On Fri, 25 Sep 2020 at 01:04, Martin KaFai Lau <kafai@xxxxxx> wrote: > > 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". > > These helpers are also added to is_ptr_cast_function(). > It ensures the returning reg (BPF_REF_0) will also carries the ref_obj_id. > That will keep the ref-tracking works properly. > > The bpf_skc_to_* helpers are made available to most of the bpf prog > types in filter.c. The bpf_skc_to_* helpers will be limited by > perfmon cap. > > This patch adds a ARG_PTR_TO_BTF_ID_SOCK_COMMON. The helper accepting > this arg can accept a btf-id-ptr (PTR_TO_BTF_ID + &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON]) > or a legacy-ctx-convert-skc-ptr (PTR_TO_SOCK_COMMON). The bpf_skc_to_*() > helpers are changed to take ARG_PTR_TO_BTF_ID_SOCK_COMMON such that > they will accept pointer obtained from skb->sk. > > Instead of specifying both arg_type and arg_btf_id in the same func_proto > which is how the current ARG_PTR_TO_BTF_ID does, the arg_btf_id of > the new ARG_PTR_TO_BTF_ID_SOCK_COMMON is specified in the > compatible_reg_types[] in verifier.c. The reason is the arg_btf_id is > always the same. Discussion in this thread: > https://lore.kernel.org/bpf/20200922070422.1917351-1-kafai@xxxxxx/ > > The ARG_PTR_TO_BTF_ID_ part gives a clear expectation that the helper is > expecting a PTR_TO_BTF_ID which could be NULL. This is the same > behavior as the existing helper taking ARG_PTR_TO_BTF_ID. > > The _SOCK_COMMON part means the helper is also expecting the legacy > SOCK_COMMON pointer. > > By excluding the _OR_NULL part, the bpf prog cannot call helper > with a literal NULL which doesn't make sense in most cases. > e.g. bpf_skc_to_tcp_sock(NULL) will be rejected. All PTR_TO_*_OR_NULL > reg has to do a NULL check first before passing into the helper or else > the bpf prog will be rejected. This behavior is nothing new and > consistent with the current expectation during bpf-prog-load. > > [ ARG_PTR_TO_BTF_ID_SOCK_COMMON will be used to replace > ARG_PTR_TO_SOCK* of other existing helpers later such that > those existing helpers can take the PTR_TO_BTF_ID returned by > the bpf_skc_to_*() helpers. > > The only special case is bpf_sk_lookup_assign() which can accept a > literal NULL ptr. It has to be handled specially in another follow > up patch if there is a need (e.g. by renaming ARG_PTR_TO_SOCKET_OR_NULL > to ARG_PTR_TO_BTF_ID_SOCK_COMMON_OR_NULL). ] > > [ When converting the older helpers that take ARG_PTR_TO_SOCK* in > the later patch, if the kernel does not support BTF, > ARG_PTR_TO_BTF_ID_SOCK_COMMON will behave like ARG_PTR_TO_SOCK_COMMON > because no reg->type could have PTR_TO_BTF_ID in this case. > > It is not a concern for the newer-btf-only helper like the bpf_skc_to_*() > here though because these helpers must require BTF vmlinux to begin > with. ] > > Signed-off-by: Martin KaFai Lau <kafai@xxxxxx> > --- > include/linux/bpf.h | 1 + > kernel/bpf/verifier.c | 34 +++++++++++++++++++-- > net/core/filter.c | 69 ++++++++++++++++++++++++++++++------------- > 3 files changed, 82 insertions(+), 22 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index fc5c901c7542..d0937f1d2980 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -292,6 +292,7 @@ enum bpf_arg_type { > ARG_PTR_TO_ALLOC_MEM, /* pointer to dynamically allocated memory */ > ARG_PTR_TO_ALLOC_MEM_OR_NULL, /* pointer to dynamically allocated memory or NULL */ > ARG_CONST_ALLOC_SIZE_OR_ZERO, /* number of allocated bytes requested */ > + ARG_PTR_TO_BTF_ID_SOCK_COMMON, /* pointer to in-kernel sock_common or bpf-mirrored bpf_sock */ > __BPF_ARG_TYPE_MAX, > }; > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 945fa2b4d096..d4ba29fb17a6 