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

[Marek Vasut]

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 ?