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 <clocksource/arm_arch_timer.h> 25 #include <vdso/helpers.h> 26 #include <vdso/vsyscall.h> 27 28 #define MAX_SYMNAME 64 29 30 static struct page **vdso_text_pagelist; 31 32 extern char vdso_start[], vdso_end[]; 33 34 /* Total number of pages needed for the data and text portions of the VDSO. */ 35 unsigned int vdso_total_pages __ro_after_init; 36 37 static union vdso_data_store vdso_data_store __page_aligned_data; 38 struct vdso_data *vdso_data = vdso_data_store.data; 39 40 static struct page *vdso_data_page __ro_after_init; 41 static const struct vm_special_mapping vdso_data_mapping = { 42 .name = "[vvar]", 43 .pages = &vdso_data_page, 44 }; 45 46 static int vdso_mremap(const struct vm_special_mapping *sm, 47 struct vm_area_struct *new_vma) 48 { 49 current->mm->context.vdso = new_vma->vm_start; 50 51 return 0; 52 } 53 54 static struct vm_special_mapping vdso_text_mapping __ro_after_init = { 55 .name = "[vdso]", 56 .mremap = vdso_mremap, 57 }; 58 59 struct elfinfo { 60 Elf32_Ehdr *hdr; /* ptr to ELF */ 61 Elf32_Sym *dynsym; /* ptr to .dynsym section */ 62 unsigned long dynsymsize; /* size of .dynsym section */ 63 char *dynstr; /* ptr to .dynstr section */ 64 }; 65 66 /* Cached result of boot-time check for whether the arch timer exists, 67 * and if so, whether the virtual counter is useable. 68 */ 69 bool cntvct_ok __ro_after_init; 70 71 static bool __init cntvct_functional(void) 72 { 73 struct device_node *np; 74 bool ret = false; 75 76 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 77 goto out; 78 79 /* The arm_arch_timer core should export 80 * arch_timer_use_virtual or similar so we don't have to do 81 * this. 82 */ 83 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); 84 if (!np) 85 np = of_find_compatible_node(NULL, NULL, "arm,armv8-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 strscpy(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 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64"); 175 } 176 } 177 178 static int __init vdso_init(void) 179 { 180 unsigned int text_pages; 181 int i; 182 183 if (memcmp(vdso_start, "\177ELF", 4)) { 184 pr_err("VDSO is not a valid ELF object!\n"); 185 return -ENOEXEC; 186 } 187 188 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; 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_lock 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