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

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Date:   Sun, 22 Jan 2023 15:29:56 -0800
From:   Yonghong Song <yhs@...a.com>
To:     nelakurthi koteswararao <koteswararao18@...il.com>,
        Yonghong Song <yhs@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org
Subject: 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