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Date: Mon, 20 Mar 2023 12:56:42 -0700 Message-Id: <20230320195644.1953096-7-kuifeng@meta.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230320195644.1953096-1-kuifeng@meta.com> References: <20230320195644.1953096-1-kuifeng@meta.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN8NAM12FT063:EE_|MN6PR15MB6050:EE_ Content-Type: text/plain X-MS-Office365-Filtering-Correlation-Id: 84dbc7f4-e3be-445b-49fe-08db297d47dc X-ETR: Bypass spam filtering X-FB-Source: Internal X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:69.171.232.181;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:69-171-232-181.mail-mxout.facebook.com;PTR:69-171-232-181.mail-mxout.facebook.com;CAT:NONE;SFS:(13230025)(4636009)(39860400002)(346002)(376002)(396003)(136003)(451199018)(36840700001)(46966006)(40470700004)(86362001)(33570700077)(40460700003)(82310400005)(40480700001)(36756003)(316002)(42186006)(83380400001)(4326008)(8676002)(478600001)(6266002)(26005)(107886003)(6666004)(2616005)(336012)(1076003)(47076005)(186003)(70206006)(356005)(5660300002)(41300700001)(82740400003)(7636003)(36860700001)(8936002)(2906002)(7596003)(15650500001);DIR:OUT;SFP:1501; X-OriginatorOrg: meta.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Mar 2023 19:57:05.5858 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 84dbc7f4-e3be-445b-49fe-08db297d47dc X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=8ae927fe-1255-47a7-a2af-5f3a069daaa2;Ip=[69.171.232.181];Helo=[69-171-232-181.mail-mxout.facebook.com] X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: TreatMessagesAsInternal-BN8NAM12FT063.eop-nam12.prod.protection.outlook.com X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN6PR15MB6050 X-Proofpoint-GUID: xi3wTEE4EqBzwv0_cmO7uyly764XBnTw X-Proofpoint-ORIG-GUID: xi3wTEE4EqBzwv0_cmO7uyly764XBnTw X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-03-20_16,2023-03-20_02,2023-02-09_01 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Introduce bpf_link__update_map(), which allows to atomically update underlying struct_ops implementation for given struct_ops BPF link Signed-off-by: Kui-Feng Lee --- tools/lib/bpf/libbpf.c | 40 ++++++++++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf.h | 1 + tools/lib/bpf/libbpf.map | 1 + 3 files changed, 42 insertions(+) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 56a60ab2ca8f..f84d68c049e3 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11639,6 +11639,11 @@ struct bpf_link *bpf_map__attach_struct_ops(cons= t struct bpf_map *map) =20 /* kern_vdata should be prepared during the loading phase. */ err =3D bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0)= ; + /* It can be EBUSY if the map has been used to create or + * update a link before. We don't allow updating the value of + * a struct_ops once it is set. That ensures that the value + * never changed. So, it is safe to skip EBUSY. + */ if (err && err !=3D -EBUSY) { free(link); return libbpf_err_ptr(err); @@ -11665,6 +11670,41 @@ struct bpf_link *bpf_map__attach_struct_ops(cons= t struct bpf_map *map) return &link->link; } =20 +/* + * Swap the back struct_ops of a link with a new struct_ops map. + */ +int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *ma= p) +{ + struct bpf_link_struct_ops *st_ops_link; + __u32 zero =3D 0; + int err; + + if (!bpf_map__is_struct_ops(map) || map->fd < 0) + return -EINVAL; + + st_ops_link =3D container_of(link, struct bpf_link_struct_ops, link); + /* Ensure the type of a link is correct */ + if (st_ops_link->map_fd < 0) + return -EINVAL; + + err =3D bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0)= ; + /* It can be EBUSY if the map has been used to create or + * update a link before. We don't allow updating the value of + * a struct_ops once it is set. That ensures that the value + * never changed. So, it is safe to skip EBUSY. + */ + if (err && err !=3D -EBUSY) + return err; + + err =3D bpf_link_update(link->fd, map->fd, NULL); + if (err < 0) + return err; + + st_ops_link->map_fd =3D map->fd; + + return 0; +} + typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct perf_ev= ent_header *hdr, void *private_data); =20 diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index db4992a036f8..1615e55e2e79 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -719,6 +719,7 @@ bpf_program__attach_freplace(const struct bpf_program= *prog, struct bpf_map; =20 LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_= map *map); +LIBBPF_API int bpf_link__update_map(struct bpf_link *link, const struct = bpf_map *map); =20 struct bpf_iter_attach_opts { size_t sz; /* size of this struct for forward/backward compatibility */ diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 50dde1f6521e..a5aa3a383d69 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -386,6 +386,7 @@ LIBBPF_1.1.0 { LIBBPF_1.2.0 { global: bpf_btf_get_info_by_fd; + bpf_link__update_map; bpf_link_get_info_by_fd; bpf_map_get_info_by_fd; bpf_prog_get_info_by_fd; --=20 2.34.1