1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * vdso setup for s390
4 *
5 * Copyright IBM Corp. 2008
6 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
7 */
8
9 #include <linux/binfmts.h>
10 #include <linux/compat.h>
11 #include <linux/elf.h>
12 #include <linux/errno.h>
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/mm.h>
16 #include <linux/slab.h>
17 #include <linux/smp.h>
18 #include <linux/time_namespace.h>
19 #include <vdso/datapage.h>
20 #include <asm/vdso.h>
21
22 extern char vdso64_start[], vdso64_end[];
23 extern char vdso32_start[], vdso32_end[];
24
25 static struct vm_special_mapping vvar_mapping;
26
27 static union {
28 struct vdso_data data[CS_BASES];
29 u8 page[PAGE_SIZE];
30 } vdso_data_store __page_aligned_data;
31
32 struct vdso_data *vdso_data = vdso_data_store.data;
33
34 enum vvar_pages {
35 VVAR_DATA_PAGE_OFFSET,
36 VVAR_TIMENS_PAGE_OFFSET,
37 VVAR_NR_PAGES,
38 };
39
40 #ifdef CONFIG_TIME_NS
arch_get_vdso_data(void * vvar_page)41 struct vdso_data *arch_get_vdso_data(void *vvar_page)
42 {
43 return (struct vdso_data *)(vvar_page);
44 }
45
find_timens_vvar_page(struct vm_area_struct * vma)46 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
47 {
48 if (likely(vma->vm_mm == current->mm))
49 return current->nsproxy->time_ns->vvar_page;
50 /*
51 * VM_PFNMAP | VM_IO protect .fault() handler from being called
52 * through interfaces like /proc/$pid/mem or
53 * process_vm_{readv,writev}() as long as there's no .access()
54 * in special_mapping_vmops().
55 * For more details check_vma_flags() and __access_remote_vm()
56 */
57 WARN(1, "vvar_page accessed remotely");
58 return NULL;
59 }
60
61 /*
62 * The VVAR page layout depends on whether a task belongs to the root or
63 * non-root time namespace. Whenever a task changes its namespace, the VVAR
64 * page tables are cleared and then they will be re-faulted with a
65 * corresponding layout.
66 * See also the comment near timens_setup_vdso_data() for details.
67 */
vdso_join_timens(struct task_struct * task,struct time_namespace * ns)68 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
69 {
70 struct mm_struct *mm = task->mm;
71 struct vm_area_struct *vma;
72
73 mmap_read_lock(mm);
74 for (vma = mm->mmap; vma; vma = vma->vm_next) {
75 unsigned long size = vma->vm_end - vma->vm_start;
76
77 if (!vma_is_special_mapping(vma, &vvar_mapping))
78 continue;
79 zap_page_range(vma, vma->vm_start, size);
80 break;
81 }
82 mmap_read_unlock(mm);
83 return 0;
84 }
85 #else
find_timens_vvar_page(struct vm_area_struct * vma)86 static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)
87 {
88 return NULL;
89 }
90 #endif
91
vvar_fault(const struct vm_special_mapping * sm,struct vm_area_struct * vma,struct vm_fault * vmf)92 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
93 struct vm_area_struct *vma, struct vm_fault *vmf)
94 {
95 struct page *timens_page = find_timens_vvar_page(vma);
96 unsigned long addr, pfn;
97 vm_fault_t err;
98
99 switch (vmf->pgoff) {
100 case VVAR_DATA_PAGE_OFFSET:
101 pfn = virt_to_pfn(vdso_data);
102 if (timens_page) {
103 /*
104 * Fault in VVAR page too, since it will be accessed
105 * to get clock data anyway.
106 */
107 addr = vmf->address + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE;
108 err = vmf_insert_pfn(vma, addr, pfn);
109 if (unlikely(err & VM_FAULT_ERROR))
110 return err;
111 pfn = page_to_pfn(timens_page);
112 }
113 break;
114 #ifdef CONFIG_TIME_NS
115 case VVAR_TIMENS_PAGE_OFFSET:
116 /*
117 * If a task belongs to a time namespace then a namespace
118 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
119 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
120 * offset.
