There is a constant need to add more fields into the bpf_tcp_sock for the bpf programs running at tc, sock_ops...etc. A current workaround could be to use bpf_probe_read_kernel(). However, other than making another helper call for reading each field and missing CO-RE, it is also not as intuitive to use as directly reading "tp->lsndtime" for example. While already having perfmon cap to do bpf_probe_read_kernel(), it will be much easier if the bpf prog can directly read from the tcp_sock. This patch tries to do that by using the existing casting-helpers bpf_skc_to_*() whose func_proto returns a btf_id. For example, the func_proto of bpf_skc_to_tcp_sock returns the btf_id of the kernel "struct tcp_sock". [ One approach is to make a separate copy of the bpf_skc_to_* func_proto and use ARG_PTR_TO_SOCK_COMMON instead of ARG_PTR_TO_BTF_ID. More on this later (1). ] This patch modifies the existing bpf_skc_to_* func_proto to take ARG_PTR_TO_SOCK_COMMON instead of taking "ARG_PTR_TO_BTF_ID + &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON]". That will allow tc, sock_ops,...etc to call these casting helpers because they already hold the PTR_TO_SOCK_COMMON (or its equivalent). For example: sk = sock_ops->sk; if (!sk) return; tp = bpf_skc_to_tcp_sock(sk); if (!tp) return; /* Read tp as a PTR_TO_BTF_ID */ lsndtime = tp->lsndtime; To ensure the current bpf prog passing a PTR_TO_BTF_ID to bpf_skc_to_*() still works as is, the verifier is modified such that ARG_PTR_TO_SOCK_COMMON can accept a reg with reg->type == PTR_TO_BTF_ID and reg->btf_id is btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON] To do that, an idea is borrowed from one of the Lorenz's patch: https://lore.kernel.org/bpf/20200904112401.667645-12-lmb@xxxxxxxxxxxxxx/ . It adds PTR_TO_BTF_ID as one of the acceptable reg->type for ARG_PTR_TO_SOCK_COMMON and also specifies what btf_id it can take. By doing this, the bpf_skc_to_* will work as before and can still take PTR_TO_BTF_ID as the arg. e.g. The bpf tcp iter will work as is. This will also make other existing helper taking ARG_PTR_TO_SOCK_COMMON works with the pointer obtained from bpf_skc_to_*(). For example: sk = bpf_skc_lookup_tcp(skb, tuple, tuplen, BPF_F_CURRENT_NETNS, 0); if (!sk) return; tp = bpf_skc_to_tcp_sock(sk); if (!tp) { bpf_sk_release(sk); return; } lsndtime = tp->lsndtime; /* Pass tp to bpf_sk_release() will also work */ bpf_sk_release(tp); [ (1) Since we need to make the existing helpers taking ARG_PTR_TO_SOCK_COMMON to work with PTR_TO_BTF_ID, the existing bpf_skc_to_*() func_proto are modified instead of making a separate copy. ] A similar change has not been done to the ARG_PTR_TO_SOCKET yet. Thus, ARG_PTR_TO_SOCKET cannot take PTR_TO_BTF_ID for now. The BPF_FUNC_skc_to_* func_id is added to is_ptr_cast_function(). It ensures the returning reg (BPF_REF_0) which is a PTR_TO_BTF_ID_OR_NULL also carries the ref_obj_id. That will keep the ref-tracking works properly. It also allow bpf_sk_release() to be called on the ptr returned by bpf_skc_to_*(), which is shown in the previous example. The bpf_skc_to_* helpers are made available to most of the bpf prog types in filter.c. They are limited by perfmon cap. Signed-off-by: Martin KaFai Lau <kafai@xxxxxx> --- kernel/bpf/verifier.c | 22 ++++++++++++-- net/core/filter.c | 69 ++++++++++++++++++++++++++++++------------- 2 files changed, 69 insertions(+), 22 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3a5932bd7c22..9eace789e88c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -486,7 +486,12 @@ static bool is_acquire_function(enum bpf_func_id func_id, static bool is_ptr_cast_function(enum bpf_func_id func_id) { return func_id == BPF_FUNC_tcp_sock || - func_id == BPF_FUNC_sk_fullsock; + func_id == BPF_FUNC_sk_fullsock || + func_id == BPF_FUNC_skc_to_tcp_sock || + func_id == BPF_FUNC_skc_to_tcp6_sock || + func_id == BPF_FUNC_skc_to_udp6_sock || + func_id == BPF_FUNC_skc_to_tcp_timewait_sock || + func_id == BPF_FUNC_skc_to_tcp_request_sock; } /* string representation of 'enum bpf_reg_type' */ @@ -3906,6 +3911,7 @@ static int resolve_map_arg_type(struct bpf_verifier_env *env, struct bpf_reg_types { const enum bpf_reg_type types[10]; + u32 *btf_id; }; static const struct bpf_reg_types map_key_value_types = { @@ -3923,7 +3929,9 @@ static const struct bpf_reg_types sock_types = { PTR_TO_SOCKET, PTR_TO_TCP_SOCK, PTR_TO_XDP_SOCK, + PTR_TO_BTF_ID, }, + .btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON], }; static const struct bpf_reg_types mem_types = { @@ -4014,7 +4022,17 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 arg, found: if (type == PTR_TO_BTF_ID) { - u32 *expected_btf_id = fn->arg_btf_id[arg]; + u32 *expected_btf_id; + + if (arg_type == ARG_PTR_TO_BTF_ID) { + expected_btf_id = fn->arg_btf_id[arg]; + } else { + expected_btf_id = compatible->btf_id; + if (!expected_btf_id) { + verbose(env, "verifier internal error: missing arg compatible BTF ID\n"); + return -EFAULT; + } + } if (!btf_struct_ids_match(&env->log, reg->off, reg->btf_id, *expected_btf_id)) { diff --git a/net/core/filter.c b/net/core/filter.c index 6014e5f40c58..115cde5aaf90 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -77,6 +77,9 @@ #include <net/transp_v6.h> #include <linux/btf_ids.h> +static const struct bpf_func_proto * +bpf_sk_base_func_proto(enum bpf_func_id func_id); + int copy_bpf_fprog_from_user(struct sock_fprog *dst, sockptr_t src, int len) { if (in_compat_syscall()) { @@ -6619,7 +6622,7 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return NULL; } default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -6638,7 +6641,7 @@ sk_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) case BPF_FUNC_perf_event_output: return &bpf_skb_event_output_proto; default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -6799,7 +6802,7 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_sk_assign_proto; #endif default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -6840,7 +6843,7 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_tcp_gen_syncookie_proto; #endif default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -6882,7 +6885,7 @@ sock_ops_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_tcp_sock_proto; #endif /* CONFIG_INET */ default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -6928,7 +6931,7 @@ sk_msg_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_get_cgroup_classid_curr_proto; #endif default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -6970,7 +6973,7 @@ sk_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_skc_lookup_tcp_proto; #endif default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -6981,7 +6984,7 @@ flow_dissector_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) case BPF_FUNC_skb_load_bytes: return &bpf_flow_dissector_load_bytes_proto; default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -7008,7 +7011,7 @@ lwt_out_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) case BPF_FUNC_skb_under_cgroup: return &bpf_skb_under_cgroup_proto; default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -9745,7 +9748,7 @@ sk_lookup_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) case BPF_FUNC_sk_release: return &bpf_sk_release_proto; default: - return bpf_base_func_proto(func_id); + return bpf_sk_base_func_proto(func_id); } } @@ -9912,8 +9915,7 @@ const struct bpf_func_proto bpf_skc_to_tcp6_sock_proto = { .func = bpf_skc_to_tcp6_sock, .gpl_only = false, .ret_type = RET_PTR_TO_BTF_ID_OR_NULL, - .arg1_type = ARG_PTR_TO_BTF_ID, - .arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON], + .arg1_type = ARG_PTR_TO_SOCK_COMMON, .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP6], }; @@ -9929,8 +9931,7 @@ const struct bpf_func_proto bpf_skc_to_tcp_sock_proto = { .func = bpf_skc_to_tcp_sock, .gpl_only = false, .ret_type = RET_PTR_TO_BTF_ID_OR_NULL, - .arg1_type = ARG_PTR_TO_BTF_ID, - .arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON], + .arg1_type = ARG_PTR_TO_SOCK_COMMON, .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP], }; @@ -9953,8 +9954,7 @@ const struct bpf_func_proto bpf_skc_to_tcp_timewait_sock_proto = { .func = bpf_skc_to_tcp_timewait_sock, .gpl_only = false, .ret_type = RET_PTR_TO_BTF_ID_OR_NULL, - .arg1_type = ARG_PTR_TO_BTF_ID, - .arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON], + .arg1_type = ARG_PTR_TO_SOCK_COMMON, .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP_TW], }; @@ -9977,8 +9977,7 @@ const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto = { .func = bpf_skc_to_tcp_request_sock, .gpl_only = false, .ret_type = RET_PTR_TO_BTF_ID_OR_NULL, - .arg1_type = ARG_PTR_TO_BTF_ID, - .arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON], + .arg1_type = ARG_PTR_TO_SOCK_COMMON, .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP_REQ], }; @@ -9999,7 +9998,37 @@ const struct bpf_func_proto bpf_skc_to_udp6_sock_proto = { .func = bpf_skc_to_udp6_sock, .gpl_only = false, .ret_type = RET_PTR_TO_BTF_ID_OR_NULL, - .arg1_type = ARG_PTR_TO_BTF_ID, - .arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON], + .arg1_type = ARG_PTR_TO_SOCK_COMMON, .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_UDP6], }; + +static const struct bpf_func_proto * +bpf_sk_base_func_proto(enum bpf_func_id func_id) +{ + const struct bpf_func_proto *func; + + switch (func_id) { + case BPF_FUNC_skc_to_tcp6_sock: + func = &bpf_skc_to_tcp6_sock_proto; + break; + case BPF_FUNC_skc_to_tcp_sock: + func = &bpf_skc_to_tcp_sock_proto; + break; + case BPF_FUNC_skc_to_tcp_timewait_sock: + func = &bpf_skc_to_tcp_timewait_sock_proto; + break; + case BPF_FUNC_skc_to_tcp_request_sock: + func = &bpf_skc_to_tcp_request_sock_proto; + break; + case BPF_FUNC_skc_to_udp6_sock: + func = &bpf_skc_to_udp6_sock_proto; + break; + default: + return bpf_base_func_proto(func_id); + } + + if (!perfmon_capable()) + return NULL; + + return func; +} -- 2.24.1
