_set_tp.c revision 145571 
1/*-
2 * Copyright (c) 2004 Doug Rabson
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 *	$FreeBSD: head/lib/libc/i386/gen/_set_tp.c 145571 2005-04-26 20:46:11Z peter $
27 */
28
29#include <string.h>
30#include <stdint.h>
31#include <machine/segments.h>
32#include <machine/sysarch.h>
33
34void
35_set_tp(void *tp)
36{
37#ifndef COMPAT_32BIT
38	union descriptor ldt;
39	int error, sel;
40
41	error = i386_set_gsbase(tp);
42	if (error == 0)
43		return;
44	memset(&ldt, 0, sizeof(ldt));
45	ldt.sd.sd_lolimit = 0xffff;	/* 4G limit */
46	ldt.sd.sd_lobase = ((uintptr_t)tp) & 0xffffff;
47	ldt.sd.sd_type = SDT_MEMRWA;
48	ldt.sd.sd_dpl = SEL_UPL;
49	ldt.sd.sd_p = 1;		/* present */
50	ldt.sd.sd_hilimit = 0xf;	/* 4G limit */
51	ldt.sd.sd_def32 = 1;		/* 32 bit */
52	ldt.sd.sd_gran = 1;		/* limit in pages */
53	ldt.sd.sd_hibase = (((uintptr_t)tp) >> 24) & 0xff;
54	sel = i386_set_ldt(LDT_AUTO_ALLOC, &ldt, 1);
55	__asm __volatile("movl %0,%%gs" : : "rm" ((sel << 3) | 7));
56#else
57	i386_set_gsbase(tp);
58#endif
59}
60