| Message ID | 20200925000350.3855720-1-kafai@fb.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | bpf: Enable bpf_skc_to_* sock casting helper to networking prog type | expand |
On Fri, 25 Sep 2020 at 01:04, Martin KaFai Lau <kafai@fb.com> 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@fb.com/ > > 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@fb.com> > --- > 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 >
On Fri, Sep 25, 2020 at 09:26:36AM +0100, Lorenz Bauer wrote: > On Fri, 25 Sep 2020 at 01:04, Martin KaFai Lau <kafai@fb.com> 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@fb.com/ > > > > 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@fb.com> > > --- > > 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? hmm... what do you mean?
On Fri, 25 Sep 2020 at 14:18, Martin KaFai Lau <kafai@fb.com> wrote: > > On Fri, Sep 25, 2020 at 09:26:36AM +0100, Lorenz Bauer wrote: > > On Fri, 25 Sep 2020 at 01:04, Martin KaFai Lau <kafai@fb.com> 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@fb.com/ > > > > > > 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@fb.com> > > > --- > > > 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? > hmm... what do you mean? Sorry, I misread the patch!
Martin KaFai Lau 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@fb.com/ > > 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@fb.com> > --- LGTM it took a bit of looking around to convince myself that we have ret_type set to PTR_TO_SOCK_*_OR_NULL types in the sk lookup helpers so that we force a null check before passing these into the skc_to_* helpers here, but I didn't see any holes. Thanks. Acked-by: John Fastabend <john.fastabend@gmail.com> > @@ -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; > + } > + I guess this case is harmless? If some other arg has a btf_id its setup wrong, so nice to fail here I think. > return true; > } >
On 9/25/20 6:50 AM, Lorenz Bauer wrote: >>>> - 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? >> hmm... what do you mean? > Sorry, I misread the patch! Folks, please trim your replies. You could have quoted just few lines above instead of most of the patch. Scrolling takes time for those of us who used tbird, mutt, etc.
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; + } + 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; +}
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@fb.com/ 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@fb.com> --- include/linux/bpf.h | 1 + kernel/bpf/verifier.c | 34 +++++++++++++++++++-- net/core/filter.c | 69 ++++++++++++++++++++++++++++++------------- 3 files changed, 82 insertions(+), 22 deletions(-)