[U-Boot] [PATCH] p2371-2180: Build position independent binary

[Thierry Reding]

On Mon, Mar 18, 2019 at 12:31:32PM -0600, Stephen Warren wrote:
> On 3/8/19 1:10 PM, Thierry Reding wrote:
> > From: Thierry Reding <treding at nvidia.com>
> > 
> > In order to support chainloading of U-Boot by an earlier bootloader,
> > make sure the binary is position independent, so that the earlier boot-
> > loader can relocate it if necessary.
> 
> Why not enable this for all 64-bit Tegra? They're all booted the exact same
> way at least with recent L4T builds.

Yeah, I think that would make sense.

> Also, U-Boot is typically linked to the address that cboot loads it to, and
> cboot typically always loads to precisely that address. I'm not sure why
> this patch is required.

I encountered this issue when I was trying to chainload U-Boot from
cboot on Jetson TX1. It seems like your above comment is no longer true,
though I suppose that could just mean that the link address for U-Boot
has become stale?

> That said, it don't think it harms anything, so I'm fine with it being
> applied.

I suppose there's a bit of extra code to do the indirect jumps, but
overall U-Boot seems to work well and not noticeably slower if this is
enabled. Might be nice for extra flexibility and to avoid any surprises
if we ever end up loading U-Boot to a location other than where it was
liked to.

My understanding is that this could happen on Tegra186 if cboot detects
bad memory blocks in the area where U-Boot was meant to be loaded to. I
guess this doesn't apply to earlier chips, but perhaps it's good to have
it there for consistency anyway.

Thierry
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://lists.denx.de/pipermail/u-boot/attachments/20190319/384b1e35/attachment.sig>