[newlib-cygwin] Cygwin: obtain stack pointer on AArch64

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=d8ba663f355e55c537761a626c88cefaf1f3bc8e

commit d8ba663f355e55c537761a626c88cefaf1f3bc8e
Author: Radek Bartoň <[email protected]>
Date:   Fri Jun 6 10:21:10 2025 +0200

    Cygwin: obtain stack pointer on AArch64
    
    Signed-off-by: Radek Bartoň <[email protected]>

Diff:
---
 winsup/cygwin/fork.cc                 | 4 +++-
 winsup/cygwin/local_includes/cygtls.h | 6 ++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/fork.cc b/winsup/cygwin/fork.cc
index f88acdbbf..4abc52598 100644
--- a/winsup/cygwin/fork.cc
+++ b/winsup/cygwin/fork.cc
@@ -660,8 +660,10 @@ dofork (void **proc, bool *with_forkables)
     ischild = !!setjmp (grouped.ch.jmp);
 
     volatile char * volatile stackp;
-#ifdef __x86_64__
+#if defined(__x86_64__)
     __asm__ volatile ("movq %%rsp,%0": "=r" (stackp));
+#elif defined(__aarch64__)
+    __asm__ volatile ("mov %0, sp" : "=r" (stackp));
 #else
 #error unimplemented for this target
 #endif
diff --git a/winsup/cygwin/local_includes/cygtls.h b/winsup/cygwin/local_includes/cygtls.h
index 615361d3f..29a539d83 100644
--- a/winsup/cygwin/local_includes/cygtls.h
+++ b/winsup/cygwin/local_includes/cygtls.h
@@ -322,7 +322,13 @@ public:
        address of the _except block to restore the context correctly.
        See comment preceeding myfault_altstack_handler in exception.cc. */
     ret = (DWORD64) _ret;
+#if defined(__x86_64__)
     __asm__ volatile ("movq %%rsp,%0": "=o" (frame));
+#elif defined(__aarch64__)
+    __asm__ volatile ("mov %0, sp" : "=r" (frame));
+#else
+#error unimplemented for this target
+#endif
   }
   ~san () __attribute__ ((always_inline))
   {