linux-kernel - Re: [PATCH 00/14] scripts/sorttable: ftrace: Remove place holders for weak functions in available_filter

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=wjg4ckXG6tQHFAU_mL5vEFedwjGe=uahb31Oju50bYbNA@mail.gmail.com>
Date: Thu, 2 Jan 2025 11:30:12 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	linux-kbuild@...r.kernel.org, bpf <bpf@...r.kernel.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Peter Zijlstra <peterz@...radead.org>, Masahiro Yamada <masahiroy@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, 
	Zheng Yejian <zhengyejian1@...wei.com>, Martin Kelly <martin.kelly@...wdstrike.com>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH 00/14] scripts/sorttable: ftrace: Remove place holders for
 weak functions in available_filter_functions

On Thu, 2 Jan 2025 at 10:59, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> Where the file created by "nm -S" is read, recording the address
> and the associated sizes of each function. It then is sorted, and
> before sorting the mcount_loc table, it is scanned to make sure
> all symbols in the mcounc_loc are within the boundaries of the functions
> defined by nm. If they are not, they are zeroed out, as they are most
> likely weak functions (I don't know what else they would be).

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?)

Because:

> Then on boot up, when creating the ftrace tables from the mcount_loc
> table, it will ignore any function that matches the kaslr_offset()
> value.

Why even do that? Why not just make the mcount_loc table be proper in
the first place.

             Linus