Debian kernel and /proc/pal

Debian kernel and /proc/pal

[Stephane Eranian]

Hello,

I recently used an Itanium machine booted with a 2.6 Linux kernel.
The exact package is:
        kernel-image-2.6.11-1-mckinley-smp_2.6.11-6_ia64.deb

It does appear that this kernel is compiled without CONFIG_PALINFO
which means there is no /proc/pal/cpu* entries.

I don't quite understand what motivates this choice. There is no
sensitive kernel information in there, just processor information
such as cache size, tlb levels, firmware revision numbers. This
information is very useful, some applications make use of it,
such as pfmon for instance. I would hope this is an oversight
on the part of the package maintainer. It did not use to be 
like that.

Any idea as to what happened?

--
-Stephane

Re: Debian kernel and /proc/pal

[Ian Wienand]

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On Fri, Aug 05, 2005 at 01:36:54PM +0200, Stephane Eranian wrote:
> I recently used an Itanium machine booted with a 2.6 Linux kernel.
> The exact package is:
>         kernel-image-2.6.11-1-mckinley-smp_2.6.11-6_ia64.deb
> 
> It does appear that this kernel is compiled without CONFIG_PALINFO
> which means there is no /proc/pal/cpu* entries.

I filed this under

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=321885

for the latest 2.6.12 packages which have the same thing.

-i

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Re: Debian kernel and /proc/pal

[dann frazier]

On Mon, 2005-08-08 at 10:17 +1000, Ian Wienand wrote:
> On Fri, Aug 05, 2005 at 01:36:54PM +0200, Stephane Eranian wrote:
> > I recently used an Itanium machine booted with a 2.6 Linux kernel.
> > The exact package is:
> >         kernel-image-2.6.11-1-mckinley-smp_2.6.11-6_ia64.deb
> > 
> > It does appear that this kernel is compiled without CONFIG_PALINFO
> > which means there is no /proc/pal/cpu* entries.
> 
> I filed this under
> 
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug21885
> 
> for the latest 2.6.12 packages which have the same thing.
> 

Note that CONFIG_PALINFO was set to m - most things in Debian kernels
are set to build as a module, if possible.

I've made 2.6.12-2 link it statically.  However, it'd probably be good
to have user apps load this module, if needed.

Re: Debian kernel and /proc/pal

[Stephane Eranian]

Dann,

On Tue, Aug 09, 2005 at 10:40:16AM -0600, dann frazier wrote:
> On Mon, 2005-08-08 at 10:17 +1000, Ian Wienand wrote:
> > On Fri, Aug 05, 2005 at 01:36:54PM +0200, Stephane Eranian wrote:
> > > I recently used an Itanium machine booted with a 2.6 Linux kernel.
> > > The exact package is:
> > >         kernel-image-2.6.11-1-mckinley-smp_2.6.11-6_ia64.deb
> > > 
> > > It does appear that this kernel is compiled without CONFIG_PALINFO
> > > which means there is no /proc/pal/cpu* entries.
> > 
> > I filed this under
> > 
> > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug21885
> > 
> > for the latest 2.6.12 packages which have the same thing.
> > 
> 
> Note that CONFIG_PALINFO was set to m - most things in Debian kernels
> are set to build as a module, if possible.
> 

What's the value of having PALINFO as module?
The firmware interface does not evolve very often.

If module is preferred then, some rc scripts should load it automatically
somehow. 

> I've made 2.6.12-2 link it statically.  However, it'd probably be good
> to have user apps load this module, if needed.

-- 
-Stephane

Re: Debian kernel and /proc/pal

[dann frazier]

On Tue, 2005-08-09 at 10:43 -0700, Stephane Eranian wrote:
> Dann,
> 
> On Tue, Aug 09, 2005 at 10:40:16AM -0600, dann frazier wrote:
> > On Mon, 2005-08-08 at 10:17 +1000, Ian Wienand wrote:
> > > On Fri, Aug 05, 2005 at 01:36:54PM +0200, Stephane Eranian wrote:
> > > > I recently used an Itanium machine booted with a 2.6 Linux kernel.
> > > > The exact package is:
> > > >         kernel-image-2.6.11-1-mckinley-smp_2.6.11-6_ia64.deb
> > > > 
> > > > It does appear that this kernel is compiled without CONFIG_PALINFO
> > > > which means there is no /proc/pal/cpu* entries.
> > > 
> > > I filed this under
> > > 
> > > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug21885
> > > 
> > > for the latest 2.6.12 packages which have the same thing.
> > > 
> > 
> > Note that CONFIG_PALINFO was set to m - most things in Debian kernels
> > are set to build as a module, if possible.
> > 
> 
> What's the value of having PALINFO as module?

(cc'ing debian-ia64, since this is really a debian issue not a kernel
one)

We don't examine all the bits of code that can be built as modules and
make a decision based on potential performance impact, security risks,
etc - its easier/more consistent to just build as a module if possible.

I don't know of any significant reason to leave palinfo as a module,
which is why I changed it :)  However, users who build their own kernels
may still build it as a module.  If they do, it'd be good if userspace
utilities either attempted to load it or complained that it wasn't
available.  (I've no idea if pfmon already does this or not)

> The firmware interface does not evolve very often.
> 
> If module is preferred then, some rc scripts should load it automatically
> somehow. 

If a user has a made a conscious choice to build it as a module, then it
probably means that they don't want the code loaded all the time.  In
such a situation, its probably better to load on demand or tell the user
to run modprobe themselves instead of auto-loading at boot.