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 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 int vdso_mremap(const struct vm_special_mapping *sm, 37 struct vm_area_struct *new_vma) 38 { 39 current->mm->context.vdso = new_vma->vm_start; 40 41 return 0; 42 } 43 44 static struct vm_special_mapping vdso_text_mapping __ro_after_init = { 45 .name = "[vdso]", 46 .mremap = vdso_mremap, 47 }; 48 49 struct elfinfo { 50 Elf32_Ehdr *hdr; /* ptr to ELF */ 51 Elf32_Sym *dynsym; /* ptr to .dynsym section */ 52 unsigned long dynsymsize; /* size of .dynsym section */ 53 char *dynstr; /* ptr to .dynstr section */ 54 }; 55 56 /* Boot-time check for whether the arch timer exists, and if so, 57 * whether the virtual counter is usable. 58 */ 59 static bool __init cntvct_functional(void) 60 { 61 struct device_node *np; 62 bool ret = false; 63 64 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) 65 goto out; 66 67 /* The arm_arch_timer core should export 68 * arch_timer_use_virtual or similar so we don't have to do 69 * this. 70 */ 71 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer"); 72 if (!np) 73 np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer"); 74 if (!np) 75 goto out_put; 76 77 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured")) 78 goto out_put; 79 80 ret = true; 81 82 out_put: 83 of_node_put(np); 84 out: 85 return ret; 86 } 87 88 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name, 89 unsigned long *size) 90 { 91 Elf32_Shdr *sechdrs; 92 unsigned int i; 93 char *secnames; 94 95 /* Grab section headers and strings so we can tell who is who */ 96 sechdrs = (void *)ehdr + ehdr->e_shoff; 97 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset; 98 99 /* Find the section they want */ 100 for (i = 1; i < ehdr->e_shnum; i++) { 101 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) { 102 if (size) 103 *size = sechdrs[i].sh_size; 104 return (void *)ehdr + sechdrs[i].sh_offset; 105 } 106 } 107 108 if (size) 109 *size = 0; 110 return NULL; 111 } 112 113 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname) 114 { 115 unsigned int i; 116 117 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) { 118 char name[MAX_SYMNAME], *c; 119 120 if (lib->dynsym[i].st_name == 0) 121 continue; 122 strscpy(name, lib->dynstr + lib->dynsym[i].st_name, 123 MAX_SYMNAME); 124 c = strchr(name, '@'); 125 if (c) 126 *c = 0; 127 if (strcmp(symname, name) == 0) 128 return &lib->dynsym[i]; 129 } 130 return NULL; 131 } 132 133 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname) 134 { 135 Elf32_Sym *sym; 136 137 sym = find_symbol(lib, symname); 138 if (!sym) 139 return; 140 141 sym->st_name = 0; 142 } 143 144 static void __init patch_vdso(void *ehdr) 145 { 146 struct elfinfo einfo; 147 148 einfo = (struct elfinfo) { 149 .hdr = ehdr, 150 }; 151 152 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize); 153 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL); 154 155 /* If the virtual counter is absent or non-functional we don't 156 * want programs to incur the slight additional overhead of 157 * dispatching through the VDSO only to fall back to syscalls. 158 */ 159 if (!cntvct_functional()) { 160 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); 161 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); 162 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64"); 163 vdso_nullpatch_one(&einfo, "__vdso_clock_getres"); 164 vdso_nullpatch_one(&einfo, "__vdso_clock_getres_time64"); 165 } 166 } 167 168 static int __init vdso_init(void) 169 { 170 unsigned int text_pages; 171 int i; 172 173 if (memcmp(vdso_start, "\177ELF", 4)) { 174 pr_err("VDSO is not a valid ELF object!\n"); 175 return -ENOEXEC; 176 } 177 178 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; 179 180 /* Allocate the VDSO text pagelist */ 181 vdso_text_pagelist = kzalloc_objs(struct page *, text_pages); 182 if (vdso_text_pagelist == NULL) 183 return -ENOMEM; 184 185 /* Grab the VDSO text pages. */ 186 for (i = 0; i < text_pages; i++) { 187 struct page *page; 188 189 page = virt_to_page(vdso_start + i * PAGE_SIZE); 190 vdso_text_pagelist[i] = page; 191 } 192 193 vdso_text_mapping.pages = vdso_text_pagelist; 194 195 vdso_total_pages = VDSO_NR_PAGES; /* for the data/vvar pages */ 196 vdso_total_pages += text_pages; 197 198 patch_vdso(vdso_start); 199 200 return 0; 201 } 202 arch_initcall(vdso_init); 203 204 static_assert(__VDSO_PAGES == VDSO_NR_PAGES); 205 206 /* assumes mmap_lock is write-locked */ 207 void arm_install_vdso(struct mm_struct *mm, unsigned long addr) 208 { 209 struct vm_area_struct *vma; 210 unsigned long len; 211 212 mm->context.vdso = 0; 213 214 if (vdso_text_pagelist == NULL) 215 return; 216 217 if (IS_ERR(vdso_install_vvar_mapping(mm, addr))) 218 return; 219 220 /* Account for vvar pages. */ 221 addr += VDSO_NR_PAGES * PAGE_SIZE; 222 len = (vdso_total_pages - VDSO_NR_PAGES) << PAGE_SHIFT; 223 224 vma = _install_special_mapping(mm, addr, len, 225 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, 226 &vdso_text_mapping); 227 228 if (!IS_ERR(vma)) 229 mm->context.vdso = addr; 230 } 231 232