mmap/mprotect reversal

gistfile1.txt

diff --git a/mono/mini/mini-exceptions.c b/mono/mini/mini-exceptions.c
index 6297bacf704..f78807139f0 100644
--- a/mono/mini/mini-exceptions.c
+++ b/mono/mini/mini-exceptions.c
@@ -2750,12 +2750,10 @@ mono_setup_altstack (MonoJitTlsData *tls)
 
        g_assert ((guint8*)&sa >= (guint8*)tls->stack_ovf_guard_base + tls->stack_ovf_guard_size);
 
-       if (mono_mprotect (tls->stack_ovf_guard_base, tls->stack_ovf_guard_size, MONO_MMAP_NONE)) {
-               /* mprotect can fail for the main thread stack */
-               gpointer gaddr = mono_valloc (tls->stack_ovf_guard_base, tls->stack_ovf_guard_size, MONO_MMAP_NONE|MONO_MMAP_PRIVATE|MONO_MMAP_ANON|MONO_MMAP_FIXED, MONO_MEM_ACCOUNT_EXCEPTIONS);
-               g_assert (gaddr == tls->stack_ovf_guard_base);
+       if (mono_valloc (tls->stack_ovf_guard_base, tls->stack_ovf_guard_size, MONO_MMAP_NONE | MONO_MMAP_PRIVATE | MONO_MMAP_ANON | MONO_MMAP_FIXED, MONO_MEM_ACCOUNT_EXCEPTIONS))
                tls->stack_ovf_valloced = TRUE;
-       }
+       else if (mono_mprotect (tls->stack_ovf_guard_base, tls->stack_ovf_guard_size, MONO_MMAP_NONE))
+               g_error ("Couldn't setup stack guard page");
 
        /* Setup an alternate signal stack */
        tls->signal_stack = mono_valloc (0, MONO_ARCH_SIGNAL_STACK_SIZE, MONO_MMAP_READ|MONO_MMAP_WRITE|MONO_MMAP_PRIVATE|MONO_MMAP_ANON, MONO_MEM_ACCOUNT_EXCEPTIONS);