[U-Boot] Current u-boot memory mapping

RgC sessyargc at gmail.com
Sat Oct 27 13:17:00 CEST 2012


Hi All,

Last week I got a weird problem on an ARM platfrom.
It is using an old version of u-boot because of our design/implementation cycle, but
let's not talk about upgrading the u-boot version that I use please.


My understanding of the u-boot memory mapping is in question :-)
I've dealt with the early versions (v1.x.x) on PowerPC and ARM. I'm now dealing with
newer u-boot versions but mostly on the PowerPC arch.  So I'm not sure if everything I
know applies to the ARM arch.

In the PowerPC arch, after relocation the actual memory mapping follows the "Memory 
Management" section in the u-boot README. Bottom of RAM for exception handlers, then
free space until we reach near the top of RAM. This is populated by the stack, global
data, malloc-area, and the u-boot code. My understanding is that this design was
never altered and was implemented across all platforms.

My understanding is that after relocation no area between the bottom and the top of
RAM is reserved. We can use it freely. Is this correct?

If writing to the the "free area" in RAM results in crashing u-boot then there is
problem in the relocation procedure or a possible linker script problem.

All the best,
RgC

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