Index: sys/amd64/amd64/db_trace.c
===================================================================
--- sys/amd64/amd64/db_trace.c
+++ sys/amd64/amd64/db_trace.c
@@ -52,6 +52,10 @@
 #include <ddb/db_sym.h>
 #include <ddb/db_variables.h>
 
+static db_varfcn_t db_cr0;
+static db_varfcn_t db_cr2;
+static db_varfcn_t db_cr3;
+static db_varfcn_t db_cr4;
 static db_varfcn_t db_dr0;
 static db_varfcn_t db_dr1;
 static db_varfcn_t db_dr2;
@@ -61,8 +65,10 @@
 static db_varfcn_t db_dr6;
 static db_varfcn_t db_dr7;
 static db_varfcn_t db_frame;
+static db_varfcn_t db_frame_seg;
 static db_varfcn_t db_rsp;
 static db_varfcn_t db_ss;
+static db_varfcn_t db_xcr;
 
 CTASSERT(sizeof(struct dbreg) == sizeof(((struct pcpu *)NULL)->pc_dbreg));
 
@@ -71,11 +77,11 @@
  */
 #define	DB_OFFSET(x)	(db_expr_t *)offsetof(struct trapframe, x)
 struct db_variable db_regs[] = {
-	{ "cs",		DB_OFFSET(tf_cs),	db_frame },
-	{ "ds",		DB_OFFSET(tf_ds),	db_frame },
-	{ "es",		DB_OFFSET(tf_es),	db_frame },
-	{ "fs",		DB_OFFSET(tf_fs),	db_frame },
-	{ "gs",		DB_OFFSET(tf_gs),	db_frame },
+	{ "cs",		DB_OFFSET(tf_cs),	db_frame_seg },
+	{ "ds",		DB_OFFSET(tf_ds),	db_frame_seg },
+	{ "es",		DB_OFFSET(tf_es),	db_frame_seg },
+	{ "fs",		DB_OFFSET(tf_fs),	db_frame_seg },
+	{ "gs",		DB_OFFSET(tf_gs),	db_frame_seg },
 	{ "ss",		NULL,			db_ss },
 	{ "rax",	DB_OFFSET(tf_rax),	db_frame },
 	{ "rcx",        DB_OFFSET(tf_rcx),	db_frame },
@@ -95,7 +101,11 @@
 	{ "r15",	DB_OFFSET(tf_r15),	db_frame },
 	{ "rip",	DB_OFFSET(tf_rip),	db_frame },
 	{ "rflags",	DB_OFFSET(tf_rflags),	db_frame },
-#define	DB_N_SHOW_REGS	24	/* Don't show registers after here. */
+	{ "cr0",	NULL,			db_cr0 },
+	{ "cr2",	NULL,			db_cr2 },
+	{ "cr3",	NULL,			db_cr3 },
+	{ "cr4",	NULL,			db_cr4 },
+	{ "xcr0",	0,			db_xcr },
 	{ "dr0",	NULL,			db_dr0 },
 	{ "dr1",	NULL,			db_dr1 },
 	{ "dr2",	NULL,			db_dr2 },
@@ -105,9 +115,9 @@
 	{ "dr6",	NULL,			db_dr6 },
 	{ "dr7",	NULL,			db_dr7 },
 };
-struct db_variable *db_eregs = db_regs + DB_N_SHOW_REGS;
+struct db_variable *db_eregs = db_regs + nitems(db_regs);
 
-#define DB_DRX_FUNC(reg)		\
+#define DB_RW_REG_FUNC(reg)		\
 static int				\
 db_ ## reg (vp, valuep, op)		\
 	struct db_variable *vp;		\
@@ -121,14 +131,32 @@
 	return (1);			\
 }
 
-DB_DRX_FUNC(dr0)
-DB_DRX_FUNC(dr1)
-DB_DRX_FUNC(dr2)
-DB_DRX_FUNC(dr3)
-DB_DRX_FUNC(dr4)
-DB_DRX_FUNC(dr5)
-DB_DRX_FUNC(dr6)
-DB_DRX_FUNC(dr7)
+#define DB_RO_REG_FUNC(reg)		\
+static int				\
+db_ ## reg (vp, valuep, op)		\
+	struct db_variable *vp;		\
+	db_expr_t * valuep;		\
+	int op;				\
+{					\
+	if (op == DB_VAR_GET) {		\
+		*valuep = r ## reg ();	\
+		return (1);		\
+	}				\
+	return (0);			\
+}
+
+DB_RW_REG_FUNC(cr0)
+DB_RO_REG_FUNC(cr2)
+DB_RW_REG_FUNC(cr3)
+DB_RW_REG_FUNC(cr4)
+DB_RW_REG_FUNC(dr0)
+DB_RW_REG_FUNC(dr1)
+DB_RW_REG_FUNC(dr2)
+DB_RW_REG_FUNC(dr3)
+DB_RW_REG_FUNC(dr4)
+DB_RW_REG_FUNC(dr5)
+DB_RW_REG_FUNC(dr6)
+DB_RW_REG_FUNC(dr7)
 
