linux-kernel - Re: [PATCH] x86: always use SYSCALL

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Message-ID: <6490B647-209A-4CE6-BFDC-5EC2F62B466D@amazon.com>
Date:   Sat, 10 Mar 2018 20:59:46 +0000
From:   "Tautschnig, Michael" <tautschn@...zon.co.uk>
To:     "x86@...nel.org" <x86@...nel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Jaswinder Singh <jaswinder@...radead.org>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] x86: always use SYSCALL_DEFINE*

On 10 Mar 2018, at 20:55, Tautschnig, Michael <tautschn@...zon.co.uk> wrote:
> 
> All syscall arguments are passed in as types of the same byte size as
> unsigned long (width of full registers). Using a smaller type without a
> cast may result in losing bits of information. SYSCALL_DEFINE* introduce
> adequate type casts. All definitions of syscalls in x86 except for those
> patched here have already been using the appropriate SYSCALL_DEFINE*.
[...]

Additional context: I had previously made an attempt to ensure type
consistency of sys_ioperm as "Syscall arguments are unsigned long (full
registers)" (https://lkml.org/lkml/2016/7/4/336). I hope the new proposal
is more acceptable.

Best,
Michael



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