1// SPDX-License-Identifier: GPL-2.0-only
2
3#include <linux/linkage.h>
4#include <linux/mmap_lock.h>
5#include <linux/mm.h>
6#include <linux/time_namespace.h>
7#include <linux/types.h>
8#include <linux/vdso_datastore.h>
9#include <vdso/datapage.h>
10
11/*
12 * The vDSO data page.
13 */
14#ifdef CONFIG_GENERIC_GETTIMEOFDAY
15static union {
16 struct vdso_time_data data;
17 u8 page[PAGE_SIZE];
18} vdso_time_data_store __page_aligned_data;
19struct vdso_time_data *vdso_k_time_data = &vdso_time_data_store.data;
20static_assert(sizeof(vdso_time_data_store) == PAGE_SIZE);
21#endif /* CONFIG_GENERIC_GETTIMEOFDAY */
22
23#ifdef CONFIG_VDSO_GETRANDOM
24static union {
25 struct vdso_rng_data data;
26 u8 page[PAGE_SIZE];
27} vdso_rng_data_store __page_aligned_data;
28struct vdso_rng_data *vdso_k_rng_data = &vdso_rng_data_store.data;
29static_assert(sizeof(vdso_rng_data_store) == PAGE_SIZE);
30#endif /* CONFIG_VDSO_GETRANDOM */
31
32#ifdef CONFIG_ARCH_HAS_VDSO_ARCH_DATA
33static union {
34 struct vdso_arch_data data;
35 u8 page[VDSO_ARCH_DATA_SIZE];
36} vdso_arch_data_store __page_aligned_data;
37struct vdso_arch_data *vdso_k_arch_data = &vdso_arch_data_store.data;
38#endif /* CONFIG_ARCH_HAS_VDSO_ARCH_DATA */
39
40static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
41 struct vm_area_struct *vma, struct vm_fault *vmf)
42{
43 struct page *timens_page = find_timens_vvar_page(vma);
44 unsigned long addr, pfn;
45 vm_fault_t err;
46
47 switch (vmf->pgoff) {
48 case VDSO_TIME_PAGE_OFFSET:
49 if (!IS_ENABLED(CONFIG_GENERIC_GETTIMEOFDAY))
50 return VM_FAULT_SIGBUS;
51 pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data));
52 if (timens_page) {
53 /*
54 * Fault in VVAR page too, since it will be accessed
55 * to get clock data anyway.
56 */
57 addr = vmf->address + VDSO_TIMENS_PAGE_OFFSET * PAGE_SIZE;
58 err = vmf_insert_pfn(vma, addr, pfn);
59 if (unlikely(err & VM_FAULT_ERROR))
60 return err;
61 pfn = page_to_pfn(timens_page);
62 }
63 break;
64 case VDSO_TIMENS_PAGE_OFFSET:
65 /*
66 * If a task belongs to a time namespace then a namespace
67 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
68 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
69 * offset.
70 * See also the comment near timens_setup_vdso_data().
71 */
72 if (!IS_ENABLED(CONFIG_TIME_NS) || !timens_page)
73 return VM_FAULT_SIGBUS;
74 pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data));
75 break;
76 case VDSO_RNG_PAGE_OFFSET:
77 if (!IS_ENABLED(CONFIG_VDSO_GETRANDOM))
78 return VM_FAULT_SIGBUS;
79 pfn = __phys_to_pfn(__pa_symbol(vdso_k_rng_data));
80 break;
81 case VDSO_ARCH_PAGES_START ... VDSO_ARCH_PAGES_END:
82 if (!IS_ENABLED(CONFIG_ARCH_HAS_VDSO_ARCH_DATA))
83 return VM_FAULT_SIGBUS;
84 pfn = __phys_to_pfn(__pa_symbol(vdso_k_arch_data)) +
85 vmf->pgoff - VDSO_ARCH_PAGES_START;
86 break;
87 default:
88 return VM_FAULT_SIGBUS;
89 }
90
91 return vmf_insert_pfn(vma, addr: vmf->address, pfn);
92}
93
94const struct vm_special_mapping vdso_vvar_mapping = {
95 .name = "[vvar]",
96 .fault = vvar_fault,
97};
98
99struct vm_area_struct *vdso_install_vvar_mapping(struct mm_struct *mm, unsigned long addr)
100{
101 return _install_special_mapping(mm, addr, len: VDSO_NR_PAGES * PAGE_SIZE,
102 VM_READ | VM_MAYREAD | VM_IO | VM_DONTDUMP |
103 VM_PFNMAP | VM_SEALED_SYSMAP,
104 spec: &vdso_vvar_mapping);
105}
106
107#ifdef CONFIG_TIME_NS
108/*
109 * The vvar page layout depends on whether a task belongs to the root or
110 * non-root time namespace. Whenever a task changes its namespace, the VVAR
111 * page tables are cleared and then they will be re-faulted with a
112 * corresponding layout.
113 * See also the comment near timens_setup_vdso_clock_data() for details.
114 */
115int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
116{
117 struct mm_struct *mm = task->mm;
118 struct vm_area_struct *vma;
119 VMA_ITERATOR(vmi, mm, 0);
120
121 mmap_read_lock(mm);
122 for_each_vma(vmi, vma) {
123 if (vma_is_special_mapping(vma, sm: &vdso_vvar_mapping))
124 zap_vma_pages(vma);
125 }
126 mmap_read_unlock(mm);
127
128 return 0;
129}
130#endif
131