[U-Boot] [PATCH] ARM: rmobile: Convert to bootm_size

[Marek Vasut]

On 11/27/2018 07:31 PM, Simon Goldschmidt wrote:
> On Tue, Nov 27, 2018 at 4:47 PM Marek Vasut <marek.vasut at gmail.com> wrote:
>>
>> On 11/27/2018 04:26 PM, Simon Goldschmidt wrote:
>>> On 27.11.2018 14:09, Marek Vasut wrote:
>>>> On 11/27/2018 01:33 PM, Simon Goldschmidt wrote:
>>>>> On Tue, Nov 27, 2018 at 1:25 PM Marek Vasut <marek.vasut at gmail.com>
>>>>> wrote:
>>>>>> On 11/27/2018 08:03 AM, Simon Goldschmidt wrote:
>>>>>>> On Tue, Nov 27, 2018 at 1:11 AM Marek Vasut <marek.vasut at gmail.com>
>>>>>>> wrote:
>>>>>>>> Convert all Renesas R-Car boards to bootm_size of 256 MiB and drop
>>>>>>>> both
>>>>>>>> fdt_high and initrd_high. This change implies that the FDT and initrd
>>>>>>>> will always be copied into the first 256 MiB of RAM instead of being
>>>>>>>> used in place, which can cause various kinds of inobvious problems.
>>>>>>>>
>>>>>>>> The simpler problems include FDT or initrd being overwritten or being
>>>>>>>> used from unaligned addresses, especially on ARM64. The overhead of
>>>>>>>> copying the FDT to aligned location is negligible and these problems
>>>>>>>> go away, so the benefit is significant.
>>>>>>>>
>>>>>>>> Regarding alignment problems with fitImage. The alignment of DT
>>>>>>>> properties
>>>>>>>> is always 32 bits, which implies that the alignment of the "data"
>>>>>>>> property
>>>>>>>> in fitImage is also 32 bits. The /incbin/ syntax plays no role
>>>>>>>> here. The
>>>>>>>> kernel expects all elements, including DT and initrd, to be
>>>>>>>> aligned to
>>>>>>>> 64 bits on ARM64, thus using them in place may not be possible.
>>>>>>>> Using the
>>>>>>>> bootm_size assures correct alignment, again with negligible overhead.
>>>>>>> In my opinion, all of these raw addresses defined in scripts or config
>>>>>>> should be removed: They are probably vulnerable to overwriting
>>>>>>> themselves as they only provide an address, not a range.
>>>>>> This is not an address, it's size. And this one at least assures that
>>>>>> the first 256 MiB are reserved for the kernel/FDT/initrd during
>>>>>> bootm time.
>>>>> Sorry I did not express myself clear enough. I meant that "fdt_high"
>>>>> and "initrd_high" are bad because they contain an address only, not a
>>>>> range. The 'bootm_size' thing is much better!
>>>> Well the fdt_high and intrd_high can also contain a special ~0 value,
>>>> which says "use the fdt/initrd in place", which is dangerous.
>>>>
>>>>>>> Just out of curiosity: is it required to put fdt and initrd into the
>>>>>>> first 256 MiB or is this just some 'random' limit to ensure we use lmb
>>>>>>> but don't overwrite U-Boot (text, heap, stack, etc)? Because if so, my
>>>>>>> series to fix the recent CVE issues improves lmb to not overwrite
>>>>>>> U-Boot and other reserved addresses and you might be able to remove
>>>>>>> 'bootm_size', too. The improved lmb code would just allocate an
>>>>>>> aligned address somewhere in the available RAM.
>>>>>> It's just the first 256 MiB from the beginning, so there's enough space
>>>>>> between that and U-Boot on all these boards.
>>>>> Of course. I wanted to know if it would be good enough if U-Boot would
>>>>> just put it somewhere without overwriting things or do you really need
>>>>> them in the first 256 MiB? Because the revised lmb code would make
>>>>> sure there's nothing overwritten, so there would be no need to trim at
>>>>> 256 MiB.
>>>> You can put them anywhere, you just need to meet the alignment
>>>> requirements. Can the new LMB code help somehow with that ? And if so,
>>>> how ?
>>>
>>> My additions to the LMB code should only ensure nothing gets overwritten
>>> so you don't have to limit boom_size to 256MiB (but use the complete RAM
>>> when bootm_size is not set).
>>> Alignment does not change but should already be OK with LMB as you use it?
>>
>> If I can use the entire RAM (except U-Boot and fitImage), that'd be
>> nice. What change do I need to do ?
> 
> I don't know yet, sorry. I basically asked this question to find out
> about the usage of 'bootm_size'. It's not really documented and I
> couldn't find out it's full meaning yet. Because e.g. it is set to 16
> MiB for socfpga gen5, which sounds a little low...
> 
> From reading the code, doesn't it already work when leaving out
> 'bootm_size'? (And leaving out 'bootm_mapsize' as well and not
> defining CONFIG_SYS_BOOTMAPSZ?)
> 
> But I don't really know, finding that out and making it work is one of
> my goals for that series I'm working on. The series started with
> allowing all subitems in a FIT to be uncompressed but I found some
> issues there and it grows...

Thanks for all that work :-)

-- 
Best regards,
Marek Vasut