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 <asm/vdso_datapage.h>
25#include <clocksource/arm_arch_timer.h>
26#include <vdso/helpers.h>
27#include <vdso/vsyscall.h>
28
29#define MAX_SYMNAME 64
30
31static struct page **vdso_text_pagelist;
32
33extern char vdso_start[], vdso_end[];
34
35/* Total number of pages needed for the data and text portions of the VDSO. */
36unsigned int vdso_total_pages __ro_after_init;
37
38/*
39 * The VDSO data page.
40 */
41static union vdso_data_store vdso_data_store __page_aligned_data;
42struct vdso_data *vdso_data = vdso_data_store.data;
43
44static struct page *vdso_data_page __ro_after_init;
45static const struct vm_special_mapping vdso_data_mapping = {
46 .name = "[vvar]",
47 .pages = &vdso_data_page,
48};
49
50static int vdso_mremap(const struct vm_special_mapping *sm,
51 struct vm_area_struct *new_vma)
52{
53 current->mm->context.vdso = new_vma->vm_start;
54
55 return 0;
56}
57
58static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
59 .name = "[vdso]",
60 .mremap = vdso_mremap,
61};
62
63struct elfinfo {
64 Elf32_Ehdr *hdr; /* ptr to ELF */
65 Elf32_Sym *dynsym; /* ptr to .dynsym section */
66 unsigned long dynsymsize; /* size of .dynsym section */
67 char *dynstr; /* ptr to .dynstr section */
68};
69
70/* Cached result of boot-time check for whether the arch timer exists,
71 * and if so, whether the virtual counter is useable.
72 */
73bool cntvct_ok __ro_after_init;
74
75static bool __init cntvct_functional(void)
76{
77 struct device_node *np;
78 bool ret = false;
79
80 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
81 goto out;
82
83 /* The arm_arch_timer core should export
84 * arch_timer_use_virtual or similar so we don't have to do
85 * this.
86 */
87 np = of_find_compatible_node(NULL, NULL, compat: "arm,armv7-timer");
88 if (!np)
89 np = of_find_compatible_node(NULL, NULL, compat: "arm,armv8-timer");
90 if (!np)
91 goto out_put;
92
93 if (of_property_read_bool(np, propname: "arm,cpu-registers-not-fw-configured"))
94 goto out_put;
95
96 ret = true;
97
98out_put:
99 of_node_put(node: np);
100out:
101 return ret;
102}
103
104static void * __init find_section(Elf32_Ehdr *ehdr, const char *name,
105 unsigned long *size)
106{
107 Elf32_Shdr *sechdrs;
108 unsigned int i;
109 char *secnames;
110
111 /* Grab section headers and strings so we can tell who is who */
112 sechdrs = (void *)ehdr + ehdr->e_shoff;
113 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
114
115 /* Find the section they want */
116 for (i = 1; i < ehdr->e_shnum; i++) {
117 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
118 if (size)
119 *size = sechdrs[i].sh_size;
120 return (void *)ehdr + sechdrs[i].sh_offset;
121 }
122 }
123
124 if (size)
125 *size = 0;
126 return NULL;
127}
128
129static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
130{
131 unsigned int i;
132
133 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
134 char name[MAX_SYMNAME], *c;
135
136 if (lib->dynsym[i].st_name == 0)
137 continue;
138 strscpy(p: name, q: lib->dynstr + lib->dynsym[i].st_name,
139 MAX_SYMNAME);
140 c = strchr(name, '@');
141 if (c)
142 *c = 0;
143 if (strcmp(symname, name) == 0)
144 return &lib->dynsym[i];
145 }
146 return NULL;
147}
148
149static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname)
150{
151 Elf32_Sym *sym;
152
153 sym = find_symbol(lib, symname);
154 if (!sym)
155 return;
156
157 sym->st_name = 0;
158}
159
160static void __init patch_vdso(void *ehdr)
161{
162 struct elfinfo einfo;
163
164 einfo = (struct elfinfo) {
165 .hdr = ehdr,
166 };
167
168 einfo.dynsym = find_section(ehdr: einfo.hdr, name: ".dynsym", size: &einfo.dynsymsize);
169 einfo.dynstr = find_section(ehdr: einfo.hdr, name: ".dynstr", NULL);
170
171 /* If the virtual counter is absent or non-functional we don't
172 * want programs to incur the slight additional overhead of
173 * dispatching through the VDSO only to fall back to syscalls.
174 */
175 if (!cntvct_ok) {
176 vdso_nullpatch_one(lib: &einfo, symname: "__vdso_gettimeofday");
177 vdso_nullpatch_one(lib: &einfo, symname: "__vdso_clock_gettime");
178 vdso_nullpatch_one(lib: &einfo, symname: "__vdso_clock_gettime64");
179 }
180}
181
182static int __init vdso_init(void)
183{
184 unsigned int text_pages;
185 int i;
186
187 if (memcmp(p: vdso_start, q: "\177ELF", size: 4)) {
188 pr_err("VDSO is not a valid ELF object!\n");
189 return -ENOEXEC;
190 }
191
192 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
193
194 /* Allocate the VDSO text pagelist */
195 vdso_text_pagelist = kcalloc(n: text_pages, size: sizeof(struct page *),
196 GFP_KERNEL);
197 if (vdso_text_pagelist == NULL)
198 return -ENOMEM;
199
200 /* Grab the VDSO data page. */
201 vdso_data_page = virt_to_page(vdso_data);
202
203 /* Grab the VDSO text pages. */
204 for (i = 0; i < text_pages; i++) {
205 struct page *page;
206
207 page = virt_to_page(vdso_start + i * PAGE_SIZE);
208 vdso_text_pagelist[i] = page;
209 }
210
211 vdso_text_mapping.pages = vdso_text_pagelist;
212
213 vdso_total_pages = 1; /* for the data/vvar page */
214 vdso_total_pages += text_pages;
215
216 cntvct_ok = cntvct_functional();
217
218 patch_vdso(ehdr: vdso_start);
219
220 return 0;
221}
222arch_initcall(vdso_init);
223
224static int install_vvar(struct mm_struct *mm, unsigned long addr)
225{
226 struct vm_area_struct *vma;
227
228 vma = _install_special_mapping(mm, addr, PAGE_SIZE,
229 VM_READ | VM_MAYREAD,
230 spec: &vdso_data_mapping);
231
232 return PTR_ERR_OR_ZERO(ptr: vma);
233}
234
235/* assumes mmap_lock is write-locked */
236void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
237{
238 struct vm_area_struct *vma;
239 unsigned long len;
240
241 mm->context.vdso = 0;
242
243 if (vdso_text_pagelist == NULL)
244 return;
245
246 if (install_vvar(mm, addr))
247 return;
248
249 /* Account for vvar page. */
250 addr += PAGE_SIZE;
251 len = (vdso_total_pages - 1) << PAGE_SHIFT;
252
253 vma = _install_special_mapping(mm, addr, len,
254 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
255 spec: &vdso_text_mapping);
256
257 if (!IS_ERR(ptr: vma))
258 mm->context.vdso = addr;
259}
260
261

source code of linux/arch/arm/kernel/vdso.c