linux-kernel - Re: [PATCH v2 0/2] vfs: Define new syscall getumask.

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Message-ID: <57144343.4090402@zytor.com>
Date:	Sun, 17 Apr 2016 19:15:31 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Josh Triplett <josh@...htriplett.org>,
	Greg KH <gregkh@...uxfoundation.org>
Cc:	"Theodore Ts'o" <tytso@....edu>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	"Richard W.M. Jones" <rjones@...hat.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	mingo@...hat.com, Andrew Morton <akpm@...ux-foundation.org>,
	luto@...nel.org, viro@...iv.linux.org.uk, zab <zab@...hat.com>,
	emunson@...mai.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Pavel Emelyanov <xemul@...allels.com>, sfr@...b.auug.org.au,
	Milosz Tanski <milosz@...in.com>,
	rostedt <rostedt@...dmis.org>, arnd@...db.de,
	ebiederm@...ssion.com, gorcunov <gorcunov@...nvz.org>,
	iulia manda21 <iulia.manda21@...il.com>,
	dave hansen <dave.hansen@...ux.intel.com>,
	mguzik <mguzik@...hat.com>, adobriyan@...il.com,
	Davidlohr Bueso <dave@...olabs.net>,
	linux-api <linux-api@...r.kernel.org>, gorcunov@...il.com,
	fw@...eb.enyo.de, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2 0/2] vfs: Define new syscall getumask.

On 04/17/16 19:12, Josh Triplett wrote:
>>
>> I really like the 'libinux' idea, did anyone every hack up a first-pass
>> at this?  And I'm guessing we have more syscalls now that would need to
>> be added (like getrandom(), but that shouldn't be too difficult.
> 
> Personally, I'd suggest that libinux should wire up *all* (non-obsolete)
> syscalls, not just those that haven't already been exposed via any
> particular libc implementation.  Each such syscall function would have
> minimal overhead, since unlike libc these wrappers would not have any
> special handling (other than use of the vdso) and would directly map to
> the kernel syscall signature.  Given a standard prefix like sys_ or
> linux_, that would provide a clear distinction between direct-syscall
> functions and libc functions, and avoid any future conflict if libc adds
> a function named the same as the syscall.
> 
> As a random example, sys_getpid() would *always* call the getpid
> syscall, rather than reading a cache within the library.  (And
> sys_gettid would call the gettid syscall, rather than failing to exist.)
> 

I'm not so sure this is a good idea.  It has definite pros and cons.  In
some ways it pushes it more to be like syscall(3).

	-hpa