Linux Kernel  3.7.1
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pgalloc.c
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1 /* pgalloc.c: page directory & page table allocation
2  *
3  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells ([email protected])
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/sched.h>
13 #include <linux/gfp.h>
14 #include <linux/mm.h>
15 #include <linux/highmem.h>
16 #include <linux/quicklist.h>
17 #include <asm/pgalloc.h>
18 #include <asm/page.h>
19 #include <asm/cacheflush.h>
20 
22 
23 pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
24 {
26  if (pte)
27  clear_page(pte);
28  return pte;
29 }
30 
31 pgtable_t pte_alloc_one(struct mm_struct *mm, unsigned long address)
32 {
33  struct page *page;
34 
35 #ifdef CONFIG_HIGHPTE
37 #else
39 #endif
40  if (page) {
41  clear_highpage(page);
42  pgtable_page_ctor(page);
43  flush_dcache_page(page);
44  }
45  return page;
46 }
47 
48 void __set_pmd(pmd_t *pmdptr, unsigned long pmd)
49 {
50  unsigned long *__ste_p = pmdptr->ste;
51  int loop;
52 
53  if (!pmd) {
54  memset(__ste_p, 0, PME_SIZE);
55  }
56  else {
57  BUG_ON(pmd & (0x3f00 | xAMPRx_SS | 0xe));
58 
59  for (loop = PME_SIZE; loop > 0; loop -= 4) {
60  *__ste_p++ = pmd;
61  pmd += __frv_PT_SIZE;
62  }
63  }
64 
65  frv_dcache_writeback((unsigned long) pmdptr, (unsigned long) (pmdptr + 1));
66 }
67 
68 /*
69  * List of all pgd's needed for non-PAE so it can invalidate entries
70  * in both cached and uncached pgd's; not needed for PAE since the
71  * kernel pmd is shared. If PAE were not to share the pmd a similar
72  * tactic would be needed. This is essentially codepath-based locking
73  * against pageattr.c; it is the unique case in which a valid change
74  * of kernel pagetables can't be lazily synchronized by vmalloc faults.
75  * vmalloc faults work because attached pagetables are never freed.
76  * If the locking proves to be non-performant, a ticketing scheme with
77  * checks at dup_mmap(), exec(), and other mmlist addition points
78  * could be used. The locking scheme was chosen on the basis of
79  * manfred's recommendations and having no core impact whatsoever.
80  * -- wli
81  */
82 DEFINE_SPINLOCK(pgd_lock);
83 struct page *pgd_list;
84 
85 static inline void pgd_list_add(pgd_t *pgd)
86 {
87  struct page *page = virt_to_page(pgd);
88  page->index = (unsigned long) pgd_list;
89  if (pgd_list)
90  set_page_private(pgd_list, (unsigned long) &page->index);
91  pgd_list = page;
92  set_page_private(page, (unsigned long)&pgd_list);
93 }
94 
95 static inline void pgd_list_del(pgd_t *pgd)
96 {
97  struct page *next, **pprev, *page = virt_to_page(pgd);
98  next = (struct page *) page->index;
99  pprev = (struct page **) page_private(page);
100  *pprev = next;
101  if (next)
102  set_page_private(next, (unsigned long) pprev);
103 }
104 
105 void pgd_ctor(void *pgd)
106 {
107  unsigned long flags;
108 
109  if (PTRS_PER_PMD == 1)
110  spin_lock_irqsave(&pgd_lock, flags);
111 
112  memcpy((pgd_t *) pgd + USER_PGDS_IN_LAST_PML4,
113  swapper_pg_dir + USER_PGDS_IN_LAST_PML4,
114  (PTRS_PER_PGD - USER_PGDS_IN_LAST_PML4) * sizeof(pgd_t));
115 
116  if (PTRS_PER_PMD > 1)
117  return;
118 
119  pgd_list_add(pgd);
120  spin_unlock_irqrestore(&pgd_lock, flags);
121  memset(pgd, 0, USER_PGDS_IN_LAST_PML4 * sizeof(pgd_t));
122 }
123 
124 /* never called when PTRS_PER_PMD > 1 */
125 void pgd_dtor(void *pgd)
126 {
127  unsigned long flags; /* can be called from interrupt context */
128 
129  spin_lock_irqsave(&pgd_lock, flags);
130  pgd_list_del(pgd);
131  spin_unlock_irqrestore(&pgd_lock, flags);
132 }
133 
135 {
136  return quicklist_alloc(0, GFP_KERNEL, pgd_ctor);
137 }
138 
139 void pgd_free(struct mm_struct *mm, pgd_t *pgd)
140 {
141  /* in the non-PAE case, clear_page_tables() clears user pgd entries */
142  quicklist_free(0, pgd_dtor, pgd);
143 }
144 
146 {
147 }
148 
149 void check_pgt_cache(void)
150 {
151  quicklist_trim(0, pgd_dtor, 25, 16);
152 }
153