linux-kernel - Re: [PATCH 0/5] Collected vdso/vsyscall fixes for 3.1

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Message-ID: <20110727154316.GA16909@dumpdata.com>
Date:	Wed, 27 Jul 2011 11:43:16 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Andrew Lutomirski <luto@....edu>
Cc:	x86@...nel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	jeremy@...p.org, keir.xen@...il.com, xen-devel@...ts.xensource.com,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 0/5] Collected vdso/vsyscall fixes for 3.1

On Wed, Jul 27, 2011 at 11:34:21AM -0400, Andrew Lutomirski wrote:
> On Wed, Jul 27, 2011 at 11:30 AM, Konrad Rzeszutek Wilk
> <konrad.wilk@...cle.com> wrote:
> >> > Anyhow, removed the benchmark code and ran it on 64-bit:
> >> >
> >> > sh-4.1# /test_vsyscall  test
> >> > Testing gettimeofday...
> >> > [  109.552261] test_vsyscall[2462] trap invalid opcode ip:400c8d sp:7fff84fab470 error:0 in test_vsyscall[400000+2000]
> >> > Illegal instruction
> >> > sh-4.1# /test_vsyscall  intcc
> >> > About to execute int 0xcc from RIP = 400959
> >> > [  114.137150] test_vsyscall[2463] illegal int 0xcc (exploit attempt?) ip:400959 cs:e033 sp:7fff8b328310 ax:2c si:0 di:7fff8b3280f0
> >> > Caught SIGSEGV: Segmentation fault (Signal sent by the kernel [(nil)])RIP = 400959
> >> >
> >> > [This is on git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git #testing, which
> >> > has todays linus/master and your patchset]
> >> >
> >>
> >> I'll set up Xen.  Something's clearly still buggy.
> >
> > You sure? This is what I get when I boot baremetal:
> >
> > sh-4.1#
> > sh-4.1# xen-detect
> > Not running on Xen.
> > sh-4.1# /test_vsyscall test
> > Testing gettimeo[   84.442819] test_vsyscall[3175] trap invalid opcode ip:400c8d sp:7fffa8a72dc0 error:0fday...
> >  in test_vsyscall[400000+2000]
> 
> $ test_vsyscall test
> Testing gettimeofday...
>   vDSO offset = 0.000001s
>   vsyscall offset = 0.000001s
> 
> Testing time...
>   vDSO offset = 0
>   vsyscall offset = 0
> Testing getcpu...
>   ok!  cpu=6 node=0
> 
> Can you send me your test_vsyscall binary so I can disassemble it?

Here it is (also including source since I uncommented parts of it).

One extra thing - I've been using AMD machines for this - I hadn't
tried this on an Intel box.

Download attachment "test_vsyscall" of type "application/octet-stream" (27973 bytes)

View attachment "test_vsyscall.cc" of type "text/x-c++src" (9659 bytes)