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Miller" , Networking , "Alexei Starovoitov" , Daniel Borkmann , "Martin Lau" , Yonghong Song , Andrii Nakryiko , =?iso-8859-1?Q?Toke_H=F8iland-J=F8rgensen?= Subject: Re: [PATCH bpf-next] libbpf: Add support for dynamic program attach target Thread-Topic: [PATCH bpf-next] libbpf: Add support for dynamic program attach target Thread-Index: AQHV4aBmkuDy8vU+NUWdt8DKhmBCX6gX0g0AgAAGM4CAAAUIAIAAA/gA Date: Wed, 12 Feb 2020 18:28:43 +0000 Message-ID: References: <158151067149.71757.2222114135650741733.stgit@xdp-tutorial> <628E972C-1156-46F8-AC61-DB0D38C34C81@fb.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3608.60.0.2.5) x-originating-ip: [2620:10d:c090:400::5:f48e] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 68062b3d-beab-4ad7-1397-08d7afe963e0 x-ms-traffictypediagnostic: MW2PR1501MB2187: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-fb-source: Internal x-ms-oob-tlc-oobclassifiers: OLM:6108; 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charset="iso-8859-1" Content-ID: <9DE9BA6927F71D489EB77B1B1B003BAD@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 68062b3d-beab-4ad7-1397-08d7afe963e0 X-MS-Exchange-CrossTenant-originalarrivaltime: 12 Feb 2020 18:28:43.3075 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: /xEw8LKzrpL6XGkQZrtkAAbH+m41pNy4iPUBkubUg0ehNv7e9MI5tAg9npU0CZNg4Kd66DOAbgyN0LMtx+N/zg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR1501MB2187 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-12_08:2020-02-12,2020-02-12 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxscore=0 lowpriorityscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 clxscore=1015 mlxlogscore=999 priorityscore=1501 impostorscore=0 suspectscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002120132 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > On Feb 12, 2020, at 10:14 AM, Andrii Nakryiko = wrote: >=20 > On Wed, Feb 12, 2020 at 10:07 AM Song Liu wrote: >>=20 >>=20 >>=20 >>> On Feb 12, 2020, at 9:34 AM, Andrii Nakryiko wrote: >>>=20 >>> On Wed, Feb 12, 2020 at 4:32 AM Eelco Chaudron wr= ote: >>>>=20 >>>> Currently when you want to attach a trace program to a bpf program >>>> the section name needs to match the tracepoint/function semantics. >>>>=20 >>>> However the addition of the bpf_program__set_attach_target() API >>>> allows you to specify the tracepoint/function dynamically. >>>>=20 >>>> The call flow would look something like this: >>>>=20 >>>> xdp_fd =3D bpf_prog_get_fd_by_id(id); >>>> trace_obj =3D bpf_object__open_file("func.o", NULL); >>>> prog =3D bpf_object__find_program_by_title(trace_obj, >>>> "fentry/myfunc"); >>>> bpf_program__set_attach_target(prog, xdp_fd, >>>> "fentry/xdpfilt_blk_all"); >>>> bpf_object__load(trace_obj) >>>>=20 >>>> Signed-off-by: Eelco Chaudron >>=20 >>=20 >> I am trying to solve the same problem with slightly different approach. >>=20 >> It works as the following (with skeleton): >>=20 >> obj =3D myobject_bpf__open_opts(&opts); >> bpf_object__for_each_program(prog, obj->obj) >> bpf_program__overwrite_section_name(prog, new_names[id++]= ); >> err =3D myobject_bpf__load(obj); >>=20 >> I don't have very strong preference. But I think my approach is simpler? >=20 > I prefer bpf_program__set_attach_target() approach. Section name is a > program identifier and a *hint* for libbpf to determine program type, > attach type, and whatever else makes sense. But there still should be > an API to set all that manually at runtime, thus > bpf_program__set_attach_target(). Doing same by overriding section > name feels like a hack, plus it doesn't handle overriding > attach_program_fd at all. We already have bpf_object_open_opts to handle different attach_program_fd.= =20 Can we depreciate bpf_object_open_opts.attach_prog_fd with the=20 bpf_program__set_attach_target() approach? Thanks, Song