[bpf-next,v3,0/4] introduce dummy BPF STRUCT_OPS

Message

Hou Tao Oct. 22, 2021, 7:55 a.m. UTC

Hi,

Currently the test of BPF STRUCT_OPS depends on the specific bpf
implementation (e.g, tcp_congestion_ops), but it can not cover all
basic functionalities (e.g, return value handling), so introduce
a dummy BPF STRUCT_OPS for test purpose.

Instead of loading a userspace-implemeted bpf_dummy_ops map into
kernel and calling the specific function by writing to sysfs provided
by bpf_testmode.ko, only loading bpf_dummy_ops related prog into
kernel and calling these prog by bpf_prog_test_run(). The latter
is more flexible and has no dependency on extra kernel module.

Now the return value handling is supported by test_1(...) ops,
and passing multiple arguments is supported by test_2(...) ops.
If more is needed, test_x(...) ops can be added afterwards.

Comments are always welcome.
Regards,
Hou

Change Log:
v3:
 * rebase on bpf-next
 * address comments for Martin, mainly include: merge patch 3 & patch 4 in v2,
   fix names of btf ctx access check helpers, handle CONFIG_NET,
   fix leak in dummy_ops_init_args(), simplify bpf_dummy_init()
 * patch 4: use a loop to check args in test_dummy_multiple_args()

v2: https://www.spinics.net/lists/bpf/msg47948.html
 * rebase on bpf-next
 * add test_2(...) ops to test the passing of multiple arguments
 * a new patch (patch #2) is added to factor out ctx access helpers
 * address comments from Martin & Andrii

v1: https://www.spinics.net/lists/bpf/msg46787.html

RFC: https://www.spinics.net/lists/bpf/msg46117.html

Hou Tao (4):
  bpf: factor out a helper to prepare trampoline for struct_ops prog
  bpf: factor out helpers to check ctx access for BTF function
  bpf: add dummy BPF STRUCT_OPS for test purpose
  selftests/bpf: add test cases for struct_ops prog

 include/linux/bpf.h                           |  47 ++++
 kernel/bpf/bpf_struct_ops.c                   |  32 ++-
 kernel/bpf/bpf_struct_ops_types.h             |   3 +
 kernel/trace/bpf_trace.c                      |  16 +-
 net/bpf/Makefile                              |   3 +
 net/bpf/bpf_dummy_struct_ops.c                | 203 ++++++++++++++++++
 net/ipv4/bpf_tcp_ca.c                         |   9 +-
 .../selftests/bpf/prog_tests/dummy_st_ops.c   | 115 ++++++++++
 .../selftests/bpf/progs/dummy_st_ops.c        |  50 +++++
 9 files changed, 446 insertions(+), 32 deletions(-)
 create mode 100644 net/bpf/bpf_dummy_struct_ops.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/dummy_st_ops.c
 create mode 100644 tools/testing/selftests/bpf/progs/dummy_st_ops.c