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.
 */
 
#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.
 */
SPINLOCK_INITIALIZE(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 address space must be locked and interruptsmust 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) };
   
    spinlock_lock(&page_ht_lock);
 
    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 = page;
        t->frame = frame;
 
        hash_table_insert(&page_ht, key, &t->link);
    }
   
    spinlock_unlock(&page_ht_lock);
}
 
/** 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 address space 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) };
   
    spinlock_lock(&page_ht_lock);
 
    /*
     * Note that removed PTE's will be freed
     * by remove_callback().
     */
    hash_table_remove(&page_ht, key, 2);
 
    spinlock_unlock(&page_ht_lock);
}
 
 
/** Find mapping for virtual page in page hash table.
 *
 * Find mapping for virtual page.
 *
 * The address space 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) };
   
    spinlock_lock(&page_ht_lock);
 
    hlp = hash_table_find(&page_ht, key);
    if (hlp)
        t = hash_table_get_instance(hlp, pte_t, link);
 
    spinlock_unlock(&page_ht_lock);
    return t;
}
 

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/genarch/src/mm/page_ht.c – Rev 902 → 922

Rev 902		Rev 922
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	#include <genarch/mm/page_ht.h>	29	#include <genarch/mm/page_ht.h>
30	#include <mm/page.h>	30	#include <mm/page.h>
31	#include <arch/mm/page.h>	31	#include <arch/mm/page.h>
32	#include <mm/frame.h>	32	#include <mm/frame.h>
33	#include <mm/slab.h>	33	#include <mm/slab.h>
34	#include <mm/as.h>	34	#include <mm/as.h>
35	#include <arch/mm/asid.h>	35	#include <arch/mm/asid.h>
36	#include <arch/types.h>	36	#include <arch/types.h>
37	#include <typedefs.h>	37	#include <typedefs.h>
38	#include <arch/asm.h>	38	#include <arch/asm.h>
39	#include <synch/spinlock.h>	39	#include <synch/spinlock.h>
40	#include <arch.h>	40	#include <arch.h>
41	#include <debug.h>	41	#include <debug.h>
42	#include <memstr.h>	42	#include <memstr.h>
43	#include <adt/hash_table.h>	43	#include <adt/hash_table.h>
-		44	#include <align.h>
44		45
45	static index_t hash(__native key[]);	46	static index_t hash(__native key[]);
46	static bool compare(__native key[], count_t keys, link_t *item);	47	static bool compare(__native key[], count_t keys, link_t *item);
47	static void remove_callback(link_t *item);	48	static void remove_callback(link_t *item);
48		49
49	static void ht_mapping_insert(as_t *as, __address page, __address frame, int flags);	50	static void ht_mapping_insert(as_t *as, __address page, __address frame, int flags);
50	static void ht_mapping_remove(as_t *as, __address page);	51	static void ht_mapping_remove(as_t *as, __address page);
51	static pte_t ht_mapping_find(as_t as, __address page);	52	static pte_t ht_mapping_find(as_t as, __address page);
52		53
53	/**	54	/**
54	* This lock protects the page hash table.	55	* This lock protects the page hash table.
55	*/	56	*/
56	SPINLOCK_INITIALIZE(page_ht_lock);	57	SPINLOCK_INITIALIZE(page_ht_lock);
57		58
58	/**	59	/**
59	* Page hash table.	60	* Page hash table.
60	* The page hash table may be accessed only when page_ht_lock is held.	61	* The page hash table may be accessed only when page_ht_lock is held.
61	*/	62	*/
62	hash_table_t page_ht;	63	hash_table_t page_ht;
63		64
64	/** Hash table operations for page hash table. */	65	/** Hash table operations for page hash table. */
65	hash_table_operations_t ht_operations = {	66	hash_table_operations_t ht_operations = {
66	.hash = hash,	67	.hash = hash,
67	.compare = compare,	68	.compare = compare,
68	.remove_callback = remove_callback	69	.remove_callback = remove_callback
69	};	70	};
70		71
71	/** Page mapping operations for page hash table architectures. */	72	/** Page mapping operations for page hash table architectures. */
72	page_mapping_operations_t ht_mapping_operations = {	73	page_mapping_operations_t ht_mapping_operations = {
73	.mapping_insert = ht_mapping_insert,	74	.mapping_insert = ht_mapping_insert,
74	.mapping_remove = ht_mapping_remove,	75	.mapping_remove = ht_mapping_remove,
75	.mapping_find = ht_mapping_find	76	.mapping_find = ht_mapping_find
76	};	77	};
77		78
78	/** Compute page hash table index.	79	/** Compute page hash table index.
79	*	80	*
