From: Steven Rostedt <rostedt@goodmis.org>
To: Artem Savkov <asavkov@redhat.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
bpf@vger.kernel.org, netdev@vger.kernel.org,
Masami Hiramatsu <mhiramat@kernel.org>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
linux-rt-users@vger.kernel.org, Jiri Olsa <jolsa@kernel.org>
Subject: Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
Date: Fri, 13 Oct 2023 10:00:23 -0400 [thread overview]
Message-ID: <20231013100023.5b0943ec@rorschach.local.home> (raw)
In-Reply-To: <ZSjdPqQiPdqa-UTs@wtfbox.lan>
On Fri, 13 Oct 2023 08:01:34 +0200
Artem Savkov <asavkov@redhat.com> wrote:
> > But looking at [0] and briefly reading some of the discussions you,
> > Steven, had. I'm just wondering if it would be best to avoid
> > increasing struct trace_entry altogether? It seems like preempt_count
> > is actually a 4-bit field in trace context, so it doesn't seem like we
> > really need to allocate an entire byte for both preempt_count and
> > preempt_lazy_count. Why can't we just combine them and not waste 8
> > extra bytes for each trace event in a ring buffer?
> >
> > [0] https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=b1773eac3f29cbdcdfd16e0339f1a164066e9f71
>
> I agree that avoiding increase in struct trace_entry size would be very
> desirable, but I have no knowledge whether rt developers had reasons to
> do it like this.
>
> Nevertheless I think the issue with verifier running against a wrong
> struct still needs to be addressed.
Correct. My Ack is based on the current way things are done upstream.
It was just that linux-rt showed the issue, where the code was not as
robust as it should have been. To me this was a correctness issue, not
an issue that had to do with how things are done in linux-rt.
As for the changes in linux-rt, they are not upstream yet. I'll have my
comments on that code when that happens.
-- Steve
next prev parent reply other threads:[~2023-10-13 14:00 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-02 13:52 [RFC PATCH] tracing: change syscall number type in struct syscall_trace_* Artem Savkov
2023-10-03 22:11 ` Andrii Nakryiko
2023-10-04 7:02 ` Artem Savkov
2023-10-04 1:38 ` Steven Rostedt
2023-10-04 12:55 ` Artem Savkov
2023-10-05 12:34 ` Artem Savkov
2023-10-12 11:45 ` [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t Artem Savkov
2023-10-12 13:44 ` Steven Rostedt
2023-10-12 23:32 ` Andrii Nakryiko
2023-10-13 5:42 ` [PATCH " Artem Savkov
2023-10-13 19:50 ` patchwork-bot+netdevbpf
2023-10-13 6:01 ` [RFC PATCH " Artem Savkov
2023-10-13 14:00 ` Steven Rostedt [this message]
2023-10-13 19:43 ` Andrii Nakryiko
2023-10-16 15:53 ` Steven Rostedt
2023-10-13 3:13 ` Rod Webster
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