[PATCH v14 bpf-next 6/6] selftests/bpf: Add test that uses fsverity and xattr to sign a file

[Song Liu]

On Tue, Nov 28, 2023 at 10:47 PM Alexei Starovoitov
<alexei.starovoitov at gmail.com> wrote:
>
> On Tue, Nov 28, 2023 at 4:37 PM Song Liu <song at kernel.org> wrote:
> > +char digest[MAGIC_SIZE + sizeof(struct fsverity_digest) + SHA256_DIGEST_SIZE];
>
> when vmlinux is built without CONFIG_FS_VERITY the above fails
> in a weird way:
>   CLNG-BPF [test_maps] test_sig_in_xattr.bpf.o
> progs/test_sig_in_xattr.c:36:26: error: invalid application of
> 'sizeof' to an incomplete type 'struct fsverity_digest'
>    36 | char digest[MAGIC_SIZE + sizeof(struct fsverity_digest) +
> SHA256_DIGEST_SIZE];
>       |                          ^     ~~~~~~~~~~~~~~~~~~~~~~~~
>
> Is there a way to somehow print a hint during the build what
> configs users need to enable to pass the build ?

Patch 5/6 added CONFIG_FS_VERITY to tools/testing/selftests/bpf/config.
This is a more general question for all required CONFIG_* specified in the
file (and the config files for other selftests).

In selftests/bpf/Makefile, we have logic to find vmlinux. We can add similar
logic to find .config used to build the vmlinux, and grep for each required
CONFIG_* from the .config file. Does this sound like a viable solution?

Thanks,
Song