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Message-ID: <YqxuSgj3DEACVukJ@worktop.programming.kicks-ass.net>
Date: Fri, 17 Jun 2022 14:06:34 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Steven Rostedt <rostedt@...dmis.org>,
"x86@...nel.org" <x86@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
"naveen.n.rao@...ux.vnet.ibm.com" <naveen.n.rao@...ux.vnet.ibm.com>,
"mbenes@...e.cz" <mbenes@...e.cz>
Subject: Re: [RFC][PATCH] ftrace,objtool: PC32 based __mcount_loc
On Fri, Jun 17, 2022 at 11:44:49AM +0000, Christophe Leroy wrote:
>
>
> Le 17/06/2022 à 13:24, Peter Zijlstra a écrit :
> >
> > Hi,
> >
> > I recently noticed that __mcount_loc is 64bit wide, containing absolute
> > addresses. Since __mcount_loc is a permanent section (not one we drop
> > after boot), this bloats the kernel memory usage for no real purpose.
>
> I guess you mean it is 64bit wide on 64 bits architectures ? Because it
> seems to be defined as 'long' so will be 32bit on 32 bits architectures ?
Right, it's an absolute address in the native size. Clearly I'm somewhat
64bit biassed :-)
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