RFR: 8320886: Unsafe_SetMemory0 is not guarded [v3]

[Jorn Vernee]

> See JBS issue.
> 
> Guard the memory access done in Unsafe_SetMemory0 to prevent a SIGBUS error from crashing the VM when a truncated memory mapped file is accessed.
> 
> Testing: local `InternalErrorTest`, Tier 1-5

Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:

  adjust whitespace

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16848/files
  - new: https://git.openjdk.org/jdk/pull/16848/files/e9a5247e..7c258f07

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16848&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16848&range=01-02

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/16848.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16848/head:pull/16848

PR: https://git.openjdk.org/jdk/pull/16848