linux-kernel - Re: [PATCH v2 16/16] scripts/sorttable: ftrace: Do not add weak functions to available_filter

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Message-ID: <aba52935dc06a1fe69f05309f5d9828a297ad787.camel@crowdstrike.com>
Date: Wed, 5 Feb 2025 00:13:26 +0000
From: Martin Kelly <martin.kelly@...wdstrike.com>
To: "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-trace-kernel@...r.kernel.org" <linux-trace-kernel@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-kbuild@...r.kernel.org"
	<linux-kbuild@...r.kernel.org>
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Subject: Re: [PATCH v2 16/16] scripts/sorttable: ftrace: Do not add weak
 functions to available_filter_functions

On Thu, 2025-01-02 at 18:26 -0500, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@...dmis.org>
> 
> When a function is annotated as "weak" and is overridden, the code is
> not
> removed. If it is traced, the fentry/mcount location in the weak
> function
> will be referenced by the "__mcount_loc" section. This will then be
> added
> to the available_filter_functions list. Since only the address of the
> functions are listed, to find the name to show, a search of kallsyms
> is
> used.
> 
> Since kallsyms will return the function by simply finding the
> function
> that the address is after but before the next function, an address of
> a
> weak function will show up as the function before it. This is because
> kallsyms does not save names of weak functions. This has caused
> issues in
> the past, as now the traced weak function will be listed in
> available_filter_functions with the name of the function before it.
> 

I'm not necessarily a qualified reviewer for this patch, but I'm very
interested in seeing it or a similar solution get merged, as the impact
when it hits is significant (silent failure) and not easy to detect or
work around. Is there any obstacle left in getting this one merged
other than further reviews?