[PATCH v4] tools: fit_image: Fallback to 8-byte alignment for flat_dt images

[Padhi, Beleswar]

On 1/28/2026 8:26 PM, Marek Vasut wrote:
> On 1/28/26 3:18 PM, Beleswar Padhi wrote:
>> From: Marek Vasut <marek.vasut+renesas at mailbox.org>
>
> Please drop this , it isnt needed.
>
>> When CONFIG_SPL_MULTI_DTB_FIT is enabled, multiple device trees are
>> packed inside the multidtb.fit FIT image. While the individual DTBs
>> and the FIT image start address are 8-byte aligned, the DTBs embedded
>> within the FIT image are not guaranteed to maintain 8-byte alignment.
>>
>> This misalignment causes -FDT_ERR_ALIGNMENT failure in
>> setup_multi_dtb_fit() when locating the next available DTB within the
>> FIT blob and setting gd->fdt_blob, because of the recent libfdt
>> hardening since commit 0535e46d55d7 ("scripts/dtc: Update to upstream
>> version v1.7.2-35-g52f07dcca47c")
>>
>> To fix this, check the image type when extracting
>
> "extracting" ? This code changes mkimage, so not "extracting" but 
> "packing" (into fitImage), right ?


Well the function name is fit_extract_data(). It is documented as extracting
all the data properties of a node to the end of the fit. So just keeping the
same terminology. Its obviously not in the same context as extracting data
out of a FIT image to consume information...

>
>> FIT image data and
>> set the alignment size to 8 bytes (if not already) only for flat_dt
>> images. This ensures correct alignment for device tree blobs as per the
>> DT spec, while also allowing different alignment sizes for other image
>> types within the FIT.
>
> [...]
>
>> diff --git a/tools/fit_image.c b/tools/fit_image.c
>> index e865f65a400..f842c845771 100644
>> --- a/tools/fit_image.c
>> +++ b/tools/fit_image.c
>> @@ -682,9 +682,17 @@ static int fit_extract_data(struct 
>> image_tool_params *params, const char *fname)
>>       for (node = fdt_first_subnode(fdt, images);
>>            node >= 0;
>>            node = fdt_next_subnode(fdt, node)) {
>> -        const char *data;
>> +        const char *data, *type;
>>           int len;
>>   +        /* Fallback to 8-byte alignment for DTBs if unaligned */
>> +        type = fdt_getprop(fdt, node, FIT_TYPE_PROP, &len);
>> +        if (type &&
>> +            len == sizeof("flat_dt") &&
>> +            !memcmp(type, "flat_dt", len) &&
>> +            align_size & 0x7)
>
> What will be the resulting alignment if align_size = 0x1f ? 8 right ? 
> I think it should be 0x20 .


I thought we agreed on resetting align_size to 8 if its not already aligned
(regardless if < or > 8) in v3 version of this patch[0]. Do we really 
have to
align the align_size var itself? It seems like a overkill to me...

[0]: 
https://lore.kernel.org/all/75b9e8b8-dbbe-4502-8d4f-9a50b332bc7f@mailbox.org/

Thanks,
Beleswar