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

Wed May 6 18:17:47 CEST 2020

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