From: Puranjay Mohan <puranjay12@gmail.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Shubham Bansal <illusionist.neo@gmail.com>,
Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>,
bpf@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next 4/8] arm32, bpf: add support for unconditional bswap instruction
Date: Wed, 06 Sep 2023 09:31:58 +0000 [thread overview]
Message-ID: <mb61pjzt33awh.fsf@amazon.com> (raw)
In-Reply-To: <ZPeecV807AVEkCJB@shell.armlinux.org.uk> (Russell King's message of "Tue, 5 Sep 2023 22:32:33 +0100")
On Tue, Sep 05 2023, Russell King (Oracle) wrote:
> On Tue, Sep 05, 2023 at 09:06:17PM +0000, Puranjay Mohan wrote:
>> The cpuv4 added a new unconditional bswap instruction with following
>> behaviour:
>>
>> BPF_ALU64 | BPF_TO_LE | BPF_END with imm = 16/32/64 means:
>> dst = bswap16(dst)
>> dst = bswap32(dst)
>> dst = bswap64(dst)
>>
>> As we already support converting to big-endian from little-endian we can
>> use the same for unconditional bswap.
>> Since ARM32 is always little-endian, just treat the unconditional scenario
>
> This is not true. Arm32 BPF is disabled for BE32 but not for BE8. It's
> entirely possible to build a kernel using BE8 for ARMv7 and have the
> BPF JIT enabled:
>
> select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32
>
> So it's not true to say "Since ARM32 is always little-endian".
Sure, I will change the commit message in next version.
Thanks,
Puranjay
next prev parent reply other threads:[~2023-09-06 9:32 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-05 21:06 [PATCH bpf-next 0/8] arm32, bpf: add support for cpuv4 insns Puranjay Mohan
2023-09-05 21:06 ` [PATCH bpf-next 1/8] arm32, bpf: add support for 32-bit offset jmp instruction Puranjay Mohan
2023-09-05 21:11 ` Russell King (Oracle)
2023-09-05 21:06 ` [PATCH bpf-next 2/8] arm32, bpf: add support for sign-extension load instruction Puranjay Mohan
2023-09-05 21:24 ` Russell King (Oracle)
2023-09-06 11:47 ` Puranjay Mohan
2023-09-05 21:06 ` [PATCH bpf-next 3/8] arm32, bpf: add support for sign-extension mov instruction Puranjay Mohan
2023-09-05 21:06 ` [PATCH bpf-next 4/8] arm32, bpf: add support for unconditional bswap instruction Puranjay Mohan
2023-09-05 21:32 ` Russell King (Oracle)
2023-09-06 9:31 ` Puranjay Mohan [this message]
2023-09-05 21:06 ` [PATCH bpf-next 5/8] arm32, bpf: add support for 32-bit signed division Puranjay Mohan
2023-09-05 21:44 ` Russell King (Oracle)
2023-09-05 21:06 ` [PATCH bpf-next 6/8] arm32, bpf: add support for 64 bit division instruction Puranjay Mohan
2023-09-05 21:50 ` Russell King (Oracle)
2023-09-06 9:29 ` Puranjay Mohan
2023-09-06 18:56 ` Russell King (Oracle)
2023-09-06 19:19 ` Puranjay Mohan
2023-09-06 20:26 ` Russell King (Oracle)
2023-09-05 21:06 ` [PATCH bpf-next 7/8] selftest, bpf: enable cpu v4 tests for arm32 Puranjay Mohan
2023-09-05 21:06 ` [PATCH bpf-next 8/8] bpf/tests: add tests for cpuv4 instructions Puranjay Mohan
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