From: "Jose E. Marchesi" <jose.marchesi@oracle.com>
To: Eduard Zingerman <eddyz87@gmail.com>
Cc: Yonghong Song <yhs@meta.com>, bpf@vger.kernel.org
Subject: Re: Encoding of V4 32-bit JA
Date: Sun, 23 Jul 2023 21:14:46 +0200 [thread overview]
Message-ID: <878rb6qw2h.fsf@oracle.com> (raw)
In-Reply-To: <32dc8c48803ff047266ee396fed3ccc9f7f0147e.camel@gmail.com> (Eduard Zingerman's message of "Sun, 23 Jul 2023 20:10:15 +0300")
> On Fri, 2023-07-21 at 18:19 +0200, Jose E. Marchesi wrote:
>> Hi Yonghong.
>>
>> This is from the v4 instructions proposal:
>>
>> ======== ===== ========================= ============
>> code value description notes
>> ======== ===== ========================= ============
>> BPF_JA 0x00 PC += imm BPF_JMP32 only
>>
>> Is this instruction using source 1 instead of 0? Otherwise, it would
>> have exactly the same encoding than the V3< JA instruction. Is that
>> what is intended?
>>
>> TIA.
>>
>
> Hi Jose,
>
> I think that assumption is that `BPF_JMP32 | BPF_JA` is currently free:
> - documentation [1] implies that only `BPF_JMP` should be used for `BPF_JA`
> (see "notes" column for the first line)
> - BPF verifier rejects `BPF_JMP32 | BPF_JA`
> - clang always generates `BPF_JMP | BPF_JA`
Makes sense, thanks for the info.
Do you know the precise pseudo-c assembly syntax to use for this
instruction?
> Thanks,
> Eduard
>
> [1] https://www.kernel.org/doc/html/latest/bpf/instruction-set.html#jump-instructions
next prev parent reply other threads:[~2023-07-23 19:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-21 16:19 Encoding of V4 32-bit JA Jose E. Marchesi
2023-07-23 17:10 ` Eduard Zingerman
2023-07-23 19:14 ` Jose E. Marchesi [this message]
2023-07-23 19:21 ` Eduard Zingerman
2023-07-23 19:57 ` Jose E. Marchesi
2023-07-23 23:51 ` Jose E. Marchesi
2023-07-24 2:37 ` Yonghong Song
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