RFR: 8253795: Implementation of JEP 391: macOS/AArch64 Port [v2]

[Phil Race]

On Sun, 24 Jan 2021 15:32:59 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 two additional commits since the last revision:
> 
>  - Address feedback for signature generators
>  - Enable -Wformat-nonliteral back

Changes requested by prr (Reviewer).

src/java.desktop/share/native/libharfbuzz/hb-common.h line 113:

> 111: 
> 112: #define HB_TAG(c1,c2,c3,c4) ((hb_tag_t)((((uint32_t)(c1)&0xFF)<<24)|(((uint32_t)(c2)&0xFF)<<16)|(((uint32_t)(c3)&0xFF)<<8)|((uint32_t)(c4)&0xFF)))
> 113: #define HB_UNTAG(tag)   (char)(((tag)>>24)&0xFF), (char)(((tag)>>16)&0xFF), (char)(((tag)>>8)&0xFF), (char)((tag)&0xFF)

I need a robust explanation of these changes.
They are not mentioned, nor are they in upstream harfbuzz.
Likely these should be pushed to upstream first if there is a reason for them.

src/java.desktop/share/native/libharfbuzz/hb-coretext.cc line 193:

> 191:    * crbug.com/549610 */
> 192:   // 0x00070000 stands for "kCTVersionNumber10_10", see CoreText.h
> 193: #if TARGET_OS_OSX && MAC_OS_X_VERSION_MIN_REQUIRED < __MAC_10_10

I need a robust explanation of these changes.
They are not mentioned, nor are they in upstream harfbuzz.
Likely these should be pushed to upstream first if there is a reason for them.

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

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