[PATCH 0/5] LoongArch: BPF: arena instruction gating, private stack and exceptions

[George Guo <dongtai.guo@linux.dev>]

From: George Guo <guodongtai@kylinos.cn>

This series adds three LoongArch BPF JIT features, plus the accompanying
selftest changes:

  1. Gate the arena instructions the JIT does not implement (atomics and
     sign-extending loads on arena pointers) via bpf_jit_supports_insn(),
     so the verifier rejects such programs early with a clear message
     instead of letting them fail late in the JIT.
  2. Per-program private stack (bpf_jit_supports_private_stack()): the BPF
     stack of deep/recursive tracing programs is moved off the kernel
     stack into a per-CPU allocation bracketed by overflow/underflow
     guards that are checked on teardown.
  3. Exceptions / bpf_throw (bpf_jit_supports_exceptions()): unwind to the
     exception boundary program via arch_bpf_stack_walk() (built on the
     ORC unwinder) and reuse its frame in the exception callback. Gated on
     CONFIG_UNWINDER_ORC.

Patches 4-5 are the selftests side: a LoongArch deny list (arena_atomics,
which patch 1 deliberately rejects) and enabling the struct_ops private
stack test on LoongArch. They touch tools/testing/selftests/bpf, hence the
bpf@vger / linux-kselftest Cc.

The series is independent of the earlier "LoongArch: BPF: Support
internal-only MOV to resolve per-CPU addrs" / "Add timed may_goto support"
patches [1] (no functional or apply dependency) and targets the LoongArch
tree.

Testing on a LoongArch board (test_progs):
  - exceptions:               117 subtests, 0 failed
  - struct_ops_private_stack: private_stack / _fail / _recur, 0 failed
  - arena list/htab/strsearch and verifier_arena*: pass
  - arena_atomics: rejected by the verifier as expected
      ("BPF_ATOMIC stores into Rn arena is not allowed"), hence the
      deny-list entry in patch 4

[1] <https://lore.kernel.org/all/20260609041407.122384-1-dongtai.guo@linux.dev/>

George Guo (5):
  LoongArch: BPF: Gate unsupported arena instructions via
    bpf_jit_supports_insn()
  LoongArch: BPF: Add private stack support
  LoongArch: BPF: Add exceptions (bpf_throw) support
  selftests/bpf: Add LoongArch deny list
  selftests/bpf: Enable struct_ops private stack test for LoongArch

 arch/loongarch/kernel/stacktrace.c            |  52 ++++++
 arch/loongarch/net/bpf_jit.c                  | 172 +++++++++++++++++-
 arch/loongarch/net/bpf_jit.h                  |   1 +
 .../testing/selftests/bpf/DENYLIST.loongarch  |   2 +
 .../bpf/prog_tests/struct_ops_private_stack.c |   2 +-
 5 files changed, 222 insertions(+), 7 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/DENYLIST.loongarch


base-commit: 186d3c4e92242351afc24d9784f31cb4cd08a4b7
-- 
2.25.1