From c4d0bfb45068d853a478b9067a95969b1886a30f Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Mon, 28 Sep 2020 12:31:05 +0100 Subject: bpf: Add bpf_snprintf_btf helper A helper is added to support tracing kernel type information in BPF using the BPF Type Format (BTF). Its signature is long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr, u32 btf_ptr_size, u64 flags); struct btf_ptr * specifies - a pointer to the data to be traced - the BTF id of the type of data pointed to - a flags field is provided for future use; these flags are not to be confused with the BTF_F_* flags below that control how the btf_ptr is displayed; the flags member of the struct btf_ptr may be used to disambiguate types in kernel versus module BTF, etc; the main distinction is the flags relate to the type and information needed in identifying it; not how it is displayed. For example a BPF program with a struct sk_buff *skb could do the following: static struct btf_ptr b = { }; b.ptr = skb; b.type_id = __builtin_btf_type_id(struct sk_buff, 1); bpf_snprintf_btf(str, sizeof(str), &b, sizeof(b), 0, 0); Default output looks like this: (struct sk_buff){ .transport_header = (__u16)65535, .mac_header = (__u16)65535, .end = (sk_buff_data_t)192, .head = (unsigned char *)0x000000007524fd8b, .data = (unsigned char *)0x000000007524fd8b, .truesize = (unsigned int)768, .users = (refcount_t){ .refs = (atomic_t){ .counter = (int)1, }, }, } Flags modifying display are as follows: - BTF_F_COMPACT: no formatting around type information - BTF_F_NONAME: no struct/union member names/types - BTF_F_PTR_RAW: show raw (unobfuscated) pointer values; equivalent to %px. - BTF_F_ZERO: show zero-valued struct/union members; they are not displayed by default Signed-off-by: Alan Maguire Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/1601292670-1616-4-git-send-email-alan.maguire@oracle.com --- include/linux/bpf.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/bpf.h') diff --git a/include/linux/bpf.h b/include/linux/bpf.h index e620a4b1290f..768b533ba48e 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1822,6 +1822,7 @@ extern const struct bpf_func_proto bpf_skc_to_tcp_timewait_sock_proto; extern const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto; extern const struct bpf_func_proto bpf_skc_to_udp6_sock_proto; extern const struct bpf_func_proto bpf_copy_from_user_proto; +extern const struct bpf_func_proto bpf_snprintf_btf_proto; const struct bpf_func_proto *bpf_tracing_func_proto( enum bpf_func_id func_id, const struct bpf_prog *prog); -- cgit v1.2.3