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