[PATCH V2] mkimage: fit: Do not tail-pad fitImage with external data

[Tom Rini <trini@konsulko.com>]

On Wed, May 06, 2020 at 05:52:45PM +0200, Marek Vasut wrote:
> On 5/6/20 5:43 PM, Alex Kiernan wrote:
> > On Wed, May 6, 2020 at 3:41 PM Marek Vasut <marex@denx.de> wrote:
> >>
> >> On 5/6/20 4:37 PM, Tom Rini wrote:
> >>> On Wed, May 06, 2020 at 04:33:37PM +0200, Marek Vasut wrote:
> >>>> On 5/6/20 4:27 PM, Tom Rini wrote:
> >>>>> On Wed, May 06, 2020 at 04:17:35PM +0200, Marek Vasut wrote:
> >>>>>> On 5/6/20 3:48 PM, Tom Rini wrote:
> >>>>>>> On Tue, May 05, 2020 at 11:17:19PM +0200, Michael Walle wrote:
> >>>>>>>> Hi all,
> >>>>>>>>
> >>>>>>>> Am 2020-05-05 20:41, schrieb Simon Glass:
> >>>>>>>>> Hi Tom,
> >>>>>>>>>
> >>>>>>>>> On Tue, 5 May 2020 at 11:50, Tom Rini <trini@konsulko.com> wrote:
> >>>>>>>>>>
> >>>>>>>>>> On Tue, May 05, 2020 at 06:39:58PM +0200, Marek Vasut wrote:
> >>>>>>>>>>> On 5/5/20 6:37 PM, Alex Kiernan wrote:
> >>>>>>>>>>>> On Tue, May 5, 2020 at 2:28 PM Marek Vasut <marex@denx.de> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On 5/5/20 3:22 PM, Alex Kiernan wrote:
> >>>>>>>>>>>>>> On Mon, May 4, 2020 at 12:28 PM Tom Rini <trini@konsulko.com> wrote:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On Fri, May 01, 2020 at 05:40:25PM +0200, Marek Vasut wrote:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> There is no reason to tail-pad fitImage with external data to 4-bytes,
> >>>>>>>>>>>>>>>> while fitImage without external data does not have any such padding and
> >>>>>>>>>>>>>>>> is often unaligned. DT spec also does not mandate any such padding.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Moreover, the tail-pad fills the last few bytes with uninitialized data,
> >>>>>>>>>>>>>>>> which could lead to a potential information leak.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> $ echo -n xy > /tmp/data ; \
> >>>>>>>>>>>>>>>>       ./tools/mkimage -E -f auto -d /tmp/data /tmp/fitImage ; \
> >>>>>>>>>>>>>>>>       hexdump -vC /tmp/fitImage | tail -n 3
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> before:
> >>>>>>>>>>>>>>>> 00000260  61 2d 6f 66 66 73 65 74  00 64 61 74 61 2d 73 69  |a-offset.data-si|
> >>>>>>>>>>>>>>>> 00000270  7a 65 00 00 78 79 64 64                           |ze..xydd|
> >>>>>>>>>>>>>>>>                    ^^       ^^ ^^
> >>>>>>>>>>>>>>>> after:
> >>>>>>>>>>>>>>>> 00000260  61 2d 6f 66 66 73 65 74  00 64 61 74 61 2d 73 69  |a-offset.data-si|
> >>>>>>>>>>>>>>>> 00000270  7a 65 00 78 79                                    |ze.xy|
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Signed-off-by: Marek Vasut <marex@denx.de>
> >>>>>>>>>>>>>>>> Reviewed-by: Simon Glass <sjg@chromium.org>
> >>>>>>>>>>>>>>>> Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
> >>>>>>>>>>>>>>>> Cc: Tom Rini <trini@konsulko.com>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Applied to u-boot/master, thanks!
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> This breaks booting on my board (am3352, eMMC boot, FIT u-boot,
> >>>>>>>>>>>>>> CONFIG_SPL_LOAD_FIT). Not got any useful diagnostics - if I boot it
> >>>>>>>>>>>>>> from eMMC I get nothing at all on the console, if I boot over ymodem
> >>>>>>>>>>>>>> it stalls at 420k, before continuing to 460k. My guess is there's some
> >>>>>>>>>>>>>> error going to the console at the 420k mark, but obviously it's lost
> >>>>>>>>>>>>>> in the ymodem... I have two DTBs in the FIT image, 420k would about
> >>>>>>>>>>>>>> align to the point between them.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> My bet would be on some padding / unaligned access problem that this
