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Date: Mon, 20 Mar 2023 12:24:08 -0700 Message-Id: <20230320192410.1624645-7-kuifeng@meta.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230320192410.1624645-1-kuifeng@meta.com> References: <20230320192410.1624645-1-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: DM6NAM12FT026:EE_|PH0PR15MB4181:EE_ Content-Type: text/plain X-MS-Office365-Filtering-Correlation-Id: 15380b66-3a80-444c-de0c-08db2978bd9a 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)(396003)(346002)(376002)(136003)(451199018)(36840700001)(46966006)(40470700004)(8936002)(5660300002)(36860700001)(82310400005)(356005)(33570700077)(40480700001)(86362001)(40460700003)(15650500001)(82740400003)(7596003)(2906002)(36756003)(7636003)(47076005)(4326008)(336012)(478600001)(83380400001)(6666004)(107886003)(6266002)(41300700001)(2616005)(186003)(1076003)(26005)(42186006)(316002)(8676002)(70206006);DIR:OUT;SFP:1501; X-OriginatorOrg: meta.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Mar 2023 19:24:35.5821 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 15380b66-3a80-444c-de0c-08db2978bd9a 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-DM6NAM12FT026.eop-nam12.prod.protection.outlook.com X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR15MB4181 X-Proofpoint-GUID: TQcum_RckEPURSNrCG0R88KVwWM72s6A X-Proofpoint-ORIG-GUID: TQcum_RckEPURSNrCG0R88KVwWM72s6A 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