[apple/xnu.git] / osfmk / i386 / user_ldt.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon 
 * the rights to redistribute these changes.
 */

/*
 */

/*
 * User LDT management.
 * Each thread in a task may have its own LDT.
 */

#include <kern/kalloc.h>
#include <kern/thread.h>
#include <kern/misc_protos.h>

#include <vm/vm_kern.h>

#include <i386/seg.h>
#include <i386/thread.h>
#include <i386/user_ldt.h>

char	acc_type[8][3] = {
    /*	code	stack	data */
    {	0,	0,	1	},	/* data */
    {	0,	1,	1	},	/* data, writable */
    {	0,	0,	1	},	/* data, expand-down */
    {	0,	1,	1	},	/* data, writable, expand-down */
    {	1,	0,	0	},	/* code */
    {	1,	0,	1	},	/* code, readable */
    {	1,	0,	0	},	/* code, conforming */
    {	1,	0,	1	},	/* code, readable, conforming */
};

extern struct fake_descriptor ldt[];	/* for system call gate */

#if 0
/* Forward */

extern boolean_t	selector_check(
				thread_t		thread,
				int			sel,
				int			type);

boolean_t
selector_check(
	thread_t		thread,
	int			sel,
	int			type)
{
	struct user_ldt	*ldt;
	int	access;

	ldt = thread->top_act->mact.pcb->ims.ldt;
	if (ldt == 0) {
	    switch (type) {
		case S_CODE:
		    return sel == USER_CS;
		case S_STACK:
		    return sel == USER_DS;
		case S_DATA:
		    return sel == 0 ||
			   sel == USER_CS ||
			   sel == USER_DS;
	    }
	}

	if (type != S_DATA && sel == 0)
	    return FALSE;
	if ((sel & (SEL_LDTS|SEL_PL)) != (SEL_LDTS|SEL_PL_U)
	  || sel > ldt->desc.limit_low)
		return FALSE;

	access = ldt->ldt[sel_idx(sel)].access;
	
	if ((access & (ACC_P|ACC_PL|ACC_TYPE_USER))
		!= (ACC_P|ACC_PL_U|ACC_TYPE_USER))
	    return FALSE;
		/* present, pl == pl.user, not system */

	return acc_type[(access & 0xe)>>1][type];
}

/*
 * Add the descriptors to the LDT, starting with
 * the descriptor for 'first_selector'.
 */

kern_return_t
i386_set_ldt(
	thread_act_t		thr_act,
	int			first_selector,
	descriptor_list_t	desc_list,
	mach_msg_type_number_t	count)
{
	user_ldt_t	new_ldt, old_ldt, temp;
	struct real_descriptor *dp;
	int		i;
	int		min_selector = 0;
	pcb_t		pcb;
	vm_size_t	ldt_size_needed;
	int		first_desc = sel_idx(first_selector);
	vm_map_copy_t	old_copy_object;
	thread_t		thread;

	if (first_desc < min_selector || first_desc > 8191)
	    return KERN_INVALID_ARGUMENT;
	if (first_desc + count >= 8192)
	    return KERN_INVALID_ARGUMENT;
	if (thr_act == THR_ACT_NULL)
	    return KERN_INVALID_ARGUMENT;
	if ((thread = act_lock_thread(thr_act)) == THREAD_NULL) {
		act_unlock_thread(thr_act);
	    return KERN_INVALID_ARGUMENT;
	}
	if (thread == current_thread())
		min_selector = LDTSZ;
	act_unlock_thread(thr_act);

	/*
	 * We must copy out desc_list to the kernel map, and wire
	 * it down (we touch it while the PCB is locked).
	 *
	 * We make a copy of the copyin object, and clear
	 * out the old one, so that the MIG stub will have a
	 * a empty (but valid) copyin object to discard.
	 */
	{
	    kern_return_t	kr;
	    vm_offset_t		dst_addr;

	    old_copy_object = (vm_map_copy_t) desc_list;

	    kr = vm_map_copyout(ipc_kernel_map, &dst_addr,
				vm_map_copy_copy(old_copy_object));
	    if (kr != KERN_SUCCESS)
		return kr;

