[uml-devel] 2.6.9-bs7 panic on check_sysemu

[uml-devel] 2.6.9-bs7 panic on check_sysemu

[Peter]

I get this error starting up a 2.6.9-bs7 guest:

Checking syscall emulation patch for ptrace...<0>Kernel panic - not 
syncing: check_sysemu : expected SIGTRAP, got status = 256

The host is 2.6.8.1 with host-skas3-2.6.7-v2.patch.

The 2.6.9-bs7 kernel runs OK on my newer host kernels.

Is this a case where I should be upgrading my host kernels (will do that 
in time anyway)?

Or is there something that can be done on the guest to make it work on 
older kernels also?

Regards, Peter



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Re: [uml-devel] 2.6.9-bs7 panic on check_sysemu

[Blaisorblade]

On Monday 04 April 2005 00:47, Peter wrote:
> I get this error starting up a 2.6.9-bs7 guest:
>
> Checking syscall emulation patch for ptrace...<0>Kernel panic - not
> syncing: check_sysemu : expected SIGTRAP, got status = 256
>
> The host is 2.6.8.1 with host-skas3-2.6.7-v2.patch.
>
> The 2.6.9-bs7 kernel runs OK on my newer host kernels.
>
> Is this a case where I should be upgrading my host kernels (will do that
> in time anyway)?

You simply need to update the SKAS patch version. -V2 is very old, and many 
bugs (including this, that is a bug in the SYSEMU part of the SKAS patch). 
Upgrading to -V7 for the SKAS patch, even on the same host kernel version 
(i.e. against 2.6.8.1), would fix that.

Also, some older guest kernels may seem to work, because they don't diagnose 
such bugs. But actually they have problems in some situations, because of the 
host bugs. For instance panicking with a simple "echo 0 > /proc/sysemu; echo 
1 > /proc/sysemu".

>
> Or is there something that can be done on the guest to make it work on
> older kernels also?
Not a lot, except disabling SYSEMU (and its performance advantage) entirely - 
add the "nosysemu" param to the UML command line and it will work.

But it won't be as slow as if you didn't use SKAS.

Bye
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade




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Re: [uml-devel] 2.6.9-bs7 panic on check_sysemu

[Rob Landley]

On Monday 04 April 2005 09:32 am, Blaisorblade wrote:

> > Is this a case where I should be upgrading my host kernels (will do that
> > in time anyway)?
>
> You simply need to update the SKAS patch version. -V2 is very old, and many
> bugs (including this, that is a bug in the SYSEMU part of the SKAS patch).
> Upgrading to -V7 for the SKAS patch, even on the same host kernel version
> (i.e. against 2.6.8.1), would fix that.
>
> Also, some older guest kernels may seem to work, because they don't
> diagnose such bugs. But actually they have problems in some situations,
> because of the host bugs. For instance panicking with a simple "echo 0 >
> /proc/sysemu; echo 1 > /proc/sysemu".
>
> > Or is there something that can be done on the guest to make it work on
> > older kernels also?
>
> Not a lot, except disabling SYSEMU (and its performance advantage) entirely
> - add the "nosysemu" param to the UML command line and it will work.
>
> But it won't be as slow as if you didn't use SKAS.
>
> Bye

Speaking of which, I ask this from time to time:

What's the minimal patch set that _just_ adds -SKAS0 mode to something like a 
2.6.11 kernel?  I'd like to try it out, but every time I sit down to whack at 
it my interest budget runs out sifting through a mountain of unrelated x86-64 
patches to try to figure out what exactly I need to apply to get just 
SKAS0...

No biggie.  I'll can always ask again later... :)

Rob


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Re: [uml-devel] 2.6.9-bs7 panic on check_sysemu

[Blaisorblade]

On Tuesday 05 April 2005 19:23, Rob Landley wrote:
> On Monday 04 April 2005 09:32 am, Blaisorblade wrote:
> > > Is this a case where I should be upgrading my host kernels (will do
> > > that in time anyway)?

> > You simply need to update the SKAS patch version. -V2 is very old, and
> > many bugs (including this, that is a bug in the SYSEMU part of the SKAS
> > patch). Upgrading to -V7 for the SKAS patch, even on the same host kernel
> > version (i.e. against 2.6.8.1), would fix that.

> > Also, some older guest kernels may seem to work, because they don't
> > diagnose such bugs. But actually they have problems in some situations,
> > because of the host bugs. For instance panicking with a simple "echo 0 >
> > /proc/sysemu; echo 1 > /proc/sysemu".

> > > Or is there something that can be done on the guest to make it work on
> > > older kernels also?

> > Not a lot, except disabling SYSEMU (and its performance advantage)
> > entirely - add the "nosysemu" param to the UML command line and it will
> > work.

