From: Anton Protopopov <a.s.protopopov@gmail.com>
To: bot+bpf-ci@kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
eddyz87@gmail.com, memxor@gmail.com, almagui@kernel.org,
john.fastabend@gmail.com, qmo@kernel.org, brauner@kernel.org,
kpsingh@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org,
emil@etsalapatis.com, ihor.solodrai@linux.dev, sashal@kernel.org,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
martin.lau@kernel.org, mason@kernel.org
Subject: Re: [PATCH v2 bpf-next 11/18] bpf: Follow PHIs in bpf_scan_ir
Date: Tue, 10 Nov 2026 14:04:41 +0000 [thread overview]
Message-ID: <avMkeelRyvo-Bzuf@mail.gmail.com> (raw)
In-Reply-To: <8ab81e05089b4f5ec1ecb1bea9e6dc5cc2953a67f16e9369db005c2f3f3ee242@mail.kernel.org>
On 26/11/09 05:42PM, bot+bpf-ci@kernel.org wrote:
> > bpf: Follow PHIs in bpf_scan_ir
>
> TL;DR: Nits only: in bpf_scan_ir.cpp, isErrnoRange() duplicates
> errnoConstant()'s errno check, so the range is defined twice; also a comment
> style nit.
>
> > diff --git a/scripts/llvm-plugins/bpf_scan_ir.cpp b/scripts/llvm-plugins/bpf_scan_ir.cpp
> > --- a/scripts/llvm-plugins/bpf_scan_ir.cpp
> > +++ b/scripts/llvm-plugins/bpf_scan_ir.cpp
>
> [ ... ]
>
> > @@ -34,9 +36,40 @@ namespace {
> >
> > static constexpr int MaxErrno = 4095;
> >
> > +// is Range in [-4095, 0) ?
> > +static bool isErrnoRange(const ConstantRange &Range)
> > +{
> > + unsigned Width = Range.getBitWidth();
> > +
> > + if (Width != 32 && Width != 64)
> > + return false;
> > +
> > + auto L = APInt(Width, 0) - APInt(Width, MaxErrno);
> > + auto R = APInt(Width, 0);
> > + return !Range.isEmptySet() && ConstantRange(L, R).contains(Range);
> > +}
> > +
>
> this isn't a bug, but could singleErrno() and errnoConstant() share one
> check?
>
> isErrnoRange() has a single caller, singleErrno(), which only passes it a
> range that getSingleElement() already showed to hold exactly one value.
> For that input the width check, the isEmptySet() test and the wrapped
> ConstantRange containment do the same thing as errnoConstant() below
> (width of 32 or 64, then N >= -MaxErrno && N < 0), so the errno range is
> now defined in two places, and the !Range.isEmptySet() test can never
> fail.
>
> For example, errnoConstant() could call
> singleErrno(ConstantRange(C->getValue()), N), or singleErrno() could test
> the sign-extended element against MaxErrno directly.
>
> Also, the "// is Range in [-4095, 0) ?" comment is the only function-level
> comment in the file using // rather than /* */, and it hardcodes -4095
> where the code uses MaxErrno.
Yes, thanks, will fix
>
> ---
> 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/42662799554
next prev parent reply other threads:[~2026-11-10 13:53 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-09 17:05 [PATCH v2 bpf-next 00/18] Auto-detect BPF fmodret targets Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 01/18] bpf: Add BTF ID sets for fmod_ret targets Anton Protopopov
2026-11-09 17:42 ` bot+bpf-ci
2026-11-10 14:00 ` Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 02/18] bpf: Add a btf_id_set8_entry helper Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 03/18] bpf: Build fmod_ret target sets from BTF decl tags Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 04/18] selftests/bpf: Declare bpf_fentry_test1 in tracing tests Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 05/18] bpf: Declare fmod_ret targets with BTF_FMODRET sets Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 06/18] selftests/bpf: Test fmod_ret BTF decl tags and attach permission Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 07/18] scripts: Add LLVM plugin infrastructure Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 08/18] bpf: Add the bpf_scan_ir LLVM plugin Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 09/18] bpf: Find fmod_ret candidates in bpf_scan_ir Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 10/18] bpf: Allow writes to private stack objects " Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 11/18] bpf: Follow PHIs " Anton Protopopov
2026-11-09 17:42 ` bot+bpf-ci
2026-11-10 14:04 ` Anton Protopopov [this message]
2026-11-09 17:05 ` [PATCH v2 bpf-next 12/18] bpf: Follow integer casts " Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 13/18] bpf: Check the return values of fmod_ret programs on found targets Anton Protopopov
2026-11-09 17:42 ` bot+bpf-ci
2026-11-10 14:30 ` Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 14/18] bpf: Require the JIT for fmod_ret programs on found 64-bit targets Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 15/18] resolve_btfids: Tag fmod_ret candidates as targets Anton Protopopov
2026-11-09 17:42 ` bot+bpf-ci
2026-11-10 15:17 ` Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 16/18] selftests/bpf: Test fmod_ret candidates found by bpf_scan_ir Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 17/18] selftests/bpf: Enable bpf_scan_ir in the config Anton Protopopov
2026-11-09 17:05 ` [PATCH v2 bpf-next 18/18] bpftool: List and show fmod_ret targets Anton Protopopov
2026-11-09 17:42 ` bot+bpf-ci
2026-11-10 15:30 ` Anton Protopopov
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