[crac] RFR: RFC: -XX:CPUFeatures=0xnumber for CPU migration

[Jan Kratochvil]

Currently if you `-XX:CRaCCheckpointTo` on a better CPU and `-XX:CRaCRestoreFrom` on a worse CPU the restored OpenJDK will crash.

1. An obvious reason is that JIT-compiled code is using CPU features not implemented on the CPU where the image is restored.
2. A second reason is that glibc has a similar problem, its PLT entries point to CPU optimized functions also crashing on the worse CPU. https://sourceware.org/glibc/wiki/GNU_IFUNC

(1) could be solved somehow automatically by deoptimizing and re-JITing all the JIT code. But that would defeat the performance goal of restoring a ready image in the first place. Therefore there had to be implemented a new OpenJDK option:

> use -XX:CPUFeatures=0xnumber with -XX:CRaCCheckpointTo when you get an error during -XX:CRaCRestoreFrom on a different machine

It is intended to specify the lowest common denominator of all CPUs in a farm. Instead of a possible crash of OpenJDK it will now refuse to run:

> Error occurred during initialization of VM
> You have to specify -XX:CPUFeatures=0x421801fcfbd7 during -XX:CRaCCheckpointTo making of the checkpoint; specified -XX:CRaCRestoreFrom file contains CPU features 0x7fff9dfcfbf7; this machine's CPU features are 0x421801fcfbd7; missing features of this CPU are 0x3de79c000020 = 3dnowpref, adx, avx512f, avx512dq, avx512cd, avx512bw, avx512vl, sha, avx512_vpopcntdq, avx512_vpclmulqdq, avx512_vaes, avx512_vnni, clflushopt, clwb, avx512_vbmi2, avx512_vbmi

(2) has been implemented according to Anton Kozlov's idea that glibc can just reset its IFUNC PLT entries any time later (after restore), not just during the first initialization of glibc. That has currently a problem that it has turned out to be very invasive into private glibc structures. It could work somehow with glibc debuginfo (*-debuginfo.rpm or *-dbg.deb) installed but that has been considered as unacceptable requirement just to run CRaC. Therefore I have provided this proof of concept while I will propose such feature for glibc upstream where it is sure easily implementable.

If upstream glibc maintainers do not like the IFUNC reset idea then I do not think this hacky IFUNC reset patching many glibc internal data structures is a good way forward for a 3rd party implementation like CRaC/OpenJDK. In such case I believe one should switch to using GLIBC_TUNABLES environment variable, re-execing OpenJDK after converting the `-XX:CPUFeatures` OpenJDK format into glibc GLIBC_TUNABLES format. Unfortunately there is a precedent OpenJDK upstream has already rejected such re-exec idea in the past: https://github.com/openjdk/crac/pull/31#issuecomment-1275707621

That IMO does not preclude trying the same for this case.

- Debian 11 x86_64: It does not work, glibc is too different and inlined there.
- Debian 12 x86_64: It works even without libc6-dbg as its offsets are the default.
- Fedora 36 x86_64: It works as on Fedoras glibc debuginfo is embedded.

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Commit messages:
 - whitespaces
 - ifunc: Fix GDB parsing.
 - +ifunc comment
 - +linux_ifunc_fetch_offsets()
 - Remove a needless workaround.
 - Adjust version dependent #defines.
 - Fixes for debian12.
 - 89757be5: <no commit message found>
 - -deoptimization
 - +Freeze tasks
 - ... and 27 more: https://git.openjdk.org/crac/compare/65e0785e...328e6b5d

Changes: https://git.openjdk.org/crac/pull/41/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=41&range=00
  Stats: 1045 lines in 17 files changed: 1034 ins; 2 del; 9 mod
  Patch: https://git.openjdk.org/crac/pull/41.diff
  Fetch: git fetch https://git.openjdk.org/crac pull/41/head:pull/41

PR: https://git.openjdk.org/crac/pull/41