RFR: 8277204: Implement PAC-RET branch protection on Linux/AArch64 [v18]

[Alan Hayward]

On Mon, 7 Feb 2022 11:58:22 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> enter_nested() ?
>> enter_inner() ?
>
> Tell you what, first put a comment here that says when it should (and therefore, should not) be used. Once it's clear exactly what this is for, thinking of a name maight be easier.

How about extending the existing enter() function: 

// Enter a new stack frame for the current method.
// nested:     Indicates a frame has already been entered (and not left) for the current method. 
void MacroAssembler::enter(bool nested=false) {
   if (nested) strip()
   protect()
   stp()
   mov()
}

This would add an additional bool check for every call of enter() - that's at code generation time, so probably not an issue.

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PR: https://git.openjdk.java.net/jdk/pull/6334