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From: Alexei Starovoitov <ast@fb.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"x86@kernel.org" <x86@kernel.org>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v2 bpf-next 05/12] libbpf: auto-detect btf_id of raw_tracepoint
Date: Sat, 12 Oct 2019 04:53:16 +0000
Message-ID: <b16deef3-c736-1979-2ce8-6b03b426be67@fb.com> (raw)
In-Reply-To: <CAEf4BzZsz-6ftv628bk9LtEFr1qUoARL32x-kGagi7esOBURyA@mail.gmail.com>

On 10/11/19 9:38 PM, Andrii Nakryiko wrote:
> On Fri, Oct 11, 2019 at 6:29 PM Alexei Starovoitov <ast@fb.com> wrote:
>>
>> On 10/11/19 5:40 PM, Alexei Starovoitov wrote:
>>>> But even if kernel supports attach_btf_id, I think users still need to
>>>> opt in into specifying attach_btf_id by libbpf. Think about existing
>>>> raw_tp programs that are using bpf_probe_read() because they were not
>>>> created with this kernel feature in mind. They will suddenly stop
>>>> working without any of user's fault.
>>>
>>> This one is excellent catch.
>>> loop1.c should have caught it, since it has
>>> SEC("raw_tracepoint/kfree_skb")
>>> {
>>>     int nested_loops(volatile struct pt_regs* ctx)
>>>      .. = PT_REGS_RC(ctx);
>>>
>>> and verifier would have rejected it.
>>> But the way the test is written it's not using libbpf's autodetect
>>> of program type, so everything is passing.
>>
>> With:
>> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
>> b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
>> index 1c01ee2600a9..e27156dce10d 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
>> @@ -67,7 +67,7 @@ void test_bpf_verif_scale(void)
>>                    */
>>                   { "pyperf600_nounroll.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
>>
>> -               { "loop1.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
>> +               { "loop1.o", BPF_PROG_TYPE_UNSPEC},
>>                   { "loop2.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
>>
>> libbpf prog auto-detection kicks in and ...
>> # ./test_progs -n 3/10
>> libbpf: load bpf program failed: Permission denied
>> libbpf: -- BEGIN DUMP LOG ---
>> libbpf:
>> raw_tp 'kfree_skb' doesn't have 10-th argument
>> invalid bpf_context access off=80 size=8
>>
>> Good :) The verifier is doing its job.
> 
> oh, another super intuitive error from verifier ;) 10th argument, what?..

I know, but there is no env->linfo and no insn_idx to call
verbose_linfo() from there. That's even bigger refactoring
that I'd rather to later.

  reply index

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-10  4:14 [PATCH v2 bpf-next 00/12] bpf: revolutionize bpf tracing Alexei Starovoitov
2019-10-10  4:14 ` [PATCH v2 bpf-next 01/12] bpf: add typecast to raw_tracepoints to help BTF generation Alexei Starovoitov
2019-10-10  4:14 ` [PATCH v2 bpf-next 02/12] bpf: add typecast to bpf helpers " Alexei Starovoitov
2019-10-10  4:14 ` [PATCH v2 bpf-next 03/12] bpf: process in-kernel BTF Alexei Starovoitov
2019-10-11 17:56   ` Andrii Nakryiko
2019-10-10  4:14 ` [PATCH v2 bpf-next 04/12] bpf: add attach_btf_id attribute to program load Alexei Starovoitov
2019-10-11 17:58   ` Andrii Nakryiko
2019-10-10  4:14 ` [PATCH v2 bpf-next 05/12] libbpf: auto-detect btf_id of raw_tracepoint Alexei Starovoitov
2019-10-11 18:02   ` Andrii Nakryiko
2019-10-11 18:07   ` Andrii Nakryiko
2019-10-12  0:40     ` Alexei Starovoitov
2019-10-12  1:29       ` Alexei Starovoitov
2019-10-12  4:38         ` Andrii Nakryiko
2019-10-12  4:53           ` Alexei Starovoitov [this message]
2019-10-12  4:39       ` Andrii Nakryiko
2019-10-10  4:14 ` [PATCH v2 bpf-next 06/12] bpf: implement accurate raw_tp context access via BTF Alexei Starovoitov
2019-10-11 18:31   ` Andrii Nakryiko
2019-10-11 23:13     ` Andrii Nakryiko
2019-10-10  4:14 ` [PATCH v2 bpf-next 07/12] bpf: attach raw_tp program with BTF via type name Alexei Starovoitov
2019-10-11 18:44   ` Andrii Nakryiko
2019-10-10  4:14 ` [PATCH v2 bpf-next 08/12] bpf: add support for BTF pointers to interpreter Alexei Starovoitov
2019-10-10  4:15 ` [PATCH v2 bpf-next 09/12] bpf: add support for BTF pointers to x86 JIT Alexei Starovoitov
2019-10-11 18:48   ` Andrii Nakryiko
2019-10-10  4:15 ` [PATCH v2 bpf-next 10/12] bpf: check types of arguments passed into helpers Alexei Starovoitov
2019-10-11 19:02   ` Andrii Nakryiko
2019-10-12  1:39     ` Alexei Starovoitov
2019-10-12  4:25       ` Andrii Nakryiko
2019-10-10  4:15 ` [PATCH v2 bpf-next 11/12] bpf: disallow bpf_probe_read[_str] helpers Alexei Starovoitov
2019-10-11 19:03   ` Andrii Nakryiko
2019-10-10  4:15 ` [PATCH v2 bpf-next 12/12] selftests/bpf: add kfree_skb raw_tp test Alexei Starovoitov
2019-10-10 11:07   ` Ido Schimmel
2019-10-10 19:07     ` Alexei Starovoitov
2019-10-11 19:05   ` Andrii Nakryiko

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