[PATCH] util/osdep: Avoid mprotect() RWX->NONE on Big Sur 11.2

[Roman Bolshakov]

There's a change in mprotect() behaviour [1] in the latest macOS on M1
and it's not yet clear if it's going to be fixed by Apple. For now we
can avoid unsupported mprotect() calls. QEMU and qtests work fine
without it.

1. https://gist.github.com/hikalium/75ae822466ee4da13cbbe486498a191f

Buglink: https://bugs.launchpad.net/qemu/+bug/1914849
Apple-Feedback: FB8994773
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 util/osdep.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/util/osdep.c b/util/osdep.c
index 66d01b9160..1edd7b1caf 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -111,6 +111,12 @@ int qemu_mprotect_none(void *addr, size_t size)
 #ifdef _WIN32
     return qemu_mprotect__osdep(addr, size, PAGE_NOACCESS);
 #else
+# if defined(__APPLE__) && defined(__arm64__)
+    if (__builtin_available(macOS 11.2, *)) {
+        /* mprotect() in macOS 11.2 can't switch RWX to NONE */
+        return 0;
+    }
+# endif
     return qemu_mprotect__osdep(addr, size, PROT_NONE);
 #endif
 }
-- 
2.30.0