	    (void) vm_map_wire(ipc_kernel_map,
			trunc_page(dst_addr),
			round_page(dst_addr + 
				count * sizeof(struct real_descriptor)),
			VM_PROT_READ|VM_PROT_WRITE, FALSE);
	    desc_list = (descriptor_list_t) dst_addr;
	}

	for (i = 0, dp = (struct real_descriptor *) desc_list;
	     i < count;
	     i++, dp++)
	{
	    switch (dp->access & ~ACC_A) {
		case 0:
		case ACC_P:
		    /* valid empty descriptor */
		    break;
		case ACC_P | ACC_CALL_GATE:
		    /* Mach kernel call */
		    *dp = *(struct real_descriptor *)
				&ldt[sel_idx(USER_SCALL)];
		    break;
		case ACC_P | ACC_PL_U | ACC_DATA:
		case ACC_P | ACC_PL_U | ACC_DATA_W:
		case ACC_P | ACC_PL_U | ACC_DATA_E:
		case ACC_P | ACC_PL_U | ACC_DATA_EW:
		case ACC_P | ACC_PL_U | ACC_CODE:
		case ACC_P | ACC_PL_U | ACC_CODE_R:
		case ACC_P | ACC_PL_U | ACC_CODE_C:
		case ACC_P | ACC_PL_U | ACC_CODE_CR:
		case ACC_P | ACC_PL_U | ACC_CALL_GATE_16:
		case ACC_P | ACC_PL_U | ACC_CALL_GATE:
		    break;
		default:
		    (void) vm_map_remove(ipc_kernel_map, 
					 (vm_offset_t) desc_list,
					 count * sizeof(struct real_descriptor),
					 VM_MAP_REMOVE_KUNWIRE);
		    return KERN_INVALID_ARGUMENT;
	    }
	}
	ldt_size_needed = sizeof(struct real_descriptor)
			* (first_desc + count);

	pcb = thr_act->mact.pcb;
	new_ldt = 0;
    Retry:
	simple_lock(&pcb->lock);
	old_ldt = pcb->ims.ldt;
	if (old_ldt == 0 ||
	    old_ldt->desc.limit_low + 1 < ldt_size_needed)
	{
	    /*
	     * No old LDT, or not big enough
	     */
	    if (new_ldt == 0) {
		simple_unlock(&pcb->lock);

		new_ldt = (user_ldt_t) kalloc(ldt_size_needed
					      + sizeof(struct real_descriptor));
		new_ldt->desc.limit_low   = ldt_size_needed - 1;
		new_ldt->desc.limit_high  = 0;
		new_ldt->desc.base_low    = 
				((vm_offset_t)&new_ldt->ldt[0]) & 0xffff;
		new_ldt->desc.base_med    = 
				(((vm_offset_t)&new_ldt->ldt[0]) >> 16)
						 & 0xff;
		new_ldt->desc.base_high   = 
				((vm_offset_t)&new_ldt->ldt[0]) >> 24;
		new_ldt->desc.access      = ACC_P | ACC_LDT;
		new_ldt->desc.granularity = 0;

		goto Retry;
	    }

	    /*
	     * Have new LDT.  If there was a an old ldt, copy descriptors
	     * from old to new.  Otherwise copy the default ldt.
	     */
	    if (old_ldt) {
		bcopy((char *)&old_ldt->ldt[0],
		      (char *)&new_ldt->ldt[0],
		      old_ldt->desc.limit_low + 1);
	    }
	    else if (thr_act == current_act()) {
		struct real_descriptor template = {0, 0, 0, ACC_P, 0, 0 ,0};

		for (dp = &new_ldt->ldt[0], i = 0; i < first_desc; i++, dp++) {
		    if (i < LDTSZ)
		    	*dp = *(struct real_descriptor *) &ldt[i];
		    else
			*dp = template;
		}
	    }

