RFR: 8253795: Implementation of JEP 391: macOS/AArch64 Port [v9]

[Bernhard Urban-Forster]

On Tue, 2 Feb 2021 18:23:04 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

>> Anton Kozlov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   support macos_aarch64 in hsdis
>
> src/hotspot/os/posix/signals_posix.cpp line 1297:
> 
>> 1295:   kern_return_t kr;
>> 1296:   kr = task_set_exception_ports(mach_task_self(),
>> 1297:                                 EXC_MASK_BAD_ACCESS | EXC_MASK_BAD_INSTRUCTION | EXC_MASK_ARITHMETIC,
> 
> Could someone elaborate on why we need to add `EXC_MASK_BAD_INSTRUCTION` to the mask here?

See comment above about `gdb`, the same applies to `lldb` today. The AArch64 backend uses `SIGILL` (~= `EXC_MASK_BAD_INSTRUCTION`) to initiate a deoptimization. Without this change you cannot continue debugging once you the debuggee receives `SIGILL`. This wasn't needed before as x86 doesn't use `SIGILL`.

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PR: https://git.openjdk.java.net/jdk/pull/2200