From: "H. Peter Anvin" <hpa@zytor.com>
To: Andrew Lutomirski <luto@mit.edu>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
mingo@redhat.com, Richard Weinberger <richard@nod.at>,
user-mode-linux-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org
Subject: Re: SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386)
Date: Sun, 21 Aug 2011 19:34:14 -0700 [thread overview]
Message-ID: <4E51C026.7000702@zytor.com> (raw)
In-Reply-To: <CAObL_7HY7qFUoqtNju42=BHTR8WuuW-cL_cQh_uUfx_7gFfHRg@mail.gmail.com>
On 08/21/2011 07:26 PM, Andrew Lutomirski wrote:
>
> Which still leaves the question of how to fix it. Restarting via an
> int 0x80-based helper might be the only option that leaves everything
> fully functional.
>
The issue is that we don't represent the entire state ... we represent
only one metalevel of it, currently the "cooked" one. The problem is
that we need the "raw" one as well, and in order to have *both* we need
to know the entry mechanism.
We need that IN EITHER CASE.
This is reasonably straightforward... we can carry the entry mechanism
forward inside the kernel, and fix it up in the IRET path.
The *really* big issue is what we drop as the sigcontext since this is
an ABI carried out to userspace. We could just say "it's currently
totally broken for SYSCALL" and just change it to drop the raw state,
but which has the potential for breaking unknown programs, *or* we could
add a bit of state (presumably by reclaiming one of the padding fields
around cs and ss) ... which *also* has the potential for breaking programs.
Right now, SYSCALL -> signal -> restart *is broken*, however, so there
is also the option of just doing nothing in this case, I guess.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2011-08-22 2:34 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-18 18:58 Subject: [PATCH 00/91] pending uml patches Al Viro
2011-08-18 19:12 ` Richard Weinberger
2011-08-18 19:19 ` Al Viro
2011-08-19 4:31 ` Al Viro
2011-08-19 8:51 ` Richard Weinberger
2011-08-20 1:18 ` [RFC] weird crap with vdso on uml/i386 Al Viro
2011-08-20 15:22 ` Richard Weinberger
2011-08-20 20:14 ` Al Viro
2011-08-20 20:55 ` Richard Weinberger
2011-08-20 21:26 ` Andrew Lutomirski
2011-08-20 21:38 ` Richard Weinberger
2011-08-20 21:40 ` Andrew Lutomirski
2011-08-21 6:34 ` Al Viro
2011-08-21 8:42 ` SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386) Al Viro
2011-08-21 11:24 ` Andrew Lutomirski
2011-08-21 13:37 ` Andrew Lutomirski
2011-08-21 14:51 ` Al Viro
2011-08-21 14:43 ` Al Viro
2011-08-21 16:41 ` Al Viro
2011-08-22 0:44 ` Andrew Lutomirski
2011-08-22 1:09 ` Linus Torvalds
2011-08-22 1:19 ` Al Viro
2011-08-22 1:19 ` H. Peter Anvin
2011-08-22 21:25 ` [tip:x86/urgent] x86-32, vdso: On system call restart after SYSENTER, use int $0x80 tip-bot for H. Peter Anvin
2011-08-23 23:40 ` tip-bot for H. Peter Anvin
2011-08-22 1:16 ` SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386) Al Viro
2011-08-22 1:41 ` Linus Torvalds
2011-08-22 1:48 ` H. Peter Anvin
2011-08-22 2:01 ` Andrew Lutomirski
2011-08-22 2:07 ` Al Viro
2011-08-22 2:26 ` Andrew Lutomirski
2011-08-22 2:34 ` H. Peter Anvin [this message]
2011-08-22 4:05 ` H. Peter Anvin
2011-08-22 9:53 ` [uml-devel] " Ingo Molnar
2011-08-22 13:34 ` Andrew Lutomirski
2011-08-22 14:40 ` Borislav Petkov
2011-08-22 15:13 ` Al Viro
2011-08-22 20:05 ` Linus Torvalds
2011-08-22 20:11 ` H. Peter Anvin
2011-08-22 21:52 ` Andrew Lutomirski
2011-08-22 22:04 ` H. Peter Anvin
2011-08-22 23:27 ` Linus Torvalds
2011-08-22 23:46 ` H. Peter Anvin
2011-08-23 0:03 ` Al Viro
2011-08-23 0:07 ` Al Viro
2011-08-23 0:07 ` H. Peter Anvin
2011-08-23 0:22 ` Linus Torvalds
2011-08-23 1:01 ` Al Viro
2011-08-23 1:13 ` Al Viro
2011-08-23 1:59 ` Linus Torvalds
2011-08-23 2:59 ` Al Viro
2011-08-23 2:17 ` Al Viro
2011-08-23 6:15 ` Al Viro
2011-08-23 14:26 ` Borislav Petkov
2011-08-23 16:30 ` Al Viro
2011-08-23 16:03 ` Linus Torvalds
2011-08-23 16:11 ` Andrew Lutomirski
2011-08-23 16:20 ` Linus Torvalds
2011-08-23 17:33 ` Al Viro
2011-08-23 18:04 ` Al Viro
2011-08-24 12:44 ` [PATCH] x86, asm: Document some of the syscall asm glue Borislav Petkov
2011-08-23 16:22 ` [uml-devel] SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386) Borislav Petkov
2011-08-23 16:29 ` Linus Torvalds
2011-08-23 16:53 ` Al Viro
2011-08-23 16:58 ` Richard Weinberger
2011-08-23 17:07 ` Al Viro
2011-08-23 17:29 ` Richard Weinberger
2011-08-25 0:05 ` Richard Weinberger
2011-08-23 19:15 ` H. Peter Anvin
2011-08-23 20:56 ` Borislav Petkov
2011-08-23 21:06 ` H. Peter Anvin
2011-08-23 21:10 ` Borislav Petkov
2011-08-23 23:04 ` H. Peter Anvin
2011-08-24 21:10 ` H. Peter Anvin
2011-08-23 16:48 ` Al Viro
2011-08-23 17:33 ` Linus Torvalds
2011-08-23 21:08 ` H. Peter Anvin
2011-08-23 21:20 ` Linus Torvalds
2011-08-23 23:04 ` H. Peter Anvin
2011-08-23 19:18 ` H. Peter Anvin
2011-08-23 19:24 ` Linus Torvalds
2011-08-23 19:26 ` H. Peter Anvin
2011-08-23 19:41 ` Al Viro
2011-08-23 19:43 ` Linus Torvalds
2011-08-23 21:17 ` Al Viro
[not found] ` <CAObL_7FG8eFTZ4djKH0T8tbRf2h6+iOm=OXr8194nvzc+w+a9A@mail.gmail.com>
2011-08-23 1:18 ` H. Peter Anvin
2011-08-22 4:07 ` Al Viro
2011-08-22 4:11 ` H. Peter Anvin
2011-08-22 4:26 ` Al Viro
2011-08-22 5:03 ` H. Peter Anvin
2011-08-23 5:10 ` Andrew Lutomirski
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4E51C026.7000702@zytor.com \
--to=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@mit.edu \
--cc=mingo@redhat.com \
--cc=richard@nod.at \
--cc=torvalds@linux-foundation.org \
--cc=user-mode-linux-devel@lists.sourceforge.net \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox