Re: Clang-14.0.6 compiled kernel/linux-5.4/samples/bpf/ failed to load on x86-64 target

On 1/22/23 10:10 AM, nelakurthi koteswararao wrote:

Dear LLVM BPF contributors

I compiled samples/bpf/ programs for target 'bpf' using clang-14.0.6 
version compiler present in linux-5.4.202/samples/bpf directory but when 
i try to load the sample programs like (sock_ex1) on target x86-64, they 
are straightway failing to load in to the kernel.
{{
/var/log/gui_upload# ./sockex2
libbpf: Error loading BTF: Invalid argument(22)
libbpf: magic: 0xeb9f
version: 1
flags: 0x0
hdr_len: 24
type_off: 0
type_len: 1000
str_off: 1000
str_len: 2290
btf_total_size: 3314
[1] PTR (anon) type_id=3
[2] INT int size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
[3] ARRAY (anon) type_id=2 index_type_id=4 nr_elems=1
[4] INT __ARRAY_SIZE_TYPE__ size=4 bits_offset=0 nr_bits=32 encoding=(none)
[5] PTR (anon) type_id=6
[6] TYPEDEF __be32 type_id=7
[7] TYPEDEF __u32 type_id=8
[8] INT unsigned int size=4 bits_offset=0 nr_bits=32 encoding=(none)
[9] PTR (anon) type_id=10
[10] STRUCT pair size=16 vlen=2
         packets type_id=11 bits_offset=0
         bytes type_id=11 bits_offset=64
[11] INT long size=8 bits_offset=0 nr_bits=64 encoding=SIGNED
[12] PTR (anon) type_id=13
[13] ARRAY (anon) type_id=2 index_type_id=4 nr_elems=1024
[14] STRUCT (anon) size=32 vlen=4
         type type_id=1 bits_offset=0
         key type_id=5 bits_offset=64
         value type_id=9 bits_offset=128
         max_entries type_id=12 bits_offset=192
[15] VAR hash_map type_id=14 linkage=1
[16] PTR (anon) type_id=17
[17] STRUCT __sk_buff size=176 vlen=31
         len type_id=7 bits_offset=0
         pkt_type type_id=7 bits_offset=32
         mark type_id=7 bits_offset=64
         queue_mapping type_id=7 bits_offset=96
         protocol type_id=7 bits_offset=128
         vlan_present type_id=7 bits_offset=160
         vlan_tci type_id=7 bits_offset=192
         vlan_proto type_id=7 bits_offset=224
         priority type_id=7 bits_offset=256
         ingress_ifindex type_id=7 bits_offset=288
         ifindex type_id=7 bits_offset=320
         tc_index type_id=7 bits_offset=352
         cb type_id=18 bits_offset=384
         hash type_id=7 bits_offset=544
         tc_classid type_id=7 bits_offset=576
         data type_id=7 bits_offset=608
         data_end type_id=7 bits_offset=640
         napi_id type_id=7 bits_offset=672
         family type_id=7 bits_offset=704
         remote_ip4 type_id=7 bits_offset=736
         local_ip4 type_id=7 bits_offset=768
         remote_ip6 type_id=19 bits_offset=800
         local_ip6 type_id=19 bits_offset=928
         remote_port type_id=7 bits_offset=1056
         local_port type_id=7 bits_offset=1088
         data_meta type_id=7 bits_offset=1120
         (anon) type_id=20 bits_offset=1152
         tstamp type_id=22 bits_offset=1216
         wire_len type_id=7 bits_offset=1280
         gso_segs type_id=7 bits_offset=1312
         (anon) type_id=24 bits_offset=1344
[18] ARRAY (anon) type_id=7 index_type_id=4 nr_elems=5
[19] ARRAY (anon) type_id=7 index_type_id=4 nr_elems=4
[20] UNION (anon) size=8 vlen=1
         flow_keys type_id=21 bits_offset=0
[21] PTR (anon) type_id=33
[22] TYPEDEF __u64 type_id=23
[23] INT unsigned long long size=8 bits_offset=0 nr_bits=64 encoding=(none)
[24] UNION (anon) size=8 vlen=1
         sk type_id=25 bits_offset=0
[25] PTR (anon) type_id=34
[26] FU

NC_PROTO (anon) return=2 args=(16 skb)
[27] FUNC bpf_prog2 type_id=26 vlen != 0

libbpf: Error loading .BTF into kernel: -22.
}}
.BTF information is generated during compile time but loading to the 
kernel is failing.
Is it due to clang-14.0.6 compatibility with libbpf version present in 
5.4.202 kernel is leading to this issue?

You need to have a later version of libbpf. libbpf will probe kernel
and do proper sanitation if the kernel does not support above [27] encoding.

Request to please provide input if possible

Regards
Koti