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cannot map /dev/zero

cannot map /dev/zero

Post by Daniel Barl » Thu, 12 Oct 1995 04:00:00





Quote:>dos.  When I tried to do a ps, I got an error message that looked similar
>to "cannot map /dev/zero" two or three times, as well as a complaint about
>not being able to open some X library-- I didn't write down what it was.
>All other commands that aren't built into tcsh gave me similar errors.
>I was able to kill it by doing a "kill -9 -1".

OK, what's happening is that the ELF dynamic loader allocates memory
to load shared libraries into by mmaping /dev/zero, and dosemu
apparently seems able to open /dev/zero exclusively, hence nothing can
start while it's running.

The current alpha version of ld.so (and I _think_ the latest
publically released version) does not do this, instead doing anonymous
maps.  You may want to check tsx-11.mit.edu:/pub/linux/packages/GCC to
see if there's a newer ld.so version than 1.7.3 there, and install that.

As for the other question (should one app be able to block others'
access to /dev/zero) I don't know.  Personally I'd say no, but maybe
someone more familiar with that stuff could comment?

Daniel
--

Fun things to see, #3421:  `****** End of newsgroups -- what next? [qnp]'

 
 
 
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cannot map /dev/zero

Post by Michael L Gerd » Thu, 12 Oct 1995 04:00:00


I was playing with dosemu today along with Turbo C++, and ran into some
problems.  I was running dosemu in a virtual console, and made the mistake
of typing tc.  This locked up dosemu, which I guess didn't really surprise
me.  I switched back to the VC that X was running on, and tried to kill
dos.  When I tried to do a ps, I got an error message that looked similar
to "cannot map /dev/zero" two or three times, as well as a complaint about
not being able to open some X library-- I didn't write down what it was.
All other commands that aren't built into tcsh gave me similar errors.
I was able to kill it by doing a "kill -9 -1".

My system:
    Linux 1.2.13, RedHat 2.0 distribution
    dosemu 0.60
    Turbo C++ 3.0

I guess my main concern is that should dosemu be able to take over
/dev/zero and any shared libraries that it may or may not be using to
the point that it makes the system unusable?

Mike

 
 
 
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1. cannot map /dev/zero: Where to fix?

Hi, All!

The problem is:

when I start netscape 3.0 on my ELF system, attempt to start
any other process (from xterm, from cron, from httpd) results
in error message
cannot map /dev/zero ... cannot load library whatever.so.it.needs

Problem arises after I've changed hard disk in my machine and
copied two linux files systems from one disk to other by
command:
 (cd /old/filesystem;tar cvlf - .)|(cd /new/filesystem;tar xf -)

I'm sure that I've missed something when copied a system
from one hard drive to another, becouse nearby machine with my
old hard disk runs netscape without this problem.

        And when I copied root filesystem, tar failed on /bin/bash on some
reason and I've copied rest of root on per-directory basis.

Possible cause is wrong permissions of some file, but
/dev and /lib looks identical on both machines.

I'm almost sure that problem is somewhere in root file system, not in /usr,
becouse /usr partition on old disk was repartitioned and copied back
from new disk and there was some things which I've missed when
copied root filesystem. (I've hoped that I fixed all of tham, but... :-()

If any expert on ELF dynamic linking can point to problem's origin, please
mail or post me.

The most suspicious place is /var

2. Security breatch

3. Netscape - cannot map /dev/zero ?

4. cvs - dumb question but..

5. Trying to purchase USEFUL glasses

6. can't map /dev/zero

7. defaultrouter or notrouter

8. bash: can't map '/dev/zero'

9. Netscape2.01 ls: can't map /dev/zero, lib not found

10. Memory mapping of /dev/zero

11. mystical can't map /dev/zero problems


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