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

[Marek Vasut]

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.

> 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.

[...]
-- 
Best regards,
Marek Vasut