linux-kernel - Re: [PATCH] perf tools: Fixup module symbol end address properly

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Date: Fri, 16 Feb 2024 20:29:02 +0800
From: Leo Yan <leo.yan@...ux.dev>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org, Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	John Garry <john.g.garry@...cle.com>,
	Mike Leach <mike.leach@...aro.org>
Subject: Re: [PATCH] perf tools: Fixup module symbol end address properly

On Thu, Feb 15, 2024 at 09:19:51PM -0800, Namhyung Kim wrote:

[...]

> > On the other hand, I am a bit concern
> > for a big function (e.g. its code size > 4KiB), we might fail to find
> > symbols in this case with the change above.
> 
> Yes, it's another problem.  But it cannot know the exact size
> so it just assumes it fits in a page.

Agreed.

> > > > If so, we should use a specific checking for eBPF program, e.g.:
> > > >
> > > >                         else if (prev_mod && strcmp(prev_mod, curr_mod) &&
> > > >                                  (!strcmp(prev->name, "bpf") ||
> > > >                                   !strcmp(curr->name, "bpf")))
> > >
> > > I suspect it can happen on any module boundary so better
> > > to handle it in a more general way.
> >
> > I don't want to introduce over complexity at here. We can apply
> > current patch as it is.
> 
> Good, can I get your Reviewed-by then? :)

Yes.

Reviewed-by: Leo Yan <leo.yan@...ux.dev>

> > A side topic, when I saw the code is hard coded for 4096 as the page
> > size, this is not always true on Arm64 (the page size can be 4KiB,
> > 16KiB or 64KiB). We need to consider to extend the environment for
> > recording the system's page size.
> 
> Sounds good.  But until then, 4K would be the reasonable choice.

This is fine for me.

Thanks,
Leo