linux-kernel - Re: [PATCH 18/18] arm64: implement syscall wrappers

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Message-ID: <20180514205744.GC26773@light.dominikbrodowski.net>
Date:   Mon, 14 May 2018 22:57:44 +0200
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, dave.martin@....com, james.morse@....com,
        linux-fsdevel@...r.kernel.org, marc.zyngier@....com,
        viro@...iv.linux.org.uk, will.deacon@....com
Subject: Re: [PATCH 18/18] arm64: implement syscall wrappers

On Mon, May 14, 2018 at 10:46:40AM +0100, Mark Rutland wrote:
> Note that we play games with sys_ni_syscall(). It can't be defined with
> SYSCALL_DEFINE0() because we must avoid the possibility of error
> injection. Additionally, there are a couple of locations where we need
> to call it from C code, and we don't (currently) have a
> ksys_ni_syscall().  While it has no wrapper, passing in a redundant
> pt_regs pointer is benign per the AAPCS.
> 
> When ARCH_HAS_SYSCALL_WRAPPER is selected, no prototype is define for
> sys_ni_syscall(). Since we need to treat it differently for in-kernel
> calls and the syscall tables, the prototype is defined as-required.

> Largely the wrappers are largely the same as their x86 counterparts, but

That's one "Largely" too much.

> simplified as we don't have a variety of compat calling conventions that
> require separate stubs. Unlike x86, we have some zero-argument compat
> syscalls, and must define COMPAT_SYSCALL_DEFINE0().

... for consistent naming, or is there another reason for that?

This patch looks good in any case.

Thanks,
	Dominik