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/init.h>
10 #include <linux/errno.h>
11 #include <linux/sched.h>
12 #include <linux/kernel.h>
13 #include <linux/mm.h>
14 #include <linux/smp.h>
15 #include <linux/stddef.h>
16 #include <linux/unistd.h>
17 #include <linux/slab.h>
18 #include <linux/user.h>
19 #include <linux/elf.h>
20 #include <linux/security.h>
21 #include <linux/memblock.h>
22 #include <linux/compat.h>
23 #include <linux/binfmts.h>
24 #include <vdso/datapage.h>
25 #include <asm/asm-offsets.h>
26 #include <asm/processor.h>
27 #include <asm/mmu.h>
28 #include <asm/mmu_context.h>
29 #include <asm/sections.h>
30 #include <asm/vdso.h>
31 #include <asm/facility.h>
32
33 extern char vdso64_start, vdso64_end;
34 static void *vdso64_kbase = &vdso64_start;
35 static unsigned int vdso64_pages;
36 static struct page **vdso64_pagelist;
37
38 /*
39 * Should the kernel map a VDSO page into processes and pass its
40 * address down to glibc upon exec()?
41 */
42 unsigned int __read_mostly vdso_enabled = 1;
43
vdso_fault(const struct vm_special_mapping * sm,struct vm_area_struct * vma,struct vm_fault * vmf)44 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
45 struct vm_area_struct *vma, struct vm_fault *vmf)
46 {
47 struct page **vdso_pagelist;
48 unsigned long vdso_pages;
49
50 vdso_pagelist = vdso64_pagelist;
51 vdso_pages = vdso64_pages;
52
53 if (vmf->pgoff >= vdso_pages)
54 return VM_FAULT_SIGBUS;
55
56 vmf->page = vdso_pagelist[vmf->pgoff];
57 get_page(vmf->page);
58 return 0;
59 }
60
vdso_mremap(const struct vm_special_mapping * sm,struct vm_area_struct * vma)61 static int vdso_mremap(const struct vm_special_mapping *sm,
62 struct vm_area_struct *vma)
63 {
64 unsigned long vdso_pages;
65
66 vdso_pages = vdso64_pages;
67
68 if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start)
69 return -EINVAL;
70
71 if (WARN_ON_ONCE(current->mm != vma->vm_mm))
72 return -EFAULT;
73
74 current->mm->context.vdso_base = vma->vm_start;
75 return 0;
76 }
77
78 static const struct vm_special_mapping vdso_mapping = {
79 .name = "[vdso]",
80 .fault = vdso_fault,
81 .mremap = vdso_mremap,
82 };
83
vdso_setup(char * str)84 static int __init vdso_setup(char *str)
85 {
86 bool enabled;
87
88 if (!kstrtobool(str, &enabled))
89 vdso_enabled = enabled;
90 return 1;
91 }
92 __setup("vdso=", vdso_setup);
93
94 /*
95 * The vdso data page
96 */
97 static union {
98 struct vdso_data data;
99 u8 page[PAGE_SIZE];
100 } vdso_data_store __page_aligned_data;
101 struct vdso_data *vdso_data = (struct vdso_data *)&vdso_data_store.data;
102 /*
103 * Allocate/free per cpu vdso data.
