linux-kernel - Re: [PATCH v5 1/3] x86/syscall: Mark exit[_group] syscall handlers _

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Date: Tue, 25 Jun 2024 22:28:25 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alexandre Chartre <alexandre.chartre@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Nikolay Borisov <nik.borisov@...e.com>,
	KP Singh <kpsingh@...nel.org>, Waiman Long <longman@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v5 1/3] x86/syscall: Mark exit[_group] syscall handlers
 __noreturn

On Tue, Jun 25, 2024 at 07:21:34PM -0700, Paul E. McKenney wrote:
> On Tue, May 07, 2024 at 07:38:32AM -0700, Paul E. McKenney wrote:
> > On Mon, May 06, 2024 at 10:30:04PM -0700, Josh Poimboeuf wrote:
> > > The direct-call syscall dispatch function doesn't know that the exit()
> > > and exit_group() syscall handlers don't return, so the call sites aren't
> > > optimized accordingly.
> > > 
> > > Fix that by marking those exit syscall declarations __noreturn.
> > > 
> > > Fixes the following warnings:
> > > 
> > >   vmlinux.o: warning: objtool: x64_sys_call+0x2804: __x64_sys_exit() is missing a __noreturn annotation
> > >   vmlinux.o: warning: objtool: ia32_sys_call+0x29b6: __ia32_sys_exit_group() is missing a __noreturn annotation
> > > 
> > > Fixes: 7390db8aea0d ("x86/bhi: Add support for clearing branch history at syscall entry")
> > > Reported-by: "Paul E. McKenney" <paulmck@...nel.org>
> > > Closes: https://lkml.kernel.org/lkml/6dba9b32-db2c-4e6d-9500-7a08852f17a3@paulmck-laptop
> > > Tested-by: Paul E. McKenney <paulmck@...nel.org>
> > 
> > Just reaffirming my Tested-by, and thank you!
> 
> And just following up, given that I do not yet see this in -next.  Any
> chance of this making the upcoming merge window?

Sorry for my slowness!  I'm traveling this week but let me repost this
(with your Tested-by) and grab somebody to merge it.

-- 
Josh