Index: fhandler.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/fhandler.cc,v
retrieving revision 1.256
diff -u -p -u -p -r1.256 fhandler.cc
--- fhandler.cc	13 Jul 2006 20:56:24 -0000	1.256
+++ fhandler.cc	17 Jul 2006 17:02:10 -0000
@@ -223,8 +223,10 @@ fhandler_base::raw_read (void *ptr, size
 
   HANDLE h = NULL;	/* grumble */
   int prio = 0;		/* ditto */
+  int try_noreserve = 1;
   DWORD len = ulen;
 
+retry:
   ulen = (size_t) -1;
   if (read_state)
     {
@@ -259,8 +261,14 @@ fhandler_base::raw_read (void *ptr, size
 	      bytes_read = 0;
 	      break;
 	    }
-	case ERROR_INVALID_FUNCTION:
 	case ERROR_INVALID_PARAMETER:
+	  if (try_noreserve)
+	    {
+	      try_noreserve = 0;
+	      if (mmap_commit_noreserve_pages (ptr, len))
+		goto retry;
+	    }
+	case ERROR_INVALID_FUNCTION:
 	case ERROR_INVALID_HANDLE:
 	  if (pc.isdir ())
 	    {
Index: mmap.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/mmap.cc,v
retrieving revision 1.130
diff -u -p -u -p -r1.130 mmap.cc
--- mmap.cc	13 Jul 2006 10:29:21 -0000	1.130
+++ mmap.cc	17 Jul 2006 17:02:11 -0000
@@ -899,6 +899,58 @@ map::del_list (unsigned i)
     }
 }
 
+/* This function should be called by all Cygwin functions that want to
+   support passing noreserve mmap page addresses to Windows system calls.
+   It should be called only after a system call indicates that the
+   application buffer passed had an invalid virtual address to avoid
+   any performance impact in non-noreserve cases.
+   
+   Check if the address range is all within "noreserve" mmap regions.
+   If so, call VirtualAlloc to commit the pages and return 1 on success.
+   If VirtualAlloc fails, raise SIGBUS and return 0.  Also return 0 if
+   the address range was not covered by a noreserve map.
+
+   On success, the calling Cygwin function should retry the Windows system
+   call. */
+int
+mmap_commit_noreserve_pages (void *addr, size_t len)
+{
+  list *map_list = mmapped_areas.get_list_by_fd (-1);
+
+  if (map_list == NULL)
+    return 0;
+
+  while (len > 0) 
+    {
+      caddr_t u_addr;
+      DWORD u_len;
+      long record_idx = map_list->search_record ((caddr_t)addr, 1,
+						 u_addr, u_len, -1);
+      if (record_idx < 0)
+	return 0;
+
+      mmap_record *rec = map_list->get_record (record_idx);
+      if (!rec->noreserve ())
+	return 0;
+
+      size_t commit_len = u_len - ((char *)addr - u_addr);
+      if (commit_len > len)
+	commit_len = len;
+
+      if (VirtualAlloc (addr, commit_len, MEM_COMMIT, rec->gen_protect ())
+	  == NULL)
+      {
+	raise(SIGBUS);
+	return 0;
+      }
+
+      addr  = (char *)addr + commit_len;
+      len  -= commit_len;
+    }
+
+    return 1;
+}
+
 /* This function is called from exception_handler when a segmentation
    violation has happened.  We have two cases to check here.
    
Index: winsup.h
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/winsup.h,v
retrieving revision 1.189
diff -u -p -u -p -r1.189 winsup.h
--- winsup.h	13 Jul 2006 08:33:34 -0000	1.189
+++ winsup.h	17 Jul 2006 17:02:11 -0000
@@ -300,6 +300,7 @@ size_t getsystempagesize ();
 /* mmap functions. */
 void mmap_init ();
 int mmap_is_attached_or_noreserve_page (ULONG_PTR addr);
+int mmap_commit_noreserve_pages (void *addr, size_t len);
 
 int winprio_to_nice (DWORD) __attribute__ ((regparm (1)));
 DWORD nice_to_winprio (int &) __attribute__ ((regparm (1)));