[PATCH V2] mkimage: fit: Do not tail-pad fitImage with external data
Alex Kiernan
alex.kiernan at gmail.com
Wed May 6 17:43:48 CEST 2020
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?
--
Alex Kiernan
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