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

[Sean Anderson]

Hi Beleswar,

On 1/28/26 09:18, Beleswar Padhi wrote:
> From: Marek Vasut <marek.vasut+renesas at mailbox.org>
> 
> 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 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.
> 
> 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: Marek Vasut <marek.vasut+renesas at mailbox.org>
> Signed-off-by: Beleswar Padhi <b-padhi at ti.com>
> ---
> Testing Done:
> 1. Boot tested on all TI K3 platforms.
> 
> v4: Changelog:
> 1. Align only the DTBs to 8-bytes, other images in a FIT can have their
>     independent alignment. [Marek]
> 
> Link to v3:
> https://lore.kernel.org/all/20260122172247.2995437-1-b-padhi@ti.com/
> 
> v3: Changelog:
> 1. Default to 8-byte alignment for DTBs in mkimage instead of
>     passing -B 0x8 in build command [Marek]
> 2. Remove previous R/Bs.
> 
> Link to v2:
> https://lore.kernel.org/all/20260112101102.1417970-2-b-padhi@ti.com/
> 
> v2: Changelog:
> 1. Carry R/B, Reported-by, Closes and Fixes tag.
> 
> Link to v1:
> https://lore.kernel.org/all/20260109190026.58464-2-b-padhi@ti.com/
> 
>   tools/fit_image.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)

Can you please update doc/mkimage.1 as well? There should be a note about
this under -E.

> 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)
> +			align_size = 8;
> +

Doesn't this increase the alignment for all images following the devicetree?

And actually, doesn't this happen too late? By the time we check whether the
node is a devicetree, buf_ptr has already been updated. This check will only
affect the alignment of the *next* image in the FIT.

--Sean

>   		data = fdt_getprop(fdt, node, FIT_DATA_PROP, &len);
>   		if (!data)
>   			continue;