RFR: 8234930: Use MAP_JIT when allocating pages for code cache on macOS [v6]

[Anton Kozlov]

On Wed, 2 Dec 2020 22:55:32 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> Do you think os::protect_memory(base, size, os::MEM_PROT_RWX) will work on all platforms?

It looks so. Not sure about AIX, it ends up with ::mprotect, at least theoretically should be fine. On Linux and macOS without hardening it should be also OK. Without this patch, we don't support macOS hardened mode at all. But I have some private hacks for CDS with hardening, they reuse some of windows code for reading the archive content instead of mapping, so the future looks even more convenient.

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PR: https://git.openjdk.java.net/jdk/pull/294