 static __inline long
 get_rsp(struct trapframe *tf)
@@ -138,6 +166,22 @@
 }
 
 static int
+db_frame_seg(struct db_variable *vp, db_expr_t *valuep, int op)
+{
+	uint16_t *reg;
+
+	if (kdb_frame == NULL)
+		return (0);
+
+	reg = (uint16_t *)((uintptr_t)kdb_frame + (db_expr_t)vp->valuep);
+	if (op == DB_VAR_GET)
+		*valuep = *reg;
+	else
+		*reg = *valuep;
+	return (1);
+}
+
+static int
 db_frame(struct db_variable *vp, db_expr_t *valuep, int op)
 {
 	long *reg;
@@ -181,6 +225,23 @@
 	return (1);
 }
 
+static int
+db_xcr(struct db_variable *vp, db_expr_t *valuep, int op)
+{
+	u_int reg;
+
+	reg = (db_expr_t)vp->valuep;
+	if (reg != 0)
+		return (0);
+	if ((rcr4() & CR4_XSAVE) == 0)
+		return (0);
+	if (op == DB_VAR_GET)
+		*valuep = rxcr(reg);
+	else
+		load_xcr(reg, *valuep);
+	return (1);
+}
+
 #define NORMAL		0
 #define	TRAP		1
 #define	INTERRUPT	2
Index: sys/ddb/db_print.c
===================================================================
--- sys/ddb/db_print.c
+++ sys/ddb/db_print.c
@@ -56,7 +56,8 @@
 	for (regp = db_regs; regp < db_eregs; regp++) {
 		if (!db_read_variable(regp, &value))
 			continue;
-		db_printf("%-12s%#10lr", regp->name, (unsigned long)value);
+		db_printf("%-12s%#*lr", regp->name,
+		    (int)(sizeof(unsigned long) * 2 + 2), (unsigned long)value);
 		db_find_xtrn_sym_and_offset((db_addr_t)value, &name, &offset);
 		if (name != NULL && offset <= (unsigned long)db_maxoff &&
 		    offset != value) {
Index: sys/i386/i386/db_trace.c
===================================================================
--- sys/i386/i386/db_trace.c
+++ sys/i386/i386/db_trace.c
@@ -48,6 +48,10 @@
 #include <ddb/db_sym.h>
 #include <ddb/db_variables.h>
 
+static db_varfcn_t db_cr0;
+static db_varfcn_t db_cr2;
+static db_varfcn_t db_cr3;
+static db_varfcn_t db_cr4;
 static db_varfcn_t db_dr0;
 static db_varfcn_t db_dr1;
 static db_varfcn_t db_dr2;
@@ -58,17 +62,21 @@
 static db_varfcn_t db_dr7;
 static db_varfcn_t db_esp;
 static db_varfcn_t db_frame;
+static db_varfcn_t db_frame_seg;
+static db_varfcn_t db_gs;
 static db_varfcn_t db_ss;
+static db_varfcn_t db_xcr;
 