121 * See also the comment near timens_setup_vdso_data().
122 */
123 if (!timens_page)
124 return VM_FAULT_SIGBUS;
125 pfn = virt_to_pfn(vdso_data);
126 break;
127 #endif /* CONFIG_TIME_NS */
128 default:
129 return VM_FAULT_SIGBUS;
130 }
131 return vmf_insert_pfn(vma, vmf->address, pfn);
132 }
133
vdso_mremap(const struct vm_special_mapping * sm,struct vm_area_struct * vma)134 static int vdso_mremap(const struct vm_special_mapping *sm,
135 struct vm_area_struct *vma)
136 {
137 current->mm->context.vdso_base = vma->vm_start;
138 return 0;
139 }
140
141 static struct vm_special_mapping vvar_mapping = {
142 .name = "[vvar]",
143 .fault = vvar_fault,
144 };
145
146 static struct vm_special_mapping vdso64_mapping = {
147 .name = "[vdso]",
148 .mremap = vdso_mremap,
149 };
150
151 static struct vm_special_mapping vdso32_mapping = {
152 .name = "[vdso]",
153 .mremap = vdso_mremap,
154 };
155
vdso_getcpu_init(void)156 int vdso_getcpu_init(void)
157 {
158 set_tod_programmable_field(smp_processor_id());
159 return 0;
160 }
161 early_initcall(vdso_getcpu_init); /* Must be called before SMP init */
162
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)163 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
164 {
165 unsigned long vdso_text_len, vdso_mapping_len;
166 unsigned long vvar_start, vdso_text_start;
167 struct vm_special_mapping *vdso_mapping;
168 struct mm_struct *mm = current->mm;
169 struct vm_area_struct *vma;
170 int rc;
171
172 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
173 if (mmap_write_lock_killable(mm))
174 return -EINTR;
175
176 if (is_compat_task()) {
177 vdso_text_len = vdso32_end - vdso32_start;
178 vdso_mapping = &vdso32_mapping;
179 } else {
180 vdso_text_len = vdso64_end - vdso64_start;
181 vdso_mapping = &vdso64_mapping;
182 }
183 vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
184 vvar_start = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
185 rc = vvar_start;
186 if (IS_ERR_VALUE(vvar_start))
187 goto out;
188 vma = _install_special_mapping(mm, vvar_start, VVAR_NR_PAGES*PAGE_SIZE,
189 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
190 VM_PFNMAP,
191 &vvar_mapping);
192 rc = PTR_ERR(vma);
193 if (IS_ERR(vma))
194 goto out;
195 vdso_text_start = vvar_start + VVAR_NR_PAGES * PAGE_SIZE;
196 /* VM_MAYWRITE for COW so gdb can set breakpoints */
197 vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len,
198 VM_READ|VM_EXEC|
199 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
200 vdso_mapping);
201 if (IS_ERR(vma)) {
202 do_munmap(mm, vvar_start, PAGE_SIZE, NULL);
203 rc = PTR_ERR(vma);
204 } else {
205 current->mm->context.vdso_base = vdso_text_start;
206 rc = 0;
207 }
208 out:
209 mmap_write_unlock(mm);
210 return rc;
211 }
212
vdso_setup_pages(void * start,void * end)213 static struct page ** __init vdso_setup_pages(void *start, void *end)
214 {
215 int pages = (end - start) >> PAGE_SHIFT;
216 struct page **pagelist;
217 int i;
218
219 pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
220 if (!pagelist)
221 panic("%s: Cannot allocate page list for VDSO", __func__);
222 for (i = 0; i < pages; i++)
223 pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
224 return pagelist;
225 }
226
vdso_init(void)227 static int __init vdso_init(void)
228 {
229 vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end);
230 if (IS_ENABLED(CONFIG_COMPAT))
231 vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end);
232 return 0;
233 }
234 arch_initcall(vdso_init);
235