[PATCH bpf-next v3 0/2] Introduce access remote cpu elem support in BPF percpu map

[Feng zhou]

From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>

Trace some functions, such as enqueue_task_fair, need to access the
corresponding cpu, not the current cpu, and bpf_map_lookup_elem percpu map
cannot do it. So add bpf_map_lookup_percpu_elem to accomplish it for
percpu_array_map, percpu_hash_map, lru_percpu_hash_map.

Changelog:
----------
v2->v3: Addressed comments from Andrii Nakryiko.
- use /* */ instead of //
- use libbpf_num_possible_cpus() instead of sysconf(_SC_NPROCESSORS_ONLN)
- use 8 bytes for value size
- fix memory leak
- use ASSERT_EQ instead of ASSERT_OK
- add bpf_loop to fetch values on each possible CPU
some details in here:
https://lore.kernel.org/lkml/20220511093854.411-1-zhoufeng.zf@xxxxxxxxxxxxx/T/

v1->v2: Addressed comments from Alexei Starovoitov.
- add a selftest for bpf_map_lookup_percpu_elem.

Feng Zhou (2):
  bpf: add bpf_map_lookup_percpu_elem for percpu map
  selftests/bpf: add test case for bpf_map_lookup_percpu_elem

 include/linux/bpf.h                           |  2 +
 include/uapi/linux/bpf.h                      |  9 +++
 kernel/bpf/arraymap.c                         | 15 ++++
 kernel/bpf/core.c                             |  1 +
 kernel/bpf/hashtab.c                          | 32 +++++++++
 kernel/bpf/helpers.c                          | 18 +++++
 kernel/bpf/verifier.c                         | 17 ++++-
 kernel/trace/bpf_trace.c                      |  2 +
 tools/include/uapi/linux/bpf.h                |  9 +++
 .../bpf/prog_tests/map_lookup_percpu_elem.c   | 59 +++++++++++++++
 .../bpf/progs/test_map_lookup_percpu_elem.c   | 71 +++++++++++++++++++
 11 files changed, 233 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/map_lookup_percpu_elem.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_map_lookup_percpu_elem.c

-- 
2.20.1