AM -0800, Dmitry Vyukov wrote:
> > > > > Hello,
> > > > > 
> > > > > We've got a boot problem on arm64 devices. Here is boot log:
> > > > > https://storage.kernelci.org/mainline/v4.9-rc4/arm64-defconfig+CONFIG_KASAN=y/lab-baylibre-seattle/boot-juno-r2.txt
> > > > > https://kernelci.org/boot/id/581ece5a59b514e448f03bd7/
> > > > > 
> > > > > Here is some debugging that Andrey and Mark did:
> > > > > 
> > > > > On Tue, Nov 8, 2016 at 2:00 AM, Andrey Ryabinin wrote:
> > > > > > I've looked at juno-r2: https://kernelci.org/boot/id/581ece5a59b514e448f03bd7/
> > > > > > So we have
> > > > > > Dtb address  0x81f00000
> > > > > > Load address 0x80000000
> > > > > > Which gives us 31Mb for kernel.
> > > > > >
> > > > > > It says that Kernel image is 24.62 MiB, but that's without BSS.
> > > > > > If bss is big enough it might overwrite dtb.
> > > > > > And indeed, build details -
> > > > > > https://kernelci.org/build/id/581e850959b514e564f03bdc/
> > > > > > shows that bss is 8.5 Mb which is enough to overlap with dtb.
> > > > > 
> > > > > On Tue, Nov 8, 2016 at 3:21 AM, Mark Rutland wrote:
> > > > > > FWIW, since v3.17 we've had an image_size field in the arm64 Image
> > > > > > header which describes the "real" size of the Image, BSS included. See
> > > > > > [1,2].
> > > > > > It should be possible to modify U-Boot to use that to automatically
> > > > > > place the DTB and initrd at non-clashing locations (or at least to
> > > > > > expose the value somehow).
> > > > > > I had assumed U-Boot already did that, but it doesn't seem to be the
> > > > > > case.
> > > > 
> > > > Yes, we've supported the image_size field since v2016.07 and that board
> > > > is running v2016.01.  Unfortunately the booting.txt changes that added
> > > > the image_size field weren't publicized widely so we didn't see it until
> > > > someone else ran into the problem you're describing.
> > > 
> > > Hmm, that's a good point. If you like, I could add something to that file
> > > asking for all changes to CC the u-boot list? We should probably do the
> > > same for edk2.
> > 
> > That would be nice, sure.  I was even thinking that something like the
> > cross-distro or boot-architecture lists that linaro runs would have had
> > this info go by as well.  Thanks!
> 
> D'oh, the u-boot list seems to be subscriber-only, so I'm not going to make
> a whole lot of friends if I ask kernel devs to add it to cc.

Ah yes.  So boot-architecture is probably best.

> Also, you apparently Acked the image_size change:
> 
> http://git.kernel.org/linus/a2c1d73b94ed
> 
> so it was at least partially publicized ;)

Ah yes, now I recall :)  In my defense, I ack'd them when it was going
around, but I never saw when it went in.

-- 
Tom
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