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@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? hmm... what do you mean?
