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Mon, 10 Aug 2026 10:10:29 -0700 (PDT) Message-ID: <704b266e251c6b7e503ba489bf87a92039369c09.camel@gmail.com> Subject: Re: [PATCH bpf-next 1/6] bpf: Derive the atomic load register in one place From: Eduard Zingerman To: Daniel Borkmann , memxor@gmail.com Cc: puranjay@kernel.org, bpf@vger.kernel.org Date: Mon, 10 Aug 2026 10:10:26 -0700 In-Reply-To: <20260810134346.466004-1-daniel@iogearbox.net> References: <20260810134346.466004-1-daniel@iogearbox.net> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2-10 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-08-10 at 15:43 +0200, Daniel Borkmann wrote: ... > --- a/include/linux/filter.h > +++ b/include/linux/filter.h > @@ -414,6 +414,30 @@ static inline bool bpf_atomic_is_load_acq(const stru= ct bpf_insn *insn) > =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 insn->imm =3D=3D BPF_LOAD_ACQ= ; > =C2=A0} > =C2=A0 > +/* > + * Given an instruction @insn, return the number of the BPF register tha= t a > + * BPF_ATOMIC reads the value at its memory operand into, or -1 if there= is > + * no such register. That is the register a BPF_PROBE_ATOMIC has to clea= r when > + * the access faults. Like bpf_atomic_is_load_acq(), @insn is not assume= d to > + * be a BPF_ATOMIC here. > + */ > +static inline int bpf_atomic_load_reg(const struct bpf_insn *insn) > +{ > + if (BPF_CLASS(insn->code) !=3D BPF_STX || > + =C2=A0=C2=A0=C2=A0 (BPF_MODE(insn->code) !=3D BPF_ATOMIC && > + =C2=A0=C2=A0=C2=A0=C2=A0 BPF_MODE(insn->code) !=3D BPF_PROBE_ATOMIC)) > + return -1; > + > + switch (insn->imm) { > + case BPF_LOAD_ACQ: > + return insn->dst_reg; > + case BPF_CMPXCHG: > + return BPF_REG_0; > + default: > + return (insn->imm & BPF_FETCH) ? insn->src_reg : -1; > + } > +} > + Hi Daniel, Note that there is already a very similar fixups.c:insn_def_regno(). Should we try to avoid duplication? ...