[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CALCETrXktM=TAtPgiOheKgBd4i9PhVPvi5epLFGUcZ+PyH31hw@mail.gmail.com>
Date: Wed, 12 Mar 2014 14:45:22 -0700
From: Andy Lutomirski <luto@...capital.net>
To: "H. Peter Anvin" <hpa@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Stefani Seibold <stefani@...bold.net>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"the arch/x86 maintainers" <x86@...nel.org>,
Dave Jones <davej@...hat.com>,
Martin Runge <Martin.Runge@...de-schwarz.com>,
Andreas Brief <Andreas.Brief@...de-schwarz.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] x86: Remove compat vdso support
On Wed, Mar 12, 2014 at 2:37 PM, H. Peter Anvin <hpa@...ux.intel.com> wrote:
> On 03/12/2014 12:41 PM, Linus Torvalds wrote:
>>
>> So my reaction was "don't do that".
>>
>> But people pointing out that we can't do what x86-64 does made me
>> think: we could avoid the whole "nasty code for a legacy case" by
>> making it the *non*-legacy case. We could get rid of the fixmap
>> HPET/VVAR entirely - on x86-64 (which can use those addresses) a
>> PC-relative addressing is probably actually better anyway, so mapping
>> them together with the vdso code shouldn't hurt.
>>
>
> How would that deal with the legacy vsyscall case for x86-64? Just rely
> on the "legacy vsyscall emulation" (which seems to have its own class of
> problems...)?
The emulated 64-bit vsyscall is completely independent of the vdso and
any user-accessible data whatsoever -- it's just a self-contained bit
of code that runs in kernel space. There is no user-executable code
involved at all. (There is code that *looks* executable to a dynamic
recompiler, but that code consists of ordinary system calls.) As far
as I know, all of the problems with it (other than the fact that it
exists at all) were solved a couple years ago.
--Andy
--
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/
Powered by blists - more mailing lists