kern/68017: fork with INHERIT_NONE miscounts VM map sizes

[Brian Fundakowski Feldman]

Please try this (admittedly untested) patch and see if it fixes the
problems you're having.  It should help clean up the rest of the
vmspace properties when forking as well, so if you were to uninherit
stack or data or text pages, they should no longer count against the
process's VM limits.

Index: vm_map.c
===================================================================
RCS file: /usr/ncvs/src/sys/vm/vm_map.c,v
retrieving revision 1.338
diff -u -r1.338 vm_map.c
--- vm_map.c	25 May 2004 18:28:52 -0000	1.338
+++ vm_map.c	23 Jun 2004 16:29:37 -0000
@@ -2342,12 +2342,44 @@
 }
 
 /*
+ * vmspace_map_entry_forked:
+ * Update the newly-forked vmspace each time a map entry is inherited
+ * or copied.  The values for vm_dsize and vm_tsize are approximate
+ * (and mostly-obsolete ideas in the face of mmap(2) et al.)
+ */
+static void
+vmspace_map_entry_forked(const struct vmspace *vm1, struct vmspace *vm2,
+    vm_map_entry_t entry)
+{
+	vm_size_t entrysize;
+	vm_offset_t newend;
+
+	entrysize = entry->end - entry->start;
+	vm2->vm_map.size += entrysize;
+	if (entry->eflags & (MAP_ENTRY_GROWS_DOWN | MAP_ENTRY_GROWS_UP)) {
+		vm2->vm_ssize += btoc(entrysize);
+	} else if (entry->start >= (vm_offset_t)vm1->vm_daddr &&
+	    entry->start < (vm_offset_t)vm1->vm_daddr + ctob(vm1->vm_dsize)) {
+		newend = min(entry->end,
+		    (vm_offset_t)vm1->vm_daddr + ctob(vm1->vm_dsize));
+		vm2->vm_dsize += btoc(newend - entry->start);
+	} else if (entry->start >= (vm_offset_t)vm1->vm_taddr &&
+	    entry->start < (vm_offset_t)vm1->vm_taddr + ctob(vm1->vm_tsize)) {
+		newend = min(entry->end,
+		    (vm_offset_t)vm1->vm_taddr + ctob(vm1->vm_tsize));
+		vm2->vm_tsize += btoc(newend - entry->start);
+	}
+}
+
+/*
  * vmspace_fork:
  * Create a new process vmspace structure and vm_map
  * based on those of an existing process.  The new map
  * is based on the old map, according to the inheritance
  * values on the regions in that map.
  *
+ * XXX It might be worth coalescing the entries added to the new vmspace.
+ *
  * The source map must not be locked.
  */
 struct vmspace *
@@ -2366,8 +2398,16 @@
 	old_map->infork = 1;
 
 	vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset);
-	bcopy(&vm1->vm_startcopy, &vm2->vm_startcopy,
-	    (caddr_t) &vm1->vm_endcopy - (caddr_t) &vm1->vm_startcopy);
+	/*
+	 * Using vm_{start,end}copy is invalid for more fields than
+	 * it is valid here.  For the most part, initialize size
+	 * fields to zero and update them as map entries are copied
+	 */
+	bzero(&vm2->vm_startcopy,
+	    (caddr_t)&vm2->vm_endcopy - (caddr_t)&vm2->vm_startcopy);
+	vm2->vm_taddr = vm1->vm_taddr;
+	vm2->vm_daddr = vm1->vm_daddr;
+	vm2->vm_maxsaddr = vm1->vm_maxsaddr;
 	new_map = &vm2->vm_map;	/* XXX */
 	new_map->timestamp = 1;
 
@@ -2431,6 +2471,7 @@
 			 */
 			vm_map_entry_link(new_map, new_map->header.prev,
 			    new_entry);
+			vmspace_map_entry_forked(vm1, vm2, new_entry);
 
 			/*
 			 * Update the physical map
@@ -2452,6 +2493,7 @@
 			new_entry->object.vm_object = NULL;
 			vm_map_entry_link(new_map, new_map->header.prev,
 			    new_entry);
+			vmspace_map_entry_forked(vm1, vm2, new_entry);
 			vm_map_copy_entry(old_map, new_map, old_entry,
 			    new_entry);
 			break;
@@ -2459,7 +2501,6 @@
 		old_entry = old_entry->next;
 	}
 
-	new_map->size = old_map->size;
 	old_map->infork = 0;
 	vm_map_unlock(old_map);
 

-- 
Brian Fundakowski Feldman                           \'[ FreeBSD ]''''''''''\
  <> green at FreeBSD.org                               \  The Power to Serve! \
 Opinions expressed are my own.                       \,,,,,,,,,,,,,,,,,,,,,,\