NetBSD specific changes:

- NetBSD overcommits
- When mapping pages, use the maximum of the alignment requested and the
  compiled-in PAGE constant which might be greater than the current kernel
  pagesize, since we compile binaries with the maximum page size supported
  by the architecture (so that they work with all kernels).

src/pages.c

@@ -14,6 +14,9 @@
 #include <vm/vm_param.h>
 #endif
 #endif
+#ifdef __NetBSD__
+#include <sys/bitops.h>	/* ilog2 */
+#endif
 
 /******************************************************************************/
 /* Data. */
@@ -74,6 +77,18 @@ os_pages_map(void *addr, size_t size, size_t alignment, bool *commit) {
 	 * of existing mappings, and we only want to create new mappings.
 	 */
 	{
+#ifdef __NetBSD__
+		/*
+		 * On NetBSD PAGE for a platform is defined to the
+		 * maximum page size of all machine architectures
+		 * for that platform, so that we can use the same
+		 * binaries across all machine architectures.
+		 */
+		if (alignment > os_page || PAGE > os_page) {
+			unsigned int a = ilog2(MAX(alignment, PAGE));
+			mmap_flags |= MAP_ALIGNED(a);
+		}
+#endif
 		int prot = *commit ? PAGES_PROT_COMMIT : PAGES_PROT_DECOMMIT;
 
 		ret = mmap(addr, size, prot, mmap_flags, -1, 0);
@@ -622,6 +637,8 @@ pages_boot(void) {
 		mmap_flags |= MAP_NORESERVE;
 	}
 #  endif
+#elif defined(__NetBSD__)
+	os_overcommits = true;
 #else
 	os_overcommits = false;
 #endif