[Bug runtime/11140] SystemTap userspace marker in shared libraries cause probed program crash

["wcohen at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

------- Additional Comments From wcohen at redhat dot com  2010-01-05 22:42 -------
Created an attachment (id=4496)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4496&action=view)
Script to find the address of the sigbus faults

To allow comparison between runs address randomization was turned off with:

sysctl -w kernel.randomize_va_space=0

The attached sigbus.stp script was run:


$ stap /tmp/sigbus.stp |grep sig
2735979:32542:0x00007ffff7fc965c:r:sigbus:2
2736032:32542:0x00007ffff7fc965e:r:sigbus:2

Got a pmap of a python process with the problem script not running.

00007ffff7c22000   1464K r-x--	/usr/lib64/libpython2.6.so.1.0
00007ffff7d90000   2044K -----	/usr/lib64/libpython2.6.so.1.0
00007ffff7f8f000    236K rw---	/usr/lib64/libpython2.6.so.1.0
00007ffff7fca000     56K rw---	  [ anon ]

Those addresses appear to be close to the end of the rw region of
/usr/lib64/libpython2.6.so.1.0

$ nm /usr/lib/debug//usr/lib64/libpython2.6.so.1.0.debug |grep sema
00000000003a765c B function__entry_semaphore
00000000003a765e B function__return_semaphore

The problem appears to be the code writing to
 function__entry_semaphore and function__return_semaphore is causing
 the sigbus error.  The number of faults is equal to the number of
 probes on a point.  

>From the sigbus.stp script output it looks like a get_user() macro is causing
the sigbus.


-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=11140

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