linux-kernel - Re: objtool warning from next-20230125

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Date:   Fri, 27 Jan 2023 11:37:45 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>, linux-kernel@...r.kernel.org,
        sfr@...b.auug.org.au
Subject: Re: objtool warning from next-20230125

On Fri, Jan 27, 2023 at 01:14:47PM +0100, Peter Zijlstra wrote:
> On Thu, Jan 26, 2023 at 12:59:54PM -0800, Josh Poimboeuf wrote:
> > On Thu, Jan 26, 2023 at 10:23:02AM -0800, Paul E. McKenney wrote:
> > > Hello!
> > > 
> > > I have started seeing these objtool warnings from a wide variety of
> > > KASAN-enabled rcutorture-related test scenarios in next-20230125.  It has
> > > been awhile since I tested -next, so I am not yet sure where this started.
> > > 
> > > vmlinux.o: warning: objtool: __asan_memset+0x34: call to __memset() with UACCESS enabled
> > > vmlinux.o: warning: objtool: __asan_memmove+0x4d: call to __memmove() with UACCESS enabled
> > > vmlinux.o: warning: objtool: __asan_memcpy+0x4d: call to __memcpy() with UACCESS enabled
> > > 
> > > As usual, should I be worried?
> > 
> > This apparently came from Peter's
> > 
> >   69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
> > 
> > but I have no idea how this is supposed to work.  Peter?
> 
> Durr.. I'm not sure why I put them in the uaccess_safe_builtin[] array.
> 
> So yeah, this reproduces using defconfig+KASAN, removing the functions
> from the array shuts it up and doesn't generate new ones -- for that
> config.
> 
> Let me try and build a few more .configs...

Again, I am glad that it is not just me...

And thank you for digging into this!

							Thanx, Paul