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Fri, 20 Nov 2020 23:05:56 +0000 Date: Fri, 20 Nov 2020 15:05:49 -0800 From: Martin KaFai Lau To: Andrii Nakryiko CC: , , , , Subject: Re: [PATCH bpf-next 4/6] libbpf: add kernel module BTF support for CO-RE relocations Message-ID: <20201120230549.37k4zsjsrxbyjin3@kafai-mbp.dhcp.thefacebook.com> References: <20201119232244.2776720-1-andrii@kernel.org> <20201119232244.2776720-5-andrii@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201119232244.2776720-5-andrii@kernel.org> X-Originating-IP: [2620:10d:c090:400::5:603e] X-ClientProxiedBy: MWHPR20CA0007.namprd20.prod.outlook.com (2603:10b6:300:13d::17) To BY5PR15MB3571.namprd15.prod.outlook.com (2603:10b6:a03:1f6::32) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from kafai-mbp.dhcp.thefacebook.com (2620:10d:c090:400::5:603e) by MWHPR20CA0007.namprd20.prod.outlook.com (2603:10b6:300:13d::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3589.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 854328a9-e2df-4177-2b07-08d88da8d63a X-MS-Exchange-CrossTenant-AuthSource: BY5PR15MB3571.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Nov 2020 23:05:56.4391 (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: cHg7h6QDm8RFAq1d57QEr4uLqjpTOKv62iWLdqJ0u+NnrYIXe/09t4KzTWvyCczk X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2584 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-20_16:2020-11-20,2020-11-20 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=7 lowpriorityscore=0 mlxlogscore=999 impostorscore=0 clxscore=1015 bulkscore=0 adultscore=0 phishscore=0 mlxscore=0 priorityscore=1501 spamscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011200151 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Nov 19, 2020 at 03:22:42PM -0800, Andrii Nakryiko wrote: [ ... ] > +static int load_module_btfs(struct bpf_object *obj) > +{ > + struct bpf_btf_info info; > + struct module_btf *mod_btf; > + struct btf *btf; > + char name[64]; > + __u32 id, len; > + int err, fd; > + > + if (obj->btf_modules_loaded) > + return 0; > + > + /* don't do this again, even if we find no module BTFs */ > + obj->btf_modules_loaded = true; > + > + /* kernel too old to support module BTFs */ > + if (!kernel_supports(FEAT_MODULE_BTF)) > + return 0; > + > + while (true) { > + err = bpf_btf_get_next_id(id, &id); > + if (err && errno == ENOENT) > + return 0; > + if (err) { > + err = -errno; > + pr_warn("failed to iterate BTF objects: %d\n", err); > + return err; > + } > + > + fd = bpf_btf_get_fd_by_id(id); > + if (fd < 0) { > + if (errno == ENOENT) > + continue; /* expected race: BTF was unloaded */ > + err = -errno; > + pr_warn("failed to get BTF object #%d FD: %d\n", id, err); > + return err; > + } > + > + len = sizeof(info); > + memset(&info, 0, sizeof(info)); > + info.name = ptr_to_u64(name); > + info.name_len = sizeof(name); > + > + err = bpf_obj_get_info_by_fd(fd, &info, &len); > + if (err) { > + err = -errno; > + pr_warn("failed to get BTF object #%d info: %d\n", id, err); close(fd); > + return err; > + } > + > + /* ignore non-module BTFs */ > + if (!info.kernel_btf || strcmp(name, "vmlinux") == 0) { > + close(fd); > + continue; > + } > + [ ... ] > @@ -8656,9 +8815,6 @@ static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name, > else > err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC); > > - if (err <= 0) > - pr_warn("%s is not found in vmlinux BTF\n", name); > - > return err; > } > > @@ -8675,6 +8831,9 @@ int libbpf_find_vmlinux_btf_id(const char *name, > } > > err = __find_vmlinux_btf_id(btf, name, attach_type); > + if (err <= 0) > + pr_warn("%s is not found in vmlinux BTF\n", name); > + Please explain this move in the commit message. > btf__free(btf); > return err; > } > -- > 2.24.1 >