Sun Bug ID 1251858 (on http://sunsolve1.sun.com) discusses the way that

Sun implemented iBCS2 compatibility on Solaris >= 2.6:  The emulator
runs in user-mode, patching the LDT so that client programs making
syscalls through the old iBCS2 call gate get handled by the emulator
process.  Unemulated syscalls therefore need their own call-gate that
bypasses the emulator.  Sun chose LDT entry 4 to implement this, which
is what we've been using as LUDATA_SEL, so we need to change LUDATA_SEL
if we want to run Solaris executables.

Discussed with: Mike Smith

sys/amd64/amd64/machdep.c

@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)machdep.c	7.4 (Berkeley) 6/3/91
- *	$Id: machdep.c,v 1.321 1999/01/09 15:41:49 bde Exp $
+ *	$Id: machdep.c,v 1.322 1999/01/15 17:24:05 msmith Exp $
  */
 
 #include "apm.h"
@@ -1069,6 +1069,15 @@ static struct soft_segment_descriptor ldt_segs[] = {
 	0, 0,
 	1,			/* default 32 vs 16 bit size */
 	1  			/* limit granularity (byte/page units)*/ },
+	/* Null Descriptor - overwritten by call gate */
+{	0x0,			/* segment base address  */
+	0x0,			/* length - all address space */
+	0,			/* segment type */
+	0,			/* segment descriptor priority level */
+	0,			/* segment descriptor present */
+	0, 0,
+	0,			/* default 32 vs 16 bit size */
+	0  			/* limit granularity (byte/page units)*/ },
 	/* Data Descriptor for user */
 {	0x0,			/* segment base address  */
 	0xfffff,		/* length - all address space */
@@ -1587,6 +1596,7 @@ init386(first)
 
 	/* XXX does this work? */
 	ldt[LBSDICALLS_SEL] = ldt[LSYS5CALLS_SEL];
+	ldt[LSOL26CALLS_SEL] = ldt[LSYS5CALLS_SEL];
 
 	/* transfer to user mode */
 

sys/amd64/include/segments.h

@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)segments.h	7.1 (Berkeley) 5/9/91
- *	$Id: segments.h,v 1.16 1997/08/18 06:58:31 charnier Exp $
+ *	$Id: segments.h,v 1.17 1997/08/21 06:32:49 charnier Exp $
  */
 
 #ifndef _MACHINE_SEGMENTS_H_
@@ -229,7 +229,8 @@ struct region_descriptor {
 #define	LSYS5SIGR_SEL	1
 #define	L43BSDCALLS_SEL	2	/* notyet */
 #define	LUCODE_SEL	3
-#define	LUDATA_SEL	4
+#define LSOL26CALLS_SEL	4	/* Solaris >= 2.6 system call gate */
+#define	LUDATA_SEL	5
 /* separate stack, es,fs,gs sels ? */
 /* #define	LPOSIXCALLS_SEL	5*/	/* notyet */
 #define LBSDICALLS_SEL	16	/* BSDI system call gate */

sys/i386/i386/machdep.c

@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)machdep.c	7.4 (Berkeley) 6/3/91
- *	$Id: machdep.c,v 1.321 1999/01/09 15:41:49 bde Exp $
+ *	$Id: machdep.c,v 1.322 1999/01/15 17:24:05 msmith Exp $
  */
 
 #include "apm.h"
@@ -1069,6 +1069,15 @@ static struct soft_segment_descriptor ldt_segs[] = {
 	0, 0,
 	1,			/* default 32 vs 16 bit size */
 	1  			/* limit granularity (byte/page units)*/ },
+	/* Null Descriptor - overwritten by call gate */
+{	0x0,			/* segment base address  */
+	0x0,			/* length - all address space */
+	0,			/* segment type */
+	0,			/* segment descriptor priority level */
+	0,			/* segment descriptor present */
+	0, 0,
+	0,			/* default 32 vs 16 bit size */
+	0  			/* limit granularity (byte/page units)*/ },
 	/* Data Descriptor for user */
 {	0x0,			/* segment base address  */
 	0xfffff,		/* length - all address space */
@@ -1587,6 +1596,7 @@ init386(first)
 
 	/* XXX does this work? */
 	ldt[LBSDICALLS_SEL] = ldt[LSYS5CALLS_SEL];
+	ldt[LSOL26CALLS_SEL] = ldt[LSYS5CALLS_SEL];
 
 	/* transfer to user mode */
 

sys/i386/include/segments.h

@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)segments.h	7.1 (Berkeley) 5/9/91
- *	$Id: segments.h,v 1.16 1997/08/18 06:58:31 charnier Exp $
+ *	$Id: segments.h,v 1.17 1997/08/21 06:32:49 charnier Exp $
  */
 
 #ifndef _MACHINE_SEGMENTS_H_
@@ -229,7 +229,8 @@ struct region_descriptor {
 #define	LSYS5SIGR_SEL	1
 #define	L43BSDCALLS_SEL	2	/* notyet */
 #define	LUCODE_SEL	3
-#define	LUDATA_SEL	4
+#define LSOL26CALLS_SEL	4	/* Solaris >= 2.6 system call gate */
+#define	LUDATA_SEL	5
 /* separate stack, es,fs,gs sels ? */
 /* #define	LPOSIXCALLS_SEL	5*/	/* notyet */
 #define LBSDICALLS_SEL	16	/* BSDI system call gate */