Valgrind meet containers.
Containers meet valgrind.
I've found what lxc doesn't like when running valgrind.
The lxc_start() checks to see if there are extra file descriptors open and
won't call __lxc_start().
vdr1: inherited fd 1024 on
/home/vallevand/trunk_s4m/s4m-appliance/src/vdrd/vgVdrTest
vdr1: inherited fd 1025 on /tmp/valgrind_proc_24989_cmdline_4fbfb9a5
(deleted)VdrTest
vdr1: inherited fd 1026 on /dev/pts/1ind_proc_24989_cmdline_4fbfb9a5
(deleted)VdrTest
vdr1: inherited fd 1027 on pipe:[768863]_proc_24989_cmdline_4fbfb9a5
(deleted)VdrTest
vdr1: inherited fd 1028 on pipe:[768863]_proc_24989_cmdline_4fbfb9a5
(deleted)VdrTest
Vdr1 is the name of my container. All those open files in the child process
are related to valgrind.
If I call __lxc_start() rather than lxc_start(), I see this:
vdr1: sync wake failure : Broken pipe
vdr1: failed to spawn 'vdr1'
And, just before that there is some complaining from valgrind:
==25086== Syscall param clone(child_tidptr) contains uninitialised byte(s)
==25086== at 0x56622E1: clone (clone.S:84)
==25086== by 0x4E3BD38: __lxc_start (in /usr/lib/lxc/liblxc.so.0.7.5)
==25086== by 0x4014C9: vgVdrStartClone (vgVdrTest.c:88)
==25086== by 0x400F0A: main (vgVdrTest.c:337)
==25086==
==1== Syscall param wait4(status) points to unaddressable byte(s)
==1== at 0x53607C4: wait (wait.c:32)
==1== by 0x4E3A400: ??? (in /usr/lib/lxc/liblxc.so.0.7.5)
==1== by 0x566231C: clone (clone.S:112)
==1== Address 0xffffffffffffffd4 is not stack'd, malloc'd or (recently) free'd
==1==
==1== Invalid write of size 4
==1== at 0x4E3A4FF: ??? (in /usr/lib/lxc/liblxc.so.0.7.5)
==1== by 0x566231C: clone (clone.S:112)
==1== Address 0xffffffffffffffc0 is not stack'd, malloc'd or (recently) free'd
==1==
==1==
==1== Process terminating with default action of signal 11 (SIGSEGV)
==1== Access not within mapped region at address 0xFFFFFFFFFFFFFFC0
==1== at 0x4E3A4FF: ??? (in /usr/lib/lxc/liblxc.so.0.7.5)
==1== by 0x566231C: clone (clone.S:112)
Our program is designed to close all open file descriptors in the child process
before calling lxc_start(). That code can try to close all file descriptors to
make sure something doesn't sneak through. However, closing the file
descriptors associated with valgrind does not work. I get errno=0 Bad File
Descriptor. Valgrind really has them held open. I am running as root in all
these tests.
I've also reproduced the problem using the 'lxc-' programs. If you do
something like 'lxc-create -n XXX' and then something like 'valgrind lxc-start
-n XXX -- ls' you'll see it. Well, the flavor of the error with open file
descriptors.
My hopes aren't high, but any ideas are very welcome.
Regards.
Mark K Vallevand
"If there are no dogs in Heaven, then when I die I want to go where they went."
-Will Rogers
THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY
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From: lxc-users [mailto:lxc-users-boun...@lists.linuxcontainers.org] On Behalf
Of Vallevand, Mark K
Sent: Thursday, September 25, 2014 09:19 AM
To: lxc-us...@lists.linuxcontainers.org
Subject: [lxc-users] Using valgrind with lxc
In our program, we do a fork() and in the child process the lxc library is
called to start a program in a container using lxc_start().
We don't care about valgrind in the child process. You can disable valgrind
messages from child processes, but you cannot detach valgrind unless you exec()
a new binary on top. However, valgrind and lxc do not play nicely, at least
with the versions in Ubuntu 12.04 LTS. I'm getting an error back from
lxc_start(). I'm having trouble getting logs to see why its failing, so I
don't know exactly what's failing, yet.
But, I'm looking for any ideas for getting valgrind to work with programs that
use lxc_start().
Any suggestions will be welcome. And, thanks!
Regards.
Mark K Vallevand
"If there are no dogs in Heaven, then when I die I want to go where they went."
-Will Rogers
THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY
MATERIAL and is thus for use only by the intended recipient. If you received
this in error, please contact the sender and delete the e-mail and its
attachments from all computers.
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