WebSVN – HelenOS-historic – Diff – /kernel/trunk/genarch/src/mm/page_ht.c


/*
 * Copyright (C) 2006 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
/**
 * @file    page_ht.c
 * @brief   Virtual Address Translation (VAT) for global page hash table.
 */
 
#include <genarch/mm/page_ht.h>
#include <mm/page.h>
#include <arch/mm/page.h>
#include <mm/frame.h>
#include <mm/slab.h>
#include <mm/as.h>
#include <arch/mm/asid.h>
#include <arch/types.h>
#include <typedefs.h>
#include <arch/asm.h>
#include <synch/spinlock.h>
#include <arch.h>
#include <debug.h>
#include <memstr.h>
#include <adt/hash_table.h>
#include <align.h>
 
static index_t hash(__native key[]);
static bool compare(__native key[], count_t keys, link_t *item);
static void remove_callback(link_t *item);
 
static void ht_mapping_insert(as_t *as, __address page, __address frame, int flags);
static void ht_mapping_remove(as_t *as, __address page);
static pte_t *ht_mapping_find(as_t *as, __address page);
 
/**
 * This lock protects the page hash table. It must be acquired
 * after address space lock and after any address space area
 * locks.
 */
mutex_t page_ht_lock;
 
/**
 * Page hash table.
 * The page hash table may be accessed only when page_ht_lock is held.
 */
hash_table_t page_ht;
 
/** Hash table operations for page hash table. */
hash_table_operations_t ht_operations = {
    .hash = hash,
    .compare = compare,
    .remove_callback = remove_callback
};
 
/** Page mapping operations for page hash table architectures. */
page_mapping_operations_t ht_mapping_operations = {
    .mapping_insert = ht_mapping_insert,
    .mapping_remove = ht_mapping_remove,
    .mapping_find = ht_mapping_find
};
 
/** Compute page hash table index.
 *
 * @param key Array of two keys (i.e. page and address space).
 *
 * @return Index into page hash table.
 */
index_t hash(__native key[])
{
    as_t *as = (as_t *) key[KEY_AS];
    __address page = (__address) key[KEY_PAGE];
    index_t index;
   
    /*
     * Virtual page addresses have roughly the same probability
     * of occurring. Least significant bits of VPN compose the
     * hash index.
     */
    index = ((page >> PAGE_WIDTH) & (PAGE_HT_ENTRIES-1));
   
    /*
     * Address space structures are likely to be allocated from
     * similar addresses. Least significant bits compose the
     * hash index.
     */
    index |= ((__native) as) & (PAGE_HT_ENTRIES-1);
   
    return index;
}
 
/** Compare page hash table item with page and/or address space.
 *
 * @param key Array of one or two keys (i.e. page and/or address space).
 * @param keys Number of keys passed.
 * @param item Item to compare the keys with.
 *
 * @return true on match, false otherwise.
 */
bool compare(__native key[], count_t keys, link_t *item)
{
    pte_t *t;
 
    ASSERT(item);
    ASSERT((keys > 0) && (keys <= PAGE_HT_KEYS));
 
    /*
     * Convert item to PTE.
     */
    t = hash_table_get_instance(item, pte_t, link);
 
    if (keys == PAGE_HT_KEYS) {
        return (key[KEY_AS] == (__address) t->as) && (key[KEY_PAGE] == t->page);
    } else {
        return (key[KEY_AS] == (__address) t->as);
    }
}
 
/** Callback on page hash table item removal.
 *
 * @param item Page hash table item being removed.
 */
void remove_callback(link_t *item)
{
    pte_t *t;
 
    ASSERT(item);
 
