From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3F772A35 for ; Fri, 11 Aug 2023 06:43:36 +0000 (UTC) Received: from out-88.mta1.migadu.com (out-88.mta1.migadu.com [95.215.58.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D78226B2 for ; Thu, 10 Aug 2023 23:43:34 -0700 (PDT) Message-ID: <371c72e1-f2b7-8309-0329-cdffc8a3f98d@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1691736212; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3YxfTeMRGbEX8XAfgT0Mgd6kR4/eyN2zbW/mvn09rfA=; b=Qfh8J2/HmPzRKh04U308PejftZy0KeHqSLodeD5upZyY/RDTThEq0WHKV0caRRBxvy2wcE Nzynd5uivQOmkuBrv8Fo8xGXMuPF7JIcAT1Krysz6qibOW9cHjAS0mah0L7TrAnZPILtM6 qsf9ooV+cZKcGiuHG4mR9amnNxd5UmM= Date: Thu, 10 Aug 2023 23:43:26 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Reply-To: yonghong.song@linux.dev Subject: Re: [PATCH bpf-next] bpf: Support default .validate() and .update() behavior for struct_ops links Content-Language: en-US To: David Vernet , bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, tj@kernel.org, clm@meta.com, thinker.li@gmail.com References: <20230810220456.521517-1-void@manifault.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <20230810220456.521517-1-void@manifault.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On 8/10/23 3:04 PM, David Vernet wrote: > Currently, if a struct_ops map is loaded with BPF_F_LINK, it must also > define the .validate() and .update() callbacks in its corresponding > struct bpf_struct_ops in the kernel. Enabling struct_ops link is useful > in its own right to ensure that the map is unloaded if an application > crashes. For example, with sched_ext, we want to automatically unload > the host-wide scheduler if the application crashes. We would likely > never support updating elements of a sched_ext struct_ops map, so we'd > have to implement these callbacks showing that they _can't_ support > element updates just to benefit from the basic lifetime management of > struct_ops links. > > Let's enable struct_ops maps to work with BPF_F_LINK even if they > haven't defined these callbacks, by assuming that a struct_ops map > element cannot be updated by default. Maybe you want to add one map_flag to indicate validate/update callbacks are optional for a struct_ops link? In this case, some struct_ops maps can still require validate() and update(), but others can skip them? > > Signed-off-by: David Vernet > --- > kernel/bpf/bpf_struct_ops.c | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-) > > diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c > index eaff04eefb31..3d2fb85186a9 100644 > --- a/kernel/bpf/bpf_struct_ops.c > +++ b/kernel/bpf/bpf_struct_ops.c > @@ -509,9 +509,12 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key, > } > > if (st_map->map.map_flags & BPF_F_LINK) { > - err = st_ops->validate(kdata); > - if (err) > - goto reset_unlock; > + err = 0; > + if (st_ops->validate) { > + err = st_ops->validate(kdata); > + if (err) > + goto reset_unlock; > + } > set_memory_rox((long)st_map->image, 1); > /* Let bpf_link handle registration & unregistration. > * > @@ -663,9 +666,6 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr) > if (attr->value_size != vt->size) > return ERR_PTR(-EINVAL); > > - if (attr->map_flags & BPF_F_LINK && (!st_ops->validate || !st_ops->update)) > - return ERR_PTR(-EOPNOTSUPP); > - > t = st_ops->type; > > st_map_size = sizeof(*st_map) + > @@ -838,6 +838,11 @@ static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map > goto err_out; > } > > + if (!st_map->st_ops->update) { > + err = -EOPNOTSUPP; > + goto err_out; > + } > + > err = st_map->st_ops->update(st_map->kvalue.data, old_st_map->kvalue.data); > if (err) > goto err_out;