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

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Date: Thu, 27 Jun 2024 08:36:49 +0200
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>
Cc: alexandre.chartre@...cle.com, 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>,
        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 6/26/24 07:28, Josh Poimboeuf wrote:
> 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.
> 

Hi Josh,

I have another BHI related patch which has been reviewed:

  [PATCH v2] x86/bhi: BHI mitigation can trigger warning in #DB handler
  https://lore.kernel.org/kvm/20240524070459.3674025-1-alexandre.chartre@oracle.com/T/#rd3e9a5aadc18931f777b9a9e9c71f1efb178b7ef


Any chance it can be merged as well?

Thanks,

alex.