[v5,bpf-next,0/2] bpf: add a ksym BPF iterator

Message

Alan Maguire July 10, 2022, 10:09 p.m. UTC

a ksym BPF iterator would be useful as it would allow more flexible
interactions with kernel symbols than are currently supported; it could
for example create more efficient map representations for lookup,
speed up symbol resolution etc.

The idea was initially discussed here [1].

Changes since v4 [2]:

- add BPF_ITER_RESCHED to improve responsiveness (Hao, patch 1)
- remove pr_warn to be consistent with other iterators (Andrii, patch 1)
- add definitions to bpf_iter.h to ensure iter tests build on older
  kernels (Andrii, patch 2)

Changes since v3 [3]:

- use late_initcall() to register iter; means we are both consistent
  with other iters and can encapsulate all iter-specific code in
  kallsyms.c in CONFIG_BPF_SYSCALL (Alexei, Yonghong, patch 1).

Changes since v2 [4]:

- set iter->show_value on initialization based on current creds
  and use it in selftest to determine if we show values
  (Yonghong, patches 1/2)
- inline iter registration into kallsyms_init (Yonghong, patch 1)

Changes since RFC [5]:

- change name of iterator (and associated structures/fields) to "ksym"
  (Andrii, patches 1, 2)
- remove dependency on CONFIG_PROC_FS; it was used for other BPF
  iterators, and I assumed it was needed because of seq ops but I
  don't think it is required on digging futher (Andrii, patch 1)

[1] https://lore.kernel.org/all/YjRPZj6Z8vuLeEZo@krava/
[2] https://lore.kernel.org/bpf/[e-mail]/
[3] https://lore.kernel.org/bpf/[e-mail]
[4] https://lore.kernel.org/bpf/[e-mail]/
[5] https://lore.kernel.org/all/[e-mail]/

Alan Maguire (2):
  bpf: add a ksym BPF iterator
  selftests/bpf: add a ksym iter subtest

 kernel/kallsyms.c                                 | 91 +++++++++++++++++++++++
 tools/testing/selftests/bpf/prog_tests/bpf_iter.c | 16 ++++
 tools/testing/selftests/bpf/progs/bpf_iter.h      | 32 ++++++++
 tools/testing/selftests/bpf/progs/bpf_iter_ksym.c | 74 ++++++++++++++++++
 4 files changed, 213 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_ksym.c