From: bot+bpf-ci@kernel.org
To: main.kalliope@gmail.com,ast@kernel.org,daniel@iogearbox.net,andrii@kernel.org,eddyz87@gmail.com,memxor@gmail.com,deller@gmx.de,James.Bottomley@HansenPartnership.com
Cc: bpf@vger.kernel.org,linux-parisc@vger.kernel.org,linux-kernel@vger.kernel.org,visitorckw@gmail.com,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,clm@meta.com,ihor.solodrai@linux.dev
Subject: Re: [PATCH bpf-next 1/2] bpf, parisc: Add support for BPF_SDIV and BPF_SMOD in the parisc64 JIT
Date: Fri, 17 Jul 2026 19:52:25 +0000 (UTC) [thread overview]
Message-ID: <730b11181226fe2aa47c5add541431bb8bd4b4fa6af6e3b41bd8a09161d2f51c@mail.kernel.org> (raw)
In-Reply-To: <20260717190544.257306-2-main.kalliope@gmail.com>
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> emit_call_libgcc_ll() zero-extends the ALU32 operands and calls the
> unsigned hppa_div64()/hppa_div64_rem() helpers regardless of the BPF
> instruction's signedness, so the parisc64 JIT does not implement
> signed BPF_SDIV and BPF_SMOD (off == 1). Signed ALU32 and ALU64
> div/mod get an unsigned quotient and remainder rather than the
> verifier's and the interpreter's signed result for negative operands.
>
> Add hppa_sdiv64()/hppa_sdiv64_rem() wrapping div64_s64(), thread
> is_signed = (insn->off == 1) through the div/mod emit sites, and on the
> signed path sign-extend the ALU32 operands (and the immediate divisor)
> instead of zero-extending them before calling the signed helpers.
> bpf_do_misc_fixups() rewrites the zero-divisor and INT_MIN/-1 cases out
> of the instruction stream before the JIT runs.
>
> Signed-off-by: Nicholas Dudar <main.kalliope@gmail.com>
This looks like a fix for a correctness bug that has been present since
the parisc64 eBPF JIT was first added, where signed div/mod produced an
unsigned result for negative operands.
Should this carry a Fixes: tag?
Fixes: c95e269773b3 ("parisc: Add 64-bit eBPF JIT compiler")
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/29607384764
next prev parent reply other threads:[~2026-07-17 19:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-17 19:05 [PATCH bpf-next 0/2] bpf, parisc: Add support for BPF_SDIV and BPF_SMOD in the parisc JITs Nicholas Dudar
2026-07-17 19:05 ` [PATCH bpf-next 1/2] bpf, parisc: Add support for BPF_SDIV and BPF_SMOD in the parisc64 JIT Nicholas Dudar
2026-07-17 19:52 ` bot+bpf-ci [this message]
2026-07-17 20:58 ` Nicholas Dudar
2026-07-17 22:27 ` Nicholas Dudar
2026-07-17 19:05 ` [PATCH bpf-next 2/2] bpf, parisc: Add support for BPF_SDIV and BPF_SMOD in the parisc32 JIT Nicholas Dudar
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