104 */
105 #define SEGMENT_ORDER 2
106
vdso_alloc_per_cpu(struct lowcore * lowcore)107 int vdso_alloc_per_cpu(struct lowcore *lowcore)
108 {
109 unsigned long segment_table, page_table, page_frame;
110 struct vdso_per_cpu_data *vd;
111
112 segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
113 page_table = get_zeroed_page(GFP_KERNEL);
114 page_frame = get_zeroed_page(GFP_KERNEL);
115 if (!segment_table || !page_table || !page_frame)
116 goto out;
117 arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER);
118 arch_set_page_dat(virt_to_page(page_table), 0);
119
120 /* Initialize per-cpu vdso data page */
121 vd = (struct vdso_per_cpu_data *) page_frame;
122 vd->cpu_nr = lowcore->cpu_nr;
123 vd->node_id = cpu_to_node(vd->cpu_nr);
124
125 /* Set up page table for the vdso address space */
126 memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES);
127 memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE);
128
129 *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
130 *(unsigned long *) page_table = _PAGE_PROTECT + page_frame;
131
132 lowcore->vdso_asce = segment_table +
133 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
134 lowcore->vdso_per_cpu_data = page_frame;
135
136 return 0;
137
138 out:
139 free_page(page_frame);
140 free_page(page_table);
141 free_pages(segment_table, SEGMENT_ORDER);
142 return -ENOMEM;
143 }
144
vdso_free_per_cpu(struct lowcore * lowcore)145 void vdso_free_per_cpu(struct lowcore *lowcore)
146 {
147 unsigned long segment_table, page_table, page_frame;
148
149 segment_table = lowcore->vdso_asce & PAGE_MASK;
150 page_table = *(unsigned long *) segment_table;
151 page_frame = *(unsigned long *) page_table;
152
153 free_page(page_frame);
154 free_page(page_table);
155 free_pages(segment_table, SEGMENT_ORDER);
156 }
157
158 /*
159 * This is called from binfmt_elf, we create the special vma for the
160 * vDSO and insert it into the mm struct tree
161 */
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)162 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
163 {
164 struct mm_struct *mm = current->mm;
165 struct vm_area_struct *vma;
166 unsigned long vdso_pages;
167 unsigned long vdso_base;
168 int rc;
169
170 if (!vdso_enabled)
171 return 0;
172
173 if (is_compat_task())
174 return 0;
175
176 vdso_pages = vdso64_pages;
177 /*
178 * vDSO has a problem and was disabled, just don't "enable" it for
179 * the process
180 */
181 if (vdso_pages == 0)
182 return 0;
183
184 /*
185 * pick a base address for the vDSO in process space. We try to put
186 * it at vdso_base which is the "natural" base for it, but we might
187 * fail and end up putting it elsewhere.
188 */
189 if (mmap_write_lock_killable(mm))
190 return -EINTR;
191 vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
192 if (IS_ERR_VALUE(vdso_base)) {
193 rc = vdso_base;
194 goto out_up;
195 }
196
197 /*
198 * our vma flags don't have VM_WRITE so by default, the process
199 * isn't allowed to write those pages.
200 * gdb can break that with ptrace interface, and thus trigger COW
201 * on those pages but it's then your responsibility to never do that
202 * on the "data" page of the vDSO or you'll stop getting kernel
203 * updates and your nice userland gettimeofday will be totally dead.
204 * It's fine to use that for setting breakpoints in the vDSO code
205 * pages though.
206 */
207 vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
208 VM_READ|VM_EXEC|
209 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
210 &vdso_mapping);
211 if (IS_ERR(vma)) {
212 rc = PTR_ERR(vma);
213 goto out_up;
214 }
215
216 current->mm->context.vdso_base = vdso_base;
217 rc = 0;
218
219 out_up:
220 mmap_write_unlock(mm);
221 return rc;
222 }
223
vdso_init(void)224 static int __init vdso_init(void)
225 {
226 int i;
227
228 /* Calculate the size of the 64 bit vDSO */
229 vdso64_pages = ((&vdso64_end - &vdso64_start
230 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
231
232 /* Make sure pages are in the correct state */
233 vdso64_pagelist = kcalloc(vdso64_pages + 1, sizeof(struct page *),
234 GFP_KERNEL);
235 BUG_ON(vdso64_pagelist == NULL);
236 for (i = 0; i < vdso64_pages - 1; i++) {
237 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
238 get_page(pg);
239 vdso64_pagelist[i] = pg;
240 }
241 vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
242 vdso64_pagelist[vdso64_pages] = NULL;
243 if (vdso_alloc_per_cpu(&S390_lowcore))
244 BUG();
245
246 get_page(virt_to_page(vdso_data));
247
248 return 0;
249 }
250 early_initcall(vdso_init);
251