[src/trunk]: src/sys/kern don't use lwp_setprivate in fork, but copy the priv...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/53993fbca954
branches:  trunk
changeset: 768636:53993fbca954
user:      christos <christos%NetBSD.org@localhost>
date:      Tue Aug 23 13:01:25 2011 +0000

description:
don't use lwp_setprivate in fork, but copy the private lwp member directly
because userland might have messed with the TLS register without letting
the kernel know. This fixes fork() on amd64. Thanks chuq!

diffstat:

 sys/kern/kern_fork.c |  13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)

diffs (34 lines):

diff -r 7ffd480eb0c4 -r 53993fbca954 sys/kern/kern_fork.c
--- a/sys/kern/kern_fork.c      Tue Aug 23 12:55:50 2011 +0000
+++ b/sys/kern/kern_fork.c      Tue Aug 23 13:01:25 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_fork.c,v 1.184 2011/05/14 18:50:07 rmind Exp $    */
+/*     $NetBSD: kern_fork.c,v 1.185 2011/08/23 13:01:25 christos Exp $ */
 
 /*-
  * Copyright (c) 1999, 2001, 2004, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.184 2011/05/14 18:50:07 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.185 2011/08/23 13:01:25 christos Exp $");
 
 #include "opt_ktrace.h"
 
@@ -423,7 +423,14 @@
        lwp_create(l1, p2, uaddr, (flags & FORK_PPWAIT) ? LWP_VFORK : 0,
            stack, stacksize, (func != NULL) ? func : child_return, arg, &l2,
            l1->l_class);
-       lwp_setprivate(l2, l1->l_private);
+
+       /*
+        * Inherit l_private from the parent.
+        * Note that we cannot use lwp_setprivate() here since that
+        * also sets the CPU TLS register, which is incorrect if the
+        * process has changed that without letting the kernel know.
+        */
+       l2->l_private = l1->l_private;
 
        /*
         * If emulation has a process fork hook, call it now.