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Thu, 06 Aug 2026 12:12:42 -0700 (PDT) Message-ID: Subject: Re: [PATCH bpf-next v2 2/6] resolve_btfids: Process KF_ARENA_* flags in resolve_btfids From: Eduard Zingerman To: Ihor Solodrai , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Kumar Kartikeya Dwivedi Cc: Alan Maguire , Jiri Olsa , Emil Tsalapatis , bpf@vger.kernel.org Date: Thu, 06 Aug 2026 12:12:39 -0700 In-Reply-To: <20260805230648.2354989-3-ihor.solodrai@linux.dev> References: <20260805230648.2354989-1-ihor.solodrai@linux.dev> <20260805230648.2354989-3-ihor.solodrai@linux.dev> 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 Wed, 2026-08-05 at 16:06 -0700, Ihor Solodrai wrote: ... > +static s32 add_arena_tagged_proto(struct btf *btf, struct kfunc *kfunc) > +{ > + const struct btf_type *func =3D btf__type_by_id(btf, kfunc->btf_id); > + u32 proto_id =3D func->type; > + const struct btf_type *proto =3D btf__type_by_id(btf, proto_id); > + const struct btf_param *params =3D btf_params(proto); > + u32 nr_params =3D btf_vlen(proto); > + s32 arg0_type_id =3D nr_params > 0 ? (s32)params[0].type : -1; > + s32 arg1_type_id =3D nr_params > 1 ? (s32)params[1].type : -1; > + s32 new_proto_id, id, param_type_id; > + s32 ret_type_id =3D proto->type; > + const char *name; > + int err; > + > + if (kfunc->flags & KF_ARENA_RET) { > + id =3D arena_tag_ptr(btf, ret_type_id); > + if (id < 0) { > + pr_err("ERROR: resolve_btfids: kfunc %s: KF_ARENA_RET but return type= is not a pointer\n", > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kfunc->name); > + return id; > + } > + ret_type_id =3D id; > + } > + > + if (kfunc->flags & KF_ARENA_ARG1) { Nit: let's avoid the copy paste and make this code prepared for the __arena suffixes by moving the logic inside the parameter processing loop below: for (i in params) { bool add_tag =3D false; param_type_id =3D params[i].type; switch(i) { 0: add_tag =3D kfunc->flags & KF_ARENA_ARG1; break; ... = } if (add_tag) param_type_id =3D arena_tag_ptr(btf, param_type_id); if (param_type_id < 0) ... } > + if (nr_params < 1) { > + pr_err("ERROR: resolve_btfids: kfunc %s: KF_ARENA_ARG1 but it has no = argument 1\n", > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kfunc->name); > + return -EINVAL; > + } > + id =3D arena_tag_ptr(btf, arg0_type_id); > + if (id < 0) { > + pr_err("ERROR: resolve_btfids: kfunc %s: KF_ARENA_ARG1 but argument 1= is not a pointer\n", > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kfunc->name); Nit: not a pointer is not the only error condition, btf__add_*() functions might fail as well, maybe just push pr_err() down to the arena_tag_ptr()? > + return id; > + } > + arg0_type_id =3D id; > + } > + > + if (kfunc->flags & KF_ARENA_ARG2) { > + if (nr_params < 2) { > + pr_err("ERROR: resolve_btfids: kfunc %s: KF_ARENA_ARG2 but it has no = argument 2\n", > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kfunc->name); > + return -EINVAL; > + } > + id =3D arena_tag_ptr(btf, arg1_type_id); > + if (id < 0) { > + pr_err("ERROR: resolve_btfids: kfunc %s: KF_ARENA_ARG2 but argument 2= is not a pointer\n", > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kfunc->name); > + return id; > + } > + arg1_type_id =3D id; > + } > + > + new_proto_id =3D btf__add_func_proto(btf, ret_type_id); > + if (new_proto_id < 0) { > + pr_err("ERROR: resolve_btfids: kfunc %s: failed to add a func proto to= BTF\n", > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kfunc->name); > + return new_proto_id; > + } > + > + for (u32 i =3D 0; i < nr_params; i++) { > + proto =3D btf__type_by_id(btf, proto_id); > + params =3D btf_params(proto); Nit: these two do not need to be in the loop body. > + name =3D btf__name_by_offset(btf, params[i].name_off); > + > + switch (i) { > + case 0: > + param_type_id =3D arg0_type_id; > + break; > + case 1: > + param_type_id =3D arg1_type_id; > + break; > + default: > + param_type_id =3D params[i].type; > + break; > + } > + > + err =3D btf__add_func_param(btf, name ?: "", param_type_id); > + if (err < 0) { > + pr_err("ERROR: resolve_btfids: kfunc %s: failed to add a proto param = to BTF\n", > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kfunc->name); > + return err; > + } > + } > + > + pr_debug("added arena-tagged proto for kfunc %s: %d\n", kfunc->name, ne= w_proto_id); > + > + return new_proto_id; > +} ...