	    temp = old_ldt;
	    old_ldt = new_ldt;	/* use new LDT from now on */
	    new_ldt = temp;	/* discard old LDT */

	    pcb->ims.ldt = old_ldt;	/* new LDT for thread */
	}

	/*
	 * Install new descriptors.
	 */
	bcopy((char *)desc_list,
	      (char *)&old_ldt->ldt[first_desc],
	      count * sizeof(struct real_descriptor));

	simple_unlock(&pcb->lock);

	if (new_ldt)
	    kfree((vm_offset_t)new_ldt,
		  new_ldt->desc.limit_low+1+sizeof(struct real_descriptor));

	/*
	 * Free the descriptor list.
	 */
	(void) vm_map_remove(ipc_kernel_map, (vm_offset_t) desc_list,
			count * sizeof(struct real_descriptor),
			VM_MAP_REMOVE_KUNWIRE);
	return KERN_SUCCESS;
}

kern_return_t
i386_get_ldt(
	thread_act_t		thr_act,
	int			first_selector,
	int			selector_count,	/* number wanted */
	descriptor_list_t	*desc_list,	/* in/out */
	mach_msg_type_number_t	*count)		/* in/out */
{
	struct user_ldt *user_ldt;
	pcb_t		pcb = thr_act->mact.pcb;
	int		first_desc = sel_idx(first_selector);
	unsigned int	ldt_count;
	vm_size_t	ldt_size;
	vm_size_t	size, size_needed;
	vm_offset_t	addr;
	thread_t		thread;

	if (thr_act == THR_ACT_NULL || (thread = thr_act->thread)==THREAD_NULL)
	    return KERN_INVALID_ARGUMENT;

	if (first_desc < 0 || first_desc > 8191)
	    return KERN_INVALID_ARGUMENT;
	if (first_desc + selector_count >= 8192)
	    return KERN_INVALID_ARGUMENT;

	addr = 0;
	size = 0;

	for (;;) {
	    simple_lock(&pcb->lock);
	    user_ldt = pcb->ims.ldt;
	    if (user_ldt == 0) {
		simple_unlock(&pcb->lock);
		if (addr)
		    kmem_free(ipc_kernel_map, addr, size);
		*count = 0;
		return KERN_SUCCESS;
	    }

	    /*
	     * Find how many descriptors we should return.
	     */
	    ldt_count = (user_ldt->desc.limit_low + 1) /
			sizeof (struct real_descriptor);
	    ldt_count -= first_desc;
	    if (ldt_count > selector_count)
		ldt_count = selector_count;

	    ldt_size = ldt_count * sizeof(struct real_descriptor);

	    /*
	     * Do we have the memory we need?
	     */
	    if (ldt_count <= *count)
		break;		/* fits in-line */

	    size_needed = round_page(ldt_size);
	    if (size_needed <= size)
		break;

	    /*
	     * Unlock the pcb and allocate more memory
	     */
	    simple_unlock(&pcb->lock);

	    if (size != 0)
		kmem_free(ipc_kernel_map, addr, size);

	    size = size_needed;

	    if (kmem_alloc(ipc_kernel_map, &addr, size)
			!= KERN_SUCCESS)
		return KERN_RESOURCE_SHORTAGE;
	}

	/*
	 * copy out the descriptors
	 */
	bcopy((char *)&user_ldt->ldt[first_desc],
	      (char *)addr,
	      ldt_size);
	*count = ldt_count;
	simple_unlock(&pcb->lock);

	if (addr) {
	    vm_size_t		size_used, size_left;
	    vm_map_copy_t	memory;

	    /*
	     * Free any unused memory beyond the end of the last page used
	     */
	    size_used = round_page(ldt_size);
	    if (size_used != size)
		kmem_free(ipc_kernel_map,
			addr + size_used, size - size_used);

