Index: exceptions.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/exceptions.cc,v
retrieving revision 1.296
diff -u -p -u -p -r1.296 exceptions.cc
--- exceptions.cc	13 Jul 2006 08:33:34 -0000	1.296
+++ exceptions.cc	17 Jul 2006 22:31:11 -0000
@@ -526,12 +526,12 @@ _cygtls::handle_exceptions (EXCEPTION_RE
       break;
 
     case STATUS_ACCESS_VIOLATION:
-      switch (mmap_is_attached_or_noreserve_page (e->ExceptionInformation[1]))
+      switch (mmap_is_attached_or_noreserve ((void *)e->ExceptionInformation[1],
+					     1))
         {
-	case 2:		/* MAP_NORESERVE page, now commited. */
+	case MMAP_NORESERVE_COMMITED:
 	  return 0;
-	case 1:		/* MAP_NORESERVE page, commit failed, or
-			   access to mmap page beyond EOF. */
+	case MMAP_RAISE_SIGBUS:	/* commit failed for noreserve or beyond EOF. */
 	  si.si_signo = SIGBUS;
 	  si.si_code = BUS_OBJERR;
 	  break;
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 22:31:11 -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)
     {
@@ -259,6 +261,19 @@ fhandler_base::raw_read (void *ptr, size
 	      bytes_read = 0;
 	      break;
 	    }
+	  if (try_noreserve)
+	    {
+	      try_noreserve = 0;
+	      switch (mmap_is_attached_or_noreserve (ptr, len))
+		{
+		case MMAP_NORESERVE_COMMITED:
+		  goto retry;
+		case MMAP_RAISE_SIGBUS:
+		  raise(SIGBUS);
+		case MMAP_NONE:
+		  break;
+		}
+	    }
 	case ERROR_INVALID_FUNCTION:
 	case ERROR_INVALID_PARAMETER:
 	case ERROR_INVALID_HANDLE:
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 22:31:12 -0000
@@ -900,44 +900,59 @@ map::del_list (unsigned i)
 }
 
 /* This function is called from exception_handler when a segmentation
-   violation has happened.  We have two cases to check here.
+   violation has occurred.  It should also be called from all Cygwin
+   functions that want to support passing noreserve mmap page addresses
+   to Windows system calls.  In that case, 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.
    
-   First, is it an address within "attached" mmap pages (indicated by
-   the __PROT_ATTACH protection, see there)?  In this case the function
-   returns 1 and the exception_handler raises SIGBUS, as demanded by the
-   memory protection extension described in SUSv3 (see the mmap man
-   page).
-   
-   Second, check if the address is within "noreserve" mmap pages
-   (indicated by MAP_NORESERVE flag).  If so, the function calls
-   VirtualAlloc to commit the page and returns 2.  The exception handler
-   then just returns with 0 and the affected application retries the
-   failing memory access.  If VirtualAlloc fails, the function returns
-   1, so that the exception handler raises a SIGBUS, as described in the
-   MAP_NORESERVE man pages for Linux and Solaris.
-   
-   In any other case 0 is returned and a normal SIGSEGV is raised. */
-int
-mmap_is_attached_or_noreserve_page (ULONG_PTR addr)
+   Check if the address range is all within noreserve mmap regions.  If so,
+   call VirtualAlloc to commit the pages and return MMAP_NORESERVE_COMMITED
+   on success.  If the page has __PROT_ATTACH (SUSv3 memory protection
+   extension), or if VirutalAlloc fails, return MMAP_RAISE_SIGBUS.
+   Otherwise, return MMAP_NONE if the address range is not covered by an
+   attached or noreserve map.
+
+   On MAP_NORESERVE_COMMITED, the exeception handler should return 0 to
+   allow the application to retry the memory access, or the calling Cygwin
+   function should retry the Windows system call. */
+mmap_region_status
+mmap_is_attached_or_noreserve (void *addr, size_t len)
 {
-  list *map_list;
-  long record_idx;
-  caddr_t u_addr;
-  DWORD u_len;
-  DWORD pagesize = getsystempagesize ();
+  list *map_list = mmapped_areas.get_list_by_fd (-1);
 
-  addr = rounddown (addr, pagesize);
-  if (!(map_list = mmapped_areas.get_list_by_fd (-1)))
-    return 0;
-  if ((record_idx = map_list->search_record ((caddr_t)addr, pagesize,
-					     u_addr, u_len, -1)) < 0)
-    return 0;
-  if (map_list->get_record (record_idx)->attached ())
-    return 1;
-  if (!map_list->get_record (record_idx)->noreserve ())
-    return 0;
-  DWORD new_prot = map_list->get_record (record_idx)->gen_protect ();
-  return VirtualAlloc ((void *)addr, pagesize, MEM_COMMIT, new_prot) ? 2 : 1;
+  if (map_list == NULL)
+    return MMAP_NONE;
+
+  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 MMAP_NONE;
+
+      mmap_record *rec = map_list->get_record (record_idx);
+      if (rec->attached ())
+	return MMAP_RAISE_SIGBUS;
+      if (!rec->noreserve ())
+	return MMAP_NONE;
+
+      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)
+	return MMAP_RAISE_SIGBUS;
+
+      addr  = (char *)addr + commit_len;
+      len  -= commit_len;
+    }
+
+    return MMAP_NORESERVE_COMMITED;
 }
 
 static caddr_t
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 22:31:12 -0000
@@ -299,7 +299,13 @@ size_t getsystempagesize ();
 
 /* mmap functions. */
 void mmap_init ();
-int mmap_is_attached_or_noreserve_page (ULONG_PTR addr);
+enum mmap_region_status
+  {
+    MMAP_NONE,
+    MMAP_RAISE_SIGBUS,
+    MMAP_NORESERVE_COMMITED
+  };
+mmap_region_status mmap_is_attached_or_noreserve (void *addr, size_t len);
 
 int winprio_to_nice (DWORD) __attribute__ ((regparm (1)));
 DWORD nice_to_winprio (int &) __attribute__ ((regparm (1)));