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/elf.h> 21 #include <linux/err.h> 22 #include <linux/kernel.h> 23 #include <linux/mm.h> 24 #include <linux/of.h> 25 #include <linux/printk.h> 26 #include <linux/slab.h> 27 #include <linux/timekeeper_internal.h> 28 #include <linux/vmalloc.h> 29 #include <asm/arch_timer.h> 30 #include <asm/barrier.h> 31 #include <asm/cacheflush.h> 32 #include <asm/page.h> 33 #include <asm/vdso.h> 34 #include <asm/vdso_datapage.h> 35 #include <clocksource/arm_arch_timer.h> 36 37 #define MAX_SYMNAME 64 38 39 static struct page **vdso_text_pagelist; 40 41 /* Total number of pages needed for the data and text portions of the VDSO. */ 42 unsigned int vdso_total_pages __read_mostly; 43 44 /* 45 * The VDSO data page. 46 */ 47 static union vdso_data_store vdso_data_store __page_aligned_data; 48 static struct vdso_data *vdso_data = &vdso_data_store.data; 49 50 static struct page *vdso_data_page; 51 static struct vm_special_mapping vdso_data_mapping = { 52 .name = "[vvar]", 53 .pages = &vdso_data_page, 54 }; 55 56 static struct vm_special_mapping vdso_text_mapping = { 57 .name = "[vdso]", 58 }; 59 60 struct elfinfo { 61 Elf32_Ehdr *hdr; /* ptr to ELF */ 62 Elf32_Sym *dynsym; /* ptr to .dynsym section */ 63 unsigned long dynsymsize; /* size of .dynsym section */ 64 char *dynstr; /* ptr to .dynstr section */ 65 }; 66 67 /* Cached result of boot-time check for whether the arch timer exists, 68 * and if so, whether the virtual counter is useable. 69 */ 70 static bool cntvct_ok __read_mostly; 71 72 static bool __init cntvct_functional(void) 73 { 74 struct device_node *np; 75 bool ret = false; 76 77 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 78 goto out; 79 80 /* The arm_arch_timer core should export 81 * arch_timer_use_virtual or similar so we don't have to do 82 * this. 83 */ 84 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); 85 if (!np) 86 goto out_put; 87 88 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) 89 goto out_put; 90 91 ret = true; 92 93 out_put: 94 of_node_put(np); 95 out: 96 return ret; 97 } 98 99 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name, 100 unsigned long *size) 101 { 102 Elf32_Shdr *sechdrs; 103 unsigned int i; 104 char *secnames; 105 106 /* Grab section headers and strings so we can tell who is who */ 107 sechdrs = (void *)ehdr + ehdr->e_shoff; 108 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset; 109 110 /* Find the section they want */ 111 for (i = 1; i < ehdr->e_shnum; i++) { 112 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) { 113 if (size) 114 *size = sechdrs[i].sh_size; 115 return (void *)ehdr + sechdrs[i].sh_offset; 116 } 117 } 118 119 if (size) 120 *size = 0; 121 return NULL; 122 } 123 124 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname) 125 { 126 unsigned int i; 127 128 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) { 129 char name[MAX_SYMNAME], *c; 130 131 if (lib->dynsym[i].st_name == 0) 132 continue; 133 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 134 MAX_SYMNAME); 135 c = strchr(name, '@'); 136 if (c) 137 *c = 0; 138 if (strcmp(symname, name) == 0) 139 return &lib->dynsym[i]; 140 } 141 return NULL; 142 } 143 144 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname) 145 { 146 Elf32_Sym *sym; 147 148 sym = find_symbol(lib, symname); 149 if (!sym) 150 return; 151 152 sym->st_name = 0; 153 } 154 155 static void __init patch_vdso(void *ehdr) 156 { 157 struct elfinfo einfo; 158 159 einfo = (struct elfinfo) { 160 .hdr = ehdr, 161 }; 162 163 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize); 164 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL); 165 166 /* If the virtual counter is absent or non-functional we don't 167 * want programs to incur the slight additional overhead of 168 * dispatching through the VDSO only to fall back to syscalls. 169 */ 170 if (!cntvct_ok) { 171 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); 172 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); 173 } 174 } 175 176 static int __init vdso_init(void) 177 { 178 unsigned int text_pages; 179 int i; 180 181 if (memcmp(&vdso_start, "\177ELF", 4)) { 182 pr_err("VDSO is not a valid ELF object!