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1 | /* | |
2 | * Adapted from arm64 version. | |
3 | * | |
4 | * Copyright (C) 2012 ARM Limited | |
5 | * Copyright (C) 2015 Mentor Graphics Corporation. | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License version 2 as | |
9 | * published by the Free Software Foundation. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | * GNU General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
17 | * along with this program. If not, see <http://www.gnu.org/licenses/>. | |
18 | */ | |
19 | ||
20 | #include <linux/elf.h> | |
21 | #include <linux/err.h> | |
22 | #include <linux/kernel.h> | |
23 | #include <linux/mm.h> | |
24 | #include <linux/of.h> | |
25 | #include <linux/printk.h> | |
26 | #include <linux/slab.h> | |
27 | #include <linux/timekeeper_internal.h> | |
28 | #include <linux/vmalloc.h> | |
29 | #include <asm/arch_timer.h> | |
30 | #include <asm/barrier.h> | |
31 | #include <asm/cacheflush.h> | |
32 | #include <asm/page.h> | |
33 | #include <asm/vdso.h> | |
34 | #include <asm/vdso_datapage.h> | |
35 | #include <clocksource/arm_arch_timer.h> | |
36 | ||
37 | #define MAX_SYMNAME 64 | |
38 | ||
39 | static struct page **vdso_text_pagelist; | |
40 | ||
41 | /* Total number of pages needed for the data and text portions of the VDSO. */ | |
42 | unsigned int vdso_total_pages __read_mostly; | |
43 | ||
44 | /* | |
45 | * The VDSO data page. | |
46 | */ | |
47 | static union vdso_data_store vdso_data_store __page_aligned_data; | |
48 | static struct vdso_data *vdso_data = &vdso_data_store.data; | |
49 | ||
50 | static struct page *vdso_data_page; | |
51 | static struct vm_special_mapping vdso_data_mapping = { | |
52 | .name = "[vvar]", | |
53 | .pages = &vdso_data_page, | |
54 | }; | |
55 | ||
56 | static struct vm_special_mapping vdso_text_mapping = { | |
57 | .name = "[vdso]", | |
58 | }; | |
59 | ||
60 | struct elfinfo { | |
61 | Elf32_Ehdr *hdr; /* ptr to ELF */ | |
62 | Elf32_Sym *dynsym; /* ptr to .dynsym section */ | |
63 | unsigned long dynsymsize; /* size of .dynsym section */ | |
64 | char *dynstr; /* ptr to .dynstr section */ | |
65 | }; | |
66 | ||
67 | /* Cached result of boot-time check for whether the arch timer exists, | |
68 | * and if so, whether the virtual counter is useable. | |
69 | */ | |
70 | static bool cntvct_ok __read_mostly; | |
71 | ||
72 | static bool __init cntvct_functional(void) | |
73 | { | |
74 | struct device_node *np; | |
75 | bool ret = false; | |
76 | ||
77 | if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) | |
78 | goto out; | |
79 | ||
80 | /* The arm_arch_timer core should export | |
81 | * arch_timer_use_virtual or similar so we don't have to do | |
82 | * this. | |
83 | */ | |
84 | np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); | |
85 | if (!np) | |
86 | goto out_put; | |
87 | ||
88 | if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) | |
89 | goto out_put; | |
90 | ||
91 | ret = true; | |
92 | ||
93 | out_put: | |
94 | of_node_put(np); | |
95 | out: | |
96 | return ret; | |
97 | } | |
98 | ||
99 | static void * __init find_section(Elf32_Ehdr *ehdr, const char *name, | |
100 | unsigned long *size) | |
101 | { | |
102 | Elf32_Shdr *sechdrs; | |
103 | unsigned int i; | |
104 | char *secnames; | |
105 | ||
106 | /* Grab section headers and strings so we can tell who is who */ | |
107 | sechdrs = (void *)ehdr + ehdr->e_shoff; | |
108 | secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset; | |
109 | ||
110 | /* Find the section they want */ | |
111 | for (i = 1; i < ehdr->e_shnum; i++) { | |
112 | if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) { | |
113 | if (size) | |
114 | *size = sechdrs[i].sh_size; | |
