[PATCH bpf-next v3 0/2] bpf, riscv: Add BPF stack arguments support for RV64 JIT

[Feng Jiang]

Port the BPF stack argument feature (BPF_REG_PARAMS / r11) to the
RV64 JIT, matching what x86 and arm64 already do.

BPF-to-BPF calls keep all extra arguments on the stack.  For kfunc
calls, the JIT loads arguments 6-8 into A5-A7 at the call site to
satisfy the RISC-V C calling convention.

Tested on riscv64 QEMU with LLVM main [1]; BPF-to-BPF and kfunc
selftests pass.

[1] https://github.com/llvm/llvm-project/pull/189060

Signed-off-by: Feng Jiang <jiangfeng@xxxxxxxxxx>
---
Changes in v3:
- Drop the exceptions.c guard change: the guarded programs use
  bpf_throw(), unsupported by the RV64 JIT, so the test is denylisted
  on riscv64 and the guard has no effect. (BPF CI)
- Link to v2: https://lore.kernel.org/r/20260813-bpf-riscv-stack-args-v2-0-efea8f9b3fe1@xxxxxxxxxx

Changes in v2:
- Sign-extend 32-bit kfunc arguments passed on the stack (args 9+),
  matching the register path and the RISC-V psABI. (Sashiko)
- Restrict the riscv selftest guard to __riscv_xlen == 64 so the
  tests are not enabled on RV32. (Sashiko)
- Link to v1: https://lore.kernel.org/r/20260812-bpf-riscv-stack-args-v1-0-67b246806e59@xxxxxxxxxx

---
Feng Jiang (2):
      bpf, riscv: Add BPF stack arguments support for RV64 JIT
      selftests/bpf: Enable stack argument tests for RV64

 arch/riscv/net/bpf_jit.h                           |  1 +
 arch/riscv/net/bpf_jit_comp64.c                    | 79 +++++++++++++++++++++-
 arch/riscv/net/bpf_jit_core.c                      |  4 ++
 .../selftests/bpf/progs/btf__stack_arg_precision.c |  3 +-
 .../bpf/progs/btf__verifier_stack_arg_order.c      |  3 +-
 tools/testing/selftests/bpf/progs/stack_arg.c      |  3 +-
 .../testing/selftests/bpf/progs/stack_arg_kfunc.c  |  3 +-
 .../selftests/bpf/progs/stack_arg_precision.c      |  3 +-
 .../selftests/bpf/progs/verifier_stack_arg.c       |  3 +-
 .../selftests/bpf/progs/verifier_stack_arg_order.c |  3 +-
 10 files changed, 95 insertions(+), 10 deletions(-)
---
base-commit: d114bb98936770c501c958bf2bc5fb6b7c0bad7b
change-id: 20260728-bpf-riscv-stack-args-6350d066a1e9

Best regards,
-- 
Feng Jiang <jiangfeng@xxxxxxxxxx>