how to tell i386 from x86-64 kernel

how to tell i386 from x86-64 kernel

[Pavel Machek]

Hi!

Quiz: on a booted system, how do you tell 32bit from 64bit kernel?

A1: zcat /proc/config.gz | grep CONFIG_64

...but config.gz is optional

A2: cat /proc/meminfo  | grep High

...but i386 kernel could have highmem disabled

What is _your_ answer? ;-)>
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: how to tell i386 from x86-64 kernel

[Ray Lee]

On Jan 31, 2008 4:42 PM, Pavel Machek <pavel@ucw.cz> wrote:
> Quiz: on a booted system, how do you tell 32bit from 64bit kernel?

Uhm, is this a trick question? What's wrong with uname(2)?

Re: how to tell i386 from x86-64 kernel

[Jan Engelhardt]

On Jan 31 2008 16:46, Ray Lee wrote:
>On Jan 31, 2008 4:42 PM, Pavel Machek <pavel@ucw.cz> wrote:
>> Quiz: on a booted system, how do you tell 32bit from 64bit kernel?
>
>Uhm, is this a trick question? What's wrong with uname(2)?

# uname -m
I won't tell you.
# linux32 uname -m
i686

Now what? :-)

Well, the answer is simple, a 64-bit kernel will allow you
(minus selinux voodoo) to load 64-bit binaries.

Re: how to tell i386 from x86-64 kernel

[Pavel Machek]

On Thu 2008-01-31 16:46:57, Ray Lee wrote:
> On Jan 31, 2008 4:42 PM, Pavel Machek <pavel@ucw.cz> wrote:
> > Quiz: on a booted system, how do you tell 32bit from 64bit kernel?
> 
> Uhm, is this a trick question? What's wrong with uname(2)?

No, it is a tricky question. You are right, uname -a tells me. Sorry.

Still, it would be nice to print it as a first message of dmesg, so
that it automatically gets included with problem reports... on
easy-to-see place.

								Pavel

Linux version 2.6.24-rc8 (pavel@amd) (gcc version 4.1.3 20071209 (prerelease) (Debian 4.1.2-18)) #65 SMP Thu Jan 31 00:02:37 CET 2008
BIOS-provided physical RAM map:


-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: how to tell i386 from x86-64 kernel

[H. Peter Anvin]

Pavel Machek wrote:
> Hi!
> 
> Quiz: on a booted system, how do you tell 32bit from 64bit kernel?
> 
> A1: zcat /proc/config.gz | grep CONFIG_64
> 
> ...but config.gz is optional
> 
> A2: cat /proc/meminfo  | grep High
> 
> ...but i386 kernel could have highmem disabled
> 
> What is _your_ answer? ;-)>
> 									Pavel

uname -m

	-hpa

Re: how to tell i386 from x86-64 kernel

[Jiri Kosina]

On Thu, 31 Jan 2008, H. Peter Anvin wrote:

> > Quiz: on a booted system, how do you tell 32bit from 64bit kernel?
> uname -m

I think that the real point here is that there is no general way how to 
determine whether the kernel is 32bit or 64bit from full dmesg output, 
which could sometimes make debugging user-reported bugs a little bit 
harder.

-- 
Jiri Kosina
SUSE Labs

Re: how to tell i386 from x86-64 kernel

[Alejandro Riveira Fernández]

El Fri, 1 Feb 2008 01:59:03 +0100 (CET)
Jan Engelhardt <jengelh@computergmbh.de> escribió:


> 
> # uname -m
> I won't tell you.
> # linux32 uname -m
> i686

 Ubuntu 7.10 64 bit userland 2.6.24

$ uname -m
x86_64
$ linux32 uname -m
i686



> 
> Now what? :-)
> 
> Well, the answer is simple, a 64-bit kernel will allow you
> (minus selinux voodoo) to load 64-bit binaries.

Re: how to tell i386 from x86-64 kernel

[Jan Engelhardt]

On Feb 1 2008 12:53, Alejandro Riveira Fernández wrote:
>> 
>> # uname -m
>> I won't tell you.
>> # linux32 uname -m
>> i686
>
> Ubuntu 7.10 64 bit userland 2.6.24
>
>$ uname -m
>x86_64
>$ linux32 uname -m
>i686

What I am saying is that uname(2) does not reliably tell you whether you 
have a 64-bit kernel underneath unless you have other sources of 
information.

