From: Alexei Starovoitov <ast@fb.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Alexei Starovoitov <ast@kernel.org>
Cc: "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 10/12] bpf: check types of arguments passed into helpers
Date: Sat, 12 Oct 2019 01:39:13 +0000 [thread overview]
Message-ID: <ba51c8c3-94fc-413a-0935-aaa307127666@fb.com> (raw)
In-Reply-To: <CAEf4BzbmE_ADjjhu-+mLkQN_5HD6Azhrb-VuprAaoqxP1bb3OQ@mail.gmail.com>
On 10/11/19 12:02 PM, Andrii Nakryiko wrote:
> On Wed, Oct 9, 2019 at 9:15 PM Alexei Starovoitov <ast@kernel.org> wrote:
>>
>> /* type of values returned from helper functions */
>> @@ -235,11 +236,17 @@ struct bpf_func_proto {
>> bool gpl_only;
>> bool pkt_access;
>> enum bpf_return_type ret_type;
>> - enum bpf_arg_type arg1_type;
>> - enum bpf_arg_type arg2_type;
>> - enum bpf_arg_type arg3_type;
>> - enum bpf_arg_type arg4_type;
>> - enum bpf_arg_type arg5_type;
>> + union {
>> + struct {
>> + enum bpf_arg_type arg1_type;
>> + enum bpf_arg_type arg2_type;
>> + enum bpf_arg_type arg3_type;
>> + enum bpf_arg_type arg4_type;
>> + enum bpf_arg_type arg5_type;
>> + };
>> + enum bpf_arg_type arg_type[5];
>> + };
>> + u32 *btf_id; /* BTF ids of arguments */
>
> are you trying to save memory with this? otherwise not sure why it's
> not just `u32 btf_id[5]`? Even in that case it will save at most 12
> bytes (and I haven't even check alignment padding and stuff). So
> doesn't seem worth it?
Glad you asked :)
It cannot be "u32 btf_id[5];".
Guess why?
I think it's a cool trick.
I was happy when I finally figured out to solve it this way
after analyzing a bunch of ugly solutions.
>> + *
>> + * The value to write, of *size*, is passed through eBPF stack and
>> + * pointed by *data*.
>
> typo? pointed __to__ by *data*?
I'm not an grammar expert. That was a copy paste from existing comment.
>> + *
>> + * *ctx* is a pointer to in-kernel sutrct sk_buff.
>> + *
>> + * This helper is similar to **bpf_perf_event_output**\ () but
>> + * restricted to raw_tracepoint bpf programs.
>
> nit: with BTF type tracking enabled?
sure.
>> + for (i = 0; i < 5; i++) {
>> + if (fn->arg_type[i] == ARG_PTR_TO_BTF_ID) {
>> + if (!fn->btf_id[i])
>> + fn->btf_id[i] = btf_resolve_helper_id(&env->log, fn->func, 0);
>
> bug: 0 -> i :)
Nice catch.
Clearly I don't have a use case yet for 2nd arg being ptr_to_btf.
next prev parent reply other threads:[~2019-10-12 1:39 UTC|newest]
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
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 [this message]
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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