linux-kernel - Re: An objtool warning from mainline

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Date:   Thu, 27 Apr 2023 11:14:21 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     jpoimboe@...nel.org, peterz@...radead.org,
        linux-kernel@...r.kernel.org
Subject: Re: An objtool warning from mainline

On Wed, Apr 26, 2023 at 04:50:49PM -0700, Paul E. McKenney wrote:
> vmlinux.o: warning: objtool: exc_nmi+0x2b3: call to __const_udelay() leaves .noinstr.text section

What does

./scripts/faddr2line vmlinux.o exc_nmi+0x2b3

say?

I guess it should point to io_check_error()'s udelay().

If so, it is noinline:

81423c37415f ("x86/timer: Don't inline __const_udelay()")

> I see this with gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04) and also with
> gcc version 8.5.0 20210514 (Red Hat 8.5.0-18) (GCC).

I can't trigger it here with

gcc-11 (Debian 11.2.0-19) 11.2.0

Which is weird because the asm looks like it should warn.

Does it go away if you remove the noinline before __const_udelay()?

-- 
Regards/Gruss,
    Boris.

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