any way to see the running kernel's "vermagic" string?

any way to see the running kernel's "vermagic" string?

[Robert P. J. Day]

  perhaps i've just overlooked it but is there an easy way to see the
current kernel's calculated "vermagic" string, as defined in the
header file include/linux/vermagic.h thusly?

... snip ...
#define VERMAGIC_STRING                                                 \
        UTS_RELEASE " "                                                 \
        MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT                     \
        MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS       \
        MODULE_ARCH_VERMAGIC

  i'm just interested in examining the vermagic string you can see for
any loadable module, as in:

$ modinfo vfat
filename:       /lib/modules/3.6.0-oct8+/kernel/fs/fat/vfat.ko
author:         Gordon Chaffee
description:    VFAT filesystem support
license:        GPL
srcversion:     68B6C644F1532E86ADCB2CB
depends:        fat
intree:         Y
vermagic:       3.6.0-oct8+ SMP mod_unload modversions

and following the load logic in kernel/module.c to see what happens at
each step of a module load, and that (obviously) involves some
comparisons.  thanks.

rday


-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

any way to see the running kernel's "vermagic" string?

[Chinmay V S]

Isn't "uname -r" on the console good enough?...
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any way to see the running kernel's "vermagic" string?

[Peter Senna Tschudin]

http://plastilinux.blogspot.fr/2009/11/how-to-know-version-of-kernel-without.html

On Tue, Oct 16, 2012 at 4:59 PM, Chinmay V S <cvs268@gmail.com> wrote:
> Isn't "uname -r" on the console good enough?...
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>



-- 
Peter

any way to see the running kernel's "vermagic" string?

[Robert P. J. Day]

On Tue, 16 Oct 2012, Chinmay V S wrote:

> Isn't "uname -r" on the console good enough?...

  no, the vermagic string is considerably more informative.  as i
mentioned, look at the definition in vermagic.h:

#define VERMAGIC_STRING                                                 \
        UTS_RELEASE " "                                                 \
        MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT                     \
        MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS       \
        MODULE_ARCH_VERMAGIC

that should (partially?) match the "vermagic" string you see with
modinfo, as in:

$ modinfo vfat
... snip ...
vermagic:       3.6.0-oct8+ SMP mod_unload modversions   <--- there!
$

  if you check the logic of module loading in kernel/module.c, you'll
see checks being made to see if the two strings are compatible, as in:

... snip ...
static const char vermagic[] = VERMAGIC_STRING;
... snip ...
static int check_modinfo(struct module *mod, struct load_info *info)
{
        const char *modmagic = get_modinfo(info, "vermagic");
        int err;

        /* This is allowed: modprobe --force will invalidate it. */
        if (!modmagic) {
                err = try_to_force_load(mod, "bad vermagic");
                if (err)
                        return err;
        } else if (!same_magic(modmagic, vermagic, info->index.vers)) {
                printk(KERN_ERR "%s: version magic '%s' should be '%s'\n",
                       mod->name, modmagic, vermagic);
                return -ENOEXEC;
        }
... snip ...

  it's not that big a deal, but it would be informative to be able to
see the kernel's full vermagic string.

rday


-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

any way to see the running kernel's "vermagic" string?

[Robert P. J. Day]

On Tue, 16 Oct 2012, Peter Senna Tschudin wrote:

> http://plastilinux.blogspot.fr/2009/11/how-to-know-version-of-kernel-without.html

  ok, hoping for something simpler but, yes, that's what i was after,
thanks muchly.

rday

any way to see the running kernel's "vermagic" string?

[Peter Senna Tschudin]

See what I've found:
http://www.kernel.org/pub/linux/kernel/people//akpm/patches/2.6/2.6.6-rc3/2.6.6-rc3-mm2/broken-out/proc-sys-kernel-vermagic.patch

On Tue, Oct 16, 2012 at 5:06 PM, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> On Tue, 16 Oct 2012, Chinmay V S wrote:
>
>> Isn't "uname -r" on the console good enough?...
>
>   no, the vermagic string is considerably more informative.  as i
> mentioned, look at the definition in vermagic.h:
>
> #define VERMAGIC_STRING                                                 \
>         UTS_RELEASE " "                                                 \
>         MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT                     \
>         MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS       \
>         MODULE_ARCH_VERMAGIC
>
> that should (partially?) match the "vermagic" string you see with
> modinfo, as in:
>
> $ modinfo vfat
> ... snip ...
> vermagic:       3.6.0-oct8+ SMP mod_unload modversions   <--- there!
> $
>
>   if you check the logic of module loading in kernel/module.c, you'll
> see checks being made to see if the two strings are compatible, as in:
>
> ... snip ...
> static const char vermagic[] = VERMAGIC_STRING;
> ... snip ...
> static int check_modinfo(struct module *mod, struct load_info *info)
> {
>         const char *modmagic = get_modinfo(info, "vermagic");
>         int err;
>
>         /* This is allowed: modprobe --force will invalidate it. */
>         if (!modmagic) {
>                 err = try_to_force_load(mod, "bad vermagic");
>                 if (err)
>                         return err;
>         } else if (!same_magic(modmagic, vermagic, info->index.vers)) {
>                 printk(KERN_ERR "%s: version magic '%s' should be '%s'\n",
>                        mod->name, modmagic, vermagic);
>                 return -ENOEXEC;
>         }
> ... snip ...
>
>   it's not that big a deal, but it would be informative to be able to
> see the kernel's full vermagic string.
>
> rday
>
>
> --
>
> ========================================================================
> Robert P. J. Day                                 Ottawa, Ontario, CANADA
>                         http://crashcourse.ca
>
> Twitter:                                       http://twitter.com/rpjday
> LinkedIn:                               http://ca.linkedin.com/in/rpjday
> ========================================================================
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies



-- 
Peter

any way to see the running kernel's "vermagic" string?

[Frank Ch. Eigler]

"Robert P. J. Day" <rpjday@crashcourse.ca> writes:

>   perhaps i've just overlooked it but is there an easy way to see the
> current kernel's calculated "vermagic" string, as defined in the
> header file include/linux/vermagic.h thusly? [...]

Another way is systemtap:

# stap -g -e 'probe begin { log ( %{ VERMAGIC_STRING /* string */ %} ) exit()  }'
3.1.0-7.fc16.x86_64 SMP mod_unload 

- FChE