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/mm.h> 16 #include <linux/slab.h> 17 #include <linux/smp.h> 18 #include <linux/time_namespace.h> 19 #include <linux/random.h> 20 #include <vdso/datapage.h> 21 #include <asm/vdso.h> 22 23 extern char vdso64_start[], vdso64_end[]; 24 extern char vdso32_start[], vdso32_end[]; 25 26 static struct vm_special_mapping vvar_mapping; 27 28 static union { 29 struct vdso_data data[CS_BASES]; 30 u8 page[PAGE_SIZE]; 31 } vdso_data_store __page_aligned_data; 32 33 struct vdso_data *vdso_data = vdso_data_store.data; 34 35 enum vvar_pages { 36 VVAR_DATA_PAGE_OFFSET, 37 VVAR_TIMENS_PAGE_OFFSET, 38 VVAR_NR_PAGES, 39 }; 40 41 #ifdef CONFIG_TIME_NS 42 struct vdso_data *arch_get_vdso_data(void *vvar_page) 43 { 44 return (struct vdso_data *)(vvar_page); 45 } 46 47 static struct page *find_timens_vvar_page(struct vm_area_struct *vma) 48 { 49 if (likely(vma->vm_mm == current->mm)) 50 return current->nsproxy->time_ns->vvar_page; 51 /* 52 * VM_PFNMAP | VM_IO protect .fault() handler from being called 53 * through interfaces like /proc/$pid/mem or 54 * process_vm_{readv,writev}() as long as there's no .access() 55 * in special_mapping_vmops(). 56 * For more details check_vma_flags() and __access_remote_vm() 57 */ 58 WARN(1, "vvar_page accessed remotely"); 59 return NULL; 60 } 61 62 /* 63 * The VVAR page layout depends on whether a task belongs to the root or 64 * non-root time namespace. Whenever a task changes its namespace, the VVAR 65 * page tables are cleared and then they will be re-faulted with a 66 * corresponding layout. 67 * See also the comment near timens_setup_vdso_data() for details. 68 */ 69 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 70 { 71 struct mm_struct *mm = task->mm; 72 struct vm_area_struct *vma; 73 74 mmap_read_lock(mm); 75 for (vma = mm->mmap; vma; vma = vma->vm_next) { 76 unsigned long size = vma->vm_end - vma->vm_start; 77 78 if (!vma_is_special_mapping(vma, &vvar_mapping)) 79 continue; 80 zap_page_range(vma, vma->vm_start, size); 81 break; 82 } 83 mmap_read_unlock(mm); 84 return 0; 85 } 86 #else 87 static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma) 88 { 89 return NULL; 90 } 91 #endif 92 93 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 94 struct vm_area_struct *vma, struct vm_fault *vmf) 95 { 96 struct page *timens_page = find_timens_vvar_page(vma); 97 unsigned long addr, pfn; 98 vm_fault_t err; 99 100 switch (vmf->pgoff) { 101 case VVAR_DATA_PAGE_OFFSET: 102 pfn = virt_to_pfn(vdso_data); 103 if (timens_page) { 104 /* 105 * Fault in VVAR page too, since it will be accessed 106 * to get clock data anyway. 107 */ 108 addr = vmf->address + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE; 109 err = vmf_insert_pfn(vma, addr, pfn); 110 if (unlikely(err & VM_FAULT_ERROR)) 111 return err; 112 pfn = page_to_pfn(timens_page); 113 } 114 break; 115 #ifdef CONFIG_TIME_NS 116 case VVAR_TIMENS_PAGE_OFFSET: 117 /* 118 * If a task belongs to a time namespace then a namespace 119 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 120 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 121 * offset. 122 * See also the comment near timens_setup_vdso_data(). 123 */ 124 if (!timens_page) 125 return VM_FAULT_SIGBUS; 126 pfn = virt_to_pfn(vdso_data); 127 break; 128 #endif /* CONFIG_TIME_NS */ 129 default: 130 return VM_FAULT_SIGBUS; 131 } 132 return vmf_insert_pfn(vma, vmf->address, pfn); 133 } 134 135 static int vdso_mremap(const struct vm_special_mapping *sm, 136 struct vm_area_struct *vma) 137 { 138 current->mm->context.vdso_base = vma->vm_start; 139 return 0; 140 } 141 142 static struct vm_special_mapping vvar_mapping = { 143 .name = "[vvar]", 144 .fault = vvar_fault, 145 }; 146 147 static struct vm_special_mapping