Use hint-safe pointer authentication stripping in NativeAOT

[Copilot]

NativeAOT executed xpaci during arm64 GC stack walking, causing SIGILL on tvOS devices without pointer authentication. This ports CoreCLR’s hint-safe PacStripPtr implementation.

Changes

• Preserve the caller’s lr.
• Move the pointer through lr and execute xpaclri.
• Return the stripped pointer through x0.
• Apply the change to Unix and Windows arm64 assembly stubs.

mov lr, x0
xpaclri
mov x0, lr

Note

This description was generated by GitHub Copilot.

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[kotlarmilos]

/azp run runtime-extra-platforms

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jkotas]

cc @SwapnilGaikwad

[SwapnilGaikwad]

The fix LGTM!
It matches with the fix in asmhelpers.S/asm. Missed to update MiscStubsS/.asm‎

[SwapnilGaikwad]

Failure seem unrelated, no SIGILL or Illegal Instruction failures.

[Copilot]

Pull request overview

Updates NativeAOT’s ARM64 PacStripPtr helper to use the same hint-safe pointer-authentication stripping sequence used by CoreCLR, avoiding execution of xpaci x0 and instead using xpaclri while preserving the caller’s lr.

Changes:

• Replace the Unix ARM64 PacStripPtr leaf stub (xpaci x0; ret) with a nested prolog/epilog that saves fp/lr, routes the input pointer through lr, executes xpaclri, and returns the stripped pointer in x0.
• Apply the same change to the Windows ARM64 stub, encoding xpaclri as a raw instruction word (consistent with existing PAC instruction encoding patterns in that file).

Show a summary per file

File	Description
src/coreclr/nativeaot/Runtime/arm64/MiscStubs.S	Switches PacStripPtr to a CoreCLR-matching, hint-safe xpaclri sequence with proper lr preservation/unwind-friendly prolog/epilog.
src/coreclr/nativeaot/Runtime/arm64/MiscStubs.asm	Mirrors the same PacStripPtr update for Windows ARM64, using DCD 0xD50320FF for xpaclri.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 0

[kotlarmilos]

Failure seem unrelated, no SIGILL or Illegal Instruction failures.

Correct, no jobs reported SIGILL, EXC_BAD_INSTRUCTION, or signal 4.

[jkotas]

/ba-g infrastructure timeouts