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ecf99a43 NL |
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 | ||
92bb8d5d | 20 | #include <linux/cache.h> |
ecf99a43 NL |
21 | #include <linux/elf.h> |
22 | #include <linux/err.h> | |
23 | #include <linux/kernel.h> | |
24 | #include <linux/mm.h> | |
25 | #include <linux/of.h> | |
26 | #include <linux/printk.h> | |
27 | #include <linux/slab.h> | |
28 | #include <linux/timekeeper_internal.h> | |
29 | #include <linux/vmalloc.h> | |
30 | #include <asm/arch_timer.h> | |
31 | #include <asm/barrier.h> | |
32 | #include <asm/cacheflush.h> | |
33 | #include <asm/page.h> | |
34 | #include <asm/vdso.h> | |
35 | #include <asm/vdso_datapage.h> | |
36 | #include <clocksource/arm_arch_timer.h> | |
37 | ||
38 | #define MAX_SYMNAME 64 | |
39 | ||
40 | static struct page **vdso_text_pagelist; | |
41 | ||
42 | /* Total number of pages needed for the data and text portions of the VDSO. */ | |
92bb8d5d | 43 | unsigned int vdso_total_pages __ro_after_init; |
ecf99a43 NL |
44 | |
45 | /* | |
46 | * The VDSO data page. | |
47 | */ | |
48 | static union vdso_data_store vdso_data_store __page_aligned_data; | |
49 | static struct vdso_data *vdso_data = &vdso_data_store.data; | |
50 | ||
92bb8d5d JZ |
51 | static struct page *vdso_data_page __ro_after_init; |
52 | static const struct vm_special_mapping vdso_data_mapping = { | |
ecf99a43 NL |
53 | .name = "[vvar]", |
54 | .pages = &vdso_data_page, | |
55 | }; | |
56 | ||
92bb8d5d | 57 | static struct vm_special_mapping vdso_text_mapping __ro_after_init = { |
ecf99a43 NL |
58 | .name = "[vdso]", |
59 | }; | |
60 | ||
61 | struct elfinfo { | |
62 | Elf32_Ehdr *hdr; /* ptr to ELF */ | |
63 | Elf32_Sym *dynsym; /* ptr to .dynsym section */ | |
64 | unsigned long dynsymsize; /* size of .dynsym section */ | |
65 | char *dynstr; /* ptr to .dynstr section */ | |
66 | }; | |
67 | ||
68 | /* Cached result of boot-time check for whether the arch timer exists, | |
69 | * and if so, whether the virtual counter is useable. | |
70 | */ | |
92bb8d5d | 71 | static bool cntvct_ok __ro_after_init; |
ecf99a43 NL |
72 | |
73 | static bool __init cntvct_functional(void) | |
74 | { | |
75 | struct device_node *np; | |
76 | bool ret = false; | |
77 | ||
78 | if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) | |
79 | goto out; | |
80 | ||
81 | /* The arm_arch_timer core should export | |
82 | * arch_timer_use_virtual or similar so we don't have to do | |
83 | * this. | |
84 | */ | |
85 | np = of_find_compatible_node(NULL, NULL, "arm,armv7-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 | strlcpy(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 | } | |
175 | } | |
176 | ||
177 | static int __init vdso_init(void) | |
178 | { | |
179 | unsigned int text_pages; | |
180 | int i; | |
181 | ||
182 | if (memcmp(&vdso_start, "\177ELF", 4)) { | |
183 | pr_err("VDSO is not a valid ELF object!\n"); | |
184 | return -ENOEXEC; | |
185 | } | |
186 | ||
187 | text_pages = (&vdso_end - &vdso_start) >> PAGE_SHIFT; | |
188 | pr_debug("vdso: %i text pages at base %p\n", text_pages, &vdso_start); | |
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 | ||
38fc2f6c | 228 | return PTR_ERR_OR_ZERO(vma); |
ecf99a43 NL |
229 | } |
230 | ||
