Re: [PATCH bpf-next v2 0/3] selftests/bpf: convert test_dev_cgroup to test_progs

[Stanislav Fomichev <sdf@fomichev.me>]

On 07/29, Alexis Lothoré (eBPF Foundation) wrote:
> Hello,
> this small series aims to integrate test_dev_cgroup in test_progs so it
> could be run automatically in CI. The new version brings a few differences
> with the current one:
> - test now uses directly syscalls instead of wrapping commandline tools
>   into system() calls
> - test_progs manipulates /dev/null (eg: redirecting test logs into it), so
>   disabling access to it in the bpf program confuses the tests. To fix this,
>   the first commit modifies the bpf program to allow access to char devices
>   1:3 (/dev/null), and disable access to char devices 1:5 (/dev/zero)
> - once test is converted, add a small subtest to also check for device type
>   interpretation (char or block)
> - paths used in mknod tests are now in /dev instead of /tmp: due to the CI
>   runner organisation and mountpoints manipulations, trying to create nodes
>   in /tmp leads to errors unrelated to the test (ie, mknod calls refused by
>   kernel, not the bpf program). I don't understand exactly the root cause
>   at the deepest point (all I see in CI is an -ENXIO error on mknod when trying to
>   create the node in tmp, and I can not make sense out of it neither
>   replicate it locally), so I would gladly take inputs from anyone more
>   educated than me about this.
> 
> The new test_progs part has been tested in a local qemu environment as well
> as in upstream CI:
> 
>  ./test_progs -a cgroup_dev
>  47/1    cgroup_dev/deny-mknod:OK
>  47/2    cgroup_dev/allow-mknod:OK
>  47/3    cgroup_dev/deny-mknod-wrong-type:OK
>  47/4    cgroup_dev/allow-read:OK
>  47/5    cgroup_dev/allow-write:OK
>  47/6    cgroup_dev/deny-read:OK
>  47/7    cgroup_dev/deny-write:OK
>  47      cgroup_dev:OK
>  Summary: 1/7 PASSED, 0 SKIPPED, 0 FAILED
> 
> ---
> Changes in v2:
> - directly pass expected ret code to subtests instead of boolean pass/not
>   pass
> - fix faulty fd check in subtest expected to fail on open
> - fix wrong subtest name
> - pass test buffer and corresponding size to read/write subtests
> - use correct series prefix
> - Link to v1: https://lore.kernel.org/r/20240725-convert_dev_cgroup-v1-0-2c8cbd487c44@bootlin.com

For the next respin (after addressing Alan's comment about
bpf_program__attach_cgroup):

Acked-by: Stanislav Fomichev <sdf@fomichev.me>