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' */ > @@ -3953,6 +3958,7 @@ 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 = { > @@ -3973,6 +3979,17 @@ static const struct bpf_reg_types sock_types = { > }, > }; > > +static const struct bpf_reg_types btf_id_sock_common_types = { > + .types = { > + PTR_TO_SOCK_COMMON, > + 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 = { > .types = { > PTR_TO_STACK, > @@ -4014,6 +4031,7 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = { > [ARG_PTR_TO_CTX] = &context_types, > [ARG_PTR_TO_CTX_OR_NULL] = &context_types, > [ARG_PTR_TO_SOCK_COMMON] = &sock_types, > + [ARG_PTR_TO_BTF_ID_SOCK_COMMON] = &btf_id_sock_common_types, > [ARG_PTR_TO_SOCKET] = &fullsock_types, > [ARG_PTR_TO_SOCKET_OR_NULL] = &fullsock_types, > [ARG_PTR_TO_BTF_ID] = &btf_ptr_types, > @@ -4059,6 +4077,14 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno, > > found: > if (type == PTR_TO_BTF_ID) { > + if (!arg_btf_id) { > + if (!compatible->btf_id) { > + verbose(env, "verifier internal error: missing arg compatible BTF ID\n"); > + return -EFAULT; > + } > + arg_btf_id = compatible->btf_id; > + } > + > if (!btf_struct_ids_match(&env->log, reg->off, reg->btf_id, > *arg_btf_id)) { > verbose(env, "R%d is of type %s but %s is expected\n", > @@ -4575,10 +4601,14 @@ static bool check_btf_id_ok(const struct bpf_func_proto *fn) > { > int i; > > - for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++) > + for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++) { > if (fn->arg_type[i] == ARG_PTR_TO_BTF_ID && !fn->arg_btf_id[i]) > return false; > > + if (fn->arg_type[i] != ARG_PTR_TO_BTF_ID && fn->arg_btf_id[i]) > + return false; > + } > + This is a hold over from the previous patchset? > return true; > } > > diff --git a/net/core/filter.c b/net/core/filter.c > index 706f8db0ccf8..6d1864f2bd51 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()) { > @@ -6620,7 +6623,7 @@ 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); > } > } > > @@ -6639,7 +6642,7 @@ 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); > } > } > > @@ -6800,7 +6803,7 @@ 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); > } > } > > @@ -6841,7 +6844,7 @@ 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); > } > } > > @@ -6883,7 +6886,7 @@ 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); > } > } > > @@ -6929,7 +6932,7 @@ 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); > } > } > > @@ -6971,7 +6974,7 @@ 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); > } > } > > @@ -6982,7 +6985,7 @@ 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); > } > } > > @@ -7009,7 +7012,7 @@ 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); > } > } > > @@ -9746,7 +9749,7 @@ 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); > } > } > > @@ -9913,8 +9916,7 @@ 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_BTF_ID_SOCK_COMMON, > .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP6], > }; > > @@ -9930,8 +9932,7 @@ 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_BTF_ID_SOCK_COMMON, > .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP], > }; > > @@ -9954,8 +9955,7 @@ 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_BTF_ID_SOCK_COMMON, > .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP_TW], > }; > > @@ -9978,8 +9978,7 @@ 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_BTF_ID_SOCK_COMMON, > .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP_REQ], > }; > > @@ -10000,7 +9999,37 @@ 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_BTF_ID_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 > -- Lorenz Bauer | Systems Engineer 6th Floor, County Hall/The Riverside Building, SE1 7PB, UK www.cloudflare.com
