arch/s390/kernel/vdso.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * vdso setup for s390
   4  *
   5  *  Copyright IBM Corp. 2008
   6  *  Author(s): Martin Schwidefsky ([email protected])
   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);