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([2620:10d:c090:500::4:d279]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-33ba4f0feaasm711470eec.21.2026.09.10.14.02.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Sep 2026 14:02:17 -0700 (PDT) Message-ID: <0157b1eca803919afa59ae658f186aa0509a239a.camel@gmail.com> Subject: Re: [PATCH bpf 3/6] bpf: Cache the jump table of a subprogram during CFG discovery From: Eduard Zingerman To: Daniel Borkmann , ast@kernel.org Cc: memxor@gmail.com, a.s.protopopov@gmail.com, info@starlabs.sg, bpf@vger.kernel.org Date: Thu, 10 Sep 2026 14:02:15 -0700 In-Reply-To: <20260909204035.24289-3-daniel@iogearbox.net> References: <20260909204035.24289-1-daniel@iogearbox.net> <20260909204035.24289-3-daniel@iogearbox.net> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2026-09-09 at 22:40 +0200, Daniel Borkmann wrote: ... > @@ -347,16 +356,33 @@ create_jt(int t, struct bpf_verifier_env *env) > struct bpf_subprog_info *subprog; > int subprog_start, subprog_end; > struct bpf_iarray *jt; > - int i; > + int i, err; > + > + if (!env->cfg.subprog_jts_ready) { > + err =3D compute_subprog_jts(env); > + if (err) > + return ERR_PTR(err); > + } > =20 > subprog =3D bpf_find_containing_subprog(env, t); > subprog_start =3D subprog->start; > subprog_end =3D (subprog + 1)->start; > - jt =3D jt_from_subprog(env, subprog_start, subprog_end); > - if (IS_ERR(jt)) > - return jt; > =20 > - /* Check that the every element of the jump table fits within the given= subprogram */ > + if (!subprog->jt) { > + verbose(env, "no jump tables found for subprog starting at %u\n", subp= rog_start); > + bpf_diag_program_structure( > + env, subprog_start, "missing jump table", > + "Make sure subprograms containing gotox instructions are accompanied = by jump tables referencing these subprograms.", > + "No jump table was found for the subprogram that starts at instructio= n %u.", > + subprog_start); > + return ERR_PTR(-EINVAL); > + } > + > + jt =3D bpf_iarray_realloc(NULL, subprog->jt->cnt); > + if (!jt) > + return ERR_PTR(-ENOMEM); > + memcpy(jt->items, subprog->jt->items, subprog->jt->cnt << 2); What would it take to change the logic such that insn_aux_data no longer owns the memory? (Thus making the copy unnecessary). > + > for (i =3D 0; i < jt->cnt; i++) { > if (jt->items[i] < subprog_start || jt->items[i] >=3D subprog_end) { > verbose(env, "jump table for insn %d points outside of the subprog [%= u,%u]\n", ...