netdev - [PATCH bpf-next v2 0/3] Allow struct

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Message-ID: <20250806162540.681679-1-ameryhung@gmail.com>
Date: Wed,  6 Aug 2025 09:25:37 -0700
From: Amery Hung <ameryhung@...il.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,
	alexei.starovoitov@...il.com,
	andrii@...nel.org,
	daniel@...earbox.net,
	tj@...nel.org,
	memxor@...il.com,
	martin.lau@...nel.org,
	ameryhung@...il.com,
	kernel-team@...a.com
Subject: [PATCH bpf-next v2 0/3] Allow struct_ops to create map id to

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