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 27 #define MAX_SYMNAME 64 28 29 static struct page **vdso_text_pagelist; 30 31 extern char vdso_start[], vdso_end[]; 32 33 /* Total number of pages needed for the data and text portions of the VDSO. */ 34 unsigned int vdso_total_pages __ro_after_init; 35 36 /* 37 * The VDSO data page. 38 */ 39 static union vdso_data_store vdso_data_store __page_aligned_data; 40 static struct vdso_data *vdso_data = &vdso_data_store.data; 41 42 static struct page *vdso_data_page __ro_after_init; 43 static const struct vm_special_mapping vdso_data_mapping = { 44 .name = "[vvar]", 45 .pages = &vdso_data_page, 46 }; 47 48 static int vdso_mremap(const struct vm_special_mapping *sm, 49 struct vm_area_struct *new_vma) 50 { 51 unsigned long new_size = new_vma->vm_end - new_vma->vm_start; 52 unsigned long vdso_size; 53 54 /* without VVAR page */ 55 vdso_size = (vdso_total_pages - 1) << PAGE_SHIFT; 56 57 if (vdso_size != new_size) 58 return -EINVAL; 59 60 current->mm->context.vdso = new_vma->vm_start; 61 62 return 0; 63 } 64 65 static struct vm_special_mapping vdso_text_mapping __ro_after_init = { 66 .name = "[vdso]", 67 .mremap = vdso_mremap, 68 }; 69 70 struct elfinfo { 71 Elf32_Ehdr *hdr; /* ptr to ELF */ 72 Elf32_Sym *dynsym; /* ptr to .dynsym section */ 73 unsigned long dynsymsize; /* size of .dynsym section */ 74 char *dynstr; /* ptr to .dynstr section */ 75 }; 76 77 /* Cached result of boot-time check for whether the arch timer exists, 78 * and if so, whether the virtual counter is useable. 79 */ 80 static bool cntvct_ok __ro_after_init; 81 82 static bool __init cntvct_functional(void) 83 { 84 struct device_node *np; 85 bool ret = false; 86 87 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 88 goto out; 89 90 /* The arm_arch_timer core should export 91 * arch_timer_use_virtual or similar so we don't have to do 92 * this. 93 */ 94 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); 95 if (!np) 96 goto out_put; 97 98 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) 99 goto out_put; 100 101 ret = true; 102 103 out_put: 104 of_node_put(np); 105 out: 106 return ret; 107 } 108 109 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name, 110 unsigned long *size) 111 { 112 Elf32_Shdr *sechdrs; 113 unsigned int i; 114 char *secnames; 115 116 /* Grab section headers and strings so we can tell who is who */ 117 sechdrs = (void *)ehdr + ehdr->e_shoff; 118 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset; 119 120 /* Find the section they want */ 121 for (i = 1; i < ehdr->e_shnum; i++) { 122 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) { 123 if (size) 124 *size = sechdrs[i].sh_size; 125 return (void *)ehdr + sechdrs[i].sh_offset; 126 } 127 } 128 129 if (size) 130 *size = 0; 131 return NULL; 132 } 133 134 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname) 135 { 136 unsigned int i; 137 138 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) { 139 char name[MAX_SYMNAME], *c; 140 141 if (lib->dynsym[i].st_name == 0) 142 continue; 143 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 144 MAX_SYMNAME); 145 c = strchr(name, '@'); 146 if (c) 147 *c = 0; 148 if (strcmp(symname, name) == 0) 149 return &lib->dynsym[i]; 150 } 151 return NULL; 152 } 153 154 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname) 155 { 156 Elf32_Sym *sym; 157 158 sym = find_symbol(lib, symname); 159 if (!sym) 160 return; 161 162 sym->st_name = 0; 163 } 164 165 static void __init patch_vdso(void *ehdr) 166 { 167 struct elfinfo einfo; 168 169 einfo = (struct elfinfo) { 170 .hdr = ehdr, 171 }; 172 173 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize); 174 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL); 175 176 /* If the virtual counter is absent or non-functional we don't 177 * want programs to incur the slight additional overhead of 178 * dispatching through the VDSO only to fall back to syscalls. 179 */ 180 if (!cntvct_ok) { 181 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); 182 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); 183 } 184 } 185 186 static int __init vdso_init(void) 187 { 188 unsigned int text_pages; 189 int i; 190 191 if (memcmp(vdso_start, "\177ELF", 4)) { 192 pr_err("VDSO is not a valid ELF object!