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Tue, 14 Apr 2020 07:04:00 +0000 From: Song Liu To: Andrii Nakryiko CC: bpf , Networking , "Alexei Starovoitov" , "daniel@iogearbox.net" , Andrey Ignatov , "andrii.nakryiko@gmail.com" , Kernel Team Subject: Re: [PATCH v2 bpf-next] libbpf: always specify expected_attach_type on program load if supported Thread-Topic: [PATCH v2 bpf-next] libbpf: always specify expected_attach_type on program load if supported Thread-Index: AQHWEhkJS7kOYuB4pEWWsARZmp1+Nqh4MYuA Date: Tue, 14 Apr 2020 07:03:59 +0000 Message-ID: <6E178D01-CF89-4AEA-8705-9789E58B1D46@fb.com> References: <20200414045613.2104756-1-andriin@fb.com> In-Reply-To: <20200414045613.2104756-1-andriin@fb.com> 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::5:2730] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 2eeb66fc-6f8e-49a6-f8ba-08d7e04201f3 x-ms-traffictypediagnostic: BYAPR15MB3222: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-fb-source: Internal x-ms-oob-tlc-oobclassifiers: OLM:8882; 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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 2eeb66fc-6f8e-49a6-f8ba-08d7e04201f3 X-MS-Exchange-CrossTenant-originalarrivaltime: 14 Apr 2020 07:03:59.9725 (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: g1b69w7DtPUN6BMJ6/mNpu6N3xHMG4AlrlbhoCD3KGneTjlHa6O46wqPGXNwv2Kc2ir6wj4QibeRIM1B7LSk5A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3222 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-04-14_02:2020-04-13,2020-04-14 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 bulkscore=0 clxscore=1011 malwarescore=0 mlxlogscore=999 spamscore=0 mlxscore=0 adultscore=0 phishscore=0 priorityscore=1501 impostorscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004140057 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > On Apr 13, 2020, at 9:56 PM, Andrii Nakryiko wrote: >=20 > For some types of BPF programs that utilize expected_attach_type, libbpf = won't > set load_attr.expected_attach_type, even if expected_attach_type is known= from > section definition. This was done to preserve backwards compatibility wit= h old > kernels that didn't recognize expected_attach_type attribute yet (which w= as > added in 5e43f899b03a ("bpf: Check attach type at prog load time"). But t= his > is problematic for some BPF programs that utilize never features that req= uire > kernel to know specific expected_attach_type (e.g., extended set of retur= n > codes for cgroup_skb/egress programs). >=20 > This patch makes libbpf specify expected_attach_type by default, but also > detect support for this field in kernel and not set it during program loa= d. > This allows to have a good metadata for bpf_program > (e.g., bpf_program__get_extected_attach_type()), but still work with old > kernels (for cases where it can work at all). >=20 > Additionally, due to expected_attach_type being always set for recognized > program types, bpf_program__attach_cgroup doesn't have to do extra checks= to > determine correct attach type, so remove that additional logic. >=20 > Also adjust section_names selftest to account for this change. >=20 > More detailed discussion can be found in [0]. >=20 > [0] https://lore.kernel.org/bpf/20200412003604.GA15986@rdna-mbp.dhcp.the= facebook.com/ >=20 > Reported-by: Andrey Ignatov > Signed-off-by: Andrii Nakryiko Acked-by: Song Liu With one nit below.=20 > --- > v1->v2: > - fixed prog_type/expected_attach_type combo (Andrey); > - added comment explaining what we are doing in probe_exp_attach_type (An= drey). >=20 > tools/lib/bpf/libbpf.c | 127 ++++++++++++------ > .../selftests/bpf/prog_tests/section_names.c | 42 +++--- > 2 files changed, 110 insertions(+), 59 deletions(-) >=20 > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index ff9174282a8c..c7393182e2ae 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -178,6 +178,8 @@ struct bpf_capabilities { > __u32 array_mmap:1; > /* BTF_FUNC_GLOBAL is supported */ > __u32 btf_func_global:1; > + /* kernel support for expected_attach_type in BPF_PROG_LOAD */ > + __u32 exp_attach_type:1; > }; [...] > -#define BPF_PROG_SEC_IMPL(string, ptype, eatype, is_attachable, btf, aty= pe) \ > - { string, sizeof(string) - 1, ptype, eatype, is_attachable, btf, atype = } > +#define BPF_PROG_SEC_IMPL(string, ptype, eatype, eatype_optional, \ > + attachable, attach_btf) \ > + { \ > + .sec =3D string, \ > + .len =3D sizeof(string) - 1, \ > + .prog_type =3D ptype, \ > + .sec =3D string, \ Two lines of ".sec =3D string".=20 > + .expected_attach_type =3D eatype, \ > + .is_exp_attach_type_optional =3D eatype_optional, \ > + .is_attachable =3D attachable, \ > + .is_attach_btf =3D attach_btf, \ > + }