115 | return (void *)ehdr + sechdrs[i].sh_offset; | |
116 | } | |
117 | } | |
118 | ||
119 | if (size) | |
120 | *size = 0; | |
121 | return NULL; | |
122 | } | |
123 | ||
124 | static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname) | |
125 | { | |
126 | unsigned int i; | |
127 | ||
128 | for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) { | |
129 | char name[MAX_SYMNAME], *c; | |
130 | ||
131 | if (lib->dynsym[i].st_name == 0) | |
132 | continue; | |
133 | strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, | |
134 | MAX_SYMNAME); | |
135 | c = strchr(name, '@'); | |
136 | if (c) | |
137 | *c = 0; | |
138 | if (strcmp(symname, name) == 0) | |
139 | return &lib->dynsym[i]; | |
140 | } | |
141 | return NULL; | |
142 | } | |
143 | ||
144 | static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname) | |
145 | { | |
146 | Elf32_Sym *sym; | |
147 | ||
148 | sym = find_symbol(lib, symname); | |
149 | if (!sym) | |
150 | return; | |
151 | ||
152 | sym->st_name = 0; | |
153 | } | |
154 | ||
155 | static void __init patch_vdso(void *ehdr) | |
156 | { | |
157 | struct elfinfo einfo; | |
158 | ||
159 | einfo = (struct elfinfo) { | |
160 | .hdr = ehdr, | |
161 | }; | |
162 | ||
163 | einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize); | |
164 | einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL); | |
165 | ||
166 | /* If the virtual counter is absent or non-functional we don't | |
167 | * want programs to incur the slight additional overhead of | |
168 | * dispatching through the VDSO only to fall back to syscalls. | |
169 | */ | |
170 | if (!cntvct_ok) { | |
171 | vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); | |
172 | vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); | |
173 | } | |
174 | } | |
175 | ||
176 | static int __init vdso_init(void) | |
177 | { | |
178 | unsigned int text_pages; | |
179 | int i; | |
180 | ||
181 | if (memcmp(&vdso_start, "\177ELF", 4)) { | |
182 | pr_err("VDSO is not a valid ELF object!\n"); | |
183 | return -ENOEXEC; | |
184 | } | |
185 | ||
186 | text_pages = (&vdso_end - &vdso_start) >> PAGE_SHIFT; | |
187 | pr_debug("vdso: %i text pages at base %p\n", text_pages, &vdso_start); | |
188 | ||
189 | /* Allocate the VDSO text pagelist */ | |
190 | vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *), | |
191 | GFP_KERNEL); | |
192 | if (vdso_text_pagelist == NULL) | |
193 | return -ENOMEM; | |
194 | ||
195 | /* Grab the VDSO data page. */ | |
196 | vdso_data_page = virt_to_page(vdso_data); | |
197 | ||
198 | /* Grab the VDSO text pages. */ | |
199 | for (i = 0; i < text_pages; i++) { | |
200 | struct page *page; | |
201 | ||
202 | page = virt_to_page(&vdso_start + i * PAGE_SIZE); | |
203 | vdso_text_pagelist[i] = page; | |
204 | } | |
205 | ||
206 | vdso_text_mapping.pages = vdso_text_pagelist; | |
207 | ||
208 | vdso_total_pages = 1; /* for the data/vvar page */ | |
209 | vdso_total_pages += text_pages; | |
210 | ||
211 | cntvct_ok = cntvct_functional(); | |
212 | ||
213 | patch_vdso(&vdso_start); | |
214 | ||
215 | return 0; | |
216 | } | |
217 | arch_initcall(vdso_init); | |
218 | ||
219 | static int install_vvar(struct mm_struct *mm, unsigned long addr) | |
220 | { | |
221 | struct vm_area_struct *vma; | |
222 | ||
223 | vma = _install_special_mapping(mm, addr, PAGE_SIZE, | |
224 | VM_READ | VM_MAYREAD, | |
225 | &vdso_data_mapping); | |
226 | ||
227 | return IS_ERR(vma) ? PTR_ERR(vma) : 0; | |
228 | } | |
229 | ||
230 | /* assumes mmap_sem is write-locked */ | |
231 | void arm_install_vdso(struct mm_struct *mm, unsigned long addr) | |
232 | { | |
233 | struct vm_area_struct *vma; | |
234 | unsigned long len; | |
235 | ||