\n"); 193 return -ENOEXEC; 194 } 195 196 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; 197 pr_debug("vdso: %i text pages at base %p\n", text_pages, vdso_start); 198 199 /* Allocate the VDSO text pagelist */ 200 vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *), 201 GFP_KERNEL); 202 if (vdso_text_pagelist == NULL) 203 return -ENOMEM; 204 205 /* Grab the VDSO data page. */ 206 vdso_data_page = virt_to_page(vdso_data); 207 208 /* Grab the VDSO text pages. */ 209 for (i = 0; i < text_pages; i++) { 210 struct page *page; 211 212 page = virt_to_page(vdso_start + i * PAGE_SIZE); 213 vdso_text_pagelist[i] = page; 214 } 215 216 vdso_text_mapping.pages = vdso_text_pagelist; 217 218 vdso_total_pages = 1; /* for the data/vvar page */ 219 vdso_total_pages += text_pages; 220 221 cntvct_ok = cntvct_functional(); 222 223 patch_vdso(vdso_start); 224 225 return 0; 226 } 227 arch_initcall(vdso_init); 228 229 static int install_vvar(struct mm_struct *mm, unsigned long addr) 230 { 231 struct vm_area_struct *vma; 232 233 vma = _install_special_mapping(mm, addr, PAGE_SIZE, 234 VM_READ | VM_MAYREAD, 235 &vdso_data_mapping); 236 237 return PTR_ERR_OR_ZERO(vma); 238 } 239 240 /* assumes mmap_sem is write-locked */ 241 void arm_install_vdso(struct mm_struct *mm, unsigned long addr) 242 { 243 struct vm_area_struct *vma; 244 unsigned long len; 245 246 mm->context.vdso = 0; 247 248 if (vdso_text_pagelist == NULL) 249 return; 250 251 if (install_vvar(mm, addr)) 252 return; 253 254 /* Account for vvar page. */ 255 addr += PAGE_SIZE; 256 len = (vdso_total_pages - 1) << PAGE_SHIFT; 257 258 vma = _install_special_mapping(mm, addr, len, 259 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, 260 &vdso_text_mapping); 261 262 if (!IS_ERR(vma)) 263 mm->context.vdso = addr; 264 } 265 266 static void vdso_write_begin(struct vdso_data *vdata) 267 { 268 ++vdso_data->seq_count; 269 smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */ 270 } 271 272 static void vdso_write_end(struct vdso_data *vdata) 273 { 274 smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */ 275 ++vdso_data->seq_count; 276 } 277 278 static bool tk_is_cntvct(const struct timekeeper *tk) 279 { 280 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 281 return false; 282 283 if (!tk->tkr_mono.clock->archdata.vdso_direct) 284 return false; 285 286 return true; 287 } 288 289 /** 290 * update_vsyscall - update the vdso data page 291 * 292 * Increment the sequence counter, making it odd, indicating to 293 * userspace that an update is in progress. Update the fields used 294 * for coarse clocks and, if the architected system timer is in use, 295 * the fields used for high precision clocks. Increment the sequence 296 * counter again, making it even, indicating to userspace that the 297 * update is finished. 298 * 299 * Userspace is expected to sample seq_count before reading any other 300 * fields from the data page. If seq_count is odd, userspace is 301 * expected to wait until it becomes even. After copying data from 302 * the page, userspace must sample seq_count again; if it has changed 303 * from its previous value, userspace must retry the whole sequence. 304 * 305 * Calls to update_vsyscall are serialized by the timekeeping core. 306 */ 307 void update_vsyscall(struct timekeeper *tk) 308 { 309 struct timespec64 *wtm = &tk->wall_to_monotonic; 310 311 if (!cntvct_ok) { 312 /* The entry points have been zeroed, so there is no 313 * point in updating the data page. 314 */ 315 return; 316 } 317 318 vdso_write_begin(vdso_data); 319 320 vdso_data->tk_is_cntvct = tk_is_cntvct(tk); 321 vdso_data->xtime_coarse_sec = tk->xtime_sec; 322 vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >> 323 tk->tkr_mono.shift); 324 vdso_data->wtm_clock_sec = wtm->tv_sec; 325 vdso_data->wtm_clock_nsec = wtm->tv_nsec; 326 327 if (vdso_data->tk_is_cntvct) { 328 vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last; 329 vdso_data->xtime_clock_sec = tk->xtime_sec; 330 vdso_data->xtime_clock_snsec = tk->tkr_mono.xtime_nsec; 331 vdso_data->cs_mult = tk->tkr_mono.mult; 332 vdso_data->cs_shift = tk->tkr_mono.shift; 333 vdso_data->cs_mask = tk->tkr_mono.mask; 334 } 335 336 vdso_write_end(vdso_data); 337 338 flush_dcache_page(virt_to_page(vdso_data)); 339 } 340 341 void update_vsyscall_tz(void) 342 { 343 vdso_data->tz_minuteswest = sys_tz.tz_minuteswest; 344 vdso_data->tz_dsttime = sys_tz.tz_dsttime; 345 flush_dcache_page(virt_to_page(vdso_data)); 346 } 347