[RFC PATCH bpf-next 0/3] bpf: freeze a task cgroup from bpf

[Djalal Harouni <tixxdz@gmail.com>]

This patch series adds support to freeze the task cgroup hierarchy
that is on a default cgroup v2 without going through kernfs interface.

For some cases we want to freeze the cgroup of a task based on some
signals, doing so from bpf is better than user space which could be
too late.

Planned users of this feature are: tetragon and systemd when freezing
a cgroup hierarchy that could be a K8s pod, container, system service
or a user session.

Patch 1: cgroup: add cgroup_freeze_no_kn() to freeze a cgroup from bpf
Patch 2: bpf: add bpf_task_freeze_cgroup() to freeze the cgroup of a task
Patch 3: selftests/bpf: add selftest for bpf_task_freeze_cgroup

 include/linux/cgroup.h                                      |   2 ++
 kernel/bpf/helpers.c                                        |  31 ++++
 kernel/cgroup/cgroup.c                                      |  67 ++++++++
 tools/testing/selftests/bpf/prog_tests/task_freeze_cgroup.c | 165 +++++++++++++++++++++
 tools/testing/selftests/bpf/progs/test_task_freeze_cgroup.c | 110 ++++++++++++++
 5 files changed, 375 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/task_freeze_cgroup.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_task_freeze_cgroup.c

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2.34.1