Re: how to tell i386 from x86-64 kernel

[Arjan van de Ven]

On Sat, 9 Feb 2008 21:13:43 +0100 (CET)
Jan Engelhardt <jengelh@computergmbh.de> wrote:

> 
> On Feb 1 2008 12:53, Alejandro Riveira Fernández wrote:
> >> 
> >> # uname -m
> >> I won't tell you.
> >> # linux32 uname -m
> >> i686
> >
> > Ubuntu 7.10 64 bit userland 2.6.24
> >
> >$ uname -m
> >x86_64
> >$ linux32 uname -m
> >i686
> 
> What I am saying is that uname(2) does not reliably tell you whether
> you have a 64-bit kernel underneath unless you have other sources of 
> information.

that's sort of a rabbit-and-the-frog problem. The 32 bit emulator tries to
look EXACTLY like the 32 bit kernel, and it really should.
If someone wants a method to detect even that... we would really want
to know the exact usecase.. because very likely it's the wrong answer
to some other problem ;-)

-- 
If you want to reach me at my work email, use arjan@linux.intel.com
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org

Re: how to tell i386 from x86-64 kernel

[Pavel Machek]

On Sat 2008-02-09 14:34:30, Arjan van de Ven wrote:
> On Sat, 9 Feb 2008 21:13:43 +0100 (CET)
> Jan Engelhardt <jengelh@computergmbh.de> wrote:
> 
> > 
> > On Feb 1 2008 12:53, Alejandro Riveira Fernández wrote:
> > >> 
> > >> # uname -m
> > >> I won't tell you.
> > >> # linux32 uname -m
> > >> i686
> > >
> > > Ubuntu 7.10 64 bit userland 2.6.24
> > >
> > >$ uname -m
> > >x86_64
> > >$ linux32 uname -m
> > >i686
> > 
> > What I am saying is that uname(2) does not reliably tell you whether
> > you have a 64-bit kernel underneath unless you have other sources of 
> > information.
> 
> that's sort of a rabbit-and-the-frog problem. The 32 bit emulator tries to
> look EXACTLY like the 32 bit kernel, and it really should.
> If someone wants a method to detect even that... we would really want
> to know the exact usecase.. because very likely it's the wrong answer
> to some other problem ;-)

dmesg should really really tell you 32 vs. 64 bit, at the first line
where it prints versions... so you easily know what you are dealing
with when someone sends a bugreport.

							Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: how to tell i386 from x86-64 kernel

[Pavel Machek]

On Fri 2008-02-01 11:47:29, Rik Bobbaers wrote:
> hi there,
> 
> since i'm not on the list... how about:
> 
> tail /proc/1/smaps and check the address size...
> on 32 bit: ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
> 
> on 64 bit: ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0
> [vdso]
> 
> there you can clearly see that your address space is double... so
> there's your 32 bit vs 64 bit
> 
> as a normal user, you can do the same but with your own processes

That tells you if _init_ is 32 or 64 bit, not kernel.

I'm running 32-bit distro on 64-bit kernel here. It works fine (as it
should).

									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: how to tell i386 from x86-64 kernel

[Rik Bobbaers]

hi there,

since i'm not on the list... how about:

tail /proc/1/smaps and check the address size...
on 32 bit: ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]

on 64 bit: ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0
[vdso]

there you can clearly see that your address space is double... so
there's your 32 bit vs 64 bit

as a normal user, you can do the same but with your own processes

greetings,

> Hi!
> 
> Quiz: on a booted system, how do you tell 32bit from 64bit kernel?
> 
> A1: zcat /proc/config.gz | grep CONFIG_64
> ...but config.gz is optional
> 
> A2: cat /proc/meminfo  | grep High
> ...but i386 kernel could have highmem disabled
> 
> What is _your_ answer? ;-)>

-- 
harry
aka Rik Bobbaers

K.U.Leuven - LUDIT            -=- Tel: +32 485 52 71 50
Rik.Bobbaers@icts.kuleuven.be -=- http://harry.enzoverder.be

Don't steal - the government hates competition.



Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm

Re: how to tell i386 from x86-64 kernel

[Jan Engelhardt]

don't strip Ccs, thanks. (and try not to tofu either.)

On Jan 31 2008 17:01, Justin Banks wrote:
>
>uname -a will tell you, though.

No. uname is generally not a reliable source to tell you the bitness (or 
more precisely, the arch). It may even happen that you cannot find out 
at all if access permissions are set 'correctly'.
You may find ELF64 files flying around in the filesystem, and while that 
is a strong indication of a 64-bit kernel being running, it is not a 
definite Yes.


02:31 ccgmbh:~ > uname -a
Linux ccgmbh 2.6.23.10-ccj62-regular #1 SMP 2007/10/26 14:17:15 UTC i686 
athlon i386 GNU/Linux

02:32 ccgmbh:~ > file `which uname`
/bin/uname: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), for 
GNU/Linux 2.6.4, dynamically linked (uses shared libs), stripped