	    /*
	     * Zero the remainder of the page being returned.
	     */
	    size_left = size_used - ldt_size;
	    if (size_left > 0)
		bzero((char *)addr + ldt_size, size_left);

	    /*
	     * Unwire the memory and make it into copyin form.
	     */
	    (void) vm_map_unwire(ipc_kernel_map, trunc_page(addr),
				 round_page(addr + size_used), FALSE);
	    (void) vm_map_copyin(ipc_kernel_map, addr, size_used,
				TRUE, &memory);
	    *desc_list = (descriptor_list_t) memory;
	}

	return KERN_SUCCESS;
}

#endif 
void
user_ldt_free(
	user_ldt_t	user_ldt)
{
	kfree((vm_offset_t)user_ldt,
		user_ldt->desc.limit_low+1+sizeof(struct real_descriptor));
}
Commit	Line	Data
1c79356b A	1	/*
	2	* Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
	6	* The contents of this file constitute Original Code as defined in and
	7	* are subject to the Apple Public Source License Version 1.1 (the
	8	* "License"). You may not use this file except in compliance with the
	9	* License. Please obtain a copy of the License at
	10	* http://www.apple.com/publicsource and read it before using this file.
	11	*
	12	* This Original Code and all software distributed under the License are
	13	* distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
	14	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
	15	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
	16	* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
	17	* License for the specific language governing rights and limitations
	18	* under the License.
	19	*
	20	* @APPLE_LICENSE_HEADER_END@
	21	*/
	22	/*
	23	* @OSF_COPYRIGHT@
	24	*/
	25	/*
	26	* Mach Operating System
	27	* Copyright (c) 1991 Carnegie Mellon University
	28	* All Rights Reserved.
	29	*
	30	* Permission to use, copy, modify and distribute this software and its
	31	* documentation is hereby granted, provided that both the copyright
	32	* notice and this permission notice appear in all copies of the
	33	* software, derivative works or modified versions, and any portions
	34	* thereof, and that both notices appear in supporting documentation.
	35	*
	36	* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
	37	* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
	38	* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
	39	*
	40	* Carnegie Mellon requests users of this software to return to
	41	*
	42	* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
	43	* School of Computer Science
	44	* Carnegie Mellon University
	45	* Pittsburgh PA 15213-3890
	46	*
	47	* any improvements or extensions that they make and grant Carnegie Mellon
	48	* the rights to redistribute these changes.
	49	*/
	50
	51	/*
	52	*/
	53
	54	/*
	55	* User LDT management.
	56	* Each thread in a task may have its own LDT.
	57	*/
	58
	59	#include <kern/kalloc.h>
	60	#include <kern/thread.h>
	61	#include <kern/misc_protos.h>
	62
	63	#include <vm/vm_kern.h>
	64
65	#include <i386/seg.h>
66	#include <i386/thread.h>
67	#include <i386/user_ldt.h>
68
69	char acc_type[8][3] = {
70	/* code stack data */
71	{ 0, 0, 1 }, /* data */
72	{ 0, 1, 1 }, /* data, writable */
