[llvm-branch-commits] [libunwind] release/22.x: [libunwind] Fix building on OpenBSD / FreeBSD aarch64 (#188397) (PR #188580)

[via llvm-branch-commits]

https://github.com/dyung updated https://github.com/llvm/llvm-project/pull/188580

>From 4592b0b6388d105ea9b688759c1810ad519fded3 Mon Sep 17 00:00:00 2001
From: Brad Smith <brad at comstyle.com>
Date: Wed, 25 Mar 2026 15:39:08 -0400
Subject: [PATCH] [libunwind] Fix building on OpenBSD / FreeBSD aarch64
 (#188397)

Just checking for the header presence of sys/auxv.h breaks the
build on OpenBSD / FreeBSD. Make use of elf_aux_info().

(cherry picked from commit 588451c160c34b888ced1c3d9263d361df22f757)
---
 libunwind/CMakeLists.txt    | 10 ++++++++++
 libunwind/src/Registers.hpp | 17 +++++++++++++----
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/libunwind/CMakeLists.txt b/libunwind/CMakeLists.txt
index fbef71f3f7446..9679d2b684ff2 100644
--- a/libunwind/CMakeLists.txt
+++ b/libunwind/CMakeLists.txt
@@ -336,6 +336,16 @@ if (RUNTIMES_EXECUTE_ONLY_CODE)
   add_compile_definitions(_LIBUNWIND_EXECUTE_ONLY_CODE)
 endif()
 
+check_symbol_exists(getauxval "sys/auxv.h" HAVE_GETAUXVAL)
+if (HAVE_GETAUXVAL)
+  add_definitions(-D_LIBUNWIND_HAVE_GETAUXVAL)
+endif()
+
+check_symbol_exists(elf_aux_info "sys/auxv.h" HAVE_ELF_AUX_INFO)
+if (HAVE_ELF_AUX_INFO)
+  add_definitions(-D_LIBUNWIND_HAVE_ELF_AUX_INFO)
+endif()
+
 add_custom_target(unwind-test-depends
   COMMENT "Build dependencies required to run the libunwind test suite.")
 
diff --git a/libunwind/src/Registers.hpp b/libunwind/src/Registers.hpp
index 474b17461bf77..88c2d3b4e8c9b 100644
--- a/libunwind/src/Registers.hpp
+++ b/libunwind/src/Registers.hpp
@@ -20,9 +20,8 @@
 #include "libunwind_ext.h"
 #include "shadow_stack_unwind.h"
 
-#if __has_include(<sys/auxv.h>)
+#if defined(_LIBUNWIND_HAVE_GETAUXVAL) || defined(_LIBUNWIND_HAVE_ELF_AUX_INFO)
 #include <sys/auxv.h>
-#define HAVE_SYS_AUXV_H
 #endif
 
 namespace libunwind {
@@ -1941,15 +1940,25 @@ class _LIBUNWIND_HIDDEN Registers_arm64 {
       _LIBUNWIND_ABORT("SME ZA disable failed");
   }
 
+#if defined(_LIBUNWIND_HAVE_GETAUXVAL)
   static bool checkHasSME() {
-#if defined(HAVE_SYS_AUXV_H)
     constexpr int hwcap2_sme = (1 << 23);
     unsigned long hwcap2 = getauxval(AT_HWCAP2);
     return (hwcap2 & hwcap2_sme) != 0;
-#endif
+  }
+#elif defined(_LIBUNWIND_HAVE_ELF_AUX_INFO)
+  static bool checkHasSME() {
+    constexpr int hwcap2_sme = (1 << 23);
+    unsigned long hwcap2 = 0;
+    elf_aux_info(AT_HWCAP2, &hwcap2, sizeof(hwcap2));
+    return (hwcap2 & hwcap2_sme) != 0;
+  }
+#else
+  static bool checkHasSME() {
     // TODO: Support other platforms.
     return false;
   }
+#endif
 
   struct GPRs {
     uint64_t __x[29] = {};        // x0-x28