Java SVC Dump analyzer

To be completed!

Overview

This is an SVC Dump analyzer written in Java. It provides an alternative to using IPCS. In answer to the obvious question "why?", this analyzer provides the following benefits:

you can save the output to a file which can then be viewed in your favourite editor allowing you to easily scroll up and down, search etc. Say no to fifties-style green-screen technology!
it knows about Java and so can display the names of Java methods in the C tracebacks.
you can run FindRoots on the heap.
automatic printing of function names for trace entries.
this is just the beginning. Now we have the basic infrastructure written in Java we can add a GUI, provide hooks for Jython and so on. There is no need to learn horribly obscure stuff like how to extend IPCS with REXX scripts. Or even how to use IPCS for that matter.

Here is some sample output:

found Usta TCB a7e288 tid 1ac30e20 caa 109f5120 Dsa Entry Offset Function --- ----- ------ -------- 10a06d90 11aa58d8 fff8909a SYSTDUMP 10a06940 11a90c48 00000414 ThreadUtils_CoreDump 10a06830 11a734b0 000004b2 userSignalHandler 10a06780 11a73a18 000000b8 intrDispatch 10a066c8 061596b8 000000c4 @@GETFN 10a06068 0628af48 0000075e __zerros 10a034d0 00000008 0638260e null 10a02a70 11a566d0 fefac3f8 CompareAndSwap_Impl 10a029c0 119223f0 000000a2 pin_object 10a02918 11740c40 00000114 jni_GetPrimitiveArrayElements 10a02710 1af1a388 000000b2 MVS_CcicsInit 10a02660 1af143b8 000000b0 Java_com_ibm_ctg_server_ServerECIRequest_CcicsInit 10a025a8 06419078 0000005c CEEPGTFN 10a02118 119a20d0 00000138 MMIPSJNI 10a02038 1199fd48 000003ce mmisInvokeJniMethodHelper (com/ibm/ctg/server/ServerECIRequest.CcicsInit) 10a01f68 1198e3f8 00000100 mmipInvokeJniMethod (com/ibm/ctg/server/ServerECIRequest.CcicsInit) 10a01e78 1198ed80 0000099e mmipInvokeJavaMethod (com/ibm/ctg/server/ServerECIRequest.initTrace) 10a01d88 1198ed80 0000099e mmipInvokeJavaMethod (com/ibm/ctg/server/ServerECIRequest.initialize) 10a01c80 1198ed80 0000099e mmipInvokeJavaMethod (com/ibm/ctg/client/LocalJavaGateway.flow) 10a01b90 1198ed80 0000099e mmipInvokeJavaMethod (com/ibm/ctg/client/JavaGateway.flow)

Usage

java -classpath svcdump.jar com.ibm.jvm.svcdump.Dump [-options]
 <filename>

where options can be one of:

-heap	print a table showing which classes have the most objects allocated
-cache	print alloc cache
-dis <addr> <n>	disassemble <n> instructions starting at <addr> (hex)
-caa <addr>	specify the caa to use when disassembling
-r<n>	include saved register <n> in stack trace
-verbose	print extra info for debugging purposes
-help	print extended help info and exit

these options are described in more detail below. If you want to run FindRoots, type

java -classpath svcdump.jar com.ibm.jvm.findroots.FindRoots -help

for more details.

-heap

Print a table showing which classes have the most objects allocated.

-cache

Print the Java alloc cache. This can give an idea of the most recently allocated objects since they will still be in the cache.

Sample output:

alloc cache info: cache_busy = 0x0 cache_size = 0x7bbc cache_block = 0x14208ef0 cache_orig_size = 0x10004 14210aac: len = 20 methods = efd7ee0 flags = 0 class = java/lang/String 14210acc: len = 70 methods = 32 flags = 2a 14210b3c: len = 68 methods = 2c flags = 2a 14210ba4: len = 20 methods = efd7ee0 flags = 0 class = java/lang/String 14210bc4: len = 20 methods = 110c4d00 flags = 0 class = java/lang/ref/Finalizer 14210be4: len = 20 methods = 110c7560 flags = 0 class = java/lang/ClassLoader$NativeLibrary 14210c04: len = 20 methods = efd7ee0 flags = 0 class = java/lang/String 14210c24: len = 50 methods = 1f flags = 2a 14210c74: len = 20 methods = efd7ee0 flags = 0 class = java/lang/String

-dis <addr> <n>

Disassemble <n> instructions starting at the hex address <addr>. The disassembler is not complete but it knows about the most common instructions. When it comes across an instruction it doesn't understand it will throw an exception and exit. This is usually because it has gone past the end of the function. I'll probably clean this up eventually but it seems good enough for now.

