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

[Marek Vasut]

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;
"

> We
> would get the same result when using mkimage -f auto -b ...dtb... -B 0x8
> I think we should be fine with this limitation for the usecases when
> generating fitImage with mixed images. Unless you have some idea?
What about the above ?