On 2026/8/17 15:24, Chen Pei wrote:
Hi, Signed loads from arena memory are currently unsupported on riscv64: bpf_jit_supports_insn() rejects BPF_MEMSX loads when in_arena is set, so the verifier fails such programs with "sign extending loads from arena are not supported yet". The x86 and arm64 JITs gained support for them in v6.18 (a91ae3c89311, eab2a71f3a6a). Since compilers are free to generate signed loads into arena memory (e.g. GCC-14 was reported to do so), otherwise valid BPF programs fail to load on riscv64. This series adds BPF_PROBE_MEM32SX support to the RV64 JIT and enables the corresponding selftests on riscv64: 1 implements signed arena loads in the RV64 JIT. The verifier already converts MEMSX loads from PTR_TO_ARENA to BPF_PROBE_MEM32SX once bpf_jit_supports_insn() allows them, so the JIT reuses the existing arena handling: the arena base (RV_REG_ARENA) is added to the source register and the load is emitted with sign extension (lb/lh/lw). BPF_PROBE_MEM32SX is also added to the add_exception_handler() mode gate so faulting loads register an exception table entry that clears the destination register and resumes execution. 2 enables the arena LDSX tests on riscv64: JIT disassembly assertions are added to arena_ldsx_disasm, and arena_ldsx_exception/s8/s16/s32 are now run on riscv64. The series was verified on riscv64 with QEMU (-M virt -cpu max): all five arena_ldsx tests pass, including the exception path (load from unallocated arena memory returns 0) and the sign-extension values (s8/s16/s32 tests return -1 as expected). Note: the __jited assertions in patch 2 were derived from the JIT register allocation (R0->a5, R1->a0, R8->s3, R9->s4, arena base in s7) and the emit_ldx() code paths; happy to adjust them if a disassembler output detail differs.
Test meets happy. For this series: Tested-by: Pu Lehui <[email protected]>
Thanks, Pei Chen Pei (2): bpf, riscv: Add support for signed arena loads selftests/bpf: Enable arena LDSX tests for riscv64 arch/riscv/net/bpf_jit_comp64.c | 15 +++++++++------ .../testing/selftests/bpf/progs/verifier_ldsx.c | 17 +++++++++++++++++ 2 files changed, 26 insertions(+), 6 deletions(-)
