Re: [PATCH v2 2/2] ARM: OMAP2+: Pad SPL binary to 8-byte alignment before DTB

[Tom Rini <trini@konsulko.com>]

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On Mon, Jan 12, 2026 at 10:56:04PM +0100, Marek Vasut wrote:
> On 1/12/26 5:48 PM, Tom Rini wrote:
> > On Mon, Jan 12, 2026 at 06:38:19PM +0530, Anshul Dalal wrote:
> > > On Mon Jan 12, 2026 at 3:41 PM IST, Beleswar Padhi wrote:
> > > > The OMAP2 SPL linker script (also used for K3 platforms) currently uses
> > > > a 4-byte alignment directive after the __u_boot_list section. This
> > > > alignment directive only advances the location counter without padding
> > > > the actual binary output.
> > > > 
> > > > When objcopy extracts u-boot-spl-nodtb.bin, it includes only actual
> > > > data, stopping at the last byte of __u_boot_list (e.g., 0x41c359fc),
> > > > not an aligned address (e.g., 0x41c35a00). So, when the FIT image
> > > > containing device trees is concatenated to the SPL binary, it gets
> > > > appended at this unaligned file size, causing libfdt validation failure.
> > > > 
> > > > To fix this, move the alignment directive into the __u_boot_list section
> > > > itself and make it 8-byte aligned as per DT spec. This forces the linker
> > > > to include padding as part of the section data, ensuring objcopy
> > > > includes the padding bytes in the binary and the appended FIT image
> > > > starts at an 8-byte aligned boundary.
> > > > 
> > > > Reported-by: Anshul Dalal <anshuld@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@ti.com>
> > > > ---
> > > > v2: Changelog:
> > > > 1. Get rid of extra ALIGN() directive, replace it with a comment
> > > > 2. Carry Reported-by, Closes and Fixes tag.
> > > > 
> > > > Link to v1:
> > > > https://lore.kernel.org/all/20260109190026.58464-3-b-padhi@ti.com/
> > > > 
> > > >   arch/arm/mach-omap2/u-boot-spl.lds | 6 +++++-
> > > >   1 file changed, 5 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/arch/arm/mach-omap2/u-boot-spl.lds b/arch/arm/mach-omap2/u-boot-spl.lds
> > > > index 3bb759d8a1c..5ad169a37b7 100644
> > > > --- a/arch/arm/mach-omap2/u-boot-spl.lds
> > > > +++ b/arch/arm/mach-omap2/u-boot-spl.lds
> > > > @@ -35,9 +35,13 @@ SECTIONS
> > > >   	. = ALIGN(4);
> > > >   	__u_boot_list : {
> > > >   		KEEP(*(SORT(__u_boot_list*)));
> > > > +		/*
> > > > +		 * Ensure 8-byte alignment at the end of the last section before
> > > > +		 * DTB is appended, to satisfy DT spec alignment requirements
> > > > +		 */
> > > > +		. = ALIGN(8);
> > > 
> > > I wonder if there could be a better way to handle this constraint,
> > > currently we have two major problems with this approach:
> > > 
> > > 1. All platforms facing similar alignment issues would have to modify
> > > their linker scripts.
> > 
> > Yes, agreed.
> > 
> > > 2. The FDT only gets appended directly to SPL binary in cases of
> > > CONFIG_SPL_SEPARATE_BSS. Otherwise we do (SPL binary + BSS + FDT) as per
> > > the $(obj)/$(SPL_BIN)-dtb.bin make target. Which means BSS would have to
> > > be 8-byte aligned as well as the SPL binary.
> > > 
> > > I wonder if we could have a new make target for say
> > > u-boot-spl-nodtb-aligned.bin which is just (SPL binary + optionally BSS
> > > + padding for alignment) and at runtime we modify the fdt addr in gd to
> > > point to the correctly aligned address?
> > 
> > Looking back at
> > https://lore.kernel.org/all/87h65ihumb.fsf@bloch.sibelius.xs4all.nl/ we
> > can use dd as a portable way to ensure that a file ends with 8-byte
> > alignmnent by doing:
> > dd if=testfile bs=8 conv=sync of=testfile_pad
> > and we get a zero-padded 8-byte aligned output file, and at the end of
> > that we can concatenate our dtb.
> You still need to make sure there is a symbol generated by the linker that
> points at the END of the u-boot binary . dd happens too late, so you cannot
> do that. The alignment has to be done by the linker, in the linker script I
> think.

I guess the question is are we:
a) Look at $sym for device tree, and so $sym must be 8-byte aligned.
b) Look at end of self, rounded up to alignment, for device tree
c) (a) on some platforms (b) on other platforms
?

-- 
Tom

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