73	{ 0, 0, 1 }, /* data, expand-down */
74	{ 0, 1, 1 }, /* data, writable, expand-down */
75	{ 1, 0, 0 }, /* code */
76	{ 1, 0, 1 }, /* code, readable */
77	{ 1, 0, 0 }, /* code, conforming */
78	{ 1, 0, 1 }, /* code, readable, conforming */
79	};
80
81	extern struct fake_descriptor ldt[]; /* for system call gate */
82
83	#if 0
84	/* Forward */
85
86	extern boolean_t selector_check(
87	thread_t thread,
88	int sel,
89	int type);
90
91	boolean_t
92	selector_check(
93	thread_t thread,
94	int sel,
95	int type)
96	{
97	struct user_ldt *ldt;
98	int access;
99
100	ldt = thread->top_act->mact.pcb->ims.ldt;
101	if (ldt == 0) {
102	switch (type) {
103	case S_CODE:
104	return sel == USER_CS;
105	case S_STACK:
106	return sel == USER_DS;
107	case S_DATA:
108	return sel == 0 \|\|
109	sel == USER_CS \|\|
110	sel == USER_DS;
111	}
112	}
113
114	if (type != S_DATA && sel == 0)
115	return FALSE;
116	if ((sel & (SEL_LDTS\|SEL_PL)) != (SEL_LDTS\|SEL_PL_U)
117	\|\| sel > ldt->desc.limit_low)
118	return FALSE;
119
120	access = ldt->ldt[sel_idx(sel)].access;
121
122	if ((access & (ACC_P\|ACC_PL\|ACC_TYPE_USER))
123	!= (ACC_P\|ACC_PL_U\|ACC_TYPE_USER))
124	return FALSE;
125	/* present, pl == pl.user, not system */
126
127	return acc_type[(access & 0xe)>>1][type];
128	}
129
130	/*
131	* Add the descriptors to the LDT, starting with
132	* the descriptor for 'first_selector'.
133	*/
134
135	kern_return_t
136	i386_set_ldt(
137	thread_act_t thr_act,
138	int first_selector,
139	descriptor_list_t desc_list,
140	mach_msg_type_number_t count)
141	{
142	user_ldt_t new_ldt, old_ldt, temp;
143	struct real_descriptor *dp;
144	int i;
145	int min_selector = 0;
146	pcb_t pcb;
147	vm_size_t ldt_size_needed;
148	int first_desc = sel_idx(first_selector);
149	vm_map_copy_t old_copy_object;
150	thread_t thread;
151
152	if (first_desc < min_selector \|\| first_desc > 8191)
153	return KERN_INVALID_ARGUMENT;
154	if (first_desc + count >= 8192)
155	return KERN_INVALID_ARGUMENT;
156	if (thr_act == THR_ACT_NULL)
157	return KERN_INVALID_ARGUMENT;
158	if ((thread = act_lock_thread(thr_act)) == THREAD_NULL) {
159	act_unlock_thread(thr_act);
160	return KERN_INVALID_ARGUMENT;
161	}
162	if (thread == current_thread())
163	min_selector = LDTSZ;
164	act_unlock_thread(thr_act);
165
166	/*
167	* We must copy out desc_list to the kernel map, and wire
168	* it down (we touch it while the PCB is locked).
169	*
170	* We make a copy of the copyin object, and clear
171	* out the old one, so that the MIG stub will have a
172	* a empty (but valid) copyin object to discard.
173	*/
174	{
175	kern_return_t kr;
176	vm_offset_t dst_addr;
177
178	old_copy_object = (vm_map_copy_t) desc_list;
179
180	kr = vm_map_copyout(ipc_kernel_map, &dst_addr,
181	vm_map_copy_copy(old_copy_object));
182	if (kr != KERN_SUCCESS)
183	return kr;
184
185	(void) vm_map_wire(ipc_kernel_map,
186	trunc_page(dst_addr),
187	round_page(dst_addr +
188	count * sizeof(struct real_descriptor)),
189	VM_PROT_READ\|VM_PROT_WRITE, FALSE);
190	desc_list = (descriptor_list_t) dst_addr;
191	}
192
