ARM memory layout
Daniel Krüger
daniel.krueger at systec-electronic.com
Fri Jun 17 01:42:41 PDT 2016
Hi Sascha,
thanks for the help. The patches work for my non-relocatable barebox.
Malloc space is now below barebox.
Best regards,
Daniel
Am 16.06.2016 um 15:22 schrieb Sascha Hauer:
> Hi Daniel,
>
> On Thu, Jun 16, 2016 at 12:11:10PM +0200, Daniel Krüger wrote:
>> 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?
>
> Most of them do, yes.
>
> It seems !CONFIG_RELOCATABLE became broken with:
>
> | commit 65071bd0910ef109c86b9645c570a6ceed7de534
> | Author: Markus Pargmann <mpa at pengutronix.de>
> | Date: Tue Dec 8 10:39:29 2015 +0100
> |
> | arm: Clarify memory layout calculation
>
> I just sent out a series from which the first patch should fix your
> issue. The malloc space should be below the barebox image, not above it.
> BTW you shouldn't have to specify the malloc size, barebox can pick a
> sensible default for you if you specify it to 0.
>
> Sascha
>
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