RFR: 8336768: Allow captureCallState and critical linker options to be combined

[Maurizio Cimadamore]

On Fri, 22 Nov 2024 14:31:23 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> Allow `captureCallState` and `critical(true)` linker options to be combined. This allows passing a Java array to capture call state.
> 
> One caveat is that the linker expects the memory to be aligned, which means that at least an `int[]` has to be used (i.e. `byte[]` will no work).
> 
> This patch contains two implementations: one for the linkers that use `CallingSequenceBuilder`. That one is quite straight-forward, as we can just mimic what we already do for other memory segment arguments, but also for the capture state segment. i.e. split it into base and offset, and pass that down to our downcall stub. The stub will then add the offset and oop together, and pass use the resulting address to write to.
> 
> The other implementation is for the fallback linker. This handles the capture state a little differently, but essentially currently just passes the native address to the back end for the native code to write the captured state into. I've just added another heap base parameter for that capture state segment to the back end, which is then turned into a native address using JNI's `GetPrimitiveArrayCritical`, similarly to what we do for other heap segments.
> 
> Testing: `jdk_foreign` test suite.

src/java.base/share/classes/jdk/internal/foreign/abi/NativeEntryPoint.java line 91:

> 89:         int checkIdx = 1;
> 90:         if ((needsReturnBuffer && methodType.parameterType(checkIdx++) != long.class)
> 91:             || (savedValueMask != 0 &&

Maybe this routine is getting too complex and it would be better to split the checks (and add some comments) ? E.g. we need to check that if there's a return buffer, a certain low-level argument is `long` and, if there's need to capture state, we either have `long`, or an `Object,long` pair.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22327#discussion_r1861153265