Sample output:

Disassembly starting at 0x11a90c48 0x11a90c48: (0x00000000): B x'22'($r15) 0x11a90c6a: (0x00000022): STM $r14,$r11,x'c'($r13) 0x11a90c6e: (0x00000026): L $r14, x'4c'($r13) 0x11a90c72: (0x0000002a): LA $r0, x'450'($r14) 0x11a90c76: (0x0000002e): CL $r0, x'314'($r12) 0x11a90c7a: (0x00000032): LA $r3, x'3a'($r15) 0x11a90c7e: (0x00000036): BGT x'14'($r15) 0x11a90c82: (0x0000003a): L $r15, x'280'($r12) 0x11a90c86: (0x0000003e): STM $r15,$r0,x'48'($r14) 0x11a90c8a: (0x00000042): MVI x'0'($r14), x'10' 0x11a90c8e: (0x00000046): ST $r13, x'4'($r14) 0x11a90c92: (0x0000004a): LR $r13, $r14 0x11a90c94: (0x0000004c): L $r4, x'1f4'($r12) 0x11a90c98: (0x00000050): L $r5, x'7ae'($r3) 0x11a90c9c: (0x00000054): LA $r2, x'c4'($r13) 0x11a90ca0: (0x00000058): LA $r1, x'98'($r13) 0x11a90ca4: (0x0000005c): ST $r2, x'98'($r13) 0x11a90ca8: (0x00000060): L $r14, x'170'($r5,$r4) 0x11a90cac: (0x00000064): LM $r15,$r0,x'8'($r14) 0x11a90cb0: (0x00000068): ST $r0, x'1f4'($r12) 0x11a90cb4: (0x0000006c): BALR $r14, $r15 0x11a90cb6: (0x0000006e): L $r7, x'7b2'($r3) 0x11a90cba: (0x00000072): L $r6, x'174'($r5,$r4) 0x11a90cbe: (0x00000076): LA $r0, x'f4'($r13) 0x11a90cc2: (0x0000007a): ST $r0, x'ac'($r13) 0x11a90cc6: (0x0000007e): LA $r1, x'407'($r7) 0x11a90cca: (0x00000082): LA $r14, x'fc'($r13) 0x11a90cce: (0x00000086): LA $r10, x'234'($r13) 0x11a90cd2: (0x0000008a): ST $r1, x'9c'($r13) 0x11a90cd6: (0x0000008e): LA $r11, x'41c'($r7) 0x11a90cda: (0x00000092): LM $r15,$r0,x'8'($r6) 0x11a90cde: (0x00000096): ST $r10, x'98'($r13) 0x11a90ce2: (0x0000009a): ST $r11, x'438'($r13) 0x11a90ce6: (0x0000009e): ST $r11, x'a0'($r13) 0x11a90cea: (0x000000a2): ST $r2, x'a4'($r13) 0x11a90cee: (0x000000a6): LA $r1, x'98'($r13) 0x11a90cf2: (0x000000aa): ST $r14, x'a8'($r13) 0x11a90cf6: (0x000000ae): ST $r0, x'1f4'($r12) 0x11a90cfa: (0x000000b2): BALR $r14, $r15

-caa <addr>

Specify the hex caa address to use when disassembling. This is for future use when I figure out how to get the address of functions.

-r<n>

Include saved register <n> in stack trace.

Sample output:

found Usta TCB a7e288 tid 1ac30e20 caa 109f5120 Dsa Entry Offset r12 Function --- ----- ------ --- -------- 10a06d90 11aa58d8 fff8909a 109f5120 SYSTDUMP 10a06940 11a90c48 00000414 109f5120 ThreadUtils_CoreDump 10a06830 11a734b0 000004b2 0ef473a0 userSignalHandler 10a06780 11a73a18 000000b8 40404040 intrDispatch 10a066c8 061596b8 000000c4 40404040 @@GETFN 10a06068 0628af48 0000075e 109f5120 __zerros 10a034d0 00000008 0638260e 109f5120 null 10a02a70 11a566d0 fefac3f8 00000000 CompareAndSwap_Impl 10a029c0 119223f0 000000a2 109f5120 pin_object 10a02918 11740c40 00000114 109f5120 jni_GetPrimitiveArrayElements 10a02710 1af1a388 000000b2 109f5120 MVS_CcicsInit 10a02660 1af143b8 000000b0 109f5120 Java_com_ibm_ctg_server_ServerECIRequest_CcicsInit 10a025a8 06419078 0000005c 109f5120 CEEPGTFN 10a02118 119a20d0 00000138 109f5120 MMIPSJNI 10a02038 1199fd48 000003ce 109f5120 mmisInvokeJniMethodHelper (com/ibm/ctg/server/ServerECIRequest.CcicsInit) 10a01f68 1198e3f8 00000100 109f5120 mmipInvokeJniMethod (com/ibm/ctg/server/ServerECIRequest.CcicsInit)

Internals

You don't want to know! I couldn't find any documentation on SVC dumps so I reverse-engineered it. There are lots of ugly heuristics in use that I developed through trial and error. Dave Clarke has also been a goldmine of information.

Feedback

Please send comments and suggestions to me at dgriff@hursley.ibm.com.

Thanks!