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Thu, 18 Jun 2020 23:31:36 +0000 Subject: Re: [PATCH bpf-next 05/13] bpf: add bpf_skc_to_tcp6_sock() helper To: Martin KaFai Lau CC: , Alexei Starovoitov , Daniel Borkmann , References: <20200617211536.1854348-1-yhs@fb.com> <20200617211542.1856028-1-yhs@fb.com> <20200618205412.6updodfkqv2lz4pm@kafai-mbp.dhcp.thefacebook.com> From: Yonghong Song Message-ID: <53c594a0-971e-8f18-d271-34e4f738a534@fb.com> Date: Thu, 18 Jun 2020 16:31:33 -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: <20200618205412.6updodfkqv2lz4pm@kafai-mbp.dhcp.thefacebook.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-ClientProxiedBy: BYAPR07CA0053.namprd07.prod.outlook.com (2603:10b6:a03:60::30) 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:c085:21cf::11f0] (2620:10d:c090:400::5:8794) by BYAPR07CA0053.namprd07.prod.outlook.com (2603:10b6:a03:60::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3109.22 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 28c334e4-faed-47c5-23db-08d813dfbdee X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Jun 2020 23:31:35.8880 (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: hXRTchq6tLTKkZ5ZuECCvtC/zMkkXTYi0IA26pMFE/I+QqtIOTJszE9e4uJhUqKZ X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2695 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-06-18_21:2020-06-18,2020-06-18 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 clxscore=1015 mlxscore=0 spamscore=0 priorityscore=1501 lowpriorityscore=0 phishscore=0 mlxlogscore=999 adultscore=0 impostorscore=0 malwarescore=0 cotscore=-2147483648 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006180180 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 6/18/20 1:54 PM, Martin KaFai Lau wrote: > On Wed, Jun 17, 2020 at 02:15:42PM -0700, 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. >> > [ ... ] > >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >> index 07052d44bca1..e455aa09039b 100644 >> --- a/include/linux/bpf.h >> +++ b/include/linux/bpf.h >> @@ -261,6 +261,7 @@ enum bpf_return_type { >> RET_PTR_TO_TCP_SOCK_OR_NULL, /* returns a pointer to a tcp_sock or NULL */ >> RET_PTR_TO_SOCK_COMMON_OR_NULL, /* returns a pointer to a sock_common or NULL */ >> RET_PTR_TO_ALLOC_MEM_OR_NULL, /* returns a pointer to dynamically allocated memory or NULL */ >> + RET_PTR_TO_BTF_ID_OR_NULL, /* returns a pointer to a btf_id or NULL */ >> }; >> >> /* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs >> @@ -283,6 +284,10 @@ struct bpf_func_proto { >> enum bpf_arg_type arg_type[5]; >> }; >> int *btf_id; /* BTF ids of arguments */ >> + bool (*check_btf_id)(u32 btf_id, u32 arg); /* If the argument could match >> + * more than one btf id's. >> + */ >> + int *ret_btf_id; /* return value btf_id */ >> }; >> >> /* bpf_context is intentionally undefined structure. Pointer to bpf_context is >> @@ -1196,6 +1201,10 @@ bool bpf_link_is_iter(struct bpf_link *link); >> struct bpf_prog *bpf_iter_get_info(struct bpf_iter_meta *meta, bool in_stop); >> int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx); >> >> +void init_sock_cast_types(struct btf *btf); > CONFIG_NET may not be set. Good catch, will add proper config guard in the next revision. > > [ ... ] > >> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >> index 34cde841ab68..22d90d47befa 100644 >> --- a/kernel/bpf/verifier.c >> +++ b/kernel/bpf/verifier.c >> @@ -3735,10 +3735,12 @@ static int int_ptr_type_to_size(enum bpf_arg_type type) >> return -EINVAL; >> } >> >> -static int check_func_arg(struct bpf_verifier_env *env, u32 regno, >> +static int check_func_arg(struct bpf_verifier_env *env, u32 arg, >> enum bpf_arg_type arg_type, >> - struct bpf_call_arg_meta *meta) >> + struct bpf_call_arg_meta *meta, >> + const struct bpf_func_proto *fn) >> { >> + u32 regno = BPF_REG_1 + arg; >> struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno]; >> enum bpf_reg_type expected_type, type = reg->type; >> int err = 0; >> @@ -3820,9 +3822,16 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, >> expected_type = PTR_TO_BTF_ID; >> if (type != expected_type) >> goto err_type; >> - if (reg->btf_id != meta->btf_id) { >> - verbose(env, "Helper has type %s got %s in R%d\n", >> - kernel_type_name(meta->btf_id), >> + if (!fn->check_btf_id) { >> + if (reg->btf_id != meta->btf_id) { >> + verbose(env, "Helper has type %s got %s in R%d\n", >> + kernel_type_name(meta->btf_id), >> + kernel_type_name(reg->btf_id), regno); >> + >> + return -EACCES; >> + } >> + } else if (!fn->check_btf_id(reg->btf_id, arg + 1)) { > Why arg "+ 1"? In verifier, arg starts from 0 (arguments 0 - 4). In func_proto, we have ARG1 - ARG5. That is why I add one here. I think I can just use 0-4 range