Re: [libvirt] Segfault in event-test.c example

2010/1/10 <pspreadborough(a)comcast.net&gt;: > > ----- "Matthias Bolte" <matthias.bolte(a)googlemail.com&gt; wrote: > >> 2010/1/10  &lt;pspreadborough(a)comcast.net&gt;: >> > >> > Hello, >> > >> > I have been trying to use the domain event C code example but >> > unfortunately it segfaults (signal 11) every time I run it: >> > >> > [root@Spring events-c]# ./event-test >> > myEventAddHandleFunc:221: Add handle 5 1 0xf081a0 0x8f727f8 >> > myEventAddHandleFunc:221: Add handle 7 1 0xf09990 0x8f727f8 >> > myEventAddHandleFunc:221: Add handle 8 1 0xed7940 0x8f727f8 >> > myEventAddTimeoutFunc:251: Adding Timeout -1 0xedefa0 0x8f727f8 >> > myEventAddHandleFunc:221: Add handle 11 1 0xed7940 0x8f727f8 >> > myEventAddTimeoutFunc:251: Adding Timeout -1 0xedefa0 0x8f727f8 >> > main:322 :: Registering domain event cbs >> > Segmentation fault (core dumped) >> > >> >  Core was generated by >> > >> `/root/libvirt-0.7.5/examples/domain-events/events-c/.libs/lt-event-test'. >> > Program terminated with signal 11, Segmentation fault. >> > [New process 21806] >> > [New process 21822] >> > #0  remoteDomainEventQueueFlush (timer=-1, opaque=0x8f727f8) at >> > remote/remote_driver.c:8720 >> > 8720        tempQueue.count = priv->domainEvents->count; >> > (gdb) bt >> > #0  remoteDomainEventQueueFlush (timer=-1, opaque=0x8f727f8) at >> > remote/remote_driver.c:8720 >> > #1  0x080490d3 in main (argc=Cannot access memory at address 0x1 >> > ) at event-test.c:347 >> > >> > The stack looks corrupted so I'm doubtful that this trace if of much >> value. >> > I have built >> > and installed libvirt-0.7.5 and it and it's tools seem to be >> operating >> > correctly. >> >> I tried the event-test with libvirt-0.7.5 and QEMU/Xen and both are >> working as expected. No segfaults. >> >> Could you inspect the values of priv and priv->domainEvents in GDB >> using 'p priv' to see if they are NULL and try to dereference them in >> GDB using 'p *priv' to see if they point to valid memory areas? >> >> Yes the backtrace looks corrupted. If there is stack/heap corruption >> involved valgrind may reveal it, so try to run the event-test in >> valgrind and see if that gives any hints. >> >> You can also try the GIT version of libvirt. There was a invalid free >> call (resulting in heap corruption) in the node device code fixed >> after the 0.7.5 release. But that should have no effect on the >> event-test. >> >> Matthias > > Matthias, > > priv->domainEvents is NULL, here's the gdb output: This explains the segfault. The next question is, why is it NULL? > (gdb) p *priv > $1 = {lock = {lock = {__data = {__lock = 1, __count = 0, __owner = 21806, __kind = 0, __nusers = 1, {__spins = 0, __list = { >            __next = 0x0}}}, __size = "\001\000\000\000\000\000\000\000.U\000\000\000\000\000\000\001\000\000\000\000\000\000", >      __align = 1}}, sock = 150469168, watch = 3, pid = 4, uses_tls = 1982791681, is_secure = 1815048801, session = 0x782f6269, Seeing uses_tls and is_secure being large numbers and knowing that both are used as boolean values in the code and should have values of 0 or 1 make me think that priv points to already freed memory here. >  type = 0x2f646e65 <Address 0x2f646e65 out of bounds>, counter = 1684956536, localUses = 1668248365, >  hostname = 0x74656b <Address 0x74656b out of bounds>, debugLog = 0x0, saslconn = 0x0, saslDecoded = 0x0, saslDecodedLength = 0, type and hostname are char pointers, but the seem to point into nowhere, confirms that this is either freed memory or priv itself got overwritten due to heap corruption. >  saslDecodedOffset = 0, saslEncoded = 0x0, saslEncodedLength = 0, saslEncodedOffset = 0, >  buffer = '\0' <repeats 68 times>, "n\000\000\000\001\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\001\000\000\000\001\000\000\000\000\000\000\000\001\000\000\000\bQ�\b����\030\034�\b\000\000\000\000�\033�\b\001\000\000\000\002\000\000\000�\033�\b\000\000\000\000\025|�\000\a", '\0' <repeats 11 times>, "X\000�\b", '\0' <repeats 12 times>, "\021\000\000\000\002\000\000\000P��\b\000\000\000\000\021", '\0' <repeats 15 times>, "\021\000\000\0008\036�\b\f\000\000\000\020\000\000\000\021\000\000\000\a\000\000\000\b\000\000\000\t\000\000\000\021\000\000\000\002\000\000\000\230\034�\b\000\000\000\000A\000\000\000\003\000\000\000\001\000\000\000\001\000"..., bufferLength = 0, >  bufferOffset = 0, callbackList = 0x0, domainEvents = 0x0, eventFlushTimer = 0, domainEventDispatching = 1, wakeupSendFD = 0, >  wakeupReadFD = 0, waitDispatch = 0x0, streams = 0x0} > > I'll try a run with valgrind and post the results. > > Pete > Could you test the Python version of this example found in examples/domain-events/events-python/event-test.py? Does this work? Otherwise lets see if valgrind gives any hints. Matthias