linux-kernel - Re: [PATCH 08/18] arm64: convert raw syscall invocation to C

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Date:   Tue, 15 May 2018 09:22:23 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Dominik Brodowski <linux@...inikbrodowski.net>
Cc:     Dave Martin <Dave.Martin@....com>,
        linux-arm-kernel@...ts.infradead.org, marc.zyngier@....com,
        catalin.marinas@....com, will.deacon@....com,
        linux-kernel@...r.kernel.org, james.morse@....com,
        viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 08/18] arm64: convert raw syscall invocation to C

On Mon, May 14, 2018 at 10:24:45PM +0200, Dominik Brodowski wrote:
> On Mon, May 14, 2018 at 12:41:10PM +0100, Mark Rutland wrote:
> > I agree it would be nicer if it had a wrapper that took a pt_regs, even
> > if it does nothing with it.
> > 
> > We can't use SYSCALL_DEFINE0() due to the fault injection muck, we'd
> > need a ksys_ni_syscall() for our traps.c logic, and adding this
> > uniformly would involve some arch-specific rework for x86, too, so I
> > decided it was not worth the effort.
> 
> Couldn't you just open-code the "return -ENOSYS;" in traps.c?

I guess so. I was just worried that debug logic might be added to the generic
ni_syscall() in future, and wanted to avoid potential divergence.

> Error injection has no reasonable stable ABI/API expectations, so that's not
> a show-stopper either.

If people are happy with using SYSCALL_DEFINE0() for ni_syscall, I'm happy to
do that -- it's just that we'll need a fixup for x86 as that will change the
symbol name.

Thanks,
Mark.