for arg parameter, it should be fine. > >> + verbose(env, "Helper does not support %s in R%d\n", >> kernel_type_name(reg->btf_id), regno); >> >> return -EACCES; >> @@ -4600,7 +4609,7 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn >> struct bpf_reg_state *regs; >> struct bpf_call_arg_meta meta; >> bool changes_data; >> - int i, err; >> + int i, err, ret_btf_id; >> >> /* find function prototype */ >> if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { >> @@ -4644,10 +4653,12 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn >> meta.func_id = func_id; >> /* check args */ >> for (i = 0; i < 5; i++) { >> - err = btf_resolve_helper_id(&env->log, fn, i); >> - if (err > 0) >> - meta.btf_id = err; >> - err = check_func_arg(env, BPF_REG_1 + i, fn->arg_type[i], &meta); >> + if (!fn->check_btf_id) { >> + err = btf_resolve_helper_id(&env->log, fn, i); >> + if (err > 0) >> + meta.btf_id = err; >> + } >> + err = check_func_arg(env, i, fn->arg_type[i], &meta, fn); > Nit. Since it is passing fn and i, may be skip passing > fn->arg_type[i] altogether? Make sense, will do. > >> if (err) >> return err; >> } >> @@ -4750,6 +4761,16 @@ 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) { >> + 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; >> + if (ret_btf_id < 0) { > If btf_vmlinux is not available, is ret_btf_id == 0? Yes, it is a global variable. Will change it to <= 0. > >> + verbose(env, "invalid return type %d of func %s#%d\n", >> + fn->ret_type, func_id_name(func_id), func_id); >> + return err; > Is err correctly set at this point? Typo, I mean return ret_btf_id. In Jiri's d_path patch, the btf_id are all non-negative values. I may adopt the same convention in the next revision to make future conversion easier. > >> + } >> + 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); >> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c >> index afaec7e082d9..478c10d1ec33 100644 >> --- a/kernel/trace/bpf_trace.c >> +++ b/kernel/trace/bpf_trace.c >> @@ -1515,6 +1515,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) >> return &bpf_skb_output_proto; >> case BPF_FUNC_xdp_output: >> return &bpf_xdp_output_proto; >> + case BPF_FUNC_skc_to_tcp6_sock: >> + return &bpf_skc_to_tcp6_sock_proto; >> #endif >> case BPF_FUNC_seq_printf: >> return prog->expected_attach_type == BPF_TRACE_ITER ? >> diff --git a/net/core/filter.c b/net/core/filter.c >> index 73395384afe2..faf6feedd78e 100644 >> --- a/net/core/filter.c >> +++ b/net/core/filter.c >> @@ -9191,3 +9191,72 @@ void bpf_prog_change_xdp(struct bpf_prog *prev_prog, struct bpf_prog *prog) >> { >> bpf_dispatcher_change_prog(BPF_DISPATCHER_PTR(xdp), prev_prog, prog); >> } >> + >> +/* Define a list of socket types which can be the argument for >> + * skc_to_*_sock() helpers. All these sockets should have >> + * sock_common as the first argument in its memory layout. >> + */ >> +static const char *sock_cast_types[] = { >> + "inet_connection_sock", >> + "inet_request_sock", >> + "inet_sock", >> + "inet_timewait_sock", >> + "request_sock", >> + "sock", >> + "sock_common", >> + "tcp_sock", >> + "tcp_request_sock", >> + "tcp_timewait_sock", >> + "tcp6_sock", >> + "udp_sock", >> + "udp6_sock", >> +}; >> + >> +static int sock_cast_btf_ids[ARRAY_SIZE(sock_cast_types)]; >> + >> +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 < ARRAY_SIZE(sock_cast_btf_ids); i++) >> + if (sock_cast_btf_ids[i] == btf_id) >> + return true; >> + return false; >> +} >> + >> +BPF_CALL_1(bpf_skc_to_tcp6_sock, struct sock *, sk) >> +{ >> + /* add an explicit cast to struct tcp6_sock to force >> + * debug_info type generation for it. >> + */ >> + if (sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP && >> + sk->sk_family == AF_INET6) >> + return (unsigned long)(struct tcp6_sock *)sk; >> + >> + return (unsigned long)NULL; >> +} >> + >> +static int bpf_skc_to_tcp6_sock_ret_btf_id; >> +const struct bpf_func_proto bpf_skc_to_tcp6_sock_proto = { >> + .func = bpf_skc_to_tcp6_sock, >> + .gpl_only = true, >> + .ret_type = RET_PTR_TO_BTF_ID_OR_NULL, >> + .arg1_type = ARG_PTR_TO_BTF_ID, >> + .check_btf_id = check_arg_btf_id, >> + .ret_btf_id = &bpf_skc_to_tcp6_sock_ret_btf_id, >> +}; >> + >> +void init_sock_cast_types(struct btf *btf) >> +{ >> + char *ret_type_name; >> + >> + /* find all possible argument btf_id's for socket cast helpers */ >> + find_array_of_btf_ids(btf, sock_cast_types, sock_cast_btf_ids, >> + ARRAY_SIZE(sock_cast_types)); >> + >> + /* find return btf_id */ >> + ret_type_name = "tcp6_sock"; >> + find_array_of_btf_ids(btf, &ret_type_name, >> + &bpf_skc_to_tcp6_sock_ret_btf_id, 1); > Instead of re-finding tcp6_sock/tcp_sock/request_sock...etc, > can the sock_cast_btf_ids[] be reused? Actually, yes, we can. Will do.