    /*
     * Convert item to PTE.
     */
    t = hash_table_get_instance(item, pte_t, link);
 
    free(t);
}
 
/** Map page to frame using page hash table.
 *
 * Map virtual address page to physical address frame
 * using flags.
 *
 * The page table must be locked and interrupts must be disabled.
 *
 * @param as Address space to which page belongs.
 * @param page Virtual address of the page to be mapped.
 * @param frame Physical address of memory frame to which the mapping is done.
 * @param flags Flags to be used for mapping.
 */
void ht_mapping_insert(as_t *as, __address page, __address frame, int flags)
{
    pte_t *t;
    __native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
   
    if (!hash_table_find(&page_ht, key)) {
        t = (pte_t *) malloc(sizeof(pte_t), FRAME_ATOMIC);
        ASSERT(t != NULL);
 
        t->g = (flags & PAGE_GLOBAL) != 0;
        t->x = (flags & PAGE_EXEC) != 0;
        t->w = (flags & PAGE_WRITE) != 0;
        t->k = !(flags & PAGE_USER);
        t->c = (flags & PAGE_CACHEABLE) != 0;
        t->p = !(flags & PAGE_NOT_PRESENT);
 
        t->as = as;
        t->page = ALIGN_DOWN(page, PAGE_SIZE);
        t->frame = ALIGN_DOWN(frame, FRAME_SIZE);
 
        hash_table_insert(&page_ht, key, &t->link);
    }
}
 
/** Remove mapping of page from page hash table.
 *
 * Remove any mapping of page within address space as.
 * TLB shootdown should follow in order to make effects of
 * this call visible.
 *
 * The page table must be locked and interrupts must be disabled.
 *
 * @param as Address space to wich page belongs.
 * @param page Virtual address of the page to be demapped.
 */
void ht_mapping_remove(as_t *as, __address page)
{
    __native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
   
    /*
     * Note that removed PTE's will be freed
     * by remove_callback().
     */
    hash_table_remove(&page_ht, key, 2);
}
 
 
/** Find mapping for virtual page in page hash table.
 *
 * Find mapping for virtual page.
 *
 * The page table must be locked and interrupts must be disabled.
 *
 * @param as Address space to wich page belongs.
 * @param page Virtual page.
 *
 * @return NULL if there is no such mapping; requested mapping otherwise.
 */
pte_t *ht_mapping_find(as_t *as, __address page)
{
    link_t *hlp;
    pte_t *t = NULL;
    __native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
   
    hlp = hash_table_find(&page_ht, key);
    if (hlp)
        t = hash_table_get_instance(hlp, pte_t, link);
 
    return t;
}
 

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/genarch/src/mm/page_ht.c – Rev 1380 → 1424

