[PATCH net-next v3 0/2] Add bpf current_task_in_cgroup helper & opensnoop example

[PATCH net-next v3 0/2] Add bpf current_task_in_cgroup helper & opensnoop example

[Sargun Dhillon]

This patchset includes a helper and an example to determine whether the probe is
currently executing in the context of a specific cgroup based on a cgroup bpf
map / array. The helper checks the cgroupsv2 hierarchy based on the handle in
the map and if the current cgroup is equal to it, or a descendant of it. The
helper was tested with the example program, and it was verified that the correct
behaviour occurs in the interrupt context.

In an earlier version of this patchset I had added an "opensnoop"-like tool, and 
I realized I was basically reimplementing a lot of the code that already exists 
in the bcc repo. So, instead I decided to write a test that creates a new mount 
namespace, mounts up the cgroupv2 hierarchy, and does some basic tests.  I used 
the sync syscall as a canary for these tests because it's a simple, 0-arg 
syscall. Once this patch is accepted, adding support to opensnoop will be easy.

I also added a task_in_cgroup_hierarchy function in cgroups.h, as this pattern
is used in a couple places. Converting those can be done in a later patchset.

Thanks to Alexei for providing review.

v1->v2: Clean up
v2->v3: Move around ifdefs out of *.c files, add an "integration" test

Sargun Dhillon (2):
  bpf: Add bpf_current_task_in_cgroup helper
  samples/bpf: Add test_current_task_in_cgroup test

 include/linux/bpf.h                            |  22 ++++
 include/linux/cgroup.h                         |  23 ++++
 include/uapi/linux/bpf.h                       |  11 ++
 kernel/bpf/arraymap.c                          |   2 +-
 kernel/bpf/verifier.c                          |   4 +-
 kernel/trace/bpf_trace.c                       |  27 +++++
 net/core/filter.c                              |  11 +-
 samples/bpf/Makefile                           |   4 +
 samples/bpf/bpf_helpers.h                      |   2 +
 samples/bpf/test_current_task_in_cgroup_kern.c |  43 ++++++++
 samples/bpf/test_current_task_in_cgroup_user.c | 145 +++++++++++++++++++++++++
 11 files changed, 285 insertions(+), 9 deletions(-)
 create mode 100644 samples/bpf/test_current_task_in_cgroup_kern.c
 create mode 100644 samples/bpf/test_current_task_in_cgroup_user.c

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2.7.4