231 | /* assumes mmap_sem 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 | static void vdso_write_begin(struct vdso_data *vdata) | |
258 | { | |
259 | ++vdso_data->seq_count; | |
260 | smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */ | |
261 | } | |
262 | ||
263 | static void vdso_write_end(struct vdso_data *vdata) | |
264 | { | |
265 | smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */ | |
266 | ++vdso_data->seq_count; | |
267 | } | |
268 | ||
269 | static bool tk_is_cntvct(const struct timekeeper *tk) | |
270 | { | |
271 | if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) | |
272 | return false; | |
273 | ||
bb0fd7ab | 274 | if (strcmp(tk->tkr_mono.clock->name, "arch_sys_counter") != 0) |
ecf99a43 NL |
275 | return false; |
276 | ||
277 | return true; | |
278 | } | |
279 | ||
280 | /** | |
281 | * update_vsyscall - update the vdso data page | |
282 | * | |
283 | * Increment the sequence counter, making it odd, indicating to | |
284 | * userspace that an update is in progress. Update the fields used | |
285 | * for coarse clocks and, if the architected system timer is in use, | |
286 | * the fields used for high precision clocks. Increment the sequence | |
287 | * counter again, making it even, indicating to userspace that the | |
288 | * update is finished. | |
289 | * | |
290 | * Userspace is expected to sample seq_count before reading any other | |
291 | * fields from the data page. If seq_count is odd, userspace is | |
292 | * expected to wait until it becomes even. After copying data from | |
293 | * the page, userspace must sample seq_count again; if it has changed | |
294 | * from its previous value, userspace must retry the whole sequence. | |
295 | * | |
296 | * Calls to update_vsyscall are serialized by the timekeeping core. | |
297 | */ | |
298 | void update_vsyscall(struct timekeeper *tk) | |
299 | { | |
ecf99a43 NL |
300 | struct timespec64 *wtm = &tk->wall_to_monotonic; |
301 | ||
302 | if (!cntvct_ok) { | |
303 | /* The entry points have been zeroed, so there is no | |
304 | * point in updating the data page. | |
305 | */ | |
306 | return; | |
307 | } | |
308 | ||
309 | vdso_write_begin(vdso_data); | |
310 | ||
ecf99a43 | 311 | vdso_data->tk_is_cntvct = tk_is_cntvct(tk); |
09edea4f NL |
312 | vdso_data->xtime_coarse_sec = tk->xtime_sec; |
313 | vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >> | |
314 | tk->tkr_mono.shift); | |
ecf99a43 NL |
315 | vdso_data->wtm_clock_sec = wtm->tv_sec; |
316 | vdso_data->wtm_clock_nsec = wtm->tv_nsec; | |
317 | ||
318 | if (vdso_data->tk_is_cntvct) { | |
bb0fd7ab | 319 | vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last; |
ecf99a43 | 320 | vdso_data->xtime_clock_sec = tk->xtime_sec; |
bb0fd7ab LT |
321 | vdso_data->xtime_clock_snsec = tk->tkr_mono.xtime_nsec; |
322 | vdso_data->cs_mult = tk->tkr_mono.mult; | |
323 | vdso_data->cs_shift = tk->tkr_mono.shift; | |
324 | vdso_data->cs_mask = tk->tkr_mono.mask; | |
ecf99a43 NL |
325 | } |
326 | ||
327 | vdso_write_end(vdso_data); | |
328 | ||
329 | flush_dcache_page(virt_to_page(vdso_data)); | |
330 | } | |
331 | ||
332 | void update_vsyscall_tz(void) | |
333 | { | |
334 | vdso_data->tz_minuteswest = sys_tz.tz_minuteswest; | |
335 | vdso_data->tz_dsttime = sys_tz.tz_dsttime; | |
336 | flush_dcache_page(virt_to_page(vdso_data)); | |
337 | } |