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 #include <vdso/helpers.h> 27 #include <vdso/vsyscall.h> 28 29 #define MAX_SYMNAME 64 30 31 static struct page **vdso_text_pagelist; 32 33 extern char vdso_start[], vdso_end[]; 34 35 /* Total number of pages needed for the data and text portions of the VDSO. */ 36 unsigned int vdso_total_pages __ro_after_init; 37 38 /* 39 * The VDSO data page. 40 */ 41 static union vdso_data_store vdso_data_store __page_aligned_data; 42 struct vdso_data *vdso_data = vdso_data_store.data; 43 44 static struct page *vdso_data_page __ro_after_init; 45 static const struct vm_special_mapping vdso_data_mapping = { 46 .name = "[vvar]", 47 .pages = &vdso_data_page, 48 }; 49 50 static int vdso_mremap(const struct vm_special_mapping *sm, 51 struct vm_area_struct *new_vma) 52 { 53 unsigned long new_size = new_vma->vm_end - new_vma->vm_start; 54 unsigned long vdso_size; 55 56 /* without VVAR page */ 57 vdso_size = (vdso_total_pages - 1) << PAGE_SHIFT; 58 59 if (vdso_size != new_size) 60 return -EINVAL; 61 62 current->mm->context.vdso = new_vma->vm_start; 63 64 return 0; 65 } 66 67 static struct vm_special_mapping vdso_text_mapping __ro_after_init = { 68 .name = "[vdso]", 69 .mremap = vdso_mremap, 70 }; 71 72 struct elfinfo { 73 Elf32_Ehdr *hdr; /* ptr to ELF */ 74 Elf32_Sym *dynsym; /* ptr to .dynsym section */ 75 unsigned long dynsymsize; /* size of .dynsym section */ 76 char *dynstr; /* ptr to .dynstr section */ 77 }; 78 79 /* Cached result of boot-time check for whether the arch timer exists, 80 * and if so, whether the virtual counter is useable. 81 */ 82 bool cntvct_ok __ro_after_init; 83 84 static bool __init cntvct_functional(void) 85 { 86 struct device_node *np; 87 bool ret = false; 88 89 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 90 goto out; 91 92 /* The arm_arch_timer core should export 93 * arch_timer_use_virtual or similar so we don't have to do 94 * this. 95 */ 96 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); 97 if (!np) 98 np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer"); 99 if (!np) 100 goto out_put; 101 102 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) 103 goto out_put; 104 105 ret = true; 106 107 out_put: 108 of_node_put(np); 109 out: 110 return ret; 111 } 112 113 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name, 114 unsigned long *size) 115 { 116 Elf32_Shdr *sechdrs; 117 unsigned int i; 118 char *secnames; 119 120 /* Grab section headers and strings so we can tell who is who */ 121 sechdrs = (void *)ehdr + ehdr->e_shoff; 122 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset; 123 124 /* Find the section they want */ 125 for (i = 1; i < ehdr->e_shnum; i++) { 126 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) { 127 if (size) 128 *size = sechdrs[i].sh_size; 129 return (void *)ehdr + sechdrs[i].sh_offset; 130 } 131 } 132 133 if (size) 134 *size = 0; 135 return NULL; 136 } 137 138 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname) 139 { 140 unsigned int i; 141 142 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) { 143 char name[MAX_SYMNAME], *c; 144 145 if (lib->dynsym[i].st_name == 0) 146 continue; 147 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 148 MAX_SYMNAME); 149 c = strchr(name, '@'); 150 if (c) 151 *c = 0; 152 if (strcmp(symname, name) == 0) 153 return &lib->dynsym[i]; 154 } 155 return NULL; 156 } 157 158 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname) 159 { 160 Elf32_Sym *sym; 161 162 sym = find_symbol(lib, symname); 163 if (!sym) 164 return; 165 166 sym->st_name = 0; 167 } 168 169 static void __init patch_vdso(void *ehdr) 170 { 171 struct elfinfo einfo; 172 173 einfo = (struct elfinfo) { 174 .hdr = ehdr, 175 }; 176 177 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize); 178 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL); 179 180 /* If the virtual counter is absent or non-functional we don't 181 * want programs to incur the slight additional overhead of 182 * dispatching through the VDSO only to fall back to syscalls. 183 */ 184 if (!cntvct_ok) { 185 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); 186 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); 187 } 188 } 189 190 static int __init vdso_init(void) 191 { 192 unsigned int text_pages; 193 int i; 194 195 if (memcmp(vdso_start, "\177ELF", 4)) { 196 pr_err("VDSO is not a valid ELF object!\n"); 197 return -ENOEXEC; 198 } 199 200 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; 201 202 /* Allocate the VDSO text pagelist */ 203 vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *), 204 GFP_KERNEL); 205 if (vdso_text_pagelist == NULL) 206 return -ENOMEM; 207 208 /* Grab the VDSO data page. */ 209 vdso_data_page = virt_to_page(vdso_data); 210 211 /* Grab the VDSO text pages. */ 212 for (i = 0; i < text_pages; i++) { 213 struct page *page; 214 215 page = virt_to_page(vdso_start + i * PAGE_SIZE); 216 vdso_text_pagelist[i] = page; 217 } 218 219 vdso_text_mapping.pages = vdso_text_pagelist; 220 221 vdso_total_pages = 1; /* for the data/vvar page */ 222 vdso_total_pages += text_pages; 223 224 cntvct_ok = cntvct_functional(); 225 226 patch_vdso(vdso_start); 227 228 return 0; 229 } 230 arch_initcall(vdso_init); 231 232 static int install_vvar(struct mm_struct *mm, unsigned long addr) 233 { 234 struct vm_area_struct *vma; 235 236 vma = _install_special_mapping(mm, addr, PAGE_SIZE, 237 VM_READ | VM_MAYREAD, 238 &vdso_data_mapping); 239 240 return PTR_ERR_OR_ZERO(vma); 241 } 242 243 /* assumes mmap_sem is write-locked */ 244 void arm_install_vdso(struct mm_struct *mm, unsigned long addr) 245 { 246 struct vm_area_struct *vma; 247 unsigned long len; 248 249 mm->context.vdso = 0; 250 251 if (vdso_text_pagelist == NULL) 252 return; 253 254 if (install_vvar(mm, addr)) 255 return; 256 257 /* Account for vvar page. */ 258 addr += PAGE_SIZE; 259 len = (vdso_total_pages - 1) << PAGE_SHIFT; 260 261 vma = _install_special_mapping(mm, addr, len, 262 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, 263 &vdso_text_mapping); 264 265 if (!IS_ERR(vma)) 266 mm->context.vdso = addr; 267 } 268 269