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 struct vm_special_mapping vdso_text_mapping __ro_after_init = { 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 */ 71 static bool cntvct_ok __ro_after_init; 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); 227 228 return PTR_ERR_OR_ZERO(vma); 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; 273 274 if (!tk->tkr_mono.clock->archdata.vdso_direct) 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 { 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); 310 311 vdso_data->tk_is_cntvct = tk_is_cntvct(tk); 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); 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) { 319 vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last; 320 vdso_data->xtime_clock_sec = tk->xtime_sec; 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; 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 } 338