linux-kernel - Re: [PATCH v2 3/3] arm64: use the correct function type for __arm64_sys_ni

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Message-ID: <20190524183551.GE9697@fuggles.cambridge.arm.com>
Date:   Fri, 24 May 2019 19:35:51 +0100
From:   Will Deacon <will.deacon@....com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 3/3] arm64: use the correct function type for
 __arm64_sys_ni_syscall

Hi Sami,

On Wed, May 15, 2019 at 12:40:39PM +0100, Will Deacon wrote:
> On Tue, May 07, 2019 at 11:32:27AM -0700, Sami Tolvanen wrote:
> > On Tue, May 07, 2019 at 06:25:12PM +0100, Mark Rutland wrote:
> > > I strongly think that we cant to fix up the common definition in
> > > kernel/sys_ni.c rather than having a point-hack in arm64. Other
> > > architectures (e.g. x86, s390) will want the same for CFI, and I'd like
> > > to ensure that our approached don't diverge.
> > 
> > s390 already has the following in arch/s390/kernel/sys_s390.c:
> > 
> >   SYSCALL_DEFINE0(ni_syscall)
> >   {
> >         return -ENOSYS;
> >   }
> > 
> > Which, I suppose, is cleaner than calling sys_ni_syscall.
> > 
> > > I took a quick look, and it looks like it's messy but possible to fix
> > > up the core.
> > 
> > OK. How would you propose fixing this?
> 
> In the absence of a patch from Mark, I'd suggest just adding a SYS_NI macro
> to our asm/syscall_wrapper.h file which avoids the error injection stuff. It
> doesn't preclude moving this to the core later on, but it unblocks the CFI
> work.

Do you plan to repost this?

Will