[bpf-next,v5,0/7] IRQ save/restore

Message

Kumar Kartikeya Dwivedi Nov. 29, 2024, 12:16 a.m. UTC

This set introduces support for managing IRQ state from BPF programs.
Two new kfuncs, bpf_local_irq_save, and bpf_local_irq_restore are
introduced to enable this functionality.

Intended use cases are writing IRQ safe data structures (e.g. memory
allocator) in BPF programs natively, and use in new spin locking
primitives intended to be introduced in the next few weeks.

The set begins with some refactoring patches before the actual
functionality is introduced. Patch 1 consolidates all resource related
state in bpf_verifier_state, and moves it out from bpf_func_state.

Patch 2 refactor acquire and release functions for reference state to
make them reusable without duplication for other resource types.

After this, patch 3 refactors stack slot liveness marking logic to be
shared between dynptr, and iterators, in preparation for introducing
same logic for irq flag object on stack.

Finally, patch 4 and 7 introduce the new kfuncs and their selftests. For
more details, please inspect the patch commit logs. Patch 5 makes the
error message in case of resource leaks under BPF_EXIT a bit clearer.
Patch 6 expands coverage of existing preempt-disable selftest to cover
sleepable kfuncs.

See individual patches for more details.

Changelog:
----------
v4 -> v5
v4: https://lore.kernel.org/bpf/[e-mail]

 * Do regno - 1 when printing argument
 * Pass verifier state explicitly into print_{insn,verifier}_state (Eduard)
 * Pass frameno instead of bpf_func_state (Eduard)
 * Move bpf_reference_state *refs after parent to fill two holes in
   bpf_verifier_state (Eduard). The hunk fixing that bug is in the
   commit adding IRQ save/restore kfuncs, as it is only needed then.
 * Fix bug in release_reference_state breaking stack property (Eduard)
 * Add selftest for triggering and reproducing bug found by Eduard
   irq_ooo_refs_array in final patch
 * Print insn_idx and active_irq_id on error (Eduard)
 * Add more acks

v3 -> v4
v3: https://lore.kernel.org/bpf/[e-mail]

 * Add yet another missing kfunc declaration to silence s390 CI

v2 -> v3
v2: https://lore.kernel.org/bpf/[e-mail]

 * Drop REF_TYPE_LOCK_MASK
 * Add kfunc declarations to selftest to silence s390 CI errors

v1 -> v2
v1: https://lore.kernel.org/bpf/[e-mail]

 * Drop reference -> resource renaming in the verifier (Eduard, Alexei)
 * Change verifier log for check_resource_leak for BPF_EXIT (Eduard)
 * Remove id parameter from acquire_resource_state, read s->id (Eduard)
 * Rename erase to release for reference state (Eduard)
 * Move resource state to bpf_verifier_state (Eduard, Alexei)
 * Drop unnecessary casting to/from u64 in helpers (Eduard)
 * Add test for arg != PTR_TO_STACK (Eduard)
 * Drop now redundant tests (Eduard)
 * Address some other misc nits
 * Add Reviewed-by and Acked-by from Eduard

Kumar Kartikeya Dwivedi (7):
  bpf: Consolidate locks and reference state in verifier state
  bpf: Refactor {acquire,release}_reference_state
  bpf: Refactor mark_{dynptr,iter}_read
  bpf: Introduce support for bpf_local_irq_{save,restore}
  bpf: Improve verifier log for resource leak on exit
  selftests/bpf: Expand coverage of preempt tests to sleepable kfunc
  selftests/bpf: Add IRQ save/restore tests

 include/linux/bpf_verifier.h                  |  27 +-
 kernel/bpf/helpers.c                          |  17 +
 kernel/bpf/log.c                              |  21 +-
 kernel/bpf/verifier.c                         | 573 +++++++++++++-----
 .../selftests/bpf/prog_tests/verifier.c       |   2 +
 .../selftests/bpf/progs/exceptions_fail.c     |   4 +-
 tools/testing/selftests/bpf/progs/irq.c       | 444 ++++++++++++++
 .../selftests/bpf/progs/preempt_lock.c        |  28 +-
 .../selftests/bpf/progs/verifier_spin_lock.c  |   2 +-
 9 files changed, 950 insertions(+), 168 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/irq.c


base-commit: c8d02b547363880d996f80c38cc8b997c7b90725