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 current->mm->context.vdso = new_vma->vm_start; 54 55 return 0; 56 } 57 58 static struct vm_special_mapping vdso_text_mapping __ro_after_init = { 59 .name = "[vdso]", 60 .mremap = vdso_mremap, 61 }; 62 63 struct elfinfo { 64 Elf32_Ehdr *hdr; /* ptr to ELF */ 65 Elf32_Sym *dynsym; /* ptr to .dynsym section */ 66 unsigned long dynsymsize; /* size of .dynsym section */ 67 char *dynstr; /* ptr to .dynstr section */ 68 }; 69 70 /* Cached result of boot-time check for whether the arch timer exists, 71 * and if so, whether the virtual counter is useable. 72 */ 73 bool cntvct_ok __ro_after_init; 74 75 static bool __init cntvct_functional(void) 76 { 77 struct device_node *np; 78 bool ret = false; 79 80 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 81 goto out; 82 83 /* The arm_arch_timer core should export 84 * arch_timer_use_virtual or similar so we don't have to do 85 * this. 86 */ 87 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); 88 if (!np) 89 np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer"); 90 if (!np) 91 goto out_put; 92 93 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) 94 goto out_put; 95 96 ret = true; 97 98 out_put: 99 of_node_put(np); 100 out: 101 return ret; 102 } 103 104 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name, 105 unsigned long *size) 106 { 107 Elf32_Shdr *sechdrs; 108 unsigned int i; 109 char *secnames; 110 111 /* Grab section headers and strings so we can tell who is who */ 112 sechdrs = (void *)ehdr + ehdr->e_shoff; 113 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset; 114 115 /* Find the section they want */ 116 for (i = 1; i < ehdr->e_shnum; i++) { 117 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) { 118 if (size) 119 *size = sechdrs[i].sh_size; 120 return (void *)ehdr + sechdrs[i].sh_offset; 121 } 122 } 123 124 if (size) 125 *size = 0; 126 return NULL; 127 } 128 129 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname) 130 { 131 unsigned int i; 132 133 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) { 134 char name[MAX_SYMNAME], *c; 135 136 if (lib->dynsym[i].st_name == 0) 137 continue; 138 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 139 MAX_SYMNAME); 140 c = strchr(name, '@'); 141 if (c) 142 *c = 0; 143 if (strcmp(symname, name) == 0) 144 return &lib->dynsym[i]; 145 } 146 return NULL; 147 } 148 149 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname) 150 { 151 Elf32_Sym *sym; 152 153 sym = find_symbol(lib, symname); 154 if (!sym) 155 return; 156 157 sym->st_name = 0; 158 } 159 160 static void __init patch_vdso(void *ehdr) 161 { 162 struct elfinfo einfo; 163 164 einfo = (struct elfinfo) { 165 .hdr = ehdr, 166 }; 167 168 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize); 169 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL); 170 171 /* If the virtual counter is absent or non-functional we don't 172 * want programs to incur the slight additional overhead of 173 * dispatching through the VDSO only to fall back to syscalls. 174 */ 175 if (!cntvct_ok) { 176 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); 177 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); 178 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64"); 179 } 180 } 181 182 static int __init vdso_init(void) 183 { 184 unsigned int text_pages; 185 int i; 186 187 if (memcmp(vdso_start, "\177ELF", 4)) { 188 pr_err("VDSO is not a valid ELF object!\n"); 189 return -ENOEXEC; 190 } 191 192 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; 193 194 /* Allocate the VDSO text pagelist */ 195 vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *), 196 GFP_KERNEL); 197 if (vdso_text_pagelist == NULL) 198 return -ENOMEM; 199 200 /* Grab the VDSO data page. */ 201 vdso_data_page = virt_to_page(vdso_data); 202 203 /* Grab the VDSO text pages. */ 204 for (i = 0; i < text_pages; i++) { 205 struct page *page; 206 207 page = virt_to_page(vdso_start + i * PAGE_SIZE); 208 vdso_text_pagelist[i] = page; 209 } 210 211 vdso_text_mapping.pages = vdso_text_pagelist; 212 213 vdso_total_pages = 1; /* for the data/vvar page */ 214 vdso_total_pages += text_pages; 215 216 cntvct_ok = cntvct_functional(); 217 218 patch_vdso(vdso_start); 219 220 return 0; 221 } 222 arch_initcall(vdso_init); 223 224 static int install_vvar(struct mm_struct *mm, unsigned long addr) 225 { 226 struct vm_area_struct *vma; 227 228 vma = _install_special_mapping(mm, addr, PAGE_SIZE, 229 VM_READ | VM_MAYREAD, 230 &vdso_data_mapping); 231 232 return PTR_ERR_OR_ZERO(vma); 233 } 234 235 /* assumes mmap_lock is write-locked */ 236 void arm_install_vdso(struct mm_struct *mm, unsigned long addr) 237 { 238 struct vm_area_struct *vma; 239 unsigned long len; 240 241 mm->context.vdso = 0; 242 243 if (vdso_text_pagelist == NULL) 244 return; 245 246 if (install_vvar(mm, addr)) 247 return; 248 249 /* Account for vvar page. */ 250 addr += PAGE_SIZE; 251 len = (vdso_total_pages - 1) << PAGE_SHIFT; 252 253 vma = _install_special_mapping(mm, addr, len, 254 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, 255 &vdso_text_mapping); 256 257 if (!IS_ERR(vma)) 258 mm->context.vdso = addr; 259 } 260 261