linux-kernel - Re: [PATCHv4 00/19] arm64: invoke syscalls with pt

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Message-ID: <20180710103901.GA31318@arm.com>
Date:   Tue, 10 Jul 2018 11:39:02 +0100
From:   Will Deacon <will.deacon@....com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, dave.martin@....com, hch@...radead.org,
        james.morse@....com, linux@...inikbrodowski.net,
        linux-fsdevel@...r.kernel.org, marc.zyngier@....com,
        viro@...iv.linux.org.uk
Subject: Re: [PATCHv4 00/19] arm64: invoke syscalls with pt_regs

On Mon, Jul 02, 2018 at 12:03:56PM +0100, Mark Rutland wrote:
> This series reworks arm64's syscall handling to minimize the propagation
> of user-controlled register values into speculated code paths. As with
> x86 [1], a wrapper is generated for each syscall, which extracts the
> argument from a struct pt_regs. During kernel entry from userspace,
> registers are zeroed.
> 
> The arm64 kernel code directly invokes some syscalls which the x86 code
> doesn't, so I've added ksys_* wrappers for these, following the x86
> example. The rest of the series is arm64-specific.
> 
> I've pushed the series out to my arm64/syscall-regs branch [2] on
> kernel.org.

One thing I noticed with this series applied is that our sys_call_table
declarations all get a bit muddled:

arm64/kernel/sys.c:		void * const sys_call_table[]
arm64/kernel/sys32.c:		void * const compat_sys_call_table[]
arm64/kernel/syscall.c:		extern syscall_fn_t sys_call_table[];
				extern syscall_fn_t compat_sys_call_table[];
arm64/include/asm/syscall.h:	extern const void *sys_call_table[];

Can we tidy this up so that syscall.h provides a declaration using
syscall_fn_t, allowing us to drop the additional externs?

Will