RFR: 8253795: Implementation of JEP 391: macOS/AArch64 Port [v10]

[Gerard Ziemski]

On Wed, 3 Feb 2021 20:01:15 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

>> Please review the implementation of JEP 391: macOS/AArch64 Port.
>> 
>> It's heavily based on existing ports to linux/aarch64, macos/x86_64, and windows/aarch64. 
>> 
>> Major changes are in:
>> * src/hotspot/cpu/aarch64: support of the new calling convention (subtasks JDK-8253817, JDK-8253818)
>> * src/hotspot/os_cpu/bsd_aarch64: copy of os_cpu/linux_aarch64 with necessary adjustments (JDK-8253819)
>> * src/hotspot/share, test/hotspot/gtest: support of write-xor-execute (W^X), required on macOS/AArch64 platform. It's implemented with pthread_jit_write_protect_np provided by Apple. The W^X mode is local to a thread, so W^X mode change relates to the java thread state change (for java threads). In most cases, JVM executes in write-only mode, except when calling a generated stub like SafeFetch, which requires a temporary switch to execute-only mode. The same execute-only mode is enabled when a java thread executes in java or native states. This approach of managing W^X mode turned out to be simple and efficient enough.
>> * src/jdk.hotspot.agent: serviceability agent implementation (JDK-8254941)
>
> Anton Kozlov has updated the pull request incrementally with six additional commits since the last revision:
> 
>  - Merge remote-tracking branch 'origin/jdk/jdk-macos' into jdk-macos
>  - Add comments to WX transitions
>    
>    + minor change of placements
>  - Use macro conditionals instead of empty functions
>  - Add W^X to tests
>  - Do not require known W^X state
>  - Revert w^x in gtests

src/hotspot/os_cpu/bsd_aarch64/os_bsd_aarch64.cpp line 291:

> 289:         bool is_unsafe_arraycopy = (thread->doing_unsafe_access() && UnsafeCopyMemory::contains_pc(pc));
> 290:         if ((nm != NULL && nm->has_unsafe_access()) || is_unsafe_arraycopy) {
> 291:           address next_pc = pc + NativeCall::instruction_size;

Replace

address next_pc = pc + NativeCall::instruction_size;

with

address next_pc = Assembler::locate_next_instruction(pc);

there is at least one other place that needs it.

src/hotspot/os_cpu/bsd_aarch64/os_bsd_aarch64.cpp line 322:

> 320: #ifdef __APPLE__
> 321:       } else if (sig == SIGFPE && info->si_code == FPE_NOOP) {
> 322:         Unimplemented();

Is there a follow up issue for this?

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