80	* @param key Array of two keys (i.e. page and address space).	81	* @param key Array of two keys (i.e. page and address space).
81	*	82	*
82	* @return Index into page hash table.	83	* @return Index into page hash table.
83	*/	84	*/
84	index_t hash(__native key[])	85	index_t hash(__native key[])
85	{	86	{
86	as_t as = (as_t ) key[KEY_AS];	87	as_t as = (as_t ) key[KEY_AS];
87	__address page = (__address) key[KEY_PAGE];	88	__address page = (__address) key[KEY_PAGE];
88	index_t index;	89	index_t index;
89		90
90	/*	91	/*
91	* Virtual page addresses have roughly the same probability	92	* Virtual page addresses have roughly the same probability
92	* of occurring. Least significant bits of VPN compose the	93	* of occurring. Least significant bits of VPN compose the
93	* hash index.	94	* hash index.
94	*/	95	*/
95	index = ((page >> PAGE_WIDTH) & (PAGE_HT_ENTRIES-1));	96	index = ((page >> PAGE_WIDTH) & (PAGE_HT_ENTRIES-1));
96		97
97	/*	98	/*
98	* Address space structures are likely to be allocated from	99	* Address space structures are likely to be allocated from
99	* similar addresses. Least significant bits compose the	100	* similar addresses. Least significant bits compose the
100	* hash index.	101	* hash index.
101	*/	102	*/
102	index \|= ((__native) as) & (PAGE_HT_ENTRIES-1);	103	index \|= ((__native) as) & (PAGE_HT_ENTRIES-1);
103		104
104	return index;	105	return index;
105	}	106	}
106		107
107	/** Compare page hash table item with page and/or address space.	108	/** Compare page hash table item with page and/or address space.
108	*	109	*
109	* @param key Array of one or two keys (i.e. page and/or address space).	110	* @param key Array of one or two keys (i.e. page and/or address space).
110	* @param keys Number of keys passed.	111	* @param keys Number of keys passed.
111	* @param item Item to compare the keys with.	112	* @param item Item to compare the keys with.
112	*	113	*
113	* @return true on match, false otherwise.	114	* @return true on match, false otherwise.
114	*/	115	*/
115	bool compare(__native key[], count_t keys, link_t *item)	116	bool compare(__native key[], count_t keys, link_t *item)
116	{	117	{
117	pte_t *t;	118	pte_t *t;
118		119
119	ASSERT(item);	120	ASSERT(item);
120	ASSERT((keys > 0) && (keys <= PAGE_HT_KEYS));	121	ASSERT((keys > 0) && (keys <= PAGE_HT_KEYS));
121		122
122	/*	123	/*
123	* Convert item to PTE.	124	* Convert item to PTE.
124	*/	125	*/
125	t = hash_table_get_instance(item, pte_t, link);	126	t = hash_table_get_instance(item, pte_t, link);
126		127
127	if (keys == PAGE_HT_KEYS) {	128	if (keys == PAGE_HT_KEYS) {
128	return (key[KEY_AS] == (__address) t->as) && (key[KEY_PAGE] == t->page);	129	return (key[KEY_AS] == (__address) t->as) && (key[KEY_PAGE] == t->page);
129	} else {	130	} else {
130	return (key[KEY_AS] == (__address) t->as);	131	return (key[KEY_AS] == (__address) t->as);
131	}	132	}
132	}	133	}
133		134
134	/** Callback on page hash table item removal.	135	/** Callback on page hash table item removal.
135	*	136	*
136	* @param item Page hash table item being removed.	137	* @param item Page hash table item being removed.
137	*/	138	*/
138	void remove_callback(link_t *item)	139	void remove_callback(link_t *item)
139	{	140	{
140	pte_t *t;	141	pte_t *t;
141		142
142	ASSERT(item);	143	ASSERT(item);
143		144
144	/*	145	/*
145	* Convert item to PTE.	146	* Convert item to PTE.
146	*/	147	*/
147	t = hash_table_get_instance(item, pte_t, link);	148	t = hash_table_get_instance(item, pte_t, link);
148		149
149	free(t);	150	free(t);
150	}	151	}
151		152
152	/** Map page to frame using page hash table.	153	/** Map page to frame using page hash table.
153	*	154	*
154	* Map virtual address 'page' to physical address 'frame'	155	* Map virtual address 'page' to physical address 'frame'
155	* using 'flags'.	156	* using 'flags'.
156	*	157	*
157	* The address space must be locked and interruptsmust be disabled.	158	* The address space must be locked and interruptsmust be disabled.
158	*	159	*
159	* @param as Address space to which page belongs.	160	* @param as Address space to which page belongs.
160	* @param page Virtual address of the page to be mapped.	161	* @param page Virtual address of the page to be mapped.
161	* @param frame Physical address of memory frame to which the mapping is done.	162	* @param frame Physical address of memory frame to which the mapping is done.
162	* @param flags Flags to be used for mapping.	163	* @param flags Flags to be used for mapping.
