Index: b/grub/asmstub.c
===================================================================
--- a/grub/asmstub.c
+++ b/grub/asmstub.c
@@ -42,6 +42,12 @@
 #include <sys/time.h>
 #include <termios.h>
 #include <signal.h>
+#include <sys/mman.h>
+
+#include <limits.h>
+#ifndef PAGESIZE
+#define PAGESIZE 4096
+#endif
 
 #ifdef __linux__
 # include <sys/ioctl.h>		/* ioctl */
@@ -148,6 +154,22 @@
   assert (grub_scratch_mem == 0);
   scratch = malloc (0x100000 + EXTENDED_MEMSIZE + 15);
   assert (scratch);
+
+  {
+    char *p;
+    int ret;
+
+    /* Align to a multiple of PAGESIZE, assumed to be a power of two. */
+    p = (char *) (((long) scratch) & ~(PAGESIZE - 1));
+
+    /* The simulated stack needs to be executable, since GCC uses stack
+     * trampolines to implement nested functions.
+     */
+    ret = mprotect (p, 0x100000 + EXTENDED_MEMSIZE + 15,
+		    PROT_READ | PROT_WRITE | PROT_EXEC);
+    assert (ret == 0);
+  }
+
   grub_scratch_mem = (char *) ((((int) scratch) >> 4) << 4);
 
   /* FIXME: simulate the memory holes using mprot, if available. */