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Tue, 23 Jun 2020 14:52:11 +0000 Subject: Re: [PATCH bpf-next v3 05/15] bpf: add bpf_skc_to_tcp6_sock() helper To: Andrii Nakryiko CC: bpf , Networking , Alexei Starovoitov , Daniel Borkmann , Kernel Team , Martin KaFai Lau References: <20200623003626.3072825-1-yhs@fb.com> <20200623003631.3073864-1-yhs@fb.com> From: Yonghong Song Message-ID: <26d6f7ee-28ea-80ba-fd76-e3b2f0327163@fb.com> Date: Tue, 23 Jun 2020 07:52:09 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BY3PR04CA0004.namprd04.prod.outlook.com (2603:10b6:a03:217::9) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2620:10d:c085:21d6::1377] (2620:10d:c090:400::5:7789) by BY3PR04CA0004.namprd04.prod.outlook.com (2603:10b6:a03:217::9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3131.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 8a12cb82-27ce-47fa-f928-08d81785024d X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jun 2020 14:52:11.1617 (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: PHuozTX1p9GP1TTfIFNJplrFim3iiWpoU4iHGO/dwJKT1g6bD/L3nJmMlFHkArcB X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB4120 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-06-23_07:2020-06-23,2020-06-23 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 clxscore=1015 impostorscore=0 suspectscore=0 phishscore=0 mlxlogscore=999 priorityscore=1501 mlxscore=0 lowpriorityscore=0 adultscore=0 spamscore=0 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006120000 definitions=main-2006230117 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 6/22/20 11:39 PM, Andrii Nakryiko wrote: > On Mon, Jun 22, 2020 at 5:38 PM Yonghong Song wrote: >> >> The helper is used in tracing programs to cast a socket >> pointer to a tcp6_sock pointer. >> The return value could be NULL if the casting is illegal. >> >> A new helper return type RET_PTR_TO_BTF_ID_OR_NULL is added >> so the verifier is able to deduce proper return types for the helper. >> >> Different from the previous BTF_ID based helpers, >> the bpf_skc_to_tcp6_sock() argument can be several possible >> btf_ids. More specifically, all possible socket data structures >> with sock_common appearing in the first in the memory layout. >> This patch only added socket types related to tcp and udp. >> >> All possible argument btf_id and return value btf_id >> for helper bpf_skc_to_tcp6_sock() are pre-calculcated and >> cached. In the future, it is even possible to precompute >> these btf_id's at kernel build time. >> >> Acked-by: Martin KaFai Lau >> Signed-off-by: Yonghong Song >> --- > > Looks good to me as is, but see a few suggestions, they will probably > save me time at some point as well :) > > Acked-by: Andrii Nakryiko > > >> include/linux/bpf.h | 12 +++++ >> include/uapi/linux/bpf.h | 9 +++- >> kernel/bpf/btf.c | 1 + >> kernel/bpf/verifier.c | 43 +++++++++++++----- >> kernel/trace/bpf_trace.c | 2 + >> net/core/filter.c | 80 ++++++++++++++++++++++++++++++++++ >> scripts/bpf_helpers_doc.py | 2 + >> tools/include/uapi/linux/bpf.h | 9 +++- >> 8 files changed, 146 insertions(+), 12 deletions(-) >> > > [...] > >> @@ -4815,6 +4826,18 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn >> regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL; >> regs[BPF_REG_0].id = ++env->id_gen; >> regs[BPF_REG_0].mem_size = meta.mem_size; >> + } else if (fn->ret_type == RET_PTR_TO_BTF_ID_OR_NULL) { >> + int ret_btf_id; >> + >> + mark_reg_known_zero(env, regs, BPF_REG_0); >> + regs[BPF_REG_0].type = PTR_TO_BTF_ID_OR_NULL; >> + ret_btf_id = *fn->ret_btf_id; > > might be a good idea to check fb->ret_btf_id for NULL and print a > warning + return -EFAULT. It's not supposed to happen on properly > configured kernel, but during development this will save a bunch of > time and frustration for next person trying to add something with > RET_PTR_TO_BTF_ID_OR_NULL. I would like prefer to delay this with current code. Otherwise, it gives an impression fn->ret_btf_id might be NULL and it is actually never NULL. We can add NULL check if the future change requires it. I am not sure what the future change could be, but you need some way to get the return btf_id, the above is one of them. > >> + if (ret_btf_id == 0) { > > This also has to be struct/union (after typedef/mods stripping, of > course). Or are there other cases? This is an "int". The func_proto difinition is below: int *ret_btf_id; /* return value btf_id */ > >> + verbose(env, "invalid return type %d of func %s#%d\n", >> + fn->ret_type, func_id_name(func_id), func_id); >> + return -EINVAL; >> + } >> + regs[BPF_REG_0].btf_id = ret_btf_id; >> } else { >> verbose(env, "unknown return type %d of func %s#%d\n", >> fn->ret_type, func_id_name(func_id), func_id); > > [...] > >> +void init_btf_sock_ids(struct btf *btf) >> +{ >> + int i, btf_id; >> + >> + for (i = 0; i < MAX_BTF_SOCK_TYPE; i++) { >> + btf_id = btf_find_by_name_kind(btf, bpf_sock_types[i], >> + BTF_KIND_STRUCT); >> + if (btf_id > 0) >> + btf_sock_ids[i] = btf_id; >> + } >> +} > > This will hopefully go away with Jiri's work on static BTF IDs, right? > So looking forward to that :) Yes. That's the plan. > >> + >> +static bool check_arg_btf_id(u32 btf_id, u32 arg) >> +{ >> + int i; >> + >> + /* only one argument, no need to check arg */ >> + for (i = 0; i < MAX_BTF_SOCK_TYPE; i++) >> + if (btf_sock_ids[i] == btf_id) >> + return true; >> + return false; >> +} >> + > > [...] >