Mercurial > hg > truffle

comparison agent/doc/transported_core.html @ 0:a61af66fc99e jdk7-b24

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Initial load
author duke
date Sat, 01 Dec 2007 00:00:00 +0000
parents
children
comparison
equal deleted inserted replaced
-1:000000000000 0:a61af66fc99e
1 <html>
2 <head>
3 <title>
4 Debugging transported core dumps
5 </title>
6 </head>
7 <body>
8 <h1>Debugging transported core dumps</h1>
9
10 <p>
11 When a core dump is moved to a machine different from the one where it was
12 produced ("transported core dump"), debuggers (dbx, gdb, windbg or SA) do not
13 always successfully open the dump. This is due to kernel, library (shared
14 objects or DLLs) mismatch between core dump machine and debugger machine.
15 </p>
16
17 <p>
18 In most platforms, core dumps do not contain text (a.k.a) Code pages.
19 There pages are to be read from executable and shared objects (or DLLs).
20 Therefore it is important to have matching executable and shared object
21 files in debugger machine.
22 </p>
23
24 <h3>Solaris transported core dumps</h3>
25
26 <p>
27 Debuggers on Solaris (and Linux) use two addtional shared objects
28 <b>rtld_db.so</b> and <b>libthread_db.so</b>. rtld_db.so is used to
29 read information on shared objects from the core dump. libthread_db.so
30 is used to get information on threads from the core dump. rtld_db.so
31 evolves along with rtld.so (the runtime linker library) and libthread_db.so
32 evolves along with libthread.so (user land multithreading library).
33 Hence, debugger machine should have right version of rtld_db.so and
34 libthread_db.so to open the core dump successfully. More details on
35 these debugger libraries can be found in
36 <a href="http://docs.sun.com/app/docs/doc/817-1984/">
37 Solaris Linkers and Libraries Guide - 817-1984</a>
38 </p>
39
40 <h3>Solaris SA against transported core dumps</h3>
41
42 <p>
43 With transported core dumps, you may get "rtld_db failures" or
44 "libthread_db failures" or SA may just throw some other error
45 (hotspot symbol is missing) when opening the core dump.
46 Enviroment variable <b>LIBSAPROC_DEBUG</b> may be set to any value
47 to debug such scenarios. With this env. var set, SA prints many
48 messages in standard error which can be useful for further debugging.
49 SA on Solaris uses <b>libproc.so</b> library. This library also
50 prints debug messages with env. var <b>LIBPROC_DEBUG</b>. But,
51 setting LIBSAPROC_DEBUG results in setting LIBPROC_DEBUG as well.
52 </p>
53 <p>
54 The best possible way to debug a transported core dump is to match the
55 debugger machine to that of core dump machine. i.e., have same Kernel
56 and libthread patch level between the machines. mdb (Solaris modular
57 debugger) may be used to find the Kernel patch level of core dump
58 machine and debugger machine may be brought to the same level.
59 </p>
60 <p>
61 If the matching machine is "far off" in your network, then
62 <ul>
63 <li>consider using rlogin and <a href="clhsdb.html">CLHSDB - SA command line HSDB interface</a> or
64 <li>use SA remote debugging and debug the core from core machine remotely.
65 </ul>
66 </p>
67
68 <p>
69 But, it may not be feasible to find matching machine to debug.
70 If so, you can copy all application shared objects (and libthread_db.so, if needed) from the core dump
71 machine into your debugger machine's directory, say, /export/applibs. Now, set <b>SA_ALTROOT</b>
72 environment variable to point to /export/applibs directory. Note that /export/applibs should either
73 contain matching 'full path' of libraries. i.e., /usr/lib/libthread_db.so from core
74 machine should be under /export/applibs/use/lib directory and /use/java/jre/lib/sparc/client/libjvm.so
75 from core machine should be under /export/applibs/use/java/jre/lib/sparc/client so on or /export/applibs
76 should just contain libthread_db.so, libjvm.so etc. directly.
77 </p>
78
79 <p>
80 Support for transported core dumps is <b>not</b> built into the standard version of libproc.so. You need to
81 set <b>LD_LIBRARY_PATH</b> env var to point to the path of a specially built version of libproc.so.
82 Note that this version of libproc.so has a special symbol to support transported core dump debugging.
83 In future, we may get this feature built into standard libproc.so -- if that happens, this step (of
84 setting LD_LIBRARY_PATH) can be skipped.
85 </p>
86
87 <h3>Ignoring libthread_db.so failures</h3>
88 <p>
89 If you are okay with missing thread related information, you can set
90 <b>SA_IGNORE_THREADDB</b> environment variable to any value. With this
91 set, SA ignores libthread_db failure, but you won't be able to get any
92 thread related information. But, you would be able to use SA and get
93 other information.
94 </p>
95
96 <h3>Linux SA against transported core dumps</h3>
97 <p>
98 On Linux, SA parses core and shared library ELF files. SA <b>does not</b> use
99 libthread_db.so or rtld_db.so for core dump debugging (although
100 libthread_db.so is used for live process debugging). But, you
101 may still face problems with transported core dumps, because matching shared
102 objects may not be in the path(s) specified in core dump file. To
103 workaround this, you can define environment variable <b>SA_ALTROOT</b>
104 to be the directory where shared libraries are kept. The semantics of
105 this env. variable is same as that for Solaris (please refer above).
106 </p>
107
108
109 </body>
110 </html>