linux-kernel - Re: [RFC patch 01/15] entry: Provide generic syscall entry functionality

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Message-ID: <alpine.DEB.2.21.1910201347460.2090@nanos.tec.linutronix.de>
Date:   Sun, 20 Oct 2019 13:49:10 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
cc:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        kvm list <kvm@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [RFC patch 01/15] entry: Provide generic syscall entry
 functionality

On Fri, 20 Sep 2019, Andy Lutomirski wrote:
> On Thu, Sep 19, 2019 at 8:09 AM Thomas Gleixner <tglx@...utronix.de> wrote:
> > +#ifndef _TIF_AUDIT
> > +# define _TIF_AUDIT                    (0)
> > +#endif
> 
> I'm wondering if these should be __TIF (double-underscore) or
> MAYBE_TIF_ or something to avoid errors where people do flags |=
> TIF_WHATEVER and get surprised.

That's what exists today already. See arch/*/include/asm/threadinfo.h
 
> > +/**
> > + * syscall_enter_from_usermode - Check and handle work before invoking
> > + *                              a syscall
> > + * @regs:      Pointer to currents pt_regs
> > + * @syscall:   The syscall number
> > + *
> > + * Invoked from architecture specific syscall entry code with interrupts
> > + * enabled.
> > + *
> > + * Returns: The original or a modified syscall number
> > + */
> 
> Maybe document that it can return -1 to skip the syscall and that, if
> this happens, it may use syscall_set_error() or
> syscall_set_return_value() first.  If neither of those is called and
> -1 is returned, then the syscall will fail with ENOSYS.

Sure.

Thanks,

	tglx