Vendor deprecated btf_ext APIs and structs

[davemarchevsky]

Some btf_ext-related APIs in libbpf are being deprecated because they
make incorrect assumptions. They're being used only by bcc currently, so
vendor them before they get deleted.

After / as part of #3660, may need to revisit the incorrect assumptions
being made here.

The functions and structs were ripped directly from libbpf with minimal
changes:

• Change void* arithmetic to uint8_t
• __u32 -> uint32_t and similar
• Add a wrapping namespace
• rec_size functions were not needed - just grab the rec_size
  directly since type is no longer opaque to bcc

[davemarchevsky]

need to remove __bcc prefix from things

edit: did so

[yonghong-song]

btf_load() is also deprecated.

/home/yhs/work/bcc/src/cc/bcc_btf.cc:600:20: warning: ‘int btf__load(btf*)’ is deprecated: libbpf v0.6+: use btf__load_into_kernel instead [-Wdeprecated-declarations]

Maybe to check to use btf__load_into_kernel()?

If we want to accommodate the external libbpf build, you can copy btf__load() function as well. Hopefully, eventually all these (bpf_ext* and btf__load) are gone and handled by libbpf library directly.

I did a simple test with profile.py with this patch and dump program xlated code. It appears the patch is working and I can see proper source annotation in xlated code.

[yonghong-song]

err is 'int' type, converting to 'struct btf_ext *' will trigger the warning:

/home/yhs/work/bcc/src/cc/bcc_btf.cc: In function ‘btf_ext_vendored::btf_ext* btf_ext_vendored::btf_ext__new(const uint8_t*, uint32_t)’:                                            
/home/yhs/work/bcc/src/cc/bcc_btf.cc:276:41: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]                                                        
                 return (struct btf_ext*)err;                                                                                                                                       
                                         ^~~ 

You can do (struct btf_ext *)(long)err.

[davemarchevsky]

fixed, but with a uintptr_t cast instead of long

[chenhengqi]

Three libbpf APIs used by BCC are deprecated.

• bpf_create_map_xattr -> bpf_map_create
• bpf_load_program_xattr -> bpf_prog_load
• btf__load -> btf__load_into_kernel

@davemarchevsky Are you going to address these in this PR ?

Or I may pick this up.

[davemarchevsky]

Maybe to check to use btf__load_into_kernel()?

@davemarchevsky Are you going to address these in this PR ?

I think those migrations away from other deprecated stuff should be addressed in a separate PR. @chenhengqi if you'd like to do it plz feel free, otherwise I will pick up late this week / early next.

[yonghong-song]

I think those migrations away from other deprecated stuff should be addressed in a separate PR. @chenhengqi if you'd like to do it plz feel free, otherwise I will pick up late this week / early next.

okay. let us address btf__load API in the separate PR. Please fix the warning and I think we will be good to go.