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/vdso_datastore.h> 11 #include <linux/elf.h> 12 #include <linux/err.h> 13 #include <linux/kernel.h> 14 #include <linux/mm.h> 15 #include <linux/of.h> 16 #include <linux/printk.h> 17 #include <linux/slab.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 int vdso_mremap(const struct vm_special_mapping *sm, 38 struct vm_area_struct *new_vma) 39 { 40 current->mm->context.vdso = new_vma->vm_start; 41 42 return 0; 43 } 44 45 static struct vm_special_mapping vdso_text_mapping __ro_after_init = { 46 .name = "[vdso]", 47 .mremap = vdso_mremap, 48 }; 49 50 struct elfinfo { 51 Elf32_Ehdr *hdr; /* ptr to ELF */ 52 Elf32_Sym *dynsym; /* ptr to .dynsym section */ 53 unsigned long dynsymsize; /* size of .dynsym section */ 54 char *dynstr; /* ptr to .dynstr section */ 55 }; 56 57 /* Cached result of boot-time check for whether the arch timer exists, 58 * and if so, whether the virtual counter is useable. 59 */ 60 bool cntvct_ok __ro_after_init; 61 62 static bool __init cntvct_functional(void) 63 { 64 struct device_node *np; 65 bool ret = false; 66 67 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 68 goto out; 69 70 /* The arm_arch_timer core should export 71 * arch_timer_use_virtual or similar so we don't have to do 72 * this. 73 */ 74 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); 75 if (!np) 76 np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer"); 77 if (!np) 78 goto out_put; 79 80 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) 81 goto out_put; 82 83 ret = true; 84 85 out_put: 86 of_node_put(np); 87 out: 88 return ret; 89 } 90 91 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name, 92 unsigned long *size) 93 { 94 Elf32_Shdr *sechdrs; 95 unsigned int i; 96 char *secnames; 97 98 /* Grab section headers and strings so we can tell who is who */ 99 sechdrs = (void *)ehdr + ehdr->e_shoff; 100 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset; 101 102 /* Find the section they want */ 103 for (i = 1; i < ehdr->e_shnum; i++) { 104 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) { 105 if (size) 106 *size = sechdrs[i].sh_size; 107 return (void *)ehdr + sechdrs[i].sh_offset; 108 } 109 } 110 111 if (size) 112 *size = 0; 113 return NULL; 114 } 115 116 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname) 117 { 118 unsigned int i; 119 120 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) { 121 char name[MAX_SYMNAME], *c; 122 123 if (lib->dynsym[i].st_name == 0) 124 continue; 125 strscpy(name, lib->dynstr + lib->dynsym[i].st_name, 126 MAX_SYMNAME); 127 c = strchr(name, '@'); 128 if (c) 129 *c = 0; 130 if (strcmp(symname, name) == 0) 131 return &lib->dynsym[i]; 132 } 133 return NULL; 134 } 135 136 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname) 137 { 138 Elf32_Sym *sym; 139 140 sym = find_symbol(lib, symname); 141 if (!sym) 142 return; 143 144 sym->st_name = 0; 145 } 146 147 static void __init patch_vdso(void *ehdr) 148 { 149 struct elfinfo einfo; 150 151 einfo = (struct elfinfo) { 152 .hdr = ehdr, 153 }; 154 155 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize); 156 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL); 157 158 /* If the virtual counter is absent or non-functional we don't 159 * want programs to incur the slight additional overhead of 160 * dispatching through the VDSO only to fall back to syscalls. 161 */ 162 if (!cntvct_ok) { 163 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); 164 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); 165 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64"); 166 } 167 } 168 169 static int __init vdso_init(void) 170 { 171 unsigned int text_pages; 172 int i; 173 174 if (memcmp(vdso_start, "\177ELF", 4)) { 175 pr_err("VDSO is not a valid ELF object!\n"); 176 return -ENOEXEC; 177 } 178 179 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; 180 181 /* Allocate the VDSO text pagelist */ 182 vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *), 183 GFP_KERNEL); 184 if (vdso_text_pagelist == NULL) 185 return -ENOMEM; 186 187 /* Grab the VDSO text pages. */ 188 for (i = 0; i < text_pages; i++) { 189 struct page *page; 190 191 page = virt_to_page(vdso_start + i * PAGE_SIZE); 192 vdso_text_pagelist[i] = page; 193 } 194 195 vdso_text_mapping.pages = vdso_text_pagelist; 196 197 vdso_total_pages = VDSO_NR_PAGES; /* for the data/vvar pages */ 198 vdso_total_pages += text_pages; 199 200 cntvct_ok = cntvct_functional(); 201 202 patch_vdso(vdso_start); 203 204 return 0; 205 } 206 arch_initcall(vdso_init); 207 208 static_assert(__VDSO_PAGES == VDSO_NR_PAGES); 209 210 /* assumes mmap_lock is write-locked */ 211 void arm_install_vdso(struct mm_struct *mm, unsigned long addr) 212 { 213 struct vm_area_struct *vma; 214 unsigned long len; 215 216 mm->context.vdso = 0; 217 218 if (vdso_text_pagelist == NULL) 219 return; 220 221 if (IS_ERR(vdso_install_vvar_mapping(mm, addr))) 222 return; 223 224 /* Account for vvar pages. */ 225 addr += VDSO_NR_PAGES * PAGE_SIZE; 226 len = (vdso_total_pages - VDSO_NR_PAGES) << PAGE_SHIFT; 227 228 vma = _install_special_mapping(mm, addr, len, 229 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, 230 &vdso_text_mapping); 231 232 if (!IS_ERR(vma)) 233 mm->context.vdso = addr; 234 } 235 236