linux-kernel - Re: [RFC 0/2] __vdso

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Message-ID: <CALCETrV-ocpugRwL7rd4GDX-Y89L7So8_6BBjOUDeR4V8RSPEA@mail.gmail.com>
Date:	Sun, 15 Jun 2014 11:54:10 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Rich Felker <dalias@...c.org>,
	Mikael Pettersson <mikpelinux@...il.com>,
	Russ Cox <rsc@...ang.org>,
	Linux API <linux-api@...r.kernel.org>,
	Ian Taylor <iant@...ang.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>
Subject: Re: [RFC 0/2] __vdso_findsym

On Sun, Jun 15, 2014 at 11:39 AM, H. Peter Anvin <hpa@...or.com> wrote:
> Symbol versioning so we can rev the ABI and still provide backwards compatibility.  Weak symbols so the libc can override symbols if it considers it appropriate.  This is a good thing.

Are we ever going to change, say, the __vdso_clock_gettime ABI without
renaming the function?  If we want to preserve that ability, I can
keep support for versions, but it seems odd.

I don't buy the weak symbol argument at all.  We currently expose a
strong symbol __vdso_clock_gettime and a weak alias clock_gettime.  I
agree that, if glibc treats us as a real DSO, then clock_gettime can't
be strong, but I don't see why it should exist at all (other than for
backwards compatibility).

--Andy
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