If a stack trace is present, examining the function running at the point of failure should give you a good indication of the code that caused the failure, and whether the failure is in IBM's JVM code, or is caused by application or vendor-supplied JNI code.
A failing instruction reported by dbx or stackit.sh as "stwu" indicates that there might have been a stack overflow. For example:
Segmentation fault in strlen at 0xd01733a0 ($t1) 0xd01733a0 (strlen+0x08) 88ac0000 stwu r1,-80(r1)
(dbx) thread info 1 thread state-k wchan state-u k-tid mode held scope function >$t1 run running 85965 k no sys oflow general: pthread addr = 0x302027e8 size = 0x22c vp addr = 0x302057e4 size = 0x294 thread errno = 0 start pc = 0x10001120 joinable = yes pthread_t = 1 scheduler: kernel = user = 1 (other) event : event = 0x0 cancel = enabled, deferred, not pending stack storage: base = 0x2df23000 size = 0x1fff7b0 limit = 0x2ff227b0 sp = 0x2df2cc70
For the second cause, currently dbx (and therefore stackit.sh) does not understand the structure of the JIT and Interpreter stack frames, and is not capable of generating a stack trace from them. The javadump, however, does not suffer from this limitation and can be used to examine the stack trace. A failure in JIT-compiled code can be verified and examined using the JIT Debugging Guide (see JIT and AOT problem determination).