Linux kernel mirror (for testing)
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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_PGALLOC_H
3#define _ASM_PGALLOC_H
4
5#include <linux/gfp.h>
6#include <linux/mm.h>
7#include <linux/threads.h>
8#include <asm/processor.h>
9#include <asm/fixmap.h>
10
11#include <asm/cache.h>
12
13#include <asm-generic/pgalloc.h> /* for pte_{alloc,free}_one */
14
15/* Allocate the top level pgd (page directory)
16 *
17 * Here (for 64 bit kernels) we implement a Hybrid L2/L3 scheme: we
18 * allocate the first pmd adjacent to the pgd. This means that we can
19 * subtract a constant offset to get to it. The pmd and pgd sizes are
20 * arranged so that a single pmd covers 4GB (giving a full 64-bit
21 * process access to 8TB) so our lookups are effectively L2 for the
22 * first 4GB of the kernel (i.e. for all ILP32 processes and all the
23 * kernel for machines with under 4GB of memory) */
24static inline pgd_t *pgd_alloc(struct mm_struct *mm)
25{
26 pgd_t *pgd = (pgd_t *)__get_free_pages(GFP_KERNEL,
27 PGD_ALLOC_ORDER);
28 pgd_t *actual_pgd = pgd;
29
30 if (likely(pgd != NULL)) {
31 memset(pgd, 0, PAGE_SIZE<<PGD_ALLOC_ORDER);
32#if CONFIG_PGTABLE_LEVELS == 3
33 actual_pgd += PTRS_PER_PGD;
34 /* Populate first pmd with allocated memory. We mark it
35 * with PxD_FLAG_ATTACHED as a signal to the system that this
36 * pmd entry may not be cleared. */
37 __pgd_val_set(*actual_pgd, (PxD_FLAG_PRESENT |
38 PxD_FLAG_VALID |
39 PxD_FLAG_ATTACHED)
40 + (__u32)(__pa((unsigned long)pgd) >> PxD_VALUE_SHIFT));
41 /* The first pmd entry also is marked with PxD_FLAG_ATTACHED as
42 * a signal that this pmd may not be freed */
43 __pgd_val_set(*pgd, PxD_FLAG_ATTACHED);
44#endif
45 }
46 spin_lock_init(pgd_spinlock(actual_pgd));
47 return actual_pgd;
48}
49
50static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
51{
52#if CONFIG_PGTABLE_LEVELS == 3
53 pgd -= PTRS_PER_PGD;
54#endif
55 free_pages((unsigned long)pgd, PGD_ALLOC_ORDER);
56}
57
58#if CONFIG_PGTABLE_LEVELS == 3
59
60/* Three Level Page Table Support for pmd's */
61
62static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmd)
63{
64 __pgd_val_set(*pgd, (PxD_FLAG_PRESENT | PxD_FLAG_VALID) +
65 (__u32)(__pa((unsigned long)pmd) >> PxD_VALUE_SHIFT));
66}
67
68static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
69{
70 pmd_t *pmd = (pmd_t *)__get_free_pages(GFP_KERNEL, PMD_ORDER);
71 if (pmd)
72 memset(pmd, 0, PAGE_SIZE<<PMD_ORDER);
73 return pmd;
74}
75
76static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
77{
78 if (pmd_flag(*pmd) & PxD_FLAG_ATTACHED) {
79 /*
80 * This is the permanent pmd attached to the pgd;
81 * cannot free it.
82 * Increment the counter to compensate for the decrement
83 * done by generic mm code.
84 */
85 mm_inc_nr_pmds(mm);
86 return;
87 }
88 free_pages((unsigned long)pmd, PMD_ORDER);
89}
90
91#else
92
93/* Two Level Page Table Support for pmd's */
94
95/*
96 * allocating and freeing a pmd is trivial: the 1-entry pmd is
97 * inside the pgd, so has no extra memory associated with it.
98 */
99
100#define pmd_alloc_one(mm, addr) ({ BUG(); ((pmd_t *)2); })
101#define pmd_free(mm, x) do { } while (0)
102#define pgd_populate(mm, pmd, pte) BUG()
103
104#endif
105
106static inline void
107pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd, pte_t *pte)
108{
109#if CONFIG_PGTABLE_LEVELS == 3
110 /* preserve the gateway marker if this is the beginning of
111 * the permanent pmd */
112 if(pmd_flag(*pmd) & PxD_FLAG_ATTACHED)
113 __pmd_val_set(*pmd, (PxD_FLAG_PRESENT |
114 PxD_FLAG_VALID |
115 PxD_FLAG_ATTACHED)
116 + (__u32)(__pa((unsigned long)pte) >> PxD_VALUE_SHIFT));
117 else
118#endif
119 __pmd_val_set(*pmd, (PxD_FLAG_PRESENT | PxD_FLAG_VALID)
120 + (__u32)(__pa((unsigned long)pte) >> PxD_VALUE_SHIFT));
121}
122
123#define pmd_populate(mm, pmd, pte_page) \
124 pmd_populate_kernel(mm, pmd, page_address(pte_page))
125#define pmd_pgtable(pmd) pmd_page(pmd)
126
127#define check_pgt_cache() do { } while (0)
128
129#endif