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 
31 static struct page **vdso_text_pagelist;
32 
33 extern char vdso_start[], vdso_end[];
34 
35 /* Total number of pages needed for the data and text portions of the VDSO. */
36 unsigned int vdso_total_pages __ro_after_init;
37 
38 /*
39  * The VDSO data page.
40  */
41 static union vdso_data_store vdso_data_store __page_aligned_data;
42 struct vdso_data *vdso_data = vdso_data_store.data;
43 
44 static struct page *vdso_data_page __ro_after_init;
45 static const struct vm_special_mapping vdso_data_mapping = {
46 	.name = "[vvar]",
47 	.pages = &vdso_data_page,
48 };
49 
vdso_mremap(const struct vm_special_mapping * sm,struct vm_area_struct * new_vma)50 static 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 
58 static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
59 	.name = "[vdso]",
60 	.mremap = vdso_mremap,
61 };
62 
63 struct 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  */
73 bool cntvct_ok __ro_after_init;
74 
cntvct_functional(void)75 static 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, "arm,armv7-timer");
88 	if (!np)
89 		np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer");
90 	if (!np)
91 		goto out_put;
92 
93 	if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
94 		goto out_put;
95 
96 	ret = true;
97 
98 out_put:
99 	of_node_put(np);
100 out:
101 	return ret;
102 }
103 
find_section(Elf32_Ehdr * ehdr,const char * name,unsigned long * size)104 static 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 
find_symbol(struct elfinfo * lib,const char * symname)129 static 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 		strlcpy(name, 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 
vdso_nullpatch_one(struct elfinfo * lib,const char * symname)149 static 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 
patch_vdso(void * ehdr)160 static 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(einfo.hdr, ".dynsym", &einfo.dynsymsize);
169 	einfo.dynstr = find_section(einfo.hdr, ".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(&einfo, "__vdso_gettimeofday");
177 		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
178 		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64");
179 	}
180 }
181 
vdso_init(void)182 static int __init vdso_init(void)
183 {
184 	unsigned int text_pages;
185 	int i;
186 
187 	if (memcmp(vdso_start, "\177ELF", 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(text_pages, 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(vdso_start);
219 
220 	return 0;
221 }
222 arch_initcall(vdso_init);
223 
install_vvar(struct mm_struct * mm,unsigned long addr)224 static 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 				       &vdso_data_mapping);
231 
232 	return PTR_ERR_OR_ZERO(vma);
233 }
234 
235 /* assumes mmap_lock is write-locked */
arm_install_vdso(struct mm_struct * mm,unsigned long addr)236 void 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 		&vdso_text_mapping);
256 
257 	if (!IS_ERR(vma))
258 		mm->context.vdso = addr;
259 }
260 
261