Rev 1380		Rev 1424
1	/*	1	/*
2	* Copyright (C) 2006 Jakub Jermar	2	* Copyright (C) 2006 Jakub Jermar
3	* All rights reserved.	3	* All rights reserved.
4	*	4	*
5	* Redistribution and use in source and binary forms, with or without	5	* Redistribution and use in source and binary forms, with or without
6	* modification, are permitted provided that the following conditions	6	* modification, are permitted provided that the following conditions
7	* are met:	7	* are met:
8	*	8	*
9	* - Redistributions of source code must retain the above copyright	9	* - Redistributions of source code must retain the above copyright
10	* notice, this list of conditions and the following disclaimer.	10	* notice, this list of conditions and the following disclaimer.
11	* - Redistributions in binary form must reproduce the above copyright	11	* - Redistributions in binary form must reproduce the above copyright
12	* notice, this list of conditions and the following disclaimer in the	12	* notice, this list of conditions and the following disclaimer in the
13	* documentation and/or other materials provided with the distribution.	13	* documentation and/or other materials provided with the distribution.
14	* - The name of the author may not be used to endorse or promote products	14	* - The name of the author may not be used to endorse or promote products
15	* derived from this software without specific prior written permission.	15	* derived from this software without specific prior written permission.
16	*	16	*
17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR	17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES	18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.	19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,	20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT	21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,	22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY	23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT	24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF	25	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.	26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27	*/	27	*/
28		28
29	/**	29	/**
30	* @file page_ht.c	30	* @file page_ht.c
31	* @brief Virtual Address Translation (VAT) for global page hash table.	31	* @brief Virtual Address Translation (VAT) for global page hash table.
32	*/	32	*/
33		33
34	#include <genarch/mm/page_ht.h>	34	#include <genarch/mm/page_ht.h>
35	#include <mm/page.h>	35	#include <mm/page.h>
36	#include <arch/mm/page.h>	36	#include <arch/mm/page.h>
37	#include <mm/frame.h>	37	#include <mm/frame.h>
38	#include <mm/slab.h>	38	#include <mm/slab.h>
39	#include <mm/as.h>	39	#include <mm/as.h>
40	#include <arch/mm/asid.h>	40	#include <arch/mm/asid.h>
41	#include <arch/types.h>	41	#include <arch/types.h>
42	#include <typedefs.h>	42	#include <typedefs.h>
43	#include <arch/asm.h>	43	#include <arch/asm.h>
44	#include <synch/spinlock.h>	44	#include <synch/spinlock.h>
45	#include <arch.h>	45	#include <arch.h>
46	#include <debug.h>	46	#include <debug.h>
47	#include <memstr.h>	47	#include <memstr.h>
48	#include <adt/hash_table.h>	48	#include <adt/hash_table.h>
49	#include <align.h>	49	#include <align.h>
50		50
51	static index_t hash(__native key[]);	51	static index_t hash(__native key[]);
52	static bool compare(__native key[], count_t keys, link_t *item);	52	static bool compare(__native key[], count_t keys, link_t *item);
53	static void remove_callback(link_t *item);	53	static void remove_callback(link_t *item);
54		54
55	static void ht_mapping_insert(as_t *as, __address page, __address frame, int flags);	55	static void ht_mapping_insert(as_t *as, __address page, __address frame, int flags);
56	static void ht_mapping_remove(as_t *as, __address page);	56	static void ht_mapping_remove(as_t *as, __address page);
57	static pte_t ht_mapping_find(as_t as, __address page);	57	static pte_t ht_mapping_find(as_t as, __address page);
58		58
59	/**	59	/**
60	* This lock protects the page hash table. It must be acquired	60	* This lock protects the page hash table. It must be acquired
61	* after address space lock and after any address space area	61	* after address space lock and after any address space area
62	* locks.	62	* locks.
63	*/	63	*/
64	mutex_t page_ht_lock;	64	mutex_t page_ht_lock;
65		65
66	/**	66	/**
67	* Page hash table.	67	* Page hash table.
68	* The page hash table may be accessed only when page_ht_lock is held.	68	* The page hash table may be accessed only when page_ht_lock is held.
69	*/	69	*/
70	hash_table_t page_ht;	70	hash_table_t page_ht;
71		71
72	/** Hash table operations for page hash table. */	72	/** Hash table operations for page hash table. */
