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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sun, 15 Jun 2014 12:31:17 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ian Lance Taylor <iant@...ang.org>
CC:	Andy Lutomirski <luto@...capital.net>,
	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>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>
Subject: Re: [RFC 0/2] __vdso_findsym

The weak symbols are well-known names.  The __vdso symbols are strong.

On June 15, 2014 12:22:17 PM PDT, Ian Lance Taylor <iant@...ang.org> wrote:
>On Sun, Jun 15, 2014 at 12:14 PM, H. Peter Anvin <hpa@...or.com> wrote:
>>
>> If it doesn't, then you incur an additional indirection penalty.  The
>strong __vdso symbol allows the libc wrapper to fall back to the vdso
>implementation, the weak symbol allows three to be no wrapper at all. 
>This is good.
>>
>> The reason for changing ABI would be shifting types.  This is very
>much how glibc manages transitions.
>
>The purpose of symbol versioning is so that symbols with well known
>names, like stat, can continue to use those same names while changing
>types.  Both old and new programs can continue to use the name stat
>and continue to work even though they use different types.
>
>I don't see how this applies to the kernel VDSO.  Those symbols do not
>use well-known names; they use names like __vdso_time.  If you change
>the types used by those symbols, you can change the name as well.
>What is the downside?
>
>Ian

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/