1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * vdso setup for s390 4 * 5 * Copyright IBM Corp. 2008 6 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com) 7 */ 8 9 #include <linux/binfmts.h> 10 #include <linux/compat.h> 11 #include <linux/elf.h> 12 #include <linux/errno.h> 13 #include <linux/init.h> 14 #include <linux/kernel.h> 15 #include <linux/module.h> 16 #include <linux/mm.h> 17 #include <linux/slab.h> 18 #include <linux/smp.h> 19 #include <linux/time_namespace.h> 20 #include <linux/random.h> 21 #include <vdso/datapage.h> 22 #include <asm/vdso/vsyscall.h> 23 #include <asm/alternative.h> 24 #include <asm/vdso.h> 25 26 extern char vdso64_start[], vdso64_end[]; 27 extern char vdso32_start[], vdso32_end[]; 28 29 static struct vm_special_mapping vvar_mapping; 30 31 static union vdso_data_store vdso_data_store __page_aligned_data; 32 33 struct vdso_data *vdso_data = vdso_data_store.data; 34 35 #ifdef CONFIG_TIME_NS 36 struct vdso_data *arch_get_vdso_data(void *vvar_page) 37 { 38 return (struct vdso_data *)(vvar_page); 39 } 40 41 /* 42 * The VVAR page layout depends on whether a task belongs to the root or 43 * non-root time namespace. Whenever a task changes its namespace, the VVAR 44 * page tables are cleared and then they will be re-faulted with a 45 * corresponding layout. 46 * See also the comment near timens_setup_vdso_data() for details. 47 */ 48 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 49 { 50 struct mm_struct *mm = task->mm; 51 VMA_ITERATOR(vmi, mm, 0); 52 struct vm_area_struct *vma; 53 54 mmap_read_lock(mm); 55 for_each_vma(vmi, vma) { 56 if (!vma_is_special_mapping(vma, &vvar_mapping)) 57 continue; 58 zap_vma_pages(vma); 59 break; 60 } 61 mmap_read_unlock(mm); 62 return 0; 63 } 64 #endif 65 66 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 67 struct vm_area_struct *vma, struct vm_fault *vmf) 68 { 69 struct page *timens_page = find_timens_vvar_page(vma); 70 unsigned long addr, pfn; 71 vm_fault_t err; 72 73 switch (vmf->pgoff) { 74 case VVAR_DATA_PAGE_OFFSET: 75 pfn = virt_to_pfn(vdso_data); 76 if (timens_page) { 77 /* 78 * Fault in VVAR page too, since it will be accessed 79 * to get clock data anyway. 80 */ 81 addr = vmf->address + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE; 82 err = vmf_insert_pfn(vma, addr, pfn); 83 if (unlikely(err & VM_FAULT_ERROR)) 84 return err; 85 pfn = page_to_pfn(timens_page); 86 } 87 break; 88 #ifdef CONFIG_TIME_NS 89 case VVAR_TIMENS_PAGE_OFFSET: 90 /* 91 * If a task belongs to a time namespace then a namespace 92 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 93 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 94 * offset. 95 * See also the comment near timens_setup_vdso_data(). 96 */ 97 if (!timens_page) 98 return VM_FAULT_SIGBUS; 99 pfn = virt_to_pfn(vdso_data); 100 break; 101 #endif /* CONFIG_TIME_NS */ 102 default: 103 return VM_FAULT_SIGBUS; 104 } 105 return vmf_insert_pfn(vma, vmf->address, pfn); 106 } 107 108 static int vdso_mremap(const struct vm_special_mapping *sm, 109 struct vm_area_struct *vma) 110 { 111 current->mm->context.vdso_base = vma->vm_start; 112 return 0; 113 } 114 115 static struct vm_special_mapping vvar_mapping = { 116 .name = "[vvar]", 117 .fault = vvar_fault, 118 }; 119 120 static struct vm_special_mapping vdso64_mapping = { 121 .name = "[vdso]", 122 .mremap = vdso_mremap, 123 }; 124 125 static struct vm_special_mapping vdso32_mapping = { 126 .name = "[vdso]", 127 .mremap = vdso_mremap, 128 }; 129 130 int vdso_getcpu_init(void) 131 { 132 set_tod_programmable_field(smp_processor_id()); 133 return 0; 134 } 135 early_initcall(vdso_getcpu_init); /* Must be called before SMP init */ 136 137 static int map_vdso(unsigned long addr, unsigned long vdso_mapping_len) 138 { 139 unsigned long vvar_start, vdso_text_start, vdso_text_len; 140 struct