73	hash_table_operations_t ht_operations = {	73	hash_table_operations_t ht_operations = {
74	.hash = hash,	74	.hash = hash,
75	.compare = compare,	75	.compare = compare,
76	.remove_callback = remove_callback	76	.remove_callback = remove_callback
77	};	77	};
78		78
79	/** Page mapping operations for page hash table architectures. */	79	/** Page mapping operations for page hash table architectures. */
80	page_mapping_operations_t ht_mapping_operations = {	80	page_mapping_operations_t ht_mapping_operations = {
81	.mapping_insert = ht_mapping_insert,	81	.mapping_insert = ht_mapping_insert,
82	.mapping_remove = ht_mapping_remove,	82	.mapping_remove = ht_mapping_remove,
83	.mapping_find = ht_mapping_find	83	.mapping_find = ht_mapping_find
84	};	84	};
85		85
86	/** Compute page hash table index.	86	/** Compute page hash table index.
87	*	87	*
88	* @param key Array of two keys (i.e. page and address space).	88	* @param key Array of two keys (i.e. page and address space).
89	*	89	*
90	* @return Index into page hash table.	90	* @return Index into page hash table.
91	*/	91	*/
92	index_t hash(__native key[])	92	index_t hash(__native key[])
93	{	93	{
94	as_t as = (as_t ) key[KEY_AS];	94	as_t as = (as_t ) key[KEY_AS];
95	__address page = (__address) key[KEY_PAGE];	95	__address page = (__address) key[KEY_PAGE];
96	index_t index;	96	index_t index;
97		97
98	/*	98	/*
99	* Virtual page addresses have roughly the same probability	99	* Virtual page addresses have roughly the same probability
100	* of occurring. Least significant bits of VPN compose the	100	* of occurring. Least significant bits of VPN compose the
101	* hash index.	101	* hash index.
102	*/	102	*/
103	index = ((page >> PAGE_WIDTH) & (PAGE_HT_ENTRIES-1));	103	index = ((page >> PAGE_WIDTH) & (PAGE_HT_ENTRIES-1));
104		104
105	/*	105	/*
106	* Address space structures are likely to be allocated from	106	* Address space structures are likely to be allocated from
107	* similar addresses. Least significant bits compose the	107	* similar addresses. Least significant bits compose the
108	* hash index.	108	* hash index.
109	*/	109	*/
110	index \|= ((__native) as) & (PAGE_HT_ENTRIES-1);	110	index \|= ((__native) as) & (PAGE_HT_ENTRIES-1);
111		111
112	return index;	112	return index;
113	}	113	}
114		114
115	/** Compare page hash table item with page and/or address space.	115	/** Compare page hash table item with page and/or address space.
116	*	116	*
117	* @param key Array of one or two keys (i.e. page and/or address space).	117	* @param key Array of one or two keys (i.e. page and/or address space).
118	* @param keys Number of keys passed.	118	* @param keys Number of keys passed.
119	* @param item Item to compare the keys with.	119	* @param item Item to compare the keys with.
120	*	120	*
121	* @return true on match, false otherwise.	121	* @return true on match, false otherwise.
122	*/	122	*/
123	bool compare(__native key[], count_t keys, link_t *item)	123	bool compare(__native key[], count_t keys, link_t *item)
124	{	124	{
125	pte_t *t;	125	pte_t *t;
126		126
127	ASSERT(item);	127	ASSERT(item);
128	ASSERT((keys > 0) && (keys <= PAGE_HT_KEYS));	128	ASSERT((keys > 0) && (keys <= PAGE_HT_KEYS));
129		129
130	/*	130	/*
131	* Convert item to PTE.	131	* Convert item to PTE.
132	*/	132	*/
133	t = hash_table_get_instance(item, pte_t, link);	133	t = hash_table_get_instance(item, pte_t, link);
134		134
135	if (keys == PAGE_HT_KEYS) {	135	if (keys == PAGE_HT_KEYS) {
136	return (key[KEY_AS] == (__address) t->as) && (key[KEY_PAGE] == t->page);	136	return (key[KEY_AS] == (__address) t->as) && (key[KEY_PAGE] == t->page);
137	} else {	137	} else {
138	return (key[KEY_AS] == (__address) t->as);	138	return (key[KEY_AS] == (__address) t->as);
139	}	139	}
140	}	140	}
141		141
142	/** Callback on page hash table item removal.	142	/** Callback on page hash table item removal.
143	*	143	*
144	* @param item Page hash table item being removed.	144	* @param item Page hash table item being removed.
145	*/	145	*/
146	void remove_callback(link_t *item)	146	void remove_callback(link_t *item)
147	{	147	{
148	pte_t *t;	148	pte_t *t;
149		149
150	ASSERT(item);	150	ASSERT(item);
151		151
152	/*	152	/*
153	* Convert item to PTE.	153	* Convert item to PTE.
154	*/	154	*/
155	t = hash_table_get_instance(item, pte_t, link);	155	t = hash_table_get_instance(item, pte_t, link);
156		156
157	free(t);	157	free(t);
158	}	158	}
159		159
160	/** Map page to frame using page hash table.	160	/** Map page to frame using page hash table.
161	*	161	*
162	* Map virtual address page to physical address frame	162	* Map virtual address page to physical address frame
163	* using flags.	163	* using flags.