vdso64_mapping = { 148 .name = "[vdso]", 149 .mremap = vdso_mremap, 150 }; 151 152 static struct vm_special_mapping vdso32_mapping = { 153 .name = "[vdso]", 154 .mremap = vdso_mremap, 155 }; 156 157 int vdso_getcpu_init(void) 158 { 159 set_tod_programmable_field(smp_processor_id()); 160 return 0; 161 } 162 early_initcall(vdso_getcpu_init); /* Must be called before SMP init */ 163 164 static int map_vdso(unsigned long addr, unsigned long vdso_mapping_len) 165 { 166 unsigned long vvar_start, vdso_text_start, vdso_text_len; 167 struct vm_special_mapping *vdso_mapping; 168 struct mm_struct *mm = current->mm; 169 struct vm_area_struct *vma; 170 int rc; 171 172 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 173 if (mmap_write_lock_killable(mm)) 174 return -EINTR; 175 176 if (is_compat_task()) { 177 vdso_text_len = vdso32_end - vdso32_start; 178 vdso_mapping = &vdso32_mapping; 179 } else { 180 vdso_text_len = vdso64_end - vdso64_start; 181 vdso_mapping = &vdso64_mapping; 182 } 183 vvar_start = get_unmapped_area(NULL, addr, vdso_mapping_len, 0, 0); 184 rc = vvar_start; 185 if (IS_ERR_VALUE(vvar_start)) 186 goto out; 187 vma = _install_special_mapping(mm, vvar_start, VVAR_NR_PAGES*PAGE_SIZE, 188 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP| 189 VM_PFNMAP, 190 &vvar_mapping); 191 rc = PTR_ERR(vma); 192 if (IS_ERR(vma)) 193 goto out; 194 vdso_text_start = vvar_start + VVAR_NR_PAGES * PAGE_SIZE; 195 /* VM_MAYWRITE for COW so gdb can set breakpoints */ 196 vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len, 197 VM_READ|VM_EXEC| 198 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 199 vdso_mapping); 200 if (IS_ERR(vma)) { 201 do_munmap(mm, vvar_start, PAGE_SIZE, NULL); 202 rc = PTR_ERR(vma); 203 } else { 204 current->mm->context.vdso_base = vdso_text_start; 205 rc = 0; 206 } 207 out: 208 mmap_write_unlock(mm); 209 return rc; 210 } 211 212 static unsigned long vdso_addr(unsigned long start, unsigned long len) 213 { 214 unsigned long addr, end, offset; 215 216 /* 217 * Round up the start address. It can start out unaligned as a result 218 * of stack start randomization. 219 */ 220 start = PAGE_ALIGN(start); 221 222 /* Round the lowest possible end address up to a PMD boundary. */ 223 end = (start + len + PMD_SIZE - 1) & PMD_MASK; 224 if (end >= VDSO_BASE) 225 end = VDSO_BASE; 226 end -= len; 227 228 if (end > start) { 229 offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1); 230 addr = start + (offset << PAGE_SHIFT); 231 } else { 232 addr = start; 233 } 234 return addr; 235 } 236 237 unsigned long vdso_size(void) 238 { 239 unsigned long size = VVAR_NR_PAGES * PAGE_SIZE; 240 241 if (is_compat_task()) 242 size += vdso32_end - vdso32_start; 243 else 244 size += vdso64_end - vdso64_start; 245 return PAGE_ALIGN(size); 246 } 247 248 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 249 { 250 unsigned long addr = VDSO_BASE; 251 unsigned long size = vdso_size(); 252 253 if (current->flags & PF_RANDOMIZE) 254 addr = vdso_addr(current->mm->start_stack + PAGE_SIZE, size); 255 return map_vdso(addr, size); 256 } 257 258 static struct page ** __init vdso_setup_pages(void *start, void *end) 259 { 260 int pages = (end - start) >> PAGE_SHIFT; 261 struct page **pagelist; 262 int i; 263 264 pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL); 265 if (!pagelist) 266 panic("%s: Cannot allocate page list for VDSO", __func__); 267 for (i = 0; i < pages; i++) 268 pagelist[i] = virt_to_page(start + i * PAGE_SIZE); 269 return pagelist; 270 } 271 272 static int __init vdso_init(void) 273 { 274 vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end); 275 if (IS_ENABLED(CONFIG_COMPAT)) 276 vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end); 277 return 0; 278 } 279 arch_initcall(vdso_init); 280