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Date: Thu, 2 Jan 2025 16:44:54 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
 linux-kbuild@vger.kernel.org, bpf <bpf@vger.kernel.org>, Masami Hiramatsu
 <mhiramat@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Mathieu
 Desnoyers <mathieu.desnoyers@efficios.com>, Andrew Morton
 <akpm@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>,
 Masahiro Yamada <masahiroy@kernel.org>, Nathan Chancellor
 <nathan@kernel.org>, Nicolas Schier <nicolas@fjasle.eu>, Zheng Yejian
 <zhengyejian1@huawei.com>, Martin Kelly <martin.kelly@crowdstrike.com>,
 Christophe Leroy <christophe.leroy@csgroup.eu>, Josh Poimboeuf
 <jpoimboe@redhat.com>
Subject: Re: [PATCH 00/14] scripts/sorttable: ftrace: Remove place holders
 for weak functions in available_filter_functions
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On Thu, 2 Jan 2025 11:30:12 -0800
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> Please just do this by sorting non-existent functions at the end,
> instead of just zeroing them out.
> 
> That makes the mcount_loc table dense in valid entries. We could then
> just rewrite the size of the table (or just add a variable containing
> the size, if you don't want to change ELF metadata - but you're
> already sorting the table, so why not?)

Well, I tried to move the __start_mcount_loc, but it appears that changing
the symbol value *after* the linking phase does nothing :-p  The references
to it have already been resolved. The Elf_Rel* will do the updates from
then on, and to read those, becomes architecture dependent.

I guess the next thing I could do is to create a "skip" variable that can
be modified, and we can skip X entries in the start_mcount_loc. As the
start_mcount_loc and stop_mcount_loc (which determines the size of the
table) cannot be modified in an architecture independent way.

-- Steve