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1// SPDX-License-Identifier: GPL-2.0-or-later
2
3/*
4 * Functions for initialisaing, allocating, freeing and duplicating VMAs. Shared
5 * between CONFIG_MMU and non-CONFIG_MMU kernel configurations.
6 */
7
8#include "vma_internal.h"
9#include "vma.h"
10
11/* SLAB cache for vm_area_struct structures */
12static struct kmem_cache *vm_area_cachep;
13
14void __init vma_state_init(void)
15{
16 struct kmem_cache_args args = {
17 .use_freeptr_offset = true,
18 .freeptr_offset = offsetof(struct vm_area_struct, vm_freeptr),
19 };
20
21 vm_area_cachep = kmem_cache_create("vm_area_struct",
22 sizeof(struct vm_area_struct), &args,
23 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
24 SLAB_ACCOUNT);
25}
26
27struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
28{
29 struct vm_area_struct *vma;
30
31 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
32 if (!vma)
33 return NULL;
34
35 vma_init(vma, mm);
36
37 return vma;
38}
39
40static void vm_area_init_from(const struct vm_area_struct *src,
41 struct vm_area_struct *dest)
42{
43 dest->vm_mm = src->vm_mm;
44 dest->vm_ops = src->vm_ops;
45 dest->vm_start = src->vm_start;
46 dest->vm_end = src->vm_end;
47 dest->anon_vma = src->anon_vma;
48 dest->vm_pgoff = src->vm_pgoff;
49 dest->vm_file = src->vm_file;
50 dest->vm_private_data = src->vm_private_data;
51 vm_flags_init(dest, src->vm_flags);
52 memcpy(&dest->vm_page_prot, &src->vm_page_prot,
53 sizeof(dest->vm_page_prot));
54 /*
55 * src->shared.rb may be modified concurrently when called from
56 * dup_mmap(), but the clone will reinitialize it.
57 */
58 data_race(memcpy(&dest->shared, &src->shared, sizeof(dest->shared)));
59 memcpy(&dest->vm_userfaultfd_ctx, &src->vm_userfaultfd_ctx,
60 sizeof(dest->vm_userfaultfd_ctx));
61#ifdef CONFIG_ANON_VMA_NAME
62 dest->anon_name = src->anon_name;
63#endif
64#ifdef CONFIG_SWAP
65 memcpy(&dest->swap_readahead_info, &src->swap_readahead_info,
66 sizeof(dest->swap_readahead_info));
67#endif
68#ifndef CONFIG_MMU
69 dest->vm_region = src->vm_region;
70#endif
71#ifdef CONFIG_NUMA
72 dest->vm_policy = src->vm_policy;
73#endif
74#ifdef __HAVE_PFNMAP_TRACKING
75 dest->pfnmap_track_ctx = NULL;
76#endif
77}
78
79#ifdef __HAVE_PFNMAP_TRACKING
80static inline int vma_pfnmap_track_ctx_dup(struct vm_area_struct *orig,
81 struct vm_area_struct *new)
82{
83 struct pfnmap_track_ctx *ctx = orig->pfnmap_track_ctx;
84
85 if (likely(!ctx))
86 return 0;
87
88 /*
89 * We don't expect to ever hit this. If ever required, we would have
90 * to duplicate the tracking.
91 */
92 if (unlikely(kref_read(&ctx->kref) >= REFCOUNT_MAX))
93 return -ENOMEM;
94 kref_get(&ctx->kref);
95 new->pfnmap_track_ctx = ctx;
96 return 0;
97}
98
99static inline void vma_pfnmap_track_ctx_release(struct vm_area_struct *vma)
100{
101 struct pfnmap_track_ctx *ctx = vma->pfnmap_track_ctx;
102
103 if (likely(!ctx))
104 return;
105
106 kref_put(&ctx->kref, pfnmap_track_ctx_release);
107 vma->pfnmap_track_ctx = NULL;
108}
109#else
110static inline int vma_pfnmap_track_ctx_dup(struct vm_area_struct *orig,
111 struct vm_area_struct *new)
112{
113 return 0;
114}
115static inline void vma_pfnmap_track_ctx_release(struct vm_area_struct *vma)
116{
117}
118#endif
119
120struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
121{
122 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
123
124 if (!new)
125 return NULL;
126
127 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
128 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
129 vm_area_init_from(orig, new);
130
131 if (vma_pfnmap_track_ctx_dup(orig, new)) {
132 kmem_cache_free(vm_area_cachep, new);
133 return NULL;
134 }
135 vma_lock_init(new, true);
136 INIT_LIST_HEAD(&new->anon_vma_chain);
137 vma_numab_state_init(new);
138 dup_anon_vma_name(orig, new);
139
140 return new;
141}
142
143void vm_area_free(struct vm_area_struct *vma)
144{
145 /* The vma should be detached while being destroyed. */
146 vma_assert_detached(vma);
147 vma_numab_state_free(vma);
148 free_anon_vma_name(vma);
149 vma_pfnmap_track_ctx_release(vma);
150 kmem_cache_free(vm_area_cachep, vma);
151}