In OpenJKD code, for big endian architecture, `XIMPreeditState` is considered `unsigned int` whereas in `xlib` code it is `unsigned long` [source](https://github.com/mirror/libX11/blob/ff8706a5eae25b8bafce300527079f68a201d27f/include/X11/Xlib.h#L1267).
Now, openjdk compiled code pushes a frame and allots the address, just 4 bytes away, because it considers state to be a int, from the store `callers_sp` : 2: /x $r15 = 0x3ff8137da20 3: x/2xg 0x3ff8137da20 0x3ff8137da20: 0x000003ff8137daf0 0x000003fffa2a9a86 `0x000003ff8137daf0` is callers sp for s390x. And this is address for `state` : (gdb) p &state $9 = (unsigned int *) 0x3ff8137da1c which is just 4 byte away from the callers sp: (gdb) p/x 0x3ff8137da20 - 4 $10 = 0x3ff8137da1c Now while executing `_XimDecodePreeditState` method from xlib library where `state` is of type `unsigned long` we are going to emit a 8-byte instruction.: (gdb) disassemble _XimDecodePreeditState Dump of assembler code for function _XimDecodePreeditState: => 0x000003ff989f3360 <+0>: llgf %r1,8(%r2) 0x000003ff989f3366 <+6>: lghi %r2,1 0x000003ff989f336a <+10>: lg %r1,0(%r3,%r1) 0x000003ff989f3370 <+16>: stg %r1,0(%r4) 0x000003ff989f3376 <+22>: br %r14 End of assembler dump. `0x000003ff989f3370 <+16>: stg %r1,0(%r4) ` here `r4` is pointing the `state` variable. And the moment this write happens we will corrupt the first 4 byte of callers_sp, which will cause issue while the stack-unwinding. And at the end JVM will crash with segmentation fault. This is always reproducible with the test case provided in the JBS. And test only failed with compiler (c1 & c2) but passed always with interpreter. ------------- Commit messages: - fix datatype mismatch Changes: https://git.openjdk.org/jdk/pull/25266/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25266&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8356643 Stats: 5 lines in 1 file changed: 0 ins; 5 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/25266.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/25266/head:pull/25266 PR: https://git.openjdk.org/jdk/pull/25266
