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Fri, 31 Jul 2020 19:02:37 +0000 Date: Fri, 31 Jul 2020 12:02:31 -0700 From: Martin KaFai Lau To: KP Singh CC: , , , Alexei Starovoitov , Daniel Borkmann , Paul Turner , Jann Horn , Florent Revest Subject: Re: [PATCH bpf-next v7 5/7] bpf: Implement bpf_local_storage for inodes Message-ID: <20200731190226.6ugmk6cnl2yortgt@kafai-mbp.dhcp.thefacebook.com> References: <20200730140716.404558-1-kpsingh@chromium.org> <20200730140716.404558-6-kpsingh@chromium.org> <20200731010822.fctk5lawnr3p7blf@kafai-mbp.dhcp.thefacebook.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: BYAPR03CA0024.namprd03.prod.outlook.com (2603:10b6:a02:a8::37) 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::5:5cdc) by BYAPR03CA0024.namprd03.prod.outlook.com (2603:10b6:a02:a8::37) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3239.19 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: e570600d-c236-4403-b4d3-08d835844a03 X-MS-Exchange-CrossTenant-AuthSource: BY5PR15MB3571.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 31 Jul 2020 19:02:36.9255 (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: ftDnyGxDwCa62IF+6F+GZC30dLd84dWvNYLAr2O+SCtXRK9LbpuL+bQIKEIycYVj X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2839 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-31_07:2020-07-31,2020-07-31 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 spamscore=0 malwarescore=0 adultscore=0 suspectscore=5 mlxlogscore=999 lowpriorityscore=0 impostorscore=0 bulkscore=0 clxscore=1015 mlxscore=0 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007310141 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Jul 31, 2020 at 02:08:55PM +0200, KP Singh wrote: [ ... ] > >> +const struct bpf_map_ops inode_storage_map_ops = { > >> + .map_alloc_check = bpf_local_storage_map_alloc_check, > >> + .map_alloc = inode_storage_map_alloc, > >> + .map_free = inode_storage_map_free, > >> + .map_get_next_key = notsupp_get_next_key, > >> + .map_lookup_elem = bpf_fd_inode_storage_lookup_elem, > >> + .map_update_elem = bpf_fd_inode_storage_update_elem, > >> + .map_delete_elem = bpf_fd_inode_storage_delete_elem, > >> + .map_check_btf = bpf_local_storage_map_check_btf, > >> + .map_btf_name = "bpf_local_storage_map", > >> + .map_btf_id = &sk_storage_map_btf_id, > >> + .map_owner_storage_ptr = inode_storage_ptr, > >> +}; > >> + > >> +BTF_ID_LIST(bpf_inode_storage_get_btf_ids) > >> +BTF_ID(struct, inode) > > The ARG_PTR_TO_BTF_ID is the second arg instead of the first > > arg in bpf_inode_storage_get_proto. > > Does it just happen to work here without needing BTF_ID_UNUSED? > > > Yeah, this surprised me as to why it worked, so I did some debugging: > > > diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c > index 9cd1428c7199..95e84bcf1a74 100644 > --- a/kernel/bpf/bpf_lsm.c > +++ b/kernel/bpf/bpf_lsm.c > @@ -52,6 +52,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > { > switch (func_id) { > case BPF_FUNC_inode_storage_get: > + pr_err("btf_ids[0]=%d\n", bpf_inode_storage_get_proto.btf_id[0]); > + pr_err("btf_ids[1]=%d\n", bpf_inode_storage_get_proto.btf_id[1]); > return &bpf_inode_storage_get_proto; > case BPF_FUNC_inode_storage_delete: > return &bpf_inode_storage_delete_proto; > > ./test_progs -t test_local_storage > > [ 21.694473] btf_ids[0]=915 > [ 21.694974] btf_ids[1]=915 > > btf dump file /sys/kernel/btf/vmlinux | grep "STRUCT 'inode'" > "[915] STRUCT 'inode' size=984 vlen=48 > > So it seems like btf_id[0] and btf_id[1] are set to the BTF ID > for inode. Now I think this might just be a coincidence as > the next helper (bpf_inode_storage_delete) > also has a BTF argument of type inode. It seems the next BTF_ID_LIST(bpf_inode_storage_delete_btf_ids) is not needed because they are the same. I think one BTF_ID_LIST(bpf_inode_btf_ids) can be used for both helpers. > > and sure enough if I call: > > bpf_inode_storage_delete from my selftests program, > it does not load: > > arg#0 type is not a struct > Unrecognized arg#0 type PTR > ; int BPF_PROG(unlink_hook, struct inode *dir, struct dentry *victim) > 0: (79) r6 = *(u64 *)(r1 +8) > func 'bpf_lsm_inode_unlink' arg1 has btf_id 912 type STRUCT 'dentry' > ; __u32 pid = bpf_get_current_pid_tgid() >> 32; > > [...] > > So, The BTF_ID_UNUSED is actually needed here. I also added a call to > bpf_inode_storage_delete in my test to catch any issues with it. > > After adding BTF_ID_UNUSED, the result is what we expect: > > ./test_progs -t test_local_storage > [ 20.577223] btf_ids[0]=0 > [ 20.577702] btf_ids[1]=915 > > Thanks for noticing this! > > - KP > > > > >> + > >> +const struct bpf_func_proto bpf_inode_storage_get_proto = { > >> + .func = bpf_inode_storage_get, > >> + .gpl_only = false, > >> + .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, > >> + .arg1_type = ARG_CONST_MAP_PTR, > >> + .arg2_type = ARG_PTR_TO_BTF_ID, > >> + .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL, > >> + .arg4_type = ARG_ANYTHING, > >> + .btf_id = bpf_inode_storage_get_btf_ids, > >> +}; > >> + > >> +BTF_ID_LIST(bpf_inode_storage_delete_btf_ids) > >> +BTF_ID(struct, inode) > >> + > >> +const struct bpf_func_proto bpf_inode_storage_delete_proto = { > >> + .func = bpf_inode_storage_delete, > >> + .gpl_only = false, > >> + .ret_type = RET_INTEGER, > >> + .arg1_type = ARG_CONST_MAP_PTR, > >> + .arg2_type = ARG_PTR_TO_BTF_ID, > >> + .btf_id = bpf_inode_storage_delete_btf_ids, > >> +};