[PATCH v3] mkimage: Default to 8-byte alignment for DTBs added via -b argument

[Marek Vasut]

On 1/23/26 11:40 AM, Anshul Dalal wrote:
> Hi Marek,
> 
> On Fri Jan 23, 2026 at 3:57 PM IST, Marek Vasut wrote:
>> On 1/23/26 4:32 AM, Beleswar Prasad Padhi wrote:
>>>
>>> On 23/01/26 00:33, Marek Vasut wrote:
>>>> On 1/22/26 6:45 PM, Tom Rini wrote:
>>>>> On Thu, Jan 22, 2026 at 10:52:47PM +0530, Beleswar Padhi wrote:
>>>>>
>>>>>> 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")
>>>>>>
>>>>>> The mkimage tool already supports enforcing this alignment via the -B
>>>>>> option, but users would have to specify it explicitly. This change
>>>>>> makes 8-byte alignment the default when using -b.
>>>>>>
>>>>>> Reported-by: Anshul Dalal <anshuld at ti.com>
>>>>>> Closes: https://lore.kernel.org/u-boot/DFJ950O0QM0D.380U0N16ZO19E@ti.com
>>>>>> Fixes: 0535e46d55d7 ("scripts/dtc: Update to upstream version v1.7.2-35-g52f07dcca47c")
>>>>>> Signed-off-by: Beleswar Padhi <b-padhi at ti.com>
>>>>>
>>>>> Tested-by: Tom Rini <trini at konsulko.com>
>>>> Doesn't this enable 8-byte alignment for everything in case a DT is specified on mkimage command line ? That doesn't seem right ?
>>>>
>>>> If I do mkimage -f auto -b ...dtb ... , then I only want the DTB to be 8-byte aligned, all the other blobs can be 4 byte aligned just fine .
>>>
>>>
>>> All the mkimage flags are parsed at once and populated in the params
>>> data structure in one shot in the code. There is no separation of code
>>> specifically for generating a FIT for a DTB vs for anything else.
>>
>> That does not seem to be true ?
>>
>> $ git grep -p '\<bl_len\>' tools/
>> tools/fit_image.c=static int fit_extract_data(struct image_tool_params
>> *params, const char *fname)
>> tools/fit_image.c:      align_size = params->bl_len ? params->bl_len : 4;
>> ...
>>
>> So something like that may work ?
>>
>> "
>> diff --git a/tools/fit_image.c b/tools/fit_image.c
>> index 0306333141e..0c606ba4cc3 100644
>> --- a/tools/fit_image.c
>> +++ b/tools/fit_image.c
>> @@ -642,9 +642,15 @@ 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;
>>
>> +               if (align_size < 8) {
>> +                       type = fdt_getprop(fdt, node, FIT_TYPE_PROP, &len);
>> +                       if (type && !strcmp(type, "flat_dt"))
>> +                               align_size = 8;
>> +               }
>> +
>>                   data = fdt_getprop(fdt, node, FIT_DATA_PROP, &len);
>>                   if (!data)
>>                           continue;
>> "
>>
> 
> I just ran a quick test with this diff and it seems to fix the issue for
> us. If it's okay can we take the change as is.
I think the strcmp needs to be some strncmp and check the 'len' too.

Let's see what others think.