> > But it won't be as slow as if you didn't use SKAS.

> > Bye

> Speaking of which, I ask this from time to time:

> What's the minimal patch set that _just_ adds -SKAS0 mode to something like
> a 2.6.11 kernel?  I'd like to try it out, but every time I sit down to
> whack at it my interest budget runs out sifting through a mountain of
> unrelated x86-64 patches to try to figure out what exactly I need to apply
> to get just SKAS0...

> No biggie.  I'll can always ask again later... :)

The problem is that I don't use the Jeff's tree nor work on SKAS0, since 
somebody must work on current releases.

While Jeff is loaded with development work and cannot handle every user. I too 
have sometimes problem to keep in touch with him.

That said, check if applying the whole tree (until the point patches apply) 
works for you.
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade




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Re: [uml-devel] 2.6.9-bs7 panic on check_sysemu

[Blaisorblade]

On Tuesday 05 April 2005 19:23, Rob Landley wrote:
> On Monday 04 April 2005 09:32 am, Blaisorblade wrote:
> > > Is this a case where I should be upgrading my host kernels (will do
> > > that in time anyway)?
> >
> > You simply need to update the SKAS patch version. -V2 is very old, and
> > many bugs (including this, that is a bug in the SYSEMU part of the SKAS
> > patch). Upgrading to -V7 for the SKAS patch, even on the same host kernel
> > version (i.e. against 2.6.8.1), would fix that.
> >
> > Also, some older guest kernels may seem to work, because they don't
> > diagnose such bugs. But actually they have problems in some situations,
> > because of the host bugs. For instance panicking with a simple "echo 0 >
> > /proc/sysemu; echo 1 > /proc/sysemu".
> >
> > > Or is there something that can be done on the guest to make it work on
> > > older kernels also?
> >
> > Not a lot, except disabling SYSEMU (and its performance advantage)
> > entirely - add the "nosysemu" param to the UML command line and it will
> > work.
> >
> > But it won't be as slow as if you didn't use SKAS.
> >
> > Bye
>
> Speaking of which, I ask this from time to time:
>
> What's the minimal patch set that _just_ adds -SKAS0 mode to something like
> a 2.6.11 kernel?  I'd like to try it out, but every time I sit down to
> whack at it my interest budget runs out sifting through a mountain of
> unrelated x86-64 patches to try to figure out what exactly I need to apply
> to get just SKAS0...
Also, I forgot: during your development work use SKAS. It doesn't give any big 
difference visible inside the Virtual Machine (except for bugs).
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade




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Re: [uml-devel] 2.6.9-bs7 panic on check_sysemu

[Jeff Dike]

On Tue, Apr 05, 2005 at 01:23:47PM -0400, Rob Landley wrote:
> What's the minimal patch set that _just_ adds -SKAS0 mode to something like a 
> 2.6.11 kernel?  I'd like to try it out, but every time I sit down to whack at 
> it my interest budget runs out sifting through a mountain of unrelated x86-64 
> patches to try to figure out what exactly I need to apply to get just 
> SKAS0...

There isn't really one right now.  Those patches need to be cleaned up, 
merged, and disentanged from other stuff.

				Jeff


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Re: [uml-devel] 2.6.9-bs7 panic on check_sysemu

[Rob Landley]

On Tuesday 05 April 2005 04:55 pm, Blaisorblade wrote:

> > Speaking of which, I ask this from time to time:
> >
> > What's the minimal patch set that _just_ adds -SKAS0 mode to something
> > like a 2.6.11 kernel?  I'd like to try it out, but every time I sit down
> > to whack at it my interest budget runs out sifting through a mountain of
> > unrelated x86-64 patches to try to figure out what exactly I need to
> > apply to get just SKAS0...
>
> Also, I forgot: during your development work use SKAS. It doesn't give any
> big difference visible inside the Virtual Machine (except for bugs).

I'm trying out the build on various different systems: knoppix, red hat, suse, 
debian.  In some cases running on borrowed machines, in other cases running 
on a knoppix boot cd.  (I care because I'm using the host tools, which vary 
slightly from system to system.)

You just suggested that I replace the kernels on all of these systems, 
(including other people's machines, and the bootable CD that uses a kernel 
with the cloop patch applied and an initramfs that's hard to extract) with a 
different kernel.  Just so I'm testing something faster that's not actually 
what I'm going to be deploying.

If I was going to replace the host kernel and run on a modified system, I'd 
just A) replace it with the version I actually need, B) run the build as root 
and use chroot instead of UML.

I'm interested in SKAS0 because it's potentially deployable.  Any SKAS that 
requires a modified host kernel is not, for my purposes.

Rob


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