netdev - Re: [PATCH] Add skb_store_bytes() for BPF_PROG_TYPE_CGROUP

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Message-ID: <2e3a072c-2734-0d54-d0c3-833a75b509bf@fb.com>
Date:   Wed, 5 Jan 2022 23:50:55 -0800
From:   Yonghong Song <yhs@...com>
To:     "Tyler Wear (QUIC)" <quic_twear@...cinc.com>,
        Martin KaFai Lau <kafai@...com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "maze@...gle.com" <maze@...gle.com>
Subject: Re: [PATCH] Add skb_store_bytes() for BPF_PROG_TYPE_CGROUP_SKB



On 1/4/22 4:27 PM, Tyler Wear (QUIC) wrote:
> 
> 
>> -----Original Message-----
>> From: Martin KaFai Lau <kafai@...com>
>> Sent: Wednesday, December 29, 2021 1:06 PM
>> To: Tyler Wear <twear@...cinc.com>
>> Cc: Yonghong Song <yhs@...com>; Tyler Wear (QUIC) <quic_twear@...cinc.com>; netdev@...r.kernel.org; bpf@...r.kernel.org;
>> maze@...gle.com
>> Subject: Re: [PATCH] Add skb_store_bytes() for BPF_PROG_TYPE_CGROUP_SKB
>>
>> WARNING: This email originated from outside of Qualcomm. Please be wary of any links or attachments, and do not enable macros.
>>
>> On Wed, Dec 29, 2021 at 06:29:05PM +0000, Tyler Wear wrote:
>>> Unable to run any bpf tests do to errors below. These occur with and without the new patch. Is this a known issue?
>>> Is the new test case required since bpf_skb_store_bytes() is already a tested function for other prog types?
>>>
>>> libbpf: failed to find BTF for extern 'bpf_testmod_invalid_mod_kfunc'
>>> [18] section: -2
>>> Error: failed to open BPF object file: No such file or directory
>>> libbpf: failed to find BTF info for global/extern symbol 'my_tid'
>>> Error: failed to link
>>> '/local/mnt/workspace/linux-stable/tools/testing/selftests/bpf/linked_
>>> funcs1.o': Unknown error -2 (-2)
>>> libbpf: failed to find BTF for extern 'bpf_kfunc_call_test1' [27]
>>> section: -2
>> tools/testing/selftests/bpf/README.rst has details on these.
>>
>> Ensure the llvm and pahole are up to date.
>> Also take a look at the "Testing patches" and "LLVM" section in Documentation/bpf/bpf_devel_QA.rst.
> 
> This will also require adding the l3/l4_ csum_replace() api's then. Adding the csum_replace() to a cgroup test case results in the below error during bpf program validation:
> "BPF_LD_[ABS|IND] instructions not allowed for this program type"

I saw you posted a new patch, so it seems you have resolved this 
BPF_LD_[ABS|IND] issue. Do you know what is the reason for this 
verification error? Here, the program type is cgroup_skb which should 
not mess up with BPF_LD_[ABS|IND] which is mostly for classic bpf to 
extended bpf conversion. Did I miss anything here?

> 
> Is there something else that needs to be added? Or would it be better to create the function just for ds_field?