[U-Boot] env: fix potential stack overflow in environment functions

[Rob Herring <robherring2@gmail.com>]

On 04/05/2013 12:13 PM, Wolfgang Denk wrote:
> Dear Rob,
> 
> In message <515EFE6F.1020609@gmail.com> you wrote:
>>
>>> In addition to commit 60d7d5a "env: fix potential stack overflow in
>>> environment functions" discussed here, I think we should also revert
>>> commit fcfa696 "ARM: increase lmb stack space reservation to 4KB"
>>> because it is conceptually broken and just papers over the real
>>> problems.
>>
>> Doing so will randomly break any system with a large command or print
>> buffer. For extra fun, it is dependent on the initrd or dtb image size
>> in terms of remainder of 4KB multiple.
> 
> Well, yes, but that's because the LMB code makes unjustified
> assumptions about the memory usage, so it needs to be fixed there.
> 
>> It is exactly the same code as PPC. It you look at the git history, PPC
>> made exactly the same change (1 to 4KB increase) around the same time
>> all the FDT boot code got copied from PPC to ARM. So ARM missed this change.
> 
> Thanks for pointing out.  This adds commit 3882d7a "ppc: unused memory
> region too close to current stack pointer" to the list of patches that
> should bne reverted.
> 
>> If the stack is all of RAM, then what address should the initrd and dtb
>> be copied to?
> 
> Why do they have to be copied at all?  Why cannot they remain where
> they have been loaded in the firtst place?  The memcpy just costs time,
> which is a precious resource.  Leave it to the user to find a
> reasonable location in RAM where he loads the data, and don't mess
> with it.

I've got no freaking idea! I do turn that crap off in my environment
with initrd_high=0xffffffff. But the default operation is to copy it.

Rob