linux-kernel - Re: [BUG] tracing: dynamic ftrace selftest detected failures

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: <20240821084351.4b1c9d4d52b5aa7e07681d69@kernel.org>
Date: Wed, 21 Aug 2024 08:43:51 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Sami Tolvanen <samitolvanen@...gle.com>, Mark Rutland
 <mark.rutland@....com>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, linux-kernel@...r.kernel.org,
 clang-built-linux <llvm@...ts.linux.dev>, Nathan Chancellor
 <nathan@...nel.org>
Subject: Re: [BUG] tracing: dynamic ftrace selftest detected failures

On Tue, 20 Aug 2024 18:11:09 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Wed, 21 Aug 2024 07:05:39 +0900
> Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:
> 
> 
> > Does the noinline attribute prevent embedding callsite too? I mean
> > 
> > extern callee()
> > 
> > noinline callee()
> > {
> > ...
> > }
> > 
> > caller()
> > {
> > 	callee() // (*)
> > }
> > 
> > In this case, does noinline prevent LTO to embed the callee at the callsite(*)
> > or prevent LTO remove the callee() symbol?
> >
> 
> Even though we have it passed as a parameter, I think the compiler and
> linker is smart enough to see that and notice its use, and that the
> function passed in is a nop, which doesn't break the flow.
> 
> Can you add the __used and see if it fixes it?

Adding __used to DYN_FTRACE_TEST_NAME() and DYN_FTRACE_TEST_NAME2() does
not change, the test still fails. Hmm, what about makes the caller
(trace_selftest_startup_dynamic_tracing()) called via a function pointer?
In that case, wouldn't it be subject to constant propagetion?

Let me try.

Thanks,

> 
> -- Steve


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>