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/cache.h> 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 extern char vdso_start[], vdso_end[]; 43 44 /* Total number of pages needed for the data and text portions of the VDSO. */ 45 unsigned int vdso_total_pages __ro_after_init; 46 47 /* 48 * The VDSO data page. 49 */ 50 static union vdso_data_store vdso_data_store __page_aligned_data; 51 static struct vdso_data *vdso_data = &vdso_data_store.data; 52 53 static struct page *vdso_data_page __ro_after_init; 54 static const struct vm_special_mapping vdso_data_mapping = { 55 .name = "[vvar]", 56 .pages = &vdso_data_page, 57 }; 58 59 static int vdso_mremap(const struct vm_special_mapping *sm, 60 struct vm_area_struct *new_vma) 61 { 62 unsigned long new_size = new_vma->vm_end - new_vma->vm_start; 63 unsigned long vdso_size; 64 65 /* without VVAR page */ 66 vdso_size = (vdso_total_pages - 1) << PAGE_SHIFT; 67 68 if (vdso_size != new_size) 69 return -EINVAL; 70 71 current->mm->context.vdso = new_vma->vm_start; 72 73 return 0; 74 } 75 76 static struct vm_special_mapping vdso_text_mapping __ro_after_init = { 77 .name = "[vdso]", 78 .mremap = vdso_mremap, 79 }; 80 81 struct elfinfo { 82 Elf32_Ehdr *hdr; /* ptr to ELF */ 83 Elf32_Sym *dynsym; /* ptr to .dynsym section */ 84 unsigned long dynsymsize; /* size of .dynsym section */ 85 char *dynstr; /* ptr to .dynstr section */ 86 }; 87 88 /* Cached result of boot-time check for whether the arch timer exists, 89 * and if so, whether the virtual counter is useable. 90 */ 91 static bool cntvct_ok __ro_after_init; 92 93 static bool __init cntvct_functional(void) 94 { 95 struct device_node *np; 96 bool ret = false; 97 98 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 99 goto out; 100 101 /* The arm_arch_timer core should export 102 * arch_timer_use_virtual or similar so we don't have to do 103 * this. 104 */ 105 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); 106 if (!np) 107 goto out_put; 108 109 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) 110 goto out_put; 111 112 ret = true; 113 114 out_put: 115 of_node_put(np); 116 out: 117 return ret; 118 } 119 120 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name, 121 unsigned long *size) 122 { 123 Elf32_Shdr *sechdrs; 124 unsigned int i; 125 char *secnames; 126 127 /* Grab section headers and strings so we can tell who is who */ 128 sechdrs = (void *)ehdr + ehdr->e_shoff; 129 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset; 130 131 /* Find the section they want */ 132 for (i = 1; i < ehdr->e_shnum; i++) { 133 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) { 134 if (size) 135 *size = sechdrs[i].sh_size; 136 return (void *)ehdr + sechdrs[i].sh_offset; 137 } 138 } 139 140 if (size) 141 *size = 0; 142 return NULL; 143 } 144 145 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname) 146 { 147 unsigned int i; 148 149 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) { 150 char name[MAX_SYMNAME], *c; 151 152 if (lib->dynsym[i].st_name == 0) 153 continue; 154 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 155 MAX_SYMNAME); 156 c = strchr(name, '@'); 157 if (c) 158 *c = 0; 159 if (strcmp(symname, name) == 0) 160 return &lib->dynsym[i]; 161 } 162 return NULL; 163 } 164 165 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname) 166 { 167 Elf32_Sym *sym; 168 169 sym = find_symbol(lib, symname); 170 if (!sym) 171 return; 172 173 sym->st_name = 0; 174 } 175 176 static void __init patch_vdso(void *ehdr) 177 { 178 struct elfinfo einfo; 179 180 einfo = (struct elfinfo) { 181 .hdr = ehdr, 182 }; 183 184 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize); 185 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL); 186 187 /* If the virtual counter is absent or non-functional we don't 188 * want programs to incur the slight additional overhead of 189 * dispatching through the VDSO only to fall back to syscalls. 190 */ 191 if (!cntvct_ok) { 192 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); 193 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); 194 } 195 } 196 197 static int __init vdso_init(void) 198 { 199 unsigned int text_pages; 200 int i; 201 202 if (memcmp(vdso_start, "\177ELF", 4)) { 203 pr_err("VDSO is not a valid ELF object!\n"); 204 return -ENOEXEC; 205 } 206 207 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; 208 pr_debug("vdso: %i text pages at base %p\n", text_pages, vdso_start); 209 210 /* Allocate the VDSO text pagelist */ 211 vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *), 212 GFP_KERNEL); 213 if (vdso_text_pagelist == NULL) 214 return -ENOMEM; 215 216 /* Grab the VDSO data page. */ 217 vdso_data_page = virt_to_page(vdso_data); 218 219 /* Grab the VDSO text pages. */ 220 for (i = 0; i < text_pages; i++) { 221 struct page *page; 222 223 page = virt_to_page(vdso_start + i * PAGE_SIZE); 224 vdso_text_pagelist[i] = page; 225 } 226 227 vdso_text_mapping.pages = vdso_text_pagelist; 228 229 vdso_total_pages = 1; /* for the data/vvar page */ 230 vdso_total_pages += text_pages; 231 232 cntvct_ok = cntvct_functional(); 233 234 patch_vdso(vdso_start); 235 236 return 0; 237 } 238 arch_initcall(vdso_init); 239 240 static int install_vvar(struct mm_struct *mm, unsigned long addr) 241 { 242 struct vm_area_struct *vma; 243 244 vma = _install_special_mapping(mm, addr, PAGE_SIZE, 245 VM_READ | VM_MAYREAD, 246 &vdso_data_mapping); 247 248 return PTR_ERR_OR_ZERO(vma); 249 } 250 251 /* assumes mmap_sem is write-locked */ 252 void arm_install_vdso(struct mm_struct *mm, unsigned long addr) 253 { 254 struct vm_area_struct *vma; 255 unsigned long len; 256 257 mm->context.vdso = 0; 258 259 if (vdso_text_pagelist == NULL) 260 return; 261 262 if (install_vvar(mm, addr)) 263 return; 264 265 /* Account for vvar page. */ 266 addr += PAGE_SIZE; 267 len = (vdso_total_pages - 1) << PAGE_SHIFT; 268 269 vma = _install_special_mapping(mm, addr, len, 270 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, 271 &vdso_text_mapping); 272 273 if (!IS_ERR(vma)) 274 mm->context.vdso = addr; 275 } 276 277 static void vdso_write_begin(struct vdso_data *vdata) 278 { 279 ++vdso_data->seq_count; 280 smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */ 281 } 282 283 static void vdso_write_end(struct vdso_data *vdata) 284 { 285 smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */ 286 ++vdso_data->seq_count; 287 } 288 289 static bool tk_is_cntvct(const struct timekeeper *tk) 290 { 291 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 292 return false; 293 294 if (!tk->tkr_mono.clock->archdata.vdso_direct) 295 return false; 296 297 return true; 298 } 299 300 /** 301 * update_vsyscall - update the vdso data page 302 * 303 * Increment the sequence counter, making it odd, indicating to 304 * userspace that an update is in progress. Update the fields used 305 * for coarse clocks and, if the architected system timer is in use, 306 * the fields used for high precision clocks. Increment the sequence 307 * counter again, making it even, indicating to userspace that the 308 * update is finished. 309 * 310 * Userspace is expected to sample seq_count before reading any other 311 * fields from the data page. If seq_count is odd, userspace is 312 * expected to wait until it becomes even. After copying data from 313 * the page, userspace must sample seq_count again; if it has changed 314 * from its previous value, userspace must retry the whole sequence. 315 * 316 * Calls to update_vsyscall are serialized by the timekeeping core. 317 */ 318 void update_vsyscall(struct timekeeper *tk) 319 { 320 struct timespec64 *wtm = &tk->wall_to_monotonic; 321 322 if (!cntvct_ok) { 323 /* The entry points have been zeroed, so there is no 324 * point in updating the data page. 325 */ 326 return; 327 } 328 329 vdso_write_begin(vdso_data); 330 331 vdso_data->tk_is_cntvct = tk_is_cntvct(tk); 332 vdso_data->xtime_coarse_sec = tk->xtime_sec; 333 vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >> 334 tk->tkr_mono.shift); 335 vdso_data->wtm_clock_sec = wtm->tv_sec; 336 vdso_data->wtm_clock_nsec = wtm->tv_nsec; 337 338 if (vdso_data->tk_is_cntvct) { 339 vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last; 340 vdso_data->xtime_clock_sec = tk->xtime_sec; 341 vdso_data->xtime_clock_snsec = tk->tkr_mono.xtime_nsec; 342 vdso_data->cs_mult = tk->tkr_mono.mult; 343 vdso_data->cs_shift = tk->tkr_mono.shift; 344 vdso_data->cs_mask = tk->tkr_mono.mask; 345 } 346 347 vdso_write_end(vdso_data); 348 349 flush_dcache_page(virt_to_page(vdso_data)); 350 } 351 352 void update_vsyscall_tz(void) 353 { 354 vdso_data->tz_minuteswest = sys_tz.tz_minuteswest; 355 vdso_data->tz_dsttime = sys_tz.tz_dsttime; 356 flush_dcache_page(virt_to_page(vdso_data)); 357 } 358