164	*	164	*
165	* The page table must be locked and interrupts must be disabled.	165	* The page table must be locked and interrupts must be disabled.
166	*	166	*
167	* @param as Address space to which page belongs.	167	* @param as Address space to which page belongs.
168	* @param page Virtual address of the page to be mapped.	168	* @param page Virtual address of the page to be mapped.
169	* @param frame Physical address of memory frame to which the mapping is done.	169	* @param frame Physical address of memory frame to which the mapping is done.
170	* @param flags Flags to be used for mapping.	170	* @param flags Flags to be used for mapping.
171	*/	171	*/
172	void ht_mapping_insert(as_t *as, __address page, __address frame, int flags)	172	void ht_mapping_insert(as_t *as, __address page, __address frame, int flags)
173	{	173	{
174	pte_t *t;	174	pte_t *t;
175	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };	175	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
176		176
177	if (!hash_table_find(&page_ht, key)) {	177	if (!hash_table_find(&page_ht, key)) {
178	t = (pte_t *) malloc(sizeof(pte_t), FRAME_ATOMIC);	178	t = (pte_t *) malloc(sizeof(pte_t), FRAME_ATOMIC);
179	ASSERT(t != NULL);	179	ASSERT(t != NULL);
180		180
181	t->g = (flags & PAGE_GLOBAL) != 0;	181	t->g = (flags & PAGE_GLOBAL) != 0;
182	t->x = (flags & PAGE_EXEC) != 0;	182	t->x = (flags & PAGE_EXEC) != 0;
183	t->w = (flags & PAGE_WRITE) != 0;	183	t->w = (flags & PAGE_WRITE) != 0;
184	t->k = !(flags & PAGE_USER);	184	t->k = !(flags & PAGE_USER);
185	t->c = (flags & PAGE_CACHEABLE) != 0;	185	t->c = (flags & PAGE_CACHEABLE) != 0;
186	t->p = !(flags & PAGE_NOT_PRESENT);	186	t->p = !(flags & PAGE_NOT_PRESENT);
187		187
188	t->as = as;	188	t->as = as;
189	t->page = page;	189	t->page = ALIGN_DOWN(page, PAGE_SIZE);
190	t->frame = frame;	190	t->frame = ALIGN_DOWN(frame, FRAME_SIZE);
191		191
192	hash_table_insert(&page_ht, key, &t->link);	192	hash_table_insert(&page_ht, key, &t->link);
193	}	193	}
194	}	194	}
195		195
196	/** Remove mapping of page from page hash table.	196	/** Remove mapping of page from page hash table.
197	*	197	*
198	* Remove any mapping of page within address space as.	198	* Remove any mapping of page within address space as.
199	* TLB shootdown should follow in order to make effects of	199	* TLB shootdown should follow in order to make effects of
200	* this call visible.	200	* this call visible.
201	*	201	*
202	* The page table must be locked and interrupts must be disabled.	202	* The page table must be locked and interrupts must be disabled.
203	*	203	*
204	* @param as Address space to wich page belongs.	204	* @param as Address space to wich page belongs.
205	* @param page Virtual address of the page to be demapped.	205	* @param page Virtual address of the page to be demapped.
206	*/	206	*/
207	void ht_mapping_remove(as_t *as, __address page)	207	void ht_mapping_remove(as_t *as, __address page)
208	{	208	{
209	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };	209	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
210		210
211	/*	211	/*
212	* Note that removed PTE's will be freed	212	* Note that removed PTE's will be freed
213	* by remove_callback().	213	* by remove_callback().
214	*/	214	*/
215	hash_table_remove(&page_ht, key, 2);	215	hash_table_remove(&page_ht, key, 2);
216	}	216	}
217		217
218		218
219	/** Find mapping for virtual page in page hash table.	219	/** Find mapping for virtual page in page hash table.
220	*	220	*
221	* Find mapping for virtual page.	221	* Find mapping for virtual page.
222	*	222	*
223	* The page table must be locked and interrupts must be disabled.	223	* The page table must be locked and interrupts must be disabled.
224	*	224	*
225	* @param as Address space to wich page belongs.	225	* @param as Address space to wich page belongs.
226	* @param page Virtual page.	226	* @param page Virtual page.
227	*	227	*
228	* @return NULL if there is no such mapping; requested mapping otherwise.	228	* @return NULL if there is no such mapping; requested mapping otherwise.
229	*/	229	*/
230	pte_t ht_mapping_find(as_t as, __address page)	230	pte_t ht_mapping_find(as_t as, __address page)
231	{	231	{
232	link_t *hlp;	232	link_t *hlp;
233	pte_t *t = NULL;	233	pte_t *t = NULL;
234	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };	234	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
235		235
236	hlp = hash_table_find(&page_ht, key);	236	hlp = hash_table_find(&page_ht, key);
237	if (hlp)	237	if (hlp)
238	t = hash_table_get_instance(hlp, pte_t, link);	238	t = hash_table_get_instance(hlp, pte_t, link);
239		239
240	return t;	240	return t;
241	}	241	}
242		242