[U-Boot] u-boot sandbox crash

[Simon Glass]

Hi,

On Sun, Mar 18, 2012 at 5:26 PM, Mike Frysinger <vapier at gentoo.org> wrote:
> On Saturday 17 March 2012 22:12:38 Marek Vasut wrote:
>> =>md 0
>> 00000000:Segmentation fault
>
> this is because the change to make this work was reverted.  i think ppc is
> broken, but haven't gone through the details to figure things out.

It's because sandbox has a 128MB memory region, which is just created
using malloc(). We want address 0 to refer to the first byte of this
region.

I did create a patch to fix this, which used the map_physmem() to get
the address in the md command. However, ppc expects that the md
command just blindly uses the address it is given (i.e. assume it is
already a virtual address if the MMU is on, and a physical address if
not). I suspect other archs would have the same requirement if they
ever mapped virtual memory differently to physical memory.

I did post about it at the time. My proposed fix was to introduce the
idea of mapping an 'apparent' address. This would be a 1-1 mapping for
all architectures except sandbox, which would map it into its malloc'd
memory.

It's a little unfortunate that sandbox has to be the only thing with a
mapping, though. Partly that's why I haven't sent a patch.  Taken to
its logical conclusion then any memory access that the user requests
would end up going through this veneer. But I don't have any better
ideas yet.

If you're interested, the original patch was here:

http://patchwork.ozlabs.org/patch/121815/

Regards,
Simon

> -mike
>
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