Re: [bug-report] Build error in tools/testing/selftests/bpf/

[Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>]

Hi Alan,

On 28/10/25 15:45, Alan Maguire wrote:
> On 28/10/2025 09:31, Harshit Mogalapalli wrote:
>> Hi all,
>>
>> I am seeing a build failure with latest bpf-next:
>>
>>
>> [root@hamogala-Kbuild bpf-next]# git describe
>> bpf-next-6.16-44604-gf9db3a38224e
>> [root@hamogala-Kbuild bpf-next]# make -j$(nproc) -C tools/testing/
>> selftests/bpf/
>> make: Entering directory '/home/opc/bpf-next/tools/testing/selftests/bpf'
>>
>> Usage:
>>         xxd [options] [infile [outfile]]
>>      or
>>         xxd -r [-s [-]offset] [-c cols] [-ps] [infile [outfile]]
>> Options:
>>      -a          toggle autoskip: A single '*' replaces nul-lines.
>> Default off.
>>      -b          binary digit dump (incompatible with -ps,-i,-r). Default
>> hex.
>>      -C          capitalize variable names in C include file style (-i).
>>      -c cols     format <cols> octets per line. Default 16 (-i: 12, -ps:
>> 30).
>>      -E          show characters in EBCDIC. Default ASCII.
>>      -e          little-endian dump (incompatible with -ps,-i,-r).
>>      -g          number of octets per group in normal output. Default 2
>> (-e: 4).
>>      -h          print this summary.
>>      -i          output in C include file style.
>>      -l len      stop after <len> octets.
>>      -o off      add <off> to the displayed file position.
>>      -ps         output in postscript plain hexdump style.
>>      -r          reverse operation: convert (or patch) hexdump into binary.
>>      -r -s off   revert with <off> added to file positions found in hexdump.
>>      -d          show offset in decimal instead of hex.
>>      -s [+][-]seek  start at <seek> bytes abs. (or +: rel.) infile offset.
>>      -u          use upper case hex letters.
>>      -v          show version: "xxd V1.10 27oct98 by Juergen Weigert".
>> make: *** [Makefile:726: verification_cert.h] Error 1
>> make: *** Deleting file 'verification_cert.h'
>> make: Leaving directory '/home/opc/bpf-next/tools/testing/selftests/bpf'
>>
>> This looks related to: commit: b720903e2b14 ("selftests/bpf: Enable
>> signature verification for some lskel tests")
>>
>>
> 
> hi Harshit, I ran into this too; it turns out the version of
> /usr/bin/xxd needs to support the -n (name) option and only the
> vim-common v9 or later version supports that. The name option allows the
> user to provide a name not derived implicitly from the file path
> apparently. It _might_ make sense to do something like the below since
> it would loosen the requirement for a very new vim-common package to be
> installed. Many distros may not have a new enough xxd packaged, and as a
> result run into this issue.
> 

Ah, thanks for explaining.

> The patch simply creates a symlink to the cert with the right name,
> allowing xxd to generate the header without the -n option.
> 
> diff --git a/tools/testing/selftests/bpf/Makefile
> b/tools/testing/selftests/bpf/Makefile
> index 7437c325179e..a276f83d7c52 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -722,7 +722,8 @@ $(VERIFICATION_CERT) $(PRIVATE_KEY): $(VERIFY_SIG_SETUP)
>          $(Q)$(VERIFY_SIG_SETUP) genkey $(BUILD_DIR)
> 
>   $(VERIFY_SIG_HDR): $(VERIFICATION_CERT)
> -       $(Q)xxd -i -n test_progs_verification_cert $< > $@
> +       $(Q)ln -fs $< test_progs_verification_cert && \
> +       xxd -i test_progs_verification_cert > $@
> 
>   # Define test_progs test runner.
>   TRUNNER_TESTS_DIR := prog_tests
> 
Agree, this works for me.
Thanks for providing a fix.

Regards,
Harshit