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Date: Thu, 29 Mar 2018 16:42:09 +0200
From: Dominik Brodowski <linux@dominikbrodowski.net>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-kernel@vger.kernel.org, viro@ZenIV.linux.org.uk,
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Subject: Re: [PATCH 000/109] remove in-kernel calls to syscalls
Message-ID: <20180329144209.GA25559@isilmar-4.linta.de>
References: <20180329112426.23043-1-linux@dominikbrodowski.net>
 <20180329142027.GA24860@bombadil.infradead.org>
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On Thu, Mar 29, 2018 at 07:20:27AM -0700, Matthew Wilcox wrote:
> On Thu, Mar 29, 2018 at 01:22:37PM +0200, Dominik Brodowski wrote:
> > At least on 64-bit x86, it will likely be a hard requirement from v4.17
> > onwards to not call system call functions in the kernel: It is better to
> > use use a different calling convention for system calls there, where 
> > struct pt_regs is decoded on-the-fly in a syscall wrapper which then hands
> > processing over to the actual syscall function. This means that only those
> > parameters which are actually needed for a specific syscall are passed on
> > during syscall entry, instead of filling in six CPU registers with random
> > user space content all the time (which may cause serious trouble down the
> > call chain).[*]
> 
> How do we stop new ones from springing up?  Some kind of linker trick
> like was used to, er, "dissuade" people from using gets()?

Once the patches which modify the syscall calling convention are merged,
it won't compile on 64-bit x86, but bark loudly. That should frighten anyone.
Meow.

Thanks,
	Dominik