Re: [PATCH v3 6/8] x86/module: perpare module loading for ROX allocations of text

From: Mike Rapoport <rppt@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andreas Larsson <andreas@gaisler.com>,
	Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Borislav Petkov <bp@alien8.de>, Brian Cain <bcain@quicinc.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Christoph Hellwig <hch@infradead.org>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Dinh Nguyen <dinguyen@kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Guo Ren <guoren@kernel.org>, Helge Deller <deller@gmx.de>,
	Huacai Chen <chenhuacai@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	Kent Overstreet <kent.overstreet@linux.dev>,
	"Liam R. Howlett" <Liam.Howlett@oracle.com>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Matt Turner <mattst88@gmail.com>,
	Max Filippov <jcmvbkbc@gmail.com>,
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Subject: Re: [PATCH v3 6/8] x86/module: perpare module loading for ROX allocations of text
Date: Mon, 9 Sep 2024 17:34:48 +0300	[thread overview]
Message-ID: <Zt8HiAzcaZS8lHT-@kernel.org> (raw)
In-Reply-To: <20240909092923.GB4723@noisy.programming.kicks-ass.net>

On Mon, Sep 09, 2024 at 11:29:23AM +0200, Peter Zijlstra wrote:
> On Mon, Sep 09, 2024 at 09:47:28AM +0300, Mike Rapoport wrote:
> > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> > index 8da0e66ca22d..563d9a890ce2 100644
> > --- a/arch/x86/kernel/ftrace.c
> > +++ b/arch/x86/kernel/ftrace.c
> 
> > @@ -654,4 +656,15 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
> >  }
> >  #endif
> >  
> > +void ftrace_swap_func(void *a, void *b, int n)
> > +{
> > +	unsigned long t;
> > +
> > +	WARN_ON_ONCE(n != sizeof(t));
> > +
> > +	t = *((unsigned long *)a);
> > +	text_poke_copy(a, b, sizeof(t));
> > +	text_poke_copy(b, &t, sizeof(t));
> > +}
> 
> This is insane, just force BUILDTIME_MCOUNT_SORT

The comment in ftrace.c says "... while mcount loc in modules can not be
sorted at build time"

I don't know enough about objtool, but I'd presume it's because the sorting
should happen after relocations, no?

-- 
Sincerely yours,
Mike.