> >>>>>>>>>>>>> patch uncovered. Can you take a look ?
> >>>>>>>>>>>>
> >>>>>>>>>>>> Seems plausible. With this change my external data starts at 0x483 and
> >>>>>>>>>>>> everything after it is non-aligned:
> >>>>>>>>>>>
> >>>>>>>>>>> Should the beginning of external data be aligned ?
> >>>>>>>>>>
> >>>>>>>>>> If in U-Boot we revert e8c2d25845c72c7202a628a97d45e31beea40668 does
> >>>>>>>>>> the
> >>>>>>>>>> problem go away?  If so, that's not a fix outright, it means we need
> >>>>>>>>>> to
> >>>>>>>>>> dig back in to the libfdt thread and find the "make this work without
> >>>>>>>>>> killing performance everywhere all the time" option.
> >>>>>>>>>
> >>>>>>>>> If it is a device tree, it must be 32-bit aligned.
> >>>>>>>>
> >>>>>>>> This commit actually breaks my board too (which I was just about to send
> >>>>>>>> upstream, but realized it was broken).
> >>>>>>>>
> >>>>>>>> Said board uses SPL and main U-Boot. SPL runs fine and main u-boot doesn't
> >>>>>>>> output anything. The only difference which I found is that fit-dtb.blob is
> >>>>>>>> 2 bytes shorter. And the content is shifted by one byte although
> >>>>>>>> data-offset is the same. Strange. In the non-working case, the inner
> >>>>>>>> FDT magic isn't 4 byte aligned.
> >>>>>>>>
> >>>>>>>> You can find the two fit-dtb.blobs here:
> >>>>>>>>
> >>>>>>>> https://walle.cc/u-boot/fit-dtb.blob.working
> >>>>>>>> https://walle.cc/u-boot/fit-dtb.blob.non-working
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Reverting e8c2d25845c72c7202a628a97d45e31beea40668 doesn't help (I might
> >>>>>>>> reverted it the wrong way, there is actually a conflict).
> >>>>>>>>
> >>>>>>>> I'll dig deeper into that tomorrow, but maybe you have some pointers where
> >>>>>>>> to look.
> >>>>>>>>
> >>>>>>>> For reference you can find the current patch here:
> >>>>>>>> https://github.com/mwalle/u-boot/tree/sl28-upstream
> >>>>>>>
> >>>>>>> I think we have a few things to fix here.  Marek's patch is breaking
> >>>>>>> things and needs to be reverted.  But it's showing a few underlying
> >>>>>>> problems that need to be fixed too:
> >>>>>>> - fit_extract_data() needs to use calloc() not malloc() so that we don't
> >>>>>>>   leak random data.
> >>>>>>> - We need to 8-byte alignment on the external data.  That's the
> >>>>>>>   requirement for Linux for device trees on both 32 and 64bit arm.
> >>>>>>>   Atish, does RISC-V require more than that?  I don't see it in Linux's
> >>>>>>>   Documentation/riscv/boot-image-header.rst (and there's no booting.rst
> >>>>>>>   file like arm/arm64).
> >>>>>>
> >>>>>> Why 8-byte alignment ? The external data are copied into the target
> >>>>>> location, so why do they need to be padded in any way?
> >>>>>
> >>>>> The start of the external data needs the alignment, to be clearer.
> >>>>
> >>>> Why ?
> >>>
> >>> Given that things which end up in external data have alignment
> >>> requirements, we need to align and meet those requirements.  And I noted
> >>> why 8 above.
> >>
> >> If you end up with external data, then you need to move those blobs into
> >> their target location anyway. That's what you specify in the load = <>
> >> property in the .its .
> >>
> > 
> > Just reading common/spl/spl_fit.c, I think that'll try and parse in
> > situ, rather than relocating it?
> 
> And is that correct or is that the same problem as we have on arm64 with
> fitImage and fdt_high=-1 ? I think it's the later.

I'm not sure that it is.  Can we easily/safely memmove the data to be
aligned?  Is that really a better option in this case than ensuring
alignment within the file?

-- 
Tom
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