\n"); 183 return -ENOEXEC; 184 } 185 186 text_pages = (&vdso_end - &vdso_start) >> PAGE_SHIFT; 187 pr_debug("vdso: %i text pages at base %p\n", text_pages, &vdso_start); 188 189 /* Allocate the VDSO text pagelist */ 190 vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *), 191 GFP_KERNEL); 192 if (vdso_text_pagelist == NULL) 193 return -ENOMEM; 194 195 /* Grab the VDSO data page. */ 196 vdso_data_page = virt_to_page(vdso_data); 197 198 /* Grab the VDSO text pages. */ 199 for (i = 0; i < text_pages; i++) { 200 struct page *page; 201 202 page = virt_to_page(&vdso_start + i * PAGE_SIZE); 203 vdso_text_pagelist[i] = page; 204 } 205 206 vdso_text_mapping.pages = vdso_text_pagelist; 207 208 vdso_total_pages = 1; /* for the data/vvar page */ 209 vdso_total_pages += text_pages; 210 211 cntvct_ok = cntvct_functional(); 212 213 patch_vdso(&vdso_start); 214 215 return 0; 216 } 217 arch_initcall(vdso_init); 218 219 static int install_vvar(struct mm_struct *mm, unsigned long addr) 220 { 221 struct vm_area_struct *vma; 222 223 vma = _install_special_mapping(mm, addr, PAGE_SIZE, 224 VM_READ | VM_MAYREAD, 225 &vdso_data_mapping); 226 227 return IS_ERR(vma) ? PTR_ERR(vma) : 0; 228 } 229 230 /* assumes mmap_sem is write-locked */ 231 void arm_install_vdso(struct mm_struct *mm, unsigned long addr) 232 { 233 struct vm_area_struct *vma; 234 unsigned long len; 235 236 mm->context.vdso = 0; 237 238 if (vdso_text_pagelist == NULL) 239 return; 240 241 if (install_vvar(mm, addr)) 242 return; 243 244 /* Account for vvar page. */ 245 addr += PAGE_SIZE; 246 len = (vdso_total_pages - 1) << PAGE_SHIFT; 247 248 vma = _install_special_mapping(mm, addr, len, 249 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, 250 &vdso_text_mapping); 251 252 if (!IS_ERR(vma)) 253 mm->context.vdso = addr; 254 } 255 256 static void vdso_write_begin(struct vdso_data *vdata) 257 { 258 ++vdso_data->seq_count; 259 smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */ 260 } 261 262 static void vdso_write_end(struct vdso_data *vdata) 263 { 264 smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */ 265 ++vdso_data->seq_count; 266 } 267 268 static bool tk_is_cntvct(const struct timekeeper *tk) 269 { 270 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 271 return false; 272 273 if (strcmp(tk->tkr_mono.clock->name, "arch_sys_counter") != 0) 274 return false; 275 276 return true; 277 } 278 279 /** 280 * update_vsyscall - update the vdso data page 281 * 282 * Increment the sequence counter, making it odd, indicating to 283 * userspace that an update is in progress. Update the fields used 284 * for coarse clocks and, if the architected system timer is in use, 285 * the fields used for high precision clocks. Increment the sequence 286 * counter again, making it even, indicating to userspace that the 287 * update is finished. 288 * 289 * Userspace is expected to sample seq_count before reading any other 290 * fields from the data page. If seq_count is odd, userspace is 291 * expected to wait until it becomes even. After copying data from 292 * the page, userspace must sample seq_count again; if it has changed 293 * from its previous value, userspace must retry the whole sequence. 294 * 295 * Calls to update_vsyscall are serialized by the timekeeping core. 296 */ 297 void update_vsyscall(struct timekeeper *tk) 298 { 299 struct timespec64 *wtm = &tk->wall_to_monotonic; 300 301 if (!cntvct_ok) { 302 /* The entry points have been zeroed, so there is no 303 * point in updating the data page. 304 */ 305 return; 306 } 307 308 vdso_write_begin(vdso_data); 309 310 vdso_data->tk_is_cntvct = tk_is_cntvct(tk); 311 vdso_data->xtime_coarse_sec = tk->xtime_sec; 312 vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >> 313 tk->tkr_mono.shift); 314 vdso_data->wtm_clock_sec = wtm->tv_sec; 315 vdso_data->wtm_clock_nsec = wtm->tv_nsec; 316 317 if (vdso_data->tk_is_cntvct) { 318 vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last; 319 vdso_data->xtime_clock_sec = tk->xtime_sec; 320 vdso_data->xtime_clock_snsec = tk->tkr_mono.xtime_nsec; 321 vdso_data->cs_mult = tk->tkr_mono.mult; 322 vdso_data->cs_shift = tk->tkr_mono.shift; 323 vdso_data->cs_mask = tk->tkr_mono.mask; 324 } 325 326 vdso_write_end(vdso_data); 327 328 flush_dcache_page(virt_to_page(vdso_data)); 329 } 330 331 void update_vsyscall_tz(void) 332 { 333 vdso_data->tz_minuteswest = sys_tz.tz_minuteswest; 334 vdso_data->tz_dsttime = sys_tz.tz_dsttime; 335 flush_dcache_page(virt_to_page(vdso_data)); 336 } 337