[PATCH 1/1] sandbox: ensure that state->ram_buf is in low memory

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

On 5/13/21 4:36 PM, Simon Glass wrote:
> Hi Heinrich,
>
> On Wed, 12 May 2021 at 15:28, Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:
>>
>> Am 12. Mai 2021 18:01:17 MESZ schrieb Simon Glass <sjg@chromium.org>:
>>> Hi Heinrich,
>>>
>>> On Tue, 11 May 2021 at 13:03, Heinrich Schuchardt <xypron.glpk@gmx.de>
>>> wrote:
>>>>
>>>> Addresses in state->ram_buf must be in the low 4 GiB of the address
>>> space.
>>>> Otherwise we cannot correctly fill SMBIOS tables. This shows up in
>>> warnings
>>>> like:
>>>>
>>>>      WARNING: SMBIOS table_address overflow 7f752735e020
>>>
>>> This sounds like a bug in the smbios-table code. For sandbox it should
>>> perhaps use addresses instead of pointers.
>>>
>>> I think that code (that I unfortunately wrote) was an expeditious way
>>> of getting it running, but is not correct.
>>
>> The field you are filling is only 32bit wide. I wonder how that table is meant to work on systems where the lowest memory address is above 4 GiB. Such ARMv8 systems exist.
>
> map_to_sysmem() will give you a 32-bit wide address. Yes SMBIOS is
> legacy and designed for 4GB.

I know map_to_sysmem(). But you wrote in lib/smbios.c:487:

/*
 ?* We must use a pointer here so things work correctly on sandbox. The
 ?* user of this table is not aware of the mapping of addresses to
 ?* sandbox's DRAM buffer.
  */

For testing you could start a binary with command 'bootefi' or 'booti'
and that binary would analyze the table. So yes, your comment holds true
and you must not use map_to_sysmem() here.

Best regards

Heinrich