[PATCH] cmd: sf: prevent overwriting the reserved memory

[Michal Simek]

On 8/8/24 08:22, Sughosh Ganu wrote:
> On Thu, 8 Aug 2024 at 11:05, Michal Simek <michal.simek at amd.com> wrote:
>>
>>
>>
>> On 8/7/24 23:12, Tom Rini wrote:
>>> On Tue, Aug 06, 2024 at 05:37:00PM +0530, Prasad Kummari wrote:
>>>
>>>> Added LMB API to prevent SF command from overwriting reserved
>>>> memory areas. The current SPI code does not use LMB APIs for
>>>> loading data into memory addresses. To resolve this, LMB APIs
>>>> were added to check the load address of an SF command and ensure it
>>>> does not overwrite reserved memory addresses. Similar checks are
>>>> used in TFTP, serial load, and boot code to prevent overwriting
>>>> reserved memory.
>>>>
>>>> Signed-off-by: Prasad Kummari <prasad.kummari at amd.com>
>>>
>>> This is a much more generic issue that should be looked in to with the
>>> LMB rewrite that Sughosh is working on.
>>
>> yes. And is it going to be the part of his series?
>> I expect that if he accepts this will be done on the top of it and there is
>> likely no reason to wait.
> 
> This change would be needed, but in a different form. The patch, since
> based on the current master branch, is assuming a local lmb memory
> map. My series is doing away with that, and so we will no longer have
> the lmb_init_and_reserve() API, for example. I would suggest that the
> patch be put out either on top of my patches, or ideally, once the lmb
> patches get merged.

I care that we can't overwrite reserved memory by any of load commands.
Better to be fixed earlier rather than later but up to Tom to decide.
 From my perspective this is incorrect behavior which is fixing issue and likely 
this can go to 2024.10 version.
Your LMB series is likely going to target 2025.01.

>> We find the issue out on system which has more dynamic behavior that spi pytest
>> read the whole memory and rewrite TF-A.
>>
>> And currently we are in situation where some commands are checking reserved
>> location and some of them not.
> 
> Like you mention in another email, there are instances where we have
> commands which are loading images to memory, but are not considering
> the lmb reservations. These should be fixed, similar to what this
> patch is attempting. Maybe we need a common function where the load
> address gets checked with the lmb module, similar to
> fs_read_lmb_check(), and then have this called from the various
> commands?

yes, it make sense not to have 4 different functions in different drivers but 
call only one. Definitely nice to have it on the top of your LMB series to be 
able to use it in nand cmd for example.

Thanks,
Michal