RFR: 8362169: Pointer passed to upcall may get wrong scope

[Maurizio Cimadamore]

On Mon, 14 Jul 2025 15:33:35 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> Issue copied from the JBS issue:
> 
> When an upcall stub accepts a by-value struct, and the struct is passed by the underlying ABI as a pointer to a temporary copy on the caller's stack (for instance on Windows when the struct doesn't fit into a single register), a scope is created for the duration of the upcall, to which the memory segment for this struct is attached.
> 
> However, if such a scope is created for the upcall, any other unrelated pointer argument will _also_ be attached to the same scope. This is incorrect, as unrelated pointer arguments should be attached to the global scope. The underlying issue is that, when deciding whether a particular argument needs to be attached to the scope, we check if _any_ of the argument needs to be attached to the created scope.
> 
> This PR fixes the issue by calling `boxAddress.needsScope()` in `BindingSpecializer::emitBoxAddress`, which checks only if that particular argument needs to be attached to the upcall scope.
> 
> I've also renamed the 'global' `needsScope` method, which checks whether _any_ of the arguments need a scope, to `anyArgNeedsScope` for clarity.
> 
> Testing: `jdk_foreign` test suite on Mac/Windows/Linux x64, and Mac/Linux aarch64

Looks good!

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

Marked as reviewed by mcimadamore (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26295#pullrequestreview-3026916106