RFR: 8262896: [macos_aarch64] Crash in jni_fast_GetLongField

[Anton Kozlov]

Hi, please review a fix for a random crash on macos/aarch64.

By default, GetXXXField JNI Interface implementation is a generated function (-XX:+UseFastJNIAccessors). Usually the function is called by JNI code running in WXExec mode and everything is fine. But sometime we attempt to call it in WXWrite context, like in the stack trace attached to the bug:

v  ~BufferBlob::jni_fast_GetLongField
V  [libjvm.dylib+0x7a6538]  Perf_Detach+0x168
j  jdk.internal.perf.Perf.detach(Ljava/nio/ByteBuffer;)V+0 java.base at 17-internal
j  jdk.internal.perf.Perf$CleanerAction.run()V+8 java.base at 17-internal
j  jdk.internal.ref.CleanerImpl$PhantomCleanableRef.performCleanup()V+4 java.base at 17-internal
j  jdk.internal.ref.PhantomCleanable.clean()V+12 java.base at 17-internal
j  jdk.internal.ref.CleanerImpl.run()V+57 java.base at 17-internal
j  java.lang.Thread.run()V+11 java.base at 17-internal
j  jdk.internal.misc.InnocuousThread.run()V+20 java.base at 17-internal
v  ~StubRoutines::call_stub

One way to fix the bug is to ensure WXExec mode before calling GetXXXField, but it depends on finding and fixing all such cases. 

This patch instead adds additional actions to GetXXXField implementation to ensure correct W^X mode regardless if it is called from WXWrite or WXExec mode.

-------------

Commit messages:
 - Add W^X in FastGetXXXField

Changes: https://git.openjdk.java.net/jdk/pull/3422/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3422&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262896
  Stats: 69 lines in 3 files changed: 61 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3422.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3422/head:pull/3422

PR: https://git.openjdk.java.net/jdk/pull/3422