Re: [PATCH 00/14] Add SPDX SBOM generation tool

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Jan 19, 2026 at 10:51:29AM +0100, Greg KH wrote:
> On Mon, Jan 19, 2026 at 07:47:17AM +0100, Luis Augenstein wrote:
> > This patch series introduces a Python-based tool for generating SBOM
> > documents in the SPDX 3.0.1 format for kernel builds.
> > 
> > A Software Bill of Materials (SBOM) describes the individual components
> > of a software product. For the kernel, the goal is to describe the
> > distributable build outputs (typically the kernel image and modules),
> > the source files involved in producing these outputs, and the build
> > process that connects the source and output files.
> > 
> > To achieve this, the SBOM tool generates three SPDX documents:
> > 
> > - sbom-output.spdx.json
> >   Describes the final build outputs together with high-level
> >   build metadata.
> > 
> > - sbom-source.spdx.json
> >   Describes all source files involved in the build, including
> >   licensing information and additional file metadata.
> > 
> > - sbom-build.spdx.json
> >   Describes the entire build process, linking source files
> >   from the source SBOM to output files in the output SBOM.
> > 
> > The sbom tool is optional and runs only when CONFIG_SBOM is enabled. It
> > is invoked after the build, once all output artifacts have been
> > generated. Starting from the kernel image and modules as root nodes,
> > the tool reconstructs the dependency graph up to the original source
> > files. Build dependencies are primarily derived from the .cmd files
> > generated by Kbuild, which record the full command used to build
> > each output file.
> > 
> > Currently, the tool only supports x86 and arm64 architectures.
> > 
> > Co-developed-by: Maximilian Huber <maximilian.huber@tngtech.com>
> > Signed-off-by: Maximilian Huber <maximilian.huber@tngtech.com>
> > Signed-off-by: Luis Augenstein <luis.augenstein@tngtech.com>
> 
> This is great work, thank you so much for doing this!
> 
> Note, I just tested the series, on 6.19-rc6, and with CONFIG_SBOM
> enabled, I get this following "message" at the end of the build when it
> generates the sbom:
> 
> 	make[3]: Nothing to be done for 'sbom'.
> 
> Is that intentional?

Ah, it's on the second run that I see this:

End of the first run that builds the sbom files:
...
  OBJCOPY arch/x86/boot/vmlinux.bin
  AS      arch/x86/boot/header.o
  LD      arch/x86/boot/setup.elf
  OBJCOPY arch/x86/boot/setup.bin
  BUILD   arch/x86/boot/bzImage
Kernel: arch/x86/boot/bzImage is ready  (#526)
  DESCEND sbom
  GEN     sbom-build.spdx.json sbom-output.spdx.json
[INFO] Skipped creating a dedicated source SBOM because source files cannot be reliably classified when the source and object trees are identical. Added source files to the build SBOM instead.

Then I build again and get the following:

  DESCEND objtool
  CALL    scripts/checksyscalls.sh
  INSTALL libsubcmd_headers
Kernel: arch/x86/boot/bzImage is ready  (#526)
  DESCEND sbom
make[3]: Nothing to be done for 'sbom'.


That make message shouldn't probably show up, right?

Also, I don't know if this is even possible, or you care about it, but if you
have ANY sbom file present, it is not regenerated:

	$ rm sbom-build.spdx.json sbom-output.spdx.json
	$ touch sbom-build.spdx.json sbom-output.spdx.json
	$ make
	  DESCEND objtool
	  CALL    scripts/checksyscalls.sh
	  INSTALL libsubcmd_headers
	Kernel: arch/x86/boot/bzImage is ready  (#526)
	  DESCEND sbom
	make[3]: Nothing to be done for 'sbom'.

So, if I change the build config, which will change the sbom output, will the
sbom be regenerated?  Should it depend on the config .h files to know this?

thanks,

greg k-h