[U-Boot] [PATCH 1/2] ARMv8: add optional Linux kernel image header

[Stephen Warren]

On 01/03/2018 06:45 AM, Tom Rini wrote:
> On Tue, Jan 02, 2018 at 04:54:21PM -0700, Stephen Warren wrote:
> 
>> From: Stephen Warren <swarren at nvidia.com>
>>
>> Allow placing a Linux kernel image header at the start of the U-Boot
>> binary. This is useful since the image header reports the amount of memory
>> (BSS and similar) that U-Boot needs to use, but that isn't part of the
>> binary size. This can be used by the code that loads U-Boot into memory to
>> determine where to load U-Boot, based on other users of memory.
>>
>> Signed-off-by: Stephen Warren <swarren at nvidia.com>
>> ---
>> This series relies (at the very least for diff context) on the previous
>> series I sent Dec 19: ARM: tegra: don't use CONFIG_SPL_TEXT_BASE when no
>> SPL ... ARM: tegra: use CONFIG_SYS_INIT_SP_BSS_OFFSET.
> 
> Neat.  Are the Linux folks encouraging other projects to re-use this
> header?

Not that I'm aware of, but mainly because I haven't talked to upstream 
kernel people about this at all. I implemented this because in recent 
versions of Linux4Tegra, for all 64-bit SoCs, our main CPU EL2/EL1 boot 
path is either:

cboot -> Linux kernel
cboot -> U-Boot -> Linux kernel

cboot is an NVIDIA binary bootloader. cboot wants to know about BSS/... 
usage of the binary it loads, which can be determined from the Linux 
kernel image header, but we don't want cboot to take different paths 
when booting Linux or U-Boot (or indeed anything at all), so the 
simplest thing was to make U-Boot look as identical to a Linux kernel as 
possible.

> Is there somewhere we can point to as reference for the format
> for the Kconfig help as well, not just the text?  Thanks!

The Linux kernel file Documentation/arm64/booting.txt does describe the 
format. Should I respin and add that filename to the Kconfig text?