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

Wed May 6 18:33:34 CEST 2020

On Wed, May 06, 2020 at 06:17:47PM +0200, Marek Vasut wrote:
> On 5/6/20 6:04 PM, Tom Rini wrote:
> > 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 at 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 at 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 at 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 at 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 at denx.de>
> >>>>>>>>>>>>>>>>>> Reviewed-by: Simon Glass <sjg at chromium.org>
> >>>>>>>>>>>>>>>>>> Cc: Heinrich Schuchardt <xypron.glpk at gmx.de>
> >>>>>>>>>>>>>>>>>> Cc: Tom Rini <trini at 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?
> 
> Can't we use the new mkimage -B option to enforce the alignment IFF and
> only IFF it is required ? 

Perhaps.  But..

> Then we can enforce it separately for 32bit
> and 64bit platforms to 4 and 8 bytes respectively even.

It's 8 bytes for both.  It's possible that Linux doesn't hard fail if
you only do 4 byte alignment but the documented requirement is 8, for
arm32.

-- 
Tom
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