svn commit: r319277 - in stable/11: lib/libc/sys sys/sys sys/vm

[Xin LI]

Author: delphij
Date: Wed May 31 05:10:03 2017
New Revision: 319277
URL: https://svnweb.freebsd.org/changeset/base/319277

Log:
  MFC r315272, r315370
  
  r315272:
  Implement INHERIT_ZERO for minherit(2).
  
  INHERIT_ZERO is an OpenBSD feature.
  
  When a page is marked as such, it would be zeroed
  upon fork().
  
  This would be used in new arc4random(3) functions.
  
  PR:	182610
  Reviewed by:	kib (earlier version)
  Differential Revision:	https://reviews.freebsd.org/D427
  
  r315370:
  The adj_free and max_free values of new_entry will be calculated and
  assigned by subsequent vm_map_entry_link(), therefore, remove the
  pointless copying.
  
  Submitted by:	alc

Modified:
  stable/11/lib/libc/sys/minherit.2
  stable/11/sys/sys/mman.h
  stable/11/sys/vm/vm.h
  stable/11/sys/vm/vm_map.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/lib/libc/sys/minherit.2
==============================================================================
--- stable/11/lib/libc/sys/minherit.2	Wed May 31 05:05:32 2017	(r319276)
+++ stable/11/lib/libc/sys/minherit.2	Wed May 31 05:10:03 2017	(r319277)
@@ -29,7 +29,7 @@
 .\"
 .\"	@(#)minherit.2	8.1 (Berkeley) 6/9/93
 .\"
-.Dd October 30, 2007
+.Dd March 15, 2017
 .Dt MINHERIT 2
 .Os
 .Sh NAME
@@ -91,6 +91,11 @@ it will no longer be shared in the parent
 after the parent forks and there is no way to get the previous
 shared-backing-store mapping without unmapping and remapping the address
 space in the parent.
+.It Dv INHERIT_ZERO
+This option causes the address space in question to be mapped as new
+anonymous pages,
+which would be initialized to all zero bytes,
+in the child process.
 .El
 .Sh RETURN VALUES
 .Rv -std minherit
@@ -130,6 +135,13 @@ system call first appeared in
 .Ox
 and then in
 .Fx 2.2 .
+.Pp
+The
+.Dv INHERIT_ZERO
+support first appeared in
+.Ox 5.6
+and then in
+.Fx 12.0 .
 .Sh BUGS
 Once you set inheritance to
 .Dv MAP_PRIVATE

Modified: stable/11/sys/sys/mman.h
==============================================================================
--- stable/11/sys/sys/mman.h	Wed May 31 05:05:32 2017	(r319276)
+++ stable/11/sys/sys/mman.h	Wed May 31 05:10:03 2017	(r319277)
@@ -43,6 +43,7 @@
 #define INHERIT_SHARE	0
 #define INHERIT_COPY	1
 #define INHERIT_NONE	2
+#define INHERIT_ZERO	3
 #endif
 
 /*

Modified: stable/11/sys/vm/vm.h
==============================================================================
--- stable/11/sys/vm/vm.h	Wed May 31 05:05:32 2017	(r319276)
+++ stable/11/sys/vm/vm.h	Wed May 31 05:10:03 2017	(r319277)
@@ -68,6 +68,7 @@ typedef char vm_inherit_t;	/* inheritance codes */
 #define	VM_INHERIT_SHARE	((vm_inherit_t) 0)
 #define	VM_INHERIT_COPY		((vm_inherit_t) 1)
 #define	VM_INHERIT_NONE		((vm_inherit_t) 2)
+#define	VM_INHERIT_ZERO		((vm_inherit_t) 3)
 #define	VM_INHERIT_DEFAULT	VM_INHERIT_COPY
 
 typedef u_char vm_prot_t;	/* protection codes */

Modified: stable/11/sys/vm/vm_map.c
==============================================================================
--- stable/11/sys/vm/vm_map.c	Wed May 31 05:05:32 2017	(r319276)
+++ stable/11/sys/vm/vm_map.c	Wed May 31 05:10:03 2017	(r319277)
@@ -2294,6 +2294,7 @@ vm_map_inherit(vm_map_t map, vm_offset_t start, vm_off
 	case VM_INHERIT_NONE:
 	case VM_INHERIT_COPY:
 	case VM_INHERIT_SHARE:
+	case VM_INHERIT_ZERO:
 		break;
 	default:
 		return (KERN_INVALID_ARGUMENT);
@@ -3451,6 +3452,34 @@ vmspace_fork(struct vmspace *vm1, vm_ooffset_t *fork_c
 			vmspace_map_entry_forked(vm1, vm2, new_entry);
 			vm_map_copy_entry(old_map, new_map, old_entry,
 			    new_entry, fork_charge);
+			break;
+
+		case VM_INHERIT_ZERO:
+			/*
+			 * Create a new anonymous mapping entry modelled from
+			 * the old one.
+			 */
+			new_entry = vm_map_entry_create(new_map);
+			memset(new_entry, 0, sizeof(*new_entry));
+
+			new_entry->start = old_entry->start;
+			new_entry->end = old_entry->end;
+			new_entry->avail_ssize = old_entry->avail_ssize;
+			new_entry->eflags = old_entry->eflags &
+			    ~(MAP_ENTRY_USER_WIRED | MAP_ENTRY_IN_TRANSITION |
+			    MAP_ENTRY_VN_WRITECNT);
+			new_entry->protection = old_entry->protection;
+			new_entry->max_protection = old_entry->max_protection;
+			new_entry->inheritance = VM_INHERIT_ZERO;
+
+			vm_map_entry_link(new_map, new_map->header.prev,
+			    new_entry);
+			vmspace_map_entry_forked(vm1, vm2, new_entry);
+
+			new_entry->cred = curthread->td_ucred;
+			crhold(new_entry->cred);
+			*fork_charge += (new_entry->end - new_entry->start);
+
 			break;
 		}
 		old_entry = old_entry->next;