[U-Boot] u-boot sandbox crash

[U-Boot] u-boot sandbox crash

[Marek Vasut]

Hello,

I think this segfault below is not wanted?


$ ./MAKEALL sandbox
Configuring for sandbox board...
   text    data     bss     dec     hex filename
 131497    6048   28488  166033   28891 ./u-boot

--------------------- SUMMARY ----------------------------
Boards compiled: 1
----------------------------------------------------------
marex at mashiro:~/U-Boot/u-boot-marex$ ./u-boot


U-Boot 2011.12-00509-ge7dc4f9 (Mar 18 2012 - 03:10:34)

DRAM:  128 MiB
Using default environment

In:    serial
Out:   serial
Err:   serial

=>base
Base Address: 0x00000000
=>md 0
00000000:Segmentation fault

Best regards,
Marek Vasut

[U-Boot] u-boot sandbox crash

[Mike Frysinger]

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.
-mike
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[U-Boot] u-boot sandbox crash

[Marek Vasut]

Dear Mike Frysinger,

> On Saturday 17 March 2012 22:12:38 Marek Vasut wrote:
> > =>md 0
> > 00000000:Segmentation fault
> 

I see.

> 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.
> -mike

Hrm ... I wish I'd be able to figure out how to run PPC/Taihu or PPC/Bamboo U-
Boot in QEMU.

Best regards,
Marek Vasut

[U-Boot] u-boot sandbox crash

[Simon Glass]

Hi,

On Sun, Mar 18, 2012 at 5:26 PM, Mike Frysinger <vapier@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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