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 unsigned long size = vma->vm_end - vma->vm_start; 63 64 if (!vma_is_special_mapping(vma, &vvar_mapping)) 65 continue; 66 zap_page_range(vma, vma->vm_start, size); 67 break; 68 } 69 mmap_read_unlock(mm); 70 return 0; 71 } 72 #endif 73 74 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 75 struct vm_area_struct *vma, struct vm_fault *vmf) 76 { 77 struct page *timens_page = find_timens_vvar_page(vma); 78 unsigned long addr, pfn; 79 vm_fault_t err; 80 81 switch (vmf->pgoff) { 82 case VVAR_DATA_PAGE_OFFSET: 83 pfn = virt_to_pfn(vdso_data); 84 if (timens_page) { 85 /* 86 * Fault in VVAR page too, since it will be accessed 87 * to get clock data anyway. 88 */ 89 addr = vmf->address + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE; 90 err = vmf_insert_pfn(vma, addr, pfn); 91 if (unlikely(err & VM_FAULT_ERROR)) 92 return err; 93 pfn = page_to_pfn(timens_page); 94 } 95 break; 96 #ifdef CONFIG_TIME_NS 97 case VVAR_TIMENS_PAGE_OFFSET: 98 /* 99 * If a task belongs to a time namespace then a namespace 100 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 101 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 102 * offset. 103 * See also the comment near timens_setup_vdso_data(). 104 */ 105 if (!timens_page) 106 return VM_FAULT_SIGBUS; 107 pfn = virt_to_pfn(vdso_data); 108 break; 109 #endif /* CONFIG_TIME_NS */ 110 default: 111 return VM_FAULT_SIGBUS; 112 } 113 return vmf_insert_pfn(vma, vmf->address, pfn); 114 } 115 116 static int vdso_mremap(const struct vm_special_mapping *sm, 117 struct vm_area_struct *vma) 118 { 119 current->mm->context.vdso_base = vma->vm_start; 120 return 0; 121 } 122 123 static struct vm_special_mapping vvar_mapping = { 124 .name = "[vvar]", 125 .fault = vvar_fault, 126 }; 127 128 static struct vm_special_mapping vdso64_mapping = { 129 .name = "[vdso]", 130 .mremap = vdso_mremap, 131 }; 132 133 static struct vm_special_mapping vdso32_mapping = { 134 .name = "[vdso]", 135 .mremap = vdso_mremap, 136 }; 137 138 int vdso_getcpu_init(void) 139 { 140 set_tod_programmable_field(smp_processor_id()); 141 return 0; 142 } 143 early_initcall(vdso_getcpu_init); /* Must be called before SMP init */ 144 145 static int map_vdso(unsigned long addr, unsigned long vdso_mapping_len) 146 { 147 unsigned long vvar_start, vdso_text_start, vdso_text_len; 148 struct vm_special_mapping *vdso_mapping; 149 struct mm_struct *mm = current->mm; 150 struct vm_area_struct *vma; 151 int rc; 152 153 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 154 if (mmap_write_lock_killable(mm)) 155 return -EINTR; 156 157 if (is_compat_task()) { 158 vdso_text_len = vdso32_end - vdso32_start; 159 vdso_mapping = &vdso32_mapping; 160 } else { 161 vdso_text_len = vdso64_end - vdso64_start; 162 vdso_mapping = &vdso64_mapping; 163 } 164 vvar_start = get_unmapped_area(NULL, addr, vdso_mapping_len, 0, 0); 165 rc = vvar_start; 166 if (IS_ERR_VALUE(vvar_start)) 167 goto out; 168 vma = _install_special_mapping(mm, vvar_start, VVAR_NR_PAGES*PAGE_SIZE, 169 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP| 170 VM_PFNMAP, 171 &vvar_mapping); 172 rc = PTR_ERR(vma); 173 if (IS_ERR(vma)) 174 goto out; 175 vdso_text_start = vvar_start + VVAR_NR_PAGES * PAGE_SIZE; 176 /* VM_MAYWRITE for COW so gdb can set breakpoints */ 177 vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len, 178 VM_READ|VM_EXEC| 179 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 180 vdso_mapping); 181 if (IS_ERR(vma)) { 182 do_munmap(mm, vvar_start, PAGE_SIZE, NULL); 183 rc = PTR_ERR(vma); 184 } else { 185 current->mm->context.vdso_base = vdso_text_start; 186 rc = 0; 187 } 188 out: 189 mmap_write_unlock(mm); 190 return rc; 191 } 192 193 static unsigned long vdso_addr(unsigned long start, unsigned long len) 194 { 195 unsigned long addr, end, offset; 196 197 /* 198 * Round up the start address. It can start out unaligned as a result 199 * of stack start randomization. 200 */ 201 start = PAGE_ALIGN(start); 202 203 /* Round the lowest possible end address up to a PMD boundary. */ 204 end = (start + len + PMD_SIZE - 1) & PMD_MASK; 205 if (end >= VDSO_BASE) 206 end = VDSO_BASE; 207 end -= len; 208 209 if (end > start) { 210 offset = get_random_u32_below(((end - start) >> PAGE_SHIFT) + 1); 211 addr = start + (offset << PAGE_SHIFT); 212 } else { 213 addr = start; 214 } 215 return addr; 216 } 217 218 unsigned long vdso_size(void) 219 { 220 unsigned long size = VVAR_NR_PAGES * PAGE_SIZE; 221 222 if (is_compat_task()) 223 size += vdso32_end - vdso32_start; 224 else 225 size += vdso64_end - vdso64_start; 226 return PAGE_ALIGN(size); 227 } 228 229 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 230 { 231 unsigned long addr = VDSO_BASE; 232 unsigned long size = vdso_size(); 233 234 if (current->flags & PF_RANDOMIZE) 235 addr = vdso_addr(current->mm->start_stack + PAGE_SIZE, size); 236 return map_vdso(addr, size); 237 } 238 239 static struct page ** __init vdso_setup_pages(void *start, void *end) 240 { 241 int pages = (end - start) >> PAGE_SHIFT; 242 struct page **pagelist; 243 int i; 244 245 pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL); 246 if (!pagelist) 247 panic("%s: Cannot allocate page list for VDSO", __func__); 248 for (i = 0; i < pages; i++) 249 pagelist[i] = virt_to_page(start + i * PAGE_SIZE); 250 return pagelist; 251 } 252 253 static int __init vdso_init(void) 254 { 255 vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end); 256 if (IS_ENABLED(CONFIG_COMPAT)) 257 vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end); 258 return 0; 259 } 260 arch_initcall(vdso_init); 261