vm_special_mapping *vdso_mapping; 141 struct mm_struct *mm = current->mm; 142 struct vm_area_struct *vma; 143 int rc; 144 145 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 146 if (mmap_write_lock_killable(mm)) 147 return -EINTR; 148 149 if (is_compat_task()) { 150 vdso_text_len = vdso32_end - vdso32_start; 151 vdso_mapping = &vdso32_mapping; 152 } else { 153 vdso_text_len = vdso64_end - vdso64_start; 154 vdso_mapping = &vdso64_mapping; 155 } 156 vvar_start = get_unmapped_area(NULL, addr, vdso_mapping_len, 0, 0); 157 rc = vvar_start; 158 if (IS_ERR_VALUE(vvar_start)) 159 goto out; 160 vma = _install_special_mapping(mm, vvar_start, VVAR_NR_PAGES*PAGE_SIZE, 161 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP| 162 VM_PFNMAP, 163 &vvar_mapping); 164 rc = PTR_ERR(vma); 165 if (IS_ERR(vma)) 166 goto out; 167 vdso_text_start = vvar_start + VVAR_NR_PAGES * PAGE_SIZE; 168 /* VM_MAYWRITE for COW so gdb can set breakpoints */ 169 vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len, 170 VM_READ|VM_EXEC| 171 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 172 vdso_mapping); 173 if (IS_ERR(vma)) { 174 do_munmap(mm, vvar_start, PAGE_SIZE, NULL); 175 rc = PTR_ERR(vma); 176 } else { 177 current->mm->context.vdso_base = vdso_text_start; 178 rc = 0; 179 } 180 out: 181 mmap_write_unlock(mm); 182 return rc; 183 } 184 185 static unsigned long vdso_addr(unsigned long start, unsigned long len) 186 { 187 unsigned long addr, end, offset; 188 189 /* 190 * Round up the start address. It can start out unaligned as a result 191 * of stack start randomization. 192 */ 193 start = PAGE_ALIGN(start); 194 195 /* Round the lowest possible end address up to a PMD boundary. */ 196 end = (start + len + PMD_SIZE - 1) & PMD_MASK; 197 if (end >= VDSO_BASE) 198 end = VDSO_BASE; 199 end -= len; 200 201 if (end > start) { 202 offset = get_random_u32_below(((end - start) >> PAGE_SHIFT) + 1); 203 addr = start + (offset << PAGE_SHIFT); 204 } else { 205 addr = start; 206 } 207 return addr; 208 } 209 210 unsigned long vdso_text_size(void) 211 { 212 unsigned long size; 213 214 if (is_compat_task()) 215 size = vdso32_end - vdso32_start; 216 else 217 size = vdso64_end - vdso64_start; 218 return PAGE_ALIGN(size); 219 } 220 221 unsigned long vdso_size(void) 222 { 223 return vdso_text_size() + VVAR_NR_PAGES * PAGE_SIZE; 224 } 225 226 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 227 { 228 unsigned long addr = VDSO_BASE; 229 unsigned long size = vdso_size(); 230 231 if (current->flags & PF_RANDOMIZE) 232 addr = vdso_addr(current->mm->start_stack + PAGE_SIZE, size); 233 return map_vdso(addr, size); 234 } 235 236 static struct page ** __init vdso_setup_pages(void *start, void *end) 237 { 238 int pages = (end - start) >> PAGE_SHIFT; 239 struct page **pagelist; 240 int i; 241 242 pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL); 243 if (!pagelist) 244 panic("%s: Cannot allocate page list for VDSO", __func__); 245 for (i = 0; i < pages; i++) 246 pagelist[i] = virt_to_page(start + i * PAGE_SIZE); 247 return pagelist; 248 } 249 250 static void vdso_apply_alternatives(void) 251 { 252 const struct elf64_shdr *alt, *shdr; 253 struct alt_instr *start, *end; 254 const struct elf64_hdr *hdr; 255 256 hdr = (struct elf64_hdr *)vdso64_start; 257 shdr = (void *)hdr + hdr->e_shoff; 258 alt = find_section(hdr, shdr, ".altinstructions"); 259 if (!alt) 260 return; 261 start = (void *)hdr + alt->sh_offset; 262 end = (void *)hdr + alt->sh_offset + alt->sh_size; 263 apply_alternatives(start, end); 264 } 265 266 static int __init vdso_init(void) 267 { 268 vdso_apply_alternatives(); 269 vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end); 270 if (IS_ENABLED(CONFIG_COMPAT)) 271 vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end); 272 return 0; 273 } 274 arch_initcall(vdso_init); 275