setting LDTs under FreeBSD

[Pierre Beyssac]

Hi all,

It seems the BSD part of ldt.c directly copies the LDT descriptor
provided by the Windows application, including the priority level.

The problem is that the application sometimes requests LDTs with a
priority of 2, whereas i386_set_ldt() will only let us set level 3
(user) LDTs, and will otherwise fail with EACCESS.

The equivalent Linux code seems to ignore priority, so I wrote the
following patch which fixes the problem by forcing user level on
all requested LDTs.

Pierre

--- ldt.c.orig	Thu Nov 23 16:16:52 2000
+++ ldt.c	Wed Aug  1 21:54:19 2001
@@ -133,7 +133,12 @@
 
 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__)
     {
-        ret = i386_set_ldt(index, (union descriptor *)entry, 1);
+	LDT_ENTRY entry_copy = *entry;
+	/* The kernel will only let us set LDTs with user priority level */
+	if (entry_copy.HighWord.Bits.Pres
+	    && entry_copy.HighWord.Bits.Dpl != 3)
+		entry_copy.HighWord.Bits.Dpl = 3;
+        ret = i386_set_ldt(index, (union descriptor *)&entry_copy, 1);
         if (ret < 0)
         {
             perror("i386_set_ldt");