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