RFR: 8285792: Posix signal handler modification checking issues.

[David Holmes]

On Mon, 25 Jul 2022 17:21:27 GMT, Harold Seigel <hseigel at openjdk.org> wrote:

> Please review this fix for JDK-8285792.  The fix removes print statements from check_signal_handler() so that it doesn't print all the handlers every time it finds one that is modified.  Instead, it returns true if the handler is modified, false otherwise.  Its caller, user_handler(), then prints all the handlers just once even if multiple signal handlers were modified.
> 
> The fix also adds a check for VMError::crash_handler_adress() to check_signal_handler() to prevent it from being treated as a signal handler modification.
> 
> The fix was tested with Mach5 tiers 1-2 on Linux and Mac OS and Mach 5 tiers 3-5 on Linux x64.  The regression test is excluded on Windows.
> 
> Thanks, Harold

Looking at [JDK-4229104](https://bugs.openjdk.org/browse/JDK-4229104) I have to wonder whether our handling of `SIGPIPE` is still necessary? Even if so, the fact we always ignore it if we get it suggests we really don't care if someone else has installed a (temporary) handler for it, so perhaps we should not include it (or `SIGXFSZ`) in these checks?

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

PR: https://git.openjdk.org/jdk/pull/9631