[U-Boot] Possible bug in u-boot standalone examples

[David George]

Hey Wolfgang,

Hmm, I think I might not have made my point clear enough ... my 
apologies! Either that or I have a fundamental misunderstanding of the 
issue (more likely).

> No.  See the FAQ entry.  The entry point address really depends on te
> code.  If you add code, it can be basically anywehre - there may other
> functions preceed the entry point, etc.

I had a look at this FAQ entry, and I think it's addressing a different 
point than the issue I'm seeing here. This part of the FAQ tells the 
user that the load point of their standalone function may differ due to 
the particular linker or link map they're using. This is totally fine 
and I understand that this is subject to change, and naturally if you're 
attempting to run a standalone application from an address other than 
its base address defined at link time, then the application won't 
execute correctly.

In my situation, I specifically told my linker to set my example 
application's start address to to be the same as the hello_world example 
(0x40000). Presumably the same problems would have occurred regardless 
of where I loaded it due to the fact that I was beginning execution four 
bytes into the code, thus skipping the first instruction (as outlined in 
the examples).

Of course, I understand that the situation becomes very different when 
alternative compilers and linkers are thrown into the mix.

I'd be very interested to know which incidents in the past had caused 
the standalone examples to fail to execute correctly from their base 
address yet work correctly from a 4 byte offset, because as a relative 
newcomer to development at this level of abstraction, this threw me a 
massive red herring until I realised that actually, for my example, the 
first instruction is -crucial- (stack frame allocation), and I can't 
work out in my head how the example actually works correctly when loaded 
at a 4 byte offset.

Thanks!

Dave George




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