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.va...@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.va...@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?
Simon
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