 /*
  * Machine register set.
  */
 #define	DB_OFFSET(x)	(db_expr_t *)offsetof(struct trapframe, x)
 struct db_variable db_regs[] = {
-	{ "cs",		DB_OFFSET(tf_cs),	db_frame },
-	{ "ds",		DB_OFFSET(tf_ds),	db_frame },
-	{ "es",		DB_OFFSET(tf_es),	db_frame },
-	{ "fs",		DB_OFFSET(tf_fs),	db_frame },
+	{ "cs",		DB_OFFSET(tf_cs),	db_frame_seg },
+	{ "ds",		DB_OFFSET(tf_ds),	db_frame_seg },
+	{ "es",		DB_OFFSET(tf_es),	db_frame_seg },
+	{ "fs",		DB_OFFSET(tf_fs),	db_frame_seg },
+	{ "gs",		NULL,			db_gs },
 	{ "ss",		NULL,			db_ss },
 	{ "eax",	DB_OFFSET(tf_eax),	db_frame },
 	{ "ecx",	DB_OFFSET(tf_ecx),	db_frame },
@@ -80,7 +88,11 @@
 	{ "edi",	DB_OFFSET(tf_edi),	db_frame },
 	{ "eip",	DB_OFFSET(tf_eip),	db_frame },
 	{ "efl",	DB_OFFSET(tf_eflags),	db_frame },
-#define	DB_N_SHOW_REGS	15	/* Don't show registers after here. */
+	{ "cr0",	NULL,			db_cr0 },
+	{ "cr2",	NULL,			db_cr2 },
+	{ "cr3",	NULL,			db_cr3 },
+	{ "cr4",	NULL,			db_cr4 },
+	{ "xcr0",	0,			db_xcr },
 	{ "dr0",	NULL,			db_dr0 },
 	{ "dr1",	NULL,			db_dr1 },
 	{ "dr2",	NULL,			db_dr2 },
@@ -90,9 +102,9 @@
 	{ "dr6",	NULL,			db_dr6 },
 	{ "dr7",	NULL,			db_dr7 },
 };
-struct db_variable *db_eregs = db_regs + DB_N_SHOW_REGS;
+struct db_variable *db_eregs = db_regs + nitems(db_regs);
 
-#define DB_DRX_FUNC(reg)		\
+#define DB_RW_REG_FUNC(reg)		\
 static int				\
 db_ ## reg (vp, valuep, op)		\
 	struct db_variable *vp;		\
@@ -106,14 +118,33 @@
 	return (1);			\
 }
 
-DB_DRX_FUNC(dr0)
-DB_DRX_FUNC(dr1)
-DB_DRX_FUNC(dr2)
-DB_DRX_FUNC(dr3)
-DB_DRX_FUNC(dr4)
-DB_DRX_FUNC(dr5)
-DB_DRX_FUNC(dr6)
-DB_DRX_FUNC(dr7)
+#define DB_RO_REG_FUNC(reg)		\
+static int				\
+db_ ## reg (vp, valuep, op)		\
+	struct db_variable *vp;		\
+	db_expr_t * valuep;		\
+	int op;				\
+{					\
+	if (op == DB_VAR_GET) {		\
+		*valuep = r ## reg ();	\
+		return (1);		\
+	}				\
+	return (0);			\
+}
+
+DB_RW_REG_FUNC(cr0)
+DB_RO_REG_FUNC(cr2)
+DB_RW_REG_FUNC(cr3)
+DB_RW_REG_FUNC(cr4)
+DB_RW_REG_FUNC(dr0)
+DB_RW_REG_FUNC(dr1)
+DB_RW_REG_FUNC(dr2)
+DB_RW_REG_FUNC(dr3)
+DB_RW_REG_FUNC(dr4)
+DB_RW_REG_FUNC(dr5)
+DB_RW_REG_FUNC(dr6)
+DB_RW_REG_FUNC(dr7)
+DB_RW_REG_FUNC(gs)
 
 static __inline int
 get_esp(struct trapframe *tf)
@@ -139,6 +170,22 @@
 }
 
 static int
+db_frame_seg(struct db_variable *vp, db_expr_t *valuep, int op)
+{
+	uint16_t *reg;
+
+	if (kdb_frame == NULL)
+		return (0);
+
+	reg = (uint16_t *)((uintptr_t)kdb_frame + (db_expr_t)vp->valuep);
+	if (op == DB_VAR_GET)
+		*valuep = *reg;
+	else
+		*reg = *valuep;
+	return (1);
+}
+
+static int
 db_esp(struct db_variable *vp, db_expr_t *valuep, int op)
 {
 
@@ -166,6 +213,23 @@
 	return (1);
 }
 
+static int
+db_xcr(struct db_variable *vp, db_expr_t *valuep, int op)
+{
+	u_int reg;
+
+	reg = (db_expr_t)vp->valuep;
+	if (reg != 0)
+		return (0);
+	if ((rcr4() & CR4_XSAVE) == 0)
+		return (0);
+	if (op == DB_VAR_GET)
+		*valuep = rxcr(reg);
+	else
+		load_xcr(reg, *valuep);
+	return (1);
+}
+
 #define NORMAL		0
 #define	TRAP		1
 #define	INTERRUPT	2