236 | mm->context.vdso = 0; | |
237 | ||
238 | if (vdso_text_pagelist == NULL) | |
239 | return; | |
240 | ||
241 | if (install_vvar(mm, addr)) | |
242 | return; | |
243 | ||
244 | /* Account for vvar page. */ | |
245 | addr += PAGE_SIZE; | |
246 | len = (vdso_total_pages - 1) << PAGE_SHIFT; | |
247 | ||
248 | vma = _install_special_mapping(mm, addr, len, | |
249 | VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, | |
250 | &vdso_text_mapping); | |
251 | ||
252 | if (!IS_ERR(vma)) | |
253 | mm->context.vdso = addr; | |
254 | } | |
255 | ||
256 | static void vdso_write_begin(struct vdso_data *vdata) | |
257 | { | |
258 | ++vdso_data->seq_count; | |
259 | smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */ | |
260 | } | |
261 | ||
262 | static void vdso_write_end(struct vdso_data *vdata) | |
263 | { | |
264 | smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */ | |
265 | ++vdso_data->seq_count; | |
266 | } | |
267 | ||
268 | static bool tk_is_cntvct(const struct timekeeper *tk) | |
269 | { | |
270 | if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) | |
271 | return false; | |
272 | ||
273 | if (strcmp(tk->tkr_mono.clock->name, "arch_sys_counter") != 0) | |
274 | return false; | |
275 | ||
276 | return true; | |
277 | } | |
278 | ||
279 | /** | |
280 | * update_vsyscall - update the vdso data page | |
281 | * | |
282 | * Increment the sequence counter, making it odd, indicating to | |
283 | * userspace that an update is in progress. Update the fields used | |
284 | * for coarse clocks and, if the architected system timer is in use, | |
285 | * the fields used for high precision clocks. Increment the sequence | |
286 | * counter again, making it even, indicating to userspace that the | |
287 | * update is finished. | |
288 | * | |
289 | * Userspace is expected to sample seq_count before reading any other | |
290 | * fields from the data page. If seq_count is odd, userspace is | |
291 | * expected to wait until it becomes even. After copying data from | |
292 | * the page, userspace must sample seq_count again; if it has changed | |
293 | * from its previous value, userspace must retry the whole sequence. | |
294 | * | |
295 | * Calls to update_vsyscall are serialized by the timekeeping core. | |
296 | */ | |
297 | void update_vsyscall(struct timekeeper *tk) | |
298 | { | |
299 | struct timespec64 *wtm = &tk->wall_to_monotonic; | |
300 | ||
301 | if (!cntvct_ok) { | |
302 | /* The entry points have been zeroed, so there is no | |
303 | * point in updating the data page. | |
304 | */ | |
305 | return; | |
306 | } | |
307 | ||
308 | vdso_write_begin(vdso_data); | |
309 | ||
310 | vdso_data->tk_is_cntvct = tk_is_cntvct(tk); | |
311 | vdso_data->xtime_coarse_sec = tk->xtime_sec; | |
312 | vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >> | |
313 | tk->tkr_mono.shift); | |
314 | vdso_data->wtm_clock_sec = wtm->tv_sec; | |
315 | vdso_data->wtm_clock_nsec = wtm->tv_nsec; | |
316 | ||
317 | if (vdso_data->tk_is_cntvct) { | |
318 | vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last; | |
319 | vdso_data->xtime_clock_sec = tk->xtime_sec; | |
320 | vdso_data->xtime_clock_snsec = tk->tkr_mono.xtime_nsec; | |
321 | vdso_data->cs_mult = tk->tkr_mono.mult; | |
322 | vdso_data->cs_shift = tk->tkr_mono.shift; | |
323 | vdso_data->cs_mask = tk->tkr_mono.mask; | |
324 | } | |
325 | ||
326 | vdso_write_end(vdso_data); | |
327 | ||
328 | flush_dcache_page(virt_to_page(vdso_data)); | |
329 | } | |
330 | ||
331 | void update_vsyscall_tz(void) | |
332 | { | |
333 | vdso_data->tz_minuteswest = sys_tz.tz_minuteswest; | |
334 | vdso_data->tz_dsttime = sys_tz.tz_dsttime; | |
335 | flush_dcache_page(virt_to_page(vdso_data)); | |
336 | } |