[PATCH v3] Cygwin: stack base initialization for AArch64

[Radek Barton]

Hello

Finally we've managed to rule out that the regressions were actually introduced by https://sourceware.org/pipermail/cygwin-patches/2025q2/013832.html, Thiru will send the fix soon.

Radek

---
>From c33f2e1b0037f9e5a3dbae4a0c82070db851cb33 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.barton@microsoft.com>
Date: Thu, 5 Jun 2025 13:15:22 +0200
Subject: [PATCH v3] Cygwin: stack base initialization for AArch64
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Radek Bartoň <radek.barton@microsoft.com>
---
 winsup/cygwin/dcrt0.cc | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc
index f4c09befd..3dceae654 100644
--- a/winsup/cygwin/dcrt0.cc
+++ b/winsup/cygwin/dcrt0.cc
@@ -1030,14 +1030,20 @@ _dll_crt0 ()
 	  PVOID stackaddr = create_new_main_thread_stack (allocationbase);
 	  if (stackaddr)
 	    {
-#ifdef __x86_64__
 	      /* Set stack pointer to new address.  Set frame pointer to
 	         stack pointer and subtract 32 bytes for shadow space. */
+#if defined(__x86_64__)
 	      __asm__ ("\n\
 		       movq %[ADDR], %%rsp \n\
 		       movq  %%rsp, %%rbp  \n\
 		       subq  $32,%%rsp     \n"
 		       : : [ADDR] "r" (stackaddr));
+#elif defined(__aarch64__)
+	      __asm__ ("\n\
+		       mov fp, %[ADDR] \n\
+		       mov sp, fp      \n"
+		       : : [ADDR] "r" (stackaddr)
+		       : "memory");
 #else
 #error unimplemented for this target
 #endif
-- 
2.49.0.vfs.0.4
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