From: Al Viro <viro@ZenIV.linux.org.uk>
To: Andrew Lutomirski <luto@mit.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>,
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 15:43:52 +0100 [thread overview]
Message-ID: <20110821144352.GJ2203@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAObL_7GXyzAzNjBtgye9BwXLyHm337oBTdjRDjbSPqoKZGWyyA@mail.gmail.com>
On Sun, Aug 21, 2011 at 07:24:35AM -0400, Andrew Lutomirski wrote:
> I don't see the point of all this hackery at all. sysenter/sysexit
> indeed screws up some registers, but we can return on the iret path in
> the case of restart.
We *do* return on iret path in case of restart, TYVM.
> So why do we lie to ptrace (and iret!) at all? Why not just fill in
> pt_regs with the registers as they were (at least the
> non-clobbered-by-sysenter ones), set the actual C parameters correctly
> to contain the six arguments (in rdi, rsi, etc.), do the syscall, and
> return back to userspace without any funny business? Is there some
> ABI reason that, once we've started lying to tracers, we have to keep
> doing so?
We do not lie to ptrace and iret. At all. We do just what you have
described. And fuck up when restart returns us to the SYSCALL / SYSENTER
instruction again, which expects the different calling conventions,
so the values arranged in registers in the way int 0x80 would expect
do us no good.
next prev parent reply other threads:[~2011-08-21 14:44 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 [this message]
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
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
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