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