[libunwind] [Unwind][AArch64] Match sigreturn instructions in big endian (PR #167139)

[via cfe-commits]

https://github.com/hstk30 updated https://github.com/llvm/llvm-project/pull/167139

>From e139054b741d2b6b2e46fe33a9351a971707fe05 Mon Sep 17 00:00:00 2001
From: hstk30 <hanwei62 at huawei.com>
Date: Sat, 8 Nov 2025 21:21:09 +0800
Subject: [PATCH 1/2] [Unwind][AArch64] Match sigreturn instructions in big
 endian

---
 libunwind/src/UnwindCursor.hpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp
index 7ec5f9e91578a..9414fd8a81525 100644
--- a/libunwind/src/UnwindCursor.hpp
+++ b/libunwind/src/UnwindCursor.hpp
@@ -58,6 +58,14 @@
 #include "RWMutex.hpp"
 #include "Unwind-EHABI.h"
 
+#if defined(__AARCH64EB__)
+#define MOVZ_X8_8B 0x681180d2
+#define SVC_0 0x010000d4
+#else
+#define MOVZ_X8_8B 0xd2801168
+#define SVC_0 0xd4000001
+#endif
+
 #if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
 // Provide a definition for the DISPATCHER_CONTEXT struct for old (Win7 and
 // earlier) SDKs.
@@ -2827,7 +2835,7 @@ bool UnwindCursor<A, R>::setInfoForSigReturn(Registers_arm64 &) {
     return false;
   auto *instructions = reinterpret_cast<const uint32_t *>(pc);
   // Look for instructions: mov x8, #0x8b; svc #0x0
-  if (instructions[0] != 0xd2801168 || instructions[1] != 0xd4000001)
+  if (instructions[0] != MOVZ_X8_8B || instructions[1] != SVC_0)
     return false;
 
   _info = {};

>From b6fed5b7407dca8ef6ef7e959c120f68c9ab6169 Mon Sep 17 00:00:00 2001
From: hstk30 <hanwei62 at huawei.com>
Date: Mon, 10 Nov 2025 23:43:40 +0800
Subject: [PATCH 2/2] Add comment about instruction sequence

---
 libunwind/src/UnwindCursor.hpp | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp
index 9414fd8a81525..35a12d28e8f37 100644
--- a/libunwind/src/UnwindCursor.hpp
+++ b/libunwind/src/UnwindCursor.hpp
@@ -58,14 +58,6 @@
 #include "RWMutex.hpp"
 #include "Unwind-EHABI.h"
 
-#if defined(__AARCH64EB__)
-#define MOVZ_X8_8B 0x681180d2
-#define SVC_0 0x010000d4
-#else
-#define MOVZ_X8_8B 0xd2801168
-#define SVC_0 0xd4000001
-#endif
-
 #if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
 // Provide a definition for the DISPATCHER_CONTEXT struct for old (Win7 and
 // earlier) SDKs.
@@ -2811,6 +2803,21 @@ void UnwindCursor<A, R>::setInfoBasedOnIPRegister(bool isReturnAddress) {
 
 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) &&                               \
     defined(_LIBUNWIND_TARGET_AARCH64)
+
+/*
+ * The linux sigreturn restorer stub will always have the form:
+ *
+ *  d2801168        movz    x8, #0x8b
+ *  d4000001        svc     #0x0
+ */
+#if defined(__AARCH64EB__)
+#define MOVZ_X8_8B 0x681180d2
+#define SVC_0 0x010000d4
+#else
+#define MOVZ_X8_8B 0xd2801168
+#define SVC_0 0xd4000001
+#endif
+
 template <typename A, typename R>
 bool UnwindCursor<A, R>::setInfoForSigReturn(Registers_arm64 &) {
   // Look for the sigreturn trampoline. The trampoline's body is two