ARM memory layout

[Daniel Krüger]

Hello,

during the porting of barebox to a new i.MX35 board I stumbled over some 
crazy things with the memory layout. The comments in file 
arch/arm/cpu/entry.c seem to be wrong or at least misleading.

We configured barebox as non-relocatable image. So I think the 
configured TEXT_BASE is very important.

I use the following configuration with 128 MB RAM:
CONFIG_TEXT_BASE=0x87000000
CONFIG_STACK_SIZE=0x100000
CONFIG_MALLOC_SIZE=0xd00000

The stack is configured very large in this project, because of other reason.

I get the following memory layout:
     0x87ffffff top of RAM
      |           free-space (see arm_mem_stack() in
      |                       arch/arm/include/asm/barebox-arm.h)
     0x87ff0000 start of 64 kB free-space (vector table)
     0x87feffff top of stack
      |
     0x87ef0000 start of 1 MB reserved stack space
     0x87eeffff
      |         16 kB early translation table
     0x87eec000 early TTB (translation table base)
     0x87eebfff malloc end
      |          13 MB malloc space
     0x871ec000 malloc start
      |         some small free space
      |         barebox binary
     0x87000000 TEXT_BASE

This does not comply to the comment in the above mentioned source file. 
There the malloc space and the vector table are missing.

I would expect some check in the source code, when TEXT_BASE is too high 
or barebox binary is too large, so they collide with malloc space or 
stack. By reverse engineering the detailed memory layout above, I 
discovered that in another project the TEXT_BASE falls within the malloc 
space.

How does is run on other ARM boards? Are they all running with 
CONFIG_RELOCATABLE=Y?

Best regards,
   Daniel

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