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/vmalloc.h> 18 #include <asm/arch_timer.h> 19 #include <asm/barrier.h> 20 #include <asm/cacheflush.h> 21 #include <asm/page.h> 22 #include <asm/vdso.h> 23 #include <clocksource/arm_arch_timer.h> 24 #include <vdso/helpers.h> 25 #include <vdso/vsyscall.h> 26 27 #define MAX_SYMNAME 64 28 29 static struct page **vdso_text_pagelist; 30 31 extern char vdso_start[], vdso_end[]; 32 33 /* Total number of pages needed for the data and text portions of the VDSO. */ 34 unsigned int vdso_total_pages __ro_after_init; 35 36 static union vdso_data_store vdso_data_store __page_aligned_data; 37 struct vdso_data *vdso_data = vdso_data_store.data; 38 39 static struct page *vdso_data_page __ro_after_init; 40 static const struct vm_special_mapping vdso_data_mapping = { 41 .name = "[vvar]", 42 .pages = &vdso_data_page, 43 }; 44 45 static int vdso_mremap(const struct vm_special_mapping *sm, 46 struct vm_area_struct *new_vma) 47 { 48 current->mm->context.vdso = new_vma->vm_start; 49 50 return 0; 51 } 52 53 static struct vm_special_mapping vdso_text_mapping __ro_after_init = { 54 .name = "[vdso]", 55 .mremap = vdso_mremap, 56 }; 57 58 struct elfinfo { 59 Elf32_Ehdr *hdr; /* ptr to ELF */ 60 Elf32_Sym *dynsym; /* ptr to .dynsym section */ 61 unsigned long dynsymsize; /* size of .dynsym section */ 62 char *dynstr; /* ptr to .dynstr section */ 63 }; 64 65 /* Cached result of boot-time check for whether the arch timer exists, 66 * and if so, whether the virtual counter is useable. 67 */ 68 bool cntvct_ok __ro_after_init; 69 70 static bool __init cntvct_functional(void) 71 { 72 struct device_node *np; 73 bool ret = false; 74 75 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 76 goto out; 77 78 /* The arm_arch_timer core should export 79 * arch_timer_use_virtual or similar so we don't have to do 80 * this. 81 */ 82 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); 83 if (!np) 84 np = of_find_compatible_node(NULL, NULL, "arm,armv8-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 strscpy(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 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64"); 174 } 175 } 176 177 static int __init vdso_init(void) 178 { 179 unsigned int text_pages; 180 int i; 181 182 if (memcmp(vdso_start, "\177ELF", 4)) { 183 pr_err("VDSO is not a valid ELF object!\n"); 184 return -ENOEXEC; 185 } 186 187 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; 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 PTR_ERR_OR_ZERO(vma); 228 } 229 230 /* assumes mmap_lock 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