Dear Wolfgang Denk,
On 02/04/2013 09:26 PM, Wolfgang Denk wrote:
Dear Nikita Kiryanov,
In message <1359977979-28585-2-git-send-email-nik...@compulab.co.il> you wrote:
Currently code that displays BMP files does two things:
* assume that any address is a valid load address for a BMP
* access in-memory BMP header fields directly
Since some BMP header fields are 32 bit wide, this has a potential
for causing data aborts when these fields are placed in unaligned
addresses.
Create an API for safely accessing BMP header data, and compile it with
$(PLATFORM_NO_UNALIGNED) to give it the ability to emulate unaligned memory
accesses.
Frankly, I think this is overkill. U-Boot is a bootloader, and it is
supposed to be lean and eficient. We don't have all levels of safety
systems and protective devices as in, for example, an aircraft. You
are supposed to know what you are doing, and if you ignore the rules,
you will quickly see the results yourself.
[...]
You talk about BMP header - but we also have alignment requirements
for image headers, well, even for a plain "md" or "mw" command. And
none of these provide any protection against accidsential (or
intentional) access to unaligned addresses.
That's true, but when md traps you simply restart the board and
everything's fine. If displaying a splash screen traps- you're stuck.
I'm not saying we should start implementing protection against every
possible mistake, but when the repercussions are this serious I feel
that protection is in order.
There's a difference between a bicycle with no training wheels and one
that falls apart when you turn it the wrong way.
My recommendation is: just don;t do it, then.
Best regards,
Wolfgang Denk
--
Regards,
Nikita.
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