From: "Ihor Solodrai" <ihor.solodrai@linux.dev>
To: "Andrii Nakryiko" <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org, andrii@kernel.org, ast@kernel.org,
daniel@iogearbox.net, eddyz87@gmail.com, mykolal@fb.com,
kernel-team@meta.com
Subject: Re: [PATCH bpf-next 1/2] libbpf: implement bpf_usdt_arg_size BPF function
Date: Mon, 24 Feb 2025 23:14:59 +0000 [thread overview]
Message-ID: <6b35b7490955800b5cc3833508c88914d59d0d85@linux.dev> (raw)
In-Reply-To: <CAEf4Bzb4T3DcySAyyCXWBK-ShyW9iuE-OM9f7EHXmBJg5Qm0eg@mail.gmail.com>
On 2/24/25 2:05 PM, Andrii Nakryiko wrote:
> [...]
>
> arg_bitshift is stored as char (which could be signed), so that's why
> you were getting signed division, just cast to unsigned and keep
> division:
>
> return (64 - (unsigned)arg_spec->arg_bitshift) / 8;
As it turns out, this doesn't work either. Presumably because
(64 - (u8)x) is still a signed int.
This works, however:
return (unsigned char)(64 - arg_spec->arg_bitshift) / 8;
>
>> [...]
next prev parent reply other threads:[~2025-02-24 23:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-20 21:59 [PATCH bpf-next 1/2] libbpf: implement bpf_usdt_arg_size BPF function Ihor Solodrai
2025-02-20 21:59 ` [PATCH bpf-next 2/2] selftests/bpf: test bpf_usdt_arg_size() function Ihor Solodrai
2025-02-24 22:05 ` [PATCH bpf-next 1/2] libbpf: implement bpf_usdt_arg_size BPF function Andrii Nakryiko
2025-02-24 22:21 ` Ihor Solodrai
2025-02-24 23:14 ` Ihor Solodrai [this message]
2025-02-24 23:25 ` Andrii Nakryiko
2025-02-24 23:38 ` Ihor Solodrai
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