163	*/	164	*/
164	void ht_mapping_insert(as_t *as, __address page, __address frame, int flags)	165	void ht_mapping_insert(as_t *as, __address page, __address frame, int flags)
165	{	166	{
166	pte_t *t;	167	pte_t *t;
167	__native key[2] = { (__address) as, page };	168	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
168		169
169	spinlock_lock(&page_ht_lock);	170	spinlock_lock(&page_ht_lock);
170		171
171	if (!hash_table_find(&page_ht, key)) {	172	if (!hash_table_find(&page_ht, key)) {
172	t = (pte_t *) malloc(sizeof(pte_t), FRAME_ATOMIC);	173	t = (pte_t *) malloc(sizeof(pte_t), FRAME_ATOMIC);
173	ASSERT(t != NULL);	174	ASSERT(t != NULL);
174		175
175	t->g = (flags & PAGE_GLOBAL) != 0;	176	t->g = (flags & PAGE_GLOBAL) != 0;
176	t->x = (flags & PAGE_EXEC) != 0;	177	t->x = (flags & PAGE_EXEC) != 0;
177	t->w = (flags & PAGE_WRITE) != 0;	178	t->w = (flags & PAGE_WRITE) != 0;
178	t->k = !(flags & PAGE_USER);	179	t->k = !(flags & PAGE_USER);
179	t->c = (flags & PAGE_CACHEABLE) != 0;	180	t->c = (flags & PAGE_CACHEABLE) != 0;
180	t->p = !(flags & PAGE_NOT_PRESENT);	181	t->p = !(flags & PAGE_NOT_PRESENT);
181		182
182	t->as = as;	183	t->as = as;
183	t->page = page;	184	t->page = page;
184	t->frame = frame;	185	t->frame = frame;
185		186
186	hash_table_insert(&page_ht, key, &t->link);	187	hash_table_insert(&page_ht, key, &t->link);
187	}	188	}
188		189
189	spinlock_unlock(&page_ht_lock);	190	spinlock_unlock(&page_ht_lock);
190	}	191	}
191		192
192	/** Remove mapping of page from page hash table.	193	/** Remove mapping of page from page hash table.
193	*	194	*
194	* Remove any mapping of 'page' within address space 'as'.	195	* Remove any mapping of 'page' within address space 'as'.
195	* TLB shootdown should follow in order to make effects of	196	* TLB shootdown should follow in order to make effects of
196	* this call visible.	197	* this call visible.
197	*	198	*
198	* The address space must be locked and interrupts must be disabled.	199	* The address space must be locked and interrupts must be disabled.
199	*	200	*
200	* @param as Address space to wich page belongs.	201	* @param as Address space to wich page belongs.
201	* @param page Virtual address of the page to be demapped.	202	* @param page Virtual address of the page to be demapped.
202	*/	203	*/
203	void ht_mapping_remove(as_t *as, __address page)	204	void ht_mapping_remove(as_t *as, __address page)
204	{	205	{
205	__native key[2] = { (__address) as, page };	206	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
206		207
207	spinlock_lock(&page_ht_lock);	208	spinlock_lock(&page_ht_lock);
208		209
209	/*	210	/*
210	* Note that removed PTE's will be freed	211	* Note that removed PTE's will be freed
211	* by remove_callback().	212	* by remove_callback().
212	*/	213	*/
213	hash_table_remove(&page_ht, key, 2);	214	hash_table_remove(&page_ht, key, 2);
214		215
215	spinlock_unlock(&page_ht_lock);	216	spinlock_unlock(&page_ht_lock);
216	}	217	}
217		218
218		219
219	/** Find mapping for virtual page in page hash table.	220	/** Find mapping for virtual page in page hash table.
220	*	221	*
221	* Find mapping for virtual page.	222	* Find mapping for virtual page.
222	*	223	*
223	* The address space must be locked and interrupts must be disabled.	224	* The address space must be locked and interrupts must be disabled.
224	*	225	*
225	* @param as Address space to wich page belongs.	226	* @param as Address space to wich page belongs.
226	* @param page Virtual page.	227	* @param page Virtual page.
227	*	228	*
228	* @return NULL if there is no such mapping; requested mapping otherwise.	229	* @return NULL if there is no such mapping; requested mapping otherwise.
229	*/	230	*/
230	pte_t ht_mapping_find(as_t as, __address page)	231	pte_t ht_mapping_find(as_t as, __address page)
231	{	232	{
232	link_t *hlp;	233	link_t *hlp;
233	pte_t *t = NULL;	234	pte_t *t = NULL;
234	__native key[2] = { (__address) as, page };	235	__native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };
235		236
236	spinlock_lock(&page_ht_lock);	237	spinlock_lock(&page_ht_lock);
237		238
238	hlp = hash_table_find(&page_ht, key);	239	hlp = hash_table_find(&page_ht, key);
239	if (hlp)	240	if (hlp)
240	t = hash_table_get_instance(hlp, pte_t, link);	241	t = hash_table_get_instance(hlp, pte_t, link);
241		242
242	spinlock_unlock(&page_ht_lock);	243	spinlock_unlock(&page_ht_lock);
243	return t;	244	return t;
244	}	245	}
245		246