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[73.241.150.58]) by smtp.gmail.com with ESMTPSA id b10sm806698pfi.122.2021.09.29.17.26.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Sep 2021 17:26:03 -0700 (PDT) Subject: Re: [RFC PATCH v2 04/13] bpf: Define a few bpf_link_ops for BPF_TRACE_MAP To: Joe Burton , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau Cc: Song Liu , Yonghong Song , John Fastabend , KP Singh , Petar Penkov , Stanislav Fomichev , Hao Luo , netdev@vger.kernel.org, bpf@vger.kernel.org, Joe Burton References: <20210929235910.1765396-1-jevburton.kernel@gmail.com> <20210929235910.1765396-5-jevburton.kernel@gmail.com> From: Eric Dumazet Message-ID: <1c148ba0-0b74-2d48-c94b-3e7ea42e8238@gmail.com> Date: Wed, 29 Sep 2021 17:26:01 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20210929235910.1765396-5-jevburton.kernel@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 9/29/21 4:59 PM, Joe Burton wrote: > From: Joe Burton > > Define release, dealloc, and update_prog for the new tracing programs. > Updates are protected by a single global mutex. > > Signed-off-by: Joe Burton > --- > kernel/bpf/map_trace.c | 71 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 71 insertions(+) > > diff --git a/kernel/bpf/map_trace.c b/kernel/bpf/map_trace.c > index 7776b8ccfe88..35906d59ba3c 100644 > --- a/kernel/bpf/map_trace.c > +++ b/kernel/bpf/map_trace.c > @@ -14,6 +14,14 @@ struct bpf_map_trace_target_info { > static struct list_head targets = LIST_HEAD_INIT(targets); > static DEFINE_MUTEX(targets_mutex); > > +struct bpf_map_trace_link { > + struct bpf_link link; > + struct bpf_map *map; > + struct bpf_map_trace_target_info *tinfo; > +}; > + > +static DEFINE_MUTEX(link_mutex); > + > int bpf_map_trace_reg_target(const struct bpf_map_trace_reg *reg_info) > { > struct bpf_map_trace_target_info *tinfo; > @@ -77,3 +85,66 @@ int bpf_map_initialize_trace_progs(struct bpf_map *map) > return 0; > } > > +static void bpf_map_trace_link_release(struct bpf_link *link) > +{ > + struct bpf_map_trace_link *map_trace_link = > + container_of(link, struct bpf_map_trace_link, link); > + enum bpf_map_trace_type trace_type = > + map_trace_link->tinfo->reg_info->trace_type; > + struct bpf_map_trace_prog *cur_prog; > + struct bpf_map_trace_progs *progs; > + > + progs = map_trace_link->map->trace_progs; > + mutex_lock(&progs->mutex); > + list_for_each_entry(cur_prog, &progs->progs[trace_type].list, list) { You might consider using list_for_each_entry_safe(), or ... > + if (cur_prog->prog == link->prog) { > + progs->length[trace_type] -= 1; > + list_del_rcu(&cur_prog->list); > + kfree_rcu(cur_prog, rcu); or add a break; if you do not expect to find multiple entries. > + } > + } > + mutex_unlock(&progs->mutex); > + bpf_map_put_with_uref(map_trace_link->map); > +} > + > +static void bpf_map_trace_link_dealloc(struct bpf_link *link) > +{ > + struct bpf_map_trace_link *map_trace_link = > + container_of(link, struct bpf_map_trace_link, link); > + > + kfree(map_trace_link); > +} > + > +static int bpf_map_trace_link_replace(struct bpf_link *link, > + struct bpf_prog *new_prog, > + struct bpf_prog *old_prog) > +{ > + int ret = 0; > + > + mutex_lock(&link_mutex); > + if (old_prog && link->prog != old_prog) { > + ret = -EPERM; > + goto out_unlock; > + } > + > + if (link->prog->type != new_prog->type || > + link->prog->expected_attach_type != new_prog->expected_attach_type || > + link->prog->aux->attach_btf_id != new_prog->aux->attach_btf_id) { > + ret = -EINVAL; > + goto out_unlock; > + } > + > + old_prog = xchg(&link->prog, new_prog); > + bpf_prog_put(old_prog); > + > +out_unlock: > + mutex_unlock(&link_mutex); > + return ret; > +} > + > +static const struct bpf_link_ops bpf_map_trace_link_ops = { > + .release = bpf_map_trace_link_release, > + .dealloc = bpf_map_trace_link_dealloc, > + .update_prog = bpf_map_trace_link_replace, > +}; > + >