[PATCH] Cygwin: obtain stack pointer on AArch64

[Radek Barton]

Hello.

This patch ports stack pointer reading to AArch64 at fork.cc and cygtls.h.

Radek

---
>From cc920233d50fe38f22610cb51f219e3c9b566109 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.barton@microsoft.com>
Date: Fri, 6 Jun 2025 10:21:10 +0200
Subject: [PATCH] Cygwin: obtain stack pointer on AArch64
MIME-Version: 1.0
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Signed-off-by: Radek Bartoň <radek.barton@microsoft.com>
---
 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 31cadd51a..44bd44e72 100644
--- a/winsup/cygwin/local_includes/cygtls.h
+++ b/winsup/cygwin/local_includes/cygtls.h
@@ -325,7 +325,13 @@ 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))
   {
-- 
2.49.0.vfs.0.4

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