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 goto out_put; 99 100 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) 101 goto out_put; 102 103 ret = true; 104 105 out_put: 106 of_node_put(np); 107 out: 108 return ret; 109 } 110 111 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name, 112 unsigned long *size) 113 { 114 Elf32_Shdr *sechdrs; 115 unsigned int i; 116 char *secnames; 117 118 /* Grab section headers and strings so we can tell who is who */ 119 sechdrs = (void *)ehdr + ehdr->e_shoff; 120 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset; 121 122 /* Find the section they want */ 123 for (i = 1; i < ehdr->e_shnum; i++) { 124 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) { 125 if (size) 126 *size = sechdrs[i].sh_size; 127 return (void *)ehdr + sechdrs[i].sh_offset; 128 } 129 } 130 131 if (size) 132 *size = 0; 133 return NULL; 134 } 135 136 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname) 137 { 138 unsigned int i; 139 140 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) { 141 char name[MAX_SYMNAME], *c; 142 143 if (lib->dynsym[i].st_name == 0) 144 continue; 145 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 146 MAX_SYMNAME); 147 c = strchr(name, '@'); 148 if (c) 149 *c = 0; 150 if (strcmp(symname, name) == 0) 151 return &lib->dynsym[i]; 152 } 153 return NULL; 154 } 155 156 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname) 157 { 158 Elf32_Sym *sym; 159 160 sym = find_symbol(lib, symname); 161 if (!sym) 162 return; 163 164 sym->st_name = 0; 165 } 166 167 static void __init patch_vdso(void *ehdr) 168 { 169 struct elfinfo einfo; 170 171 einfo = (struct elfinfo) { 172 .hdr = ehdr, 173 }; 174 175 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize); 176 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL); 177 178 /* If the virtual counter is absent or non-functional we don't 179 * want programs to incur the slight additional overhead of 180 * dispatching through the VDSO only to fall back to syscalls. 181 */ 182 if (!cntvct_ok) { 183 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); 184 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); 185 } 186 } 187 188 static int __init vdso_init(void) 189 { 190 unsigned int text_pages; 191 int i; 192 193 if (memcmp(vdso_start, "\177ELF", 4)) { 194 pr_err("VDSO is not a valid ELF object!\n"); 195 return -ENOEXEC; 196 } 197 198 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; 199 200 /* Allocate the VDSO text pagelist */ 201 vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *), 202 GFP_KERNEL); 203 if (vdso_text_pagelist == NULL) 204 return -ENOMEM; 205 206 /* Grab the VDSO data page. */ 207 vdso_data_page = virt_to_page(vdso_data); 208 209 /* Grab the VDSO text pages. */ 210 for (i = 0; i < text_pages; i++) { 211 struct page *page; 212 213 page = virt_to_page(vdso_start + i * PAGE_SIZE); 214 vdso_text_pagelist[i] = page; 215 } 216 217 vdso_text_mapping.pages = vdso_text_pagelist; 218 219 vdso_total_pages = 1; /* for the data/vvar page */ 220 vdso_total_pages += text_pages; 221 222 cntvct_ok = cntvct_functional(); 223 224 patch_vdso(vdso_start); 225 226 return 0; 227 } 228 arch_initcall(vdso_init); 229 230 static int install_vvar(struct mm_struct *mm, unsigned long addr) 231 { 232 struct vm_area_struct *vma; 233 234 vma = _install_special_mapping(mm, addr, PAGE_SIZE, 235 VM_READ | VM_MAYREAD, 236 &vdso_data_mapping); 237 238 return PTR_ERR_OR_ZERO(vma); 239 } 240 241 /* assumes mmap_sem is write-locked */ 242 void arm_install_vdso(struct mm_struct *mm, unsigned long addr) 243 { 244 struct vm_area_struct *vma; 245 unsigned long len; 246 247 mm->context.vdso = 0; 248 249 if (vdso_text_pagelist == NULL) 250 return; 251 252 if (install_vvar(mm, addr)) 253 return; 254 255 /* Account for vvar page. */ 256 addr += PAGE_SIZE; 257 len = (vdso_total_pages - 1) << PAGE_SHIFT; 258 259 vma = _install_special_mapping(mm, addr, len, 260 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, 261 &vdso_text_mapping); 262 263 if (!IS_ERR(vma)) 264 mm->context.vdso = addr; 265 } 266 267