vm_map_lookup: Add parameter for keeping map locked

This adds a parameter called keep_map_locked to vm_map_lookup()
that allows the function to return with the map locked.

This is to prepare for fixing a bug with gsync where the map
is locked twice by mistake.

Co-Authored-By: Sergey Bugaev <bugaevc@gmail.com>
Message-ID: <20240222082410.422869-3-damien@zamaudio.com>

5 files changed, 12 insertions, 9 deletions

diff --git a/i386/intel/read_fault.c b/i386/intel/read_fault.c
index 0b79e3d8..356145e1 100644
--- a/i386/intel/read_fault.c
+++ b/i386/intel/read_fault.c
@@ -61,7 +61,7 @@ intel_read_fault(
 	 *	Find the backing store object and offset into it
 	 *	to begin search.
 	 */
-	result = vm_map_lookup(&map, vaddr, VM_PROT_READ, &version,
+	result = vm_map_lookup(&map, vaddr, VM_PROT_READ, FALSE, &version,
 			&object, &offset, &prot, &wired);
 	if (result != KERN_SUCCESS)
 	    return (result);
@@ -133,7 +133,7 @@ intel_read_fault(
 	    vm_offset_t		retry_offset;
 	    vm_prot_t		retry_prot;
 
-	    result = vm_map_lookup(&map, vaddr, VM_PROT_READ, &version,
+	    result = vm_map_lookup(&map, vaddr, VM_PROT_READ, FALSE, &version,
 				&retry_object, &retry_offset, &retry_prot,
 				&wired);
 	    if (result != KERN_SUCCESS) {
diff --git a/kern/gsync.c b/kern/gsync.c
index e73a6cf0..19190349 100644
--- a/kern/gsync.c
+++ b/kern/gsync.c
@@ -134,7 +134,7 @@ probe_address (vm_map_t map, vm_offset_t addr,
   vm_prot_t rprot;
   boolean_t wired_p;
 
-  if (vm_map_lookup (&map, addr, prot, &ver,
+  if (vm_map_lookup (&map, addr, prot, FALSE, &ver,
       &vap->obj, &vap->off, &rprot, &wired_p) != KERN_SUCCESS)
     return (-1);
   else if ((rprot & prot) != prot)
diff --git a/vm/vm_fault.c b/vm/vm_fault.c
index c6e28004..d99425a3 100644
--- a/vm/vm_fault.c
+++ b/vm/vm_fault.c
@@ -1213,7 +1213,7 @@ kern_return_t vm_fault(
 	 *	it to begin the search.
 	 */
 
-	if ((kr = vm_map_lookup(&map, vaddr, fault_type, &version,
+	if ((kr = vm_map_lookup(&map, vaddr, fault_type, FALSE, &version,
 				&object, &offset,
 				&prot, &wired)) != KERN_SUCCESS) {
 		goto done;
@@ -1375,7 +1375,7 @@ kern_return_t vm_fault(
 		 *	take another fault.
 		 */
 		kr = vm_map_lookup(&map, vaddr,
-				   fault_type & ~VM_PROT_WRITE, &version,
+				   fault_type & ~VM_PROT_WRITE, FALSE, &version,
 				   &retry_object, &retry_offset, &retry_prot,
 				   &wired);
 
diff --git a/vm/vm_map.c b/vm/vm_map.c
index e454bb2a..c237afbe 100644
--- a/vm/vm_map.c
+++ b/vm/vm_map.c
@@ -4607,8 +4607,9 @@ vm_map_t vm_map_fork(vm_map_t old_map)
  *	In order to later verify this lookup, a "version"
  *	is returned.
  *
- *	The map should not be locked; it will not be
- *	locked on exit.  In order to guarantee the
+ *	The map should not be locked; it will be
+ *	unlocked on exit unless keep_map_locked is set and
+ *	the lookup succeeds.  In order to guarantee the
  *	existence of the returned object, it is returned
  *	locked.
  *
@@ -4621,6 +4622,7 @@ kern_return_t vm_map_lookup(
 	vm_map_t		*var_map,	/* IN/OUT */
 	vm_offset_t		vaddr,
 	vm_prot_t		fault_type,
+	boolean_t		keep_map_locked,
 
 	vm_map_version_t	*out_version,	/* OUT */
 	vm_object_t		*object,	/* OUT */
@@ -4642,7 +4644,8 @@ kern_return_t vm_map_lookup(
 
 #define	RETURN(why) \
 		{ \
-		vm_map_unlock_read(map); \
+		if (!(keep_map_locked && (why == KERN_SUCCESS))) \
+		  vm_map_unlock_read(map); \
 		return(why); \
 		}
 
diff --git a/vm/vm_map.h b/vm/vm_map.h
index a4949e4e..7e25d9f4 100644
--- a/vm/vm_map.h
+++ b/vm/vm_map.h
@@ -412,7 +412,7 @@ extern kern_return_t	vm_map_inherit(vm_map_t, vm_offset_t, vm_offset_t,
 				       vm_inherit_t);
 
 /* Look up an address */
-extern kern_return_t	vm_map_lookup(vm_map_t *, vm_offset_t, vm_prot_t,
+extern kern_return_t	vm_map_lookup(vm_map_t *, vm_offset_t, vm_prot_t, boolean_t,
 				      vm_map_version_t *, vm_object_t *,
 				      vm_offset_t *, vm_prot_t *, boolean_t *);
 /* Find a map entry */