Re: [PATCH bpf-next 1/2] bpf, parisc: Add support for BPF_SDIV and BPF_SMOD in the parisc64 JIT

Nicholas Dudar <[email protected]> Fri, 17 Jul 2026 16:58:27 -0400

Newsgroups	org.kernel.vger.linux-parisc,org.kernel.vger.bpf,org.kernel.vger.linux-kernel
Message-ID	<CAJZwKkjUR3FLKwY-WBSwFgK_nLrV20nGGtHZOt3Jf6SXpgyurg@mail.gmail.com>

On Fri, Jul 17, 2026 at 19:16 UTC, [email protected] wrote:
> [High] The patch implements BPF_SDIV and BPF_SMOD for the 64-bit
> PA-RISC JIT but omits the 32-bit JIT, causing signed divisions to be
> silently miscompiled as unsigned.

This is a 2-patch series, and patch 2/2 ("bpf, parisc: Add support for
BPF_SDIV and BPF_SMOD in the parisc32 JIT") is the one that modifies
bpf_jit_comp32.c. It threads is_signed = (insn->off == 1) through
emit_alu_r32()/emit_alu_r64() and uses the $$divI/$$remI signed
millicode (ALU32) and the hppa_sdiv64()/hppa_sdiv64_rem() helpers
(ALU64) on the signed path instead of $$divU/$$remU/hppa_div64().

Patch 1/2 adds those shared helpers in bpf_jit_core.c, which is why it
does not touch bpf_jit_comp32.c. With both patches applied the parisc32
JIT returns the signed result the verifier and interpreter compute; the
ALU32/ALU64 SDIV/SMOD test_bpf cases pass.

Nicholas