linux-kernel - Re: [PATCH v5 2/3] tracing: Add a tracepoint verification check at build time

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Message-ID: <20250725094121.1521e14d@gandalf.local.home>
Date: Fri, 25 Jul 2025 09:41:21 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Steven Rostedt <rostedt@...nel.org>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
 llvm@...ts.linux.dev, Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland
 <mark.rutland@....com>, Andrew Morton <akpm@...ux-foundation.org>, Arnd
 Bergmann <arnd@...db.de>, Masahiro Yamada <masahiroy@...nel.org>, Nathan
 Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas.schier@...ux.dev>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>, Catalin Marinas
 <catalin.marinas@....com>, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v5 2/3] tracing: Add a tracepoint verification check at
 build time

On Fri, 25 Jul 2025 09:15:34 -0400
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:


> > Add a verifier that injects a string of the name of the tracepoint it
> > calls that is added to the discarded section "__tracepoint_check".
> > For every builtin tracepoint, it's   
> 
> its

Weird Al would be ashamed of me!

Although, you shouldn't delete the word that comes next in your reply, as
I can't tell if you were correct or not from the context you kept.

> 
> [...]
> 
> > +	/*
> > +	 * The __tracepoint_check section is filled with strings of the
> > +	 * names of tracepoints (in tracepoint_strings). Create an array
> > +	 * that points to each string and then sort the array.
> > +	 */
> > +	for_each_shdr_str(len, ehdr, check_data_sec) {
> > +		if (!len)
> > +			continue;  
> 
> The len==0 case would be when this skips section alignment padding when
> the linker decides to align the beginning of each .o sections, which
> ends up appearing as zeroed padding within the resulting vmlinux.o
> section after the individual sections have been stitched together, am I
> correct ?

I'm guessing. But when I walked through it in the debugger, there was more
zero length strings than strings with content. But it had all the strings I
was looking for.

-- Steve