linux-kernel - Re: [PATCH v2 06/11] x86/unwind/orc: Convert global variables to static

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Message-ID: <20240229004252.awmammhp63f5udyy@treble>
Date: Wed, 28 Feb 2024 16:42:52 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	Vince Weaver <vincent.weaver@...ne.edu>, Dave Jones <dsj@...com>,
	Jann Horn <jannh@...gle.com>, Miroslav Benes <mbenes@...e.cz>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Nilay Vaish <nilayvaish@...gle.com>
Subject: Re: [PATCH v2 06/11] x86/unwind/orc: Convert global variables to
 static

On Wed, Feb 28, 2024 at 07:14:06PM -0500, Steven Rostedt wrote:
> On Wed, 28 Feb 2024 16:03:09 -0800
> Josh Poimboeuf <jpoimboe@...nel.org> wrote:
> 
> > On Wed, Feb 28, 2024 at 06:35:07PM -0500, Steven Rostedt wrote:
> > > On Sat, 25 Apr 2020 05:03:05 -0500
> > > Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> > >   
> > > > These variables aren't used outside of unwind_orc.c, make them static.
> > > > 
> > > > Also annotate some of them with '__ro_after_init', as applicable.  
> > > 
> > > So it appears that crash uses "lookup_num_blocks" to be able to do
> > > back-traces with the ORC unwinder. But because it's now static, crash can no
> > > longer do that.  
> > 
> > Hm, but why?  Even a static variable has a known address.
> > 
> 
> I'm guessing because we don't have the full dwarf info?

DWARF isn't needed for that.  Even the symbol table has it (as does
System.map).  For both globals and statics.

-- 
Josh