v1 -> v2
Add bpf_struct_ops_id() instead of using bpf_struct_ops_get()
Hi,
This patchset allows struct_ops implementors to get map id from kdata in
reg(), unreg() and update() so that they create an id to struct_ops
instance mapping. This in turn allows struct_ops kfuncs to refer to the
calling instance without passing a pointer to the struct_ops. The selftest
provides an end-to-end example.
Some struct_ops users extend themselves with other bpf programs, which
also need to call struct_ops kfuncs. For example, scx_layered uses
syscall bpf programs as a scx_layered specific control plane and uses
tracing programs to get additional information for scheduling [0].
The kfuncs may need to refer to the struct_ops instance and perform
jobs accordingly. To allow calling struct_ops kfuncs referring to
specific instances from different program types and context (e.g.,
struct_ops, tracing, async callbacks), the traditional way is to pass
the struct_ops pointer to kfuncs.
This patchset provides an alternative way, through a combination of
bpf map id and global variable. First, a struct_ops implementor will
use the map id of the struct_ops map as the id of an instance. Then,
it needs to maintain an id to instance mapping: inserting a new mapping
during reg() and removing it during unreg(). The map id can be acquired
by calling bpf_struct_ops_id().
[0] https://github.com/sched-ext/scx/blob/main/scheds/rust/scx_layered/src/bpf/main.bpf.c
Amery Hung (3):
bpf: Allow struct_ops to get map id by kdata
selftests/bpf: Add multi_st_ops that supports multiple instances
selftests/bpf: Test multi_st_ops and calling kfuncs from different
programs
include/linux/bpf.h | 1 +
kernel/bpf/bpf_struct_ops.c | 12 ++
.../test_struct_ops_id_ops_mapping.c | 77 +++++++++++++
.../bpf/progs/struct_ops_id_ops_mapping1.c | 59 ++++++++++
.../bpf/progs/struct_ops_id_ops_mapping2.c | 59 ++++++++++
.../selftests/bpf/test_kmods/bpf_testmod.c | 109 ++++++++++++++++++
.../selftests/bpf/test_kmods/bpf_testmod.h | 8 ++
.../bpf/test_kmods/bpf_testmod_kfunc.h | 2 +
8 files changed, 327 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/test_struct_ops_id_ops_mapping.c
create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_id_ops_mapping1.c
create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_id_ops_mapping2.c
--
2.47.3
