From: richard -rw- weinberger <richard.weinberger@gmail.com>
To: Andrew Lutomirski <luto@mit.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Adrian Bunk <bunk@stusta.de>,
"H. Peter Anvin" <hpa@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [3.1 patch] x86: default to vsyscall=native
Date: Mon, 10 Oct 2011 13:19:12 +0200 [thread overview]
Message-ID: <CAFLxGvx0QMrvG_ZsFE6C_xHn9JpWJ-aW-V=K9pm3OoXZc=NKxQ@mail.gmail.com> (raw)
In-Reply-To: <CAObL_7HUhxsOVHYFovgxYu7r5YNju+n4Q45GZ9viCCW-GrxWhg@mail.gmail.com>
On Fri, Oct 7, 2011 at 2:48 AM, Andrew Lutomirski <luto@mit.edu> wrote:
> On Thu, Oct 6, 2011 at 11:34 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>> On Thu, Oct 6, 2011 at 11:16 AM, Andrew Lutomirski <luto@mit.edu> wrote:
>>>
>>> Fixing it will be annoying because the attached fancier version needs
>>> to work, too. I could implement the whole mess in software, but it
>>> might be nicer to arrange for uaccess errors to stash some information
>>> somewhere (like in the thread_struct cr2 variable).
>>
>> That should be easy enough to do. Just add it to the
>> "fixup_exception()" case in no_context().
>
> This code is rather messy. We stash the cr2, err, and trap fields of
> sigcontext in thread_struct and we *never* reset them until the next
> segfault. So userspace sees stale garbage on every signal that isn't
> a (genuine) segfault. I can imagine this breaking UML is remarkably
> bizarre ways even without vsyscall emulation because UML actually
> seems to rely on that stuff to determine the source of a signal.
>
>From UML's point of view the current situation is odd.
UML will no longer run on top of a default 3.1 kernel.
Why is this odd?
One of the major reasons why people are still using UML is because you
can run it as non-privileged user on any x86 Linux host.
An user which has root privileges can setup and use KVM which is much
nicer than UML...
--
Thanks,
//richard
next prev parent reply other threads:[~2011-10-10 11:19 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-03 9:08 [3.1 patch] x86: default to vsyscall=native Adrian Bunk
2011-10-03 13:04 ` Andrew Lutomirski
2011-10-03 17:33 ` Adrian Bunk
2011-10-03 18:06 ` Andrew Lutomirski
2011-10-03 18:41 ` Adrian Bunk
2011-10-05 22:13 ` Andrew Lutomirski
2011-10-05 22:22 ` richard -rw- weinberger
2011-10-05 22:30 ` Adrian Bunk
2011-10-05 22:41 ` richard -rw- weinberger
2011-10-05 22:46 ` Andrew Lutomirski
2011-10-05 23:36 ` Andrew Lutomirski
2011-10-06 3:06 ` Andrew Lutomirski
2011-10-06 12:12 ` richard -rw- weinberger
2011-10-06 15:37 ` richard -rw- weinberger
2011-10-06 18:16 ` Andrew Lutomirski
2011-10-06 18:34 ` Linus Torvalds
2011-10-07 0:48 ` Andrew Lutomirski
2011-10-10 11:19 ` richard -rw- weinberger [this message]
2011-10-10 11:48 ` Ingo Molnar
2011-10-10 15:31 ` Andrew Lutomirski
2011-10-11 6:22 ` Ingo Molnar
2011-10-11 17:24 ` [RFC] fixing the UML failure root cause Andrew Lutomirski
2011-10-13 6:19 ` Linus Torvalds
2011-10-13 8:40 ` Andrew Lutomirski
2011-10-14 4:46 ` Linus Torvalds
2011-10-14 6:30 ` Andrew Lutomirski
2011-10-14 20:10 ` Linus Torvalds
2011-10-21 21:01 ` [PATCH] x86-64: Set siginfo and context on vsyscall emulation faults Andy Lutomirski
2011-10-22 4:46 ` Linus Torvalds
2011-10-22 9:07 ` Andy Lutomirski
2011-11-08 0:33 ` [PATCH 0/2] Fix and re-enable vsyscall=emulate Andy Lutomirski
2011-11-08 0:33 ` [PATCH 1/2] x86-64: Set siginfo and context on vsyscall emulation faults Andy Lutomirski
2011-12-05 13:23 ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2011-11-08 0:33 ` [PATCH 2/2] x86: Default to vsyscall=emulate Andy Lutomirski
2011-12-05 13:24 ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2011-12-02 22:47 ` [PATCH 0/2] Fix and re-enable vsyscall=emulate Andy Lutomirski
2011-12-05 11:18 ` H. Peter Anvin
2011-10-14 19:53 ` [RFC] fixing the UML failure root cause richard -rw- weinberger
2011-10-14 20:17 ` Andrew Lutomirski
2011-10-14 20:23 ` richard -rw- weinberger
2011-10-14 20:31 ` Andrew Lutomirski
2011-10-14 20:39 ` richard -rw- weinberger
2011-10-14 22:28 ` richard -rw- weinberger
2011-10-15 16:57 ` Ingo Molnar
2011-10-05 22:24 ` [3.1 patch] x86: default to vsyscall=native Adrian Bunk
2011-10-03 13:19 ` richard -rw- weinberger
2011-10-03 17:46 ` Adrian Bunk
2011-10-05 21:40 Adrian Bunk
2011-10-05 22:01 ` Thomas Gleixner
2011-10-09 13:45 ` Adrian Bunk
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