193	for (i = 0, dp = (struct real_descriptor *) desc_list;
194	i < count;
195	i++, dp++)
196	{
197	switch (dp->access & ~ACC_A) {
198	case 0:
199	case ACC_P:
200	/* valid empty descriptor */
201	break;
202	case ACC_P \| ACC_CALL_GATE:
203	/* Mach kernel call */
204	dp = (struct real_descriptor *)
205	&ldt[sel_idx(USER_SCALL)];
206	break;
207	case ACC_P \| ACC_PL_U \| ACC_DATA:
208	case ACC_P \| ACC_PL_U \| ACC_DATA_W:
209	case ACC_P \| ACC_PL_U \| ACC_DATA_E:
210	case ACC_P \| ACC_PL_U \| ACC_DATA_EW:
211	case ACC_P \| ACC_PL_U \| ACC_CODE:
212	case ACC_P \| ACC_PL_U \| ACC_CODE_R:
213	case ACC_P \| ACC_PL_U \| ACC_CODE_C:
214	case ACC_P \| ACC_PL_U \| ACC_CODE_CR:
215	case ACC_P \| ACC_PL_U \| ACC_CALL_GATE_16:
216	case ACC_P \| ACC_PL_U \| ACC_CALL_GATE:
217	break;
218	default:
219	(void) vm_map_remove(ipc_kernel_map,
220	(vm_offset_t) desc_list,
221	count * sizeof(struct real_descriptor),
222	VM_MAP_REMOVE_KUNWIRE);
223	return KERN_INVALID_ARGUMENT;
224	}
225	}
226	ldt_size_needed = sizeof(struct real_descriptor)
227	* (first_desc + count);
228
229	pcb = thr_act->mact.pcb;
230	new_ldt = 0;
231	Retry:
232	simple_lock(&pcb->lock);
233	old_ldt = pcb->ims.ldt;
234	if (old_ldt == 0 \|\|
235	old_ldt->desc.limit_low + 1 < ldt_size_needed)
236	{
237	/*
238	* No old LDT, or not big enough
239	*/
240	if (new_ldt == 0) {
241	simple_unlock(&pcb->lock);
242
243	new_ldt = (user_ldt_t) kalloc(ldt_size_needed
244	+ sizeof(struct real_descriptor));
245	new_ldt->desc.limit_low = ldt_size_needed - 1;
246	new_ldt->desc.limit_high = 0;
247	new_ldt->desc.base_low =
248	((vm_offset_t)&new_ldt->ldt[0]) & 0xffff;
249	new_ldt->desc.base_med =
250	(((vm_offset_t)&new_ldt->ldt[0]) >> 16)
251	& 0xff;
252	new_ldt->desc.base_high =
253	((vm_offset_t)&new_ldt->ldt[0]) >> 24;
254	new_ldt->desc.access = ACC_P \| ACC_LDT;
255	new_ldt->desc.granularity = 0;
256
257	goto Retry;
258	}
259
260	/*
261	* Have new LDT. If there was a an old ldt, copy descriptors
262	* from old to new. Otherwise copy the default ldt.
263	*/
264	if (old_ldt) {
265	bcopy((char *)&old_ldt->ldt[0],
266	(char *)&new_ldt->ldt[0],
267	old_ldt->desc.limit_low + 1);
268	}
269	else if (thr_act == current_act()) {
270	struct real_descriptor template = {0, 0, 0, ACC_P, 0, 0 ,0};
271
272	for (dp = &new_ldt->ldt[0], i = 0; i < first_desc; i++, dp++) {
273	if (i < LDTSZ)
274	dp = (struct real_descriptor *) &ldt[i];
275	else
276	*dp = template;
277	}
278	}
279
280	temp = old_ldt;
281	old_ldt = new_ldt; /* use new LDT from now on */
282	new_ldt = temp; /* discard old LDT */
283
284	pcb->ims.ldt = old_ldt; /* new LDT for thread */
285	}
286
287	/*
288	* Install new descriptors.
289	*/
290	bcopy((char *)desc_list,
291	(char *)&old_ldt->ldt[first_desc],
292	count * sizeof(struct real_descriptor));
293
294	simple_unlock(&pcb->lock);
295
296	if (new_ldt)
297	kfree((vm_offset_t)new_ldt,
298	new_ldt->desc.limit_low+1+sizeof(struct real_descriptor));
299
300	/*
301	* Free the descriptor list.
302	*/
303	(void) vm_map_remove(ipc_kernel_map, (vm_offset_t) desc_list,
304	count * sizeof(struct real_descriptor),
