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 /* 48 * The VVAR page layout depends on whether a task belongs to the root or 49 * non-root time namespace. Whenever a task changes its namespace, the VVAR 50 * page tables are cleared and then they will be re-faulted with a 51 * corresponding layout. 52 * See also the comment near timens_setup_vdso_data() for details. 53 */ 54 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 55 { 56 struct mm_struct *mm = task->mm; 57 VMA_ITERATOR(vmi, mm, 0); 58 struct vm_area_struct *vma; 59 60 mmap_read_lock(mm); 61 for_each_vma(vmi, vma) { 62 if (!vma_is_special_mapping(vma, &vvar_mapping)) 63 continue; 64 zap_vma_pages(vma); 65 break; 66 } 67 mmap_read_unlock(mm); 68 return 0; 69 } 70 #endif 71 72 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 73 struct vm_area_struct *vma, struct vm_fault *vmf) 74 { 75 struct page *timens_page = find_timens_vvar_page(vma); 76 unsigned long addr, pfn; 77 vm_fault_t err; 78 79 switch (vmf->pgoff) { 80 case VVAR_DATA_PAGE_OFFSET: 81 pfn = virt_to_pfn(vdso_data); 82 if (timens_page) { 83 /* 84 * Fault in VVAR page too, since it will be accessed 85 * to get clock data anyway. 86 */ 87 addr = vmf->address + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE; 88 err = vmf_insert_pfn(vma, addr, pfn); 89 if (unlikely(err & VM_FAULT_ERROR)) 90 return err; 91 pfn = page_to_pfn(timens_page); 92 } 93 break; 94 #ifdef CONFIG_TIME_NS 95 case VVAR_TIMENS_PAGE_OFFSET: 96 /* 97 * If a task belongs to a time namespace then a namespace 98 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 99 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 100 * offset. 101 * See also the comment near timens_setup_vdso_data(). 102 */ 103 if (!timens_page) 104 return VM_FAULT_SIGBUS; 105 pfn = virt_to_pfn(vdso_data); 106 break; 107 #endif /* CONFIG_TIME_NS */ 108 default: 109 return VM_FAULT_SIGBUS; 110 } 111 return vmf_insert_pfn(vma, vmf->address, pfn); 112 } 113 114 static int vdso_mremap(const struct vm_special_mapping *sm, 115 struct vm_area_struct *vma) 116 { 117 current->mm->context.vdso_base = vma->vm_start; 118 return 0; 119 } 120 121 static struct vm_special_mapping vvar_mapping = { 122 .name = "[vvar]", 123 .fault = vvar_fault, 124 }; 125 126 static struct vm_special_mapping vdso64_mapping = { 127 .name = "[vdso]", 128 .mremap = vdso_mremap, 129 }; 130 131 static struct vm_special_mapping vdso32_mapping = { 132 .name = "[vdso]", 133 .mremap = vdso_mremap, 134 }; 135 136 int vdso_getcpu_init(void) 137 { 138 set_tod_programmable_field(smp_processor_id()); 139 return 0; 140 } 141 early_initcall(vdso_getcpu_init); /* Must be called before SMP init */ 142 143 static int map_vdso(unsigned long addr, unsigned long vdso_mapping_len) 144 { 145 unsigned long vvar_start, vdso_text_start, vdso_text_len; 146 struct vm_special_mapping *vdso_mapping; 147 struct mm_struct *mm = current->mm; 148 struct vm_area_struct *vma; 149 int rc; 150 151 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 152 if (mmap_write_lock_killable(mm)) 153 return -EINTR; 154 155 if (is_compat_task()) { 156 vdso_text_len = vdso32_end - vdso32_start; 157 vdso_mapping = &vdso32_mapping; 158 } else { 159 vdso_text_len = vdso64_end - vdso64_start; 160 vdso_mapping = &vdso64_mapping; 161 } 162 vvar_start = get_unmapped_area(NULL, addr, vdso_mapping_len, 0, 0); 163 rc = vvar_start; 164 if (IS_ERR_VALUE(vvar_start)) 165 goto out; 166 vma = _install_special_mapping(mm, vvar_start, VVAR_NR_PAGES*PAGE_SIZE, 167 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP| 168 VM_PFNMAP, 169 &vvar_mapping); 170 rc = PTR_ERR(vma); 171 if (IS_ERR(vma)) 172 goto out; 173 vdso_text_start = vvar_start + VVAR_NR_PAGES * PAGE_SIZE; 174 /* VM_MAYWRITE for COW so gdb can set breakpoints */ 175 vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len, 176 VM_READ|VM_EXEC| 177 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 178 vdso_mapping); 179 if (IS_ERR(vma)) { 180 do_munmap(mm, vvar_start, PAGE_SIZE, NULL); 181 rc = PTR_ERR(vma); 182 } else { 183 current->mm->context.vdso_base = vdso_text_start; 184 rc = 0; 185 } 186 out: 187 mmap_write_unlock(mm); 188 return rc; 189 } 190 191 static unsigned long vdso_addr(unsigned long start, unsigned long len) 192 { 193 unsigned long addr, end, offset; 194 195 /* 196 * Round up the start address. It can start out unaligned as a result 197 * of stack start randomization. 198 */ 199 start = PAGE_ALIGN(start); 200 201 /* Round the lowest possible end address up to a PMD boundary. */ 202 end = (start + len + PMD_SIZE - 1) & PMD_MASK; 203 if (end >= VDSO_BASE) 204 end = VDSO_BASE; 205 end -= len; 206 207 if (end > start) { 208 offset = get_random_u32_below(((end - start) >> PAGE_SHIFT) + 1); 209 addr = start + (offset << PAGE_SHIFT); 210 } else { 211 addr = start; 212 } 213 return addr; 214 } 215 216 unsigned long vdso_size(void) 217 { 218 unsigned long size = VVAR_NR_PAGES * PAGE_SIZE; 219 220 if (is_compat_task()) 221 size += vdso32_end - vdso32_start; 222 else 223 size += vdso64_end - vdso64_start; 224 return PAGE_ALIGN(size); 225 } 226 227 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 228 { 229 unsigned long addr = VDSO_BASE; 230 unsigned long size = vdso_size(); 231 232 if (current->flags & PF_RANDOMIZE) 233 addr = vdso_addr(current->mm->start_stack + PAGE_SIZE, size); 234 return map_vdso(addr, size); 235 } 236 237 static struct page ** __init vdso_setup_pages(void *start, void *end) 238 { 239 int pages = (end - start) >> PAGE_SHIFT; 240 struct page **pagelist; 241 int i; 242 243 pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL); 244 if (!pagelist) 245 panic("%s: Cannot allocate page list for VDSO", __func__); 246 for (i = 0; i < pages; i++) 247 pagelist[i] = virt_to_page(start + i * PAGE_SIZE); 248 return pagelist; 249 } 250 251 static int __init vdso_init(void) 252 { 253 vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end); 254 if (IS_ENABLED(CONFIG_COMPAT)) 255 vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end); 256 return 0; 257 } 258 arch_initcall(vdso_init); 259