1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Adapted from arm64 version.
4 *
5 * Copyright (C) 2012 ARM Limited
6 * Copyright (C) 2015 Mentor Graphics Corporation.
7 */
8
9 #include <linux/cache.h>
10 #include <linux/elf.h>
11 #include <linux/err.h>
12 #include <linux/kernel.h>
13 #include <linux/mm.h>
14 #include <linux/of.h>
15 #include <linux/printk.h>
16 #include <linux/slab.h>
17 #include <linux/timekeeper_internal.h>
18 #include <linux/vmalloc.h>
19 #include <asm/arch_timer.h>
20 #include <asm/barrier.h>
21 #include <asm/cacheflush.h>
22 #include <asm/page.h>
23 #include <asm/vdso.h>
24 #include <clocksource/arm_arch_timer.h>
25 #include <vdso/helpers.h>
26 #include <vdso/vsyscall.h>
27
28 #define MAX_SYMNAME 64
29
30 static struct page **vdso_text_pagelist;
31
32 extern char vdso_start[], vdso_end[];
33
34 /* Total number of pages needed for the data and text portions of the VDSO. */
35 unsigned int vdso_total_pages __ro_after_init;
36
37 static union vdso_data_store vdso_data_store __page_aligned_data;
38 struct vdso_data *vdso_data = vdso_data_store.data;
39
40 static struct page *vdso_data_page __ro_after_init;
41 static const struct vm_special_mapping vdso_data_mapping = {
42 .name = "[vvar]",
43 .pages = &vdso_data_page,
44 };
45
46 static int vdso_mremap(const struct vm_special_mapping *sm,
47 struct vm_area_struct *new_vma)
48 {
49 current->mm->context.vdso = new_vma->vm_start;
50
51 return 0;
52 }
53
54 static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
55 .name = "[vdso]",
56 .mremap = vdso_mremap,
57 };
58
59 struct elfinfo {
60 Elf32_Ehdr *hdr; /* ptr to ELF */
61 Elf32_Sym *dynsym; /* ptr to .dynsym section */
62 unsigned long dynsymsize; /* size of .dynsym section */
63 char *dynstr; /* ptr to .dynstr section */
64 };
65
66 /* Cached result of boot-time check for whether the arch timer exists,
67 * and if so, whether the virtual counter is useable.
68 */
69 bool cntvct_ok __ro_after_init;
70
71 static bool __init cntvct_functional(void)
72 {
73 struct device_node *np;
74 bool ret = false;
75
76 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
77 goto out;
78
79 /* The arm_arch_timer core should export
80 * arch_timer_use_virtual or similar so we don't have to do
81 * this.
82 */
83 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
84 if (!np)
85 np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer");
86 if (!np)
87 goto out_put;
88
89 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
90 goto out_put;
91
92 ret = true;
93
94 out_put:
95 of_node_put(np);
96 out:
97 return ret;
98 }
99
100 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name,
101 unsigned long *size)
102 {
103 Elf32_Shdr *sechdrs;
104 unsigned int i;
105 char *secnames;
106
107 /* Grab section headers and strings so we can tell who is who */
108 sechdrs = (void *)ehdr + ehdr->e_shoff;
109 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
110
111 /* Find the section they want */
112 for (i = 1; i < ehdr->e_shnum; i++) {
113 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
114 if (size)
115 *size = sechdrs[i].sh_size;
116 return (void *)ehdr + sechdrs[i].sh_offset;
117 }
118 }
119
120 if (size)
121 *size = 0;
122 return NULL;
123 }
124
125 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
126 {
127 unsigned int i;
128
129 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
130 char name[MAX_SYMNAME], *c;
131
132 if (lib->dynsym[i].st_name == 0)
133 continue;
134 strscpy(name, lib->dynstr + lib->dynsym[i].st_name,
135 MAX_SYMNAME);
136 c = strchr(name, '@');
137 if (c)
138 *c = 0;
139 if (strcmp(symname, name) == 0)
140 return &lib->dynsym[i];
141 }
142 return NULL;
143 }
144
145 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname)
146 {
147 Elf32_Sym *sym;
148
149 sym = find_symbol(lib, symname);
150 if (!sym)
151 return;
152
153 sym->st_name = 0;
154 }
155
156 static void __init patch_vdso(void *ehdr)
157 {
158 struct elfinfo einfo;
159
160 einfo = (struct elfinfo) {
161 .hdr = ehdr,
162 };
163
164 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
165 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);
166
167 /* If the virtual counter is absent or non-functional we don't
168 * want programs to incur the slight additional overhead of
169 * dispatching through the VDSO only to fall back to syscalls.
170 */
171 if (!cntvct_ok) {
172 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
173 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
174 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64");
175 }
176 }
177
178 static int __init vdso_init(void)
179 {
180 unsigned int text_pages;
181 int i;
182
183 if (memcmp(vdso_start, "\177ELF", 4)) {
184 pr_err("VDSO is not a valid ELF object!\n");
185 return -ENOEXEC;
186 }
187
188 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
189
190 /* Allocate the VDSO text pagelist */
191 vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
192 GFP_KERNEL);
193 if (vdso_text_pagelist == NULL)
194 return -ENOMEM;
195
196 /* Grab the VDSO data page. */
197 vdso_data_page = virt_to_page(vdso_data);
198
199 /* Grab the VDSO text pages. */
200 for (i = 0; i < text_pages; i++) {
201 struct page *page;
202
203 page = virt_to_page(vdso_start + i * PAGE_SIZE);
204 vdso_text_pagelist[i] = page;
205 }
206
207 vdso_text_mapping.pages = vdso_text_pagelist;
208
209 vdso_total_pages = 1; /* for the data/vvar page */
210 vdso_total_pages += text_pages;
211
212 cntvct_ok = cntvct_functional();
213
214 patch_vdso(vdso_start);
215
216 return 0;
217 }
218 arch_initcall(vdso_init);
219
220 static int install_vvar(struct mm_struct *mm, unsigned long addr)
221 {
222 struct vm_area_struct *vma;
223
224 vma = _install_special_mapping(mm, addr, PAGE_SIZE,
225 VM_READ | VM_MAYREAD,
226 &vdso_data_mapping);
227
228 return PTR_ERR_OR_ZERO(vma);
229 }
230
231 /* assumes mmap_lock is write-locked */
232 void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
233 {
234 struct vm_area_struct *vma;
235 unsigned long len;
236
237 mm->context.vdso = 0;
238
239 if (vdso_text_pagelist == NULL)
240 return;
241
242 if (install_vvar(mm, addr))
243 return;
244
245 /* Account for vvar page. */
246 addr += PAGE_SIZE;
247 len = (vdso_total_pages - 1) << PAGE_SHIFT;
248
249 vma = _install_special_mapping(mm, addr, len,
250 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
251 &vdso_text_mapping);
252
253 if (!IS_ERR(vma))
254 mm->context.vdso = addr;
255 }
256
257
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