305	VM_MAP_REMOVE_KUNWIRE);
306	return KERN_SUCCESS;
307	}
308
309	kern_return_t
310	i386_get_ldt(
311	thread_act_t thr_act,
312	int first_selector,
313	int selector_count, /* number wanted */
314	descriptor_list_t desc_list, / in/out */
315	mach_msg_type_number_t count) / in/out */
316	{
317	struct user_ldt *user_ldt;
318	pcb_t pcb = thr_act->mact.pcb;
319	int first_desc = sel_idx(first_selector);
320	unsigned int ldt_count;
321	vm_size_t ldt_size;
322	vm_size_t size, size_needed;
323	vm_offset_t addr;
324	thread_t thread;
325
326	if (thr_act == THR_ACT_NULL \|\| (thread = thr_act->thread)==THREAD_NULL)
327	return KERN_INVALID_ARGUMENT;
328
329	if (first_desc < 0 \|\| first_desc > 8191)
330	return KERN_INVALID_ARGUMENT;
331	if (first_desc + selector_count >= 8192)
332	return KERN_INVALID_ARGUMENT;
333
334	addr = 0;
335	size = 0;
336
337	for (;;) {
338	simple_lock(&pcb->lock);
339	user_ldt = pcb->ims.ldt;
340	if (user_ldt == 0) {
341	simple_unlock(&pcb->lock);
342	if (addr)
343	kmem_free(ipc_kernel_map, addr, size);
344	*count = 0;
345	return KERN_SUCCESS;
346	}
347
348	/*
349	* Find how many descriptors we should return.
350	*/
351	ldt_count = (user_ldt->desc.limit_low + 1) /
352	sizeof (struct real_descriptor);
353	ldt_count -= first_desc;
354	if (ldt_count > selector_count)
355	ldt_count = selector_count;
356
357	ldt_size = ldt_count * sizeof(struct real_descriptor);
358
359	/*
360	* Do we have the memory we need?
361	*/
362	if (ldt_count <= *count)
363	break; /* fits in-line */
364
365	size_needed = round_page(ldt_size);
366	if (size_needed <= size)
367	break;
368
369	/*
370	* Unlock the pcb and allocate more memory
371	*/
372	simple_unlock(&pcb->lock);
373
374	if (size != 0)
375	kmem_free(ipc_kernel_map, addr, size);
376
377	size = size_needed;
378
379	if (kmem_alloc(ipc_kernel_map, &addr, size)
380	!= KERN_SUCCESS)
381	return KERN_RESOURCE_SHORTAGE;
382	}
383
384	/*
385	* copy out the descriptors
386	*/
387	bcopy((char *)&user_ldt->ldt[first_desc],
388	(char *)addr,
389	ldt_size);
390	*count = ldt_count;
391	simple_unlock(&pcb->lock);
392
393	if (addr) {
394	vm_size_t size_used, size_left;
395	vm_map_copy_t memory;
396
397	/*
398	* Free any unused memory beyond the end of the last page used
399	*/
400	size_used = round_page(ldt_size);
401	if (size_used != size)
402	kmem_free(ipc_kernel_map,
403	addr + size_used, size - size_used);
404
405	/*
406	* Zero the remainder of the page being returned.
407	*/
408	size_left = size_used - ldt_size;
409	if (size_left > 0)
410	bzero((char *)addr + ldt_size, size_left);
411
412	/*
413	* Unwire the memory and make it into copyin form.
414	*/
415	(void) vm_map_unwire(ipc_kernel_map, trunc_page(addr),
416	round_page(addr + size_used), FALSE);
417	(void) vm_map_copyin(ipc_kernel_map, addr, size_used,
418	TRUE, &memory);
419	*desc_list = (descriptor_list_t) memory;
420	}
421
422	return KERN_SUCCESS;
423	}
424
425	#endif
426	void
427	user_ldt_free(
428	user_ldt_t user_ldt)
429	{
430	kfree((vm_offset_t)user_ldt,
431	user_ldt->desc.limit_low+1+sizeof(struct real_descriptor));
432	}