linux-kernel - Re: [linus:master] [x86/entry] be5341eb0d: WARNING:CPU:#PID:#at_int80

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Message-ID: <CAHk-=wh=z-aXw6o8Hi9SiC5-vwP403-ZpDHUOXdXmLbaG93dvQ@mail.gmail.com>
Date: Tue, 19 Dec 2023 12:17:40 -0800
From: Linus Torvalds <torvalds@...uxfoundation.org>
To: Andrew Cooper <andrew.cooper3@...rix.com>
Cc: Borislav Petkov <bp@...en8.de>, kernel test robot <oliver.sang@...el.com>, 
	Thomas Gleixner <tglx@...utronix.de>, oe-lkp@...ts.linux.dev, lkp@...el.com, 
	linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...ux.intel.com>, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, xen-devel@...ts.xenproject.org
Subject: Re: [linus:master] [x86/entry] be5341eb0d: WARNING:CPU:#PID:#at_int80_emulation

On Tue, 19 Dec 2023 at 11:15, Andrew Cooper <andrew.cooper3@...rix.com> wrote:
>
> -asmlinkage long sys_ni_posix_timers(void);
> +asmlinkage long sys_ni_posix_timers(const struct pt_regs *regs);

I don't think it should be asmlinkage. That means "use legacy asm
calling conventions", and for x86-32 that means pass on stack. Which I
don't think these actually are.

I think it's an old artefect, and it doesn't matter for something that
doesn't take any arguments, but when you add an argument it's actively
wrong.

Of course, that argument isn't _used_, so it still doesn't matter, but
if the point is to use the right prototype, I think we should just
make it be

    long sys_ni_posix_timers(const struct pt_regs *regs);

although I think Sami's suggestion is probably nicer.

That said, I still think that just getting rid of this horrid special
case for posix timers is the right thing, and we should just remove
that SYS_NI() alias thing entirely.

          Linus