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 (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/module.h>
  16 #include <linux/mm.h>
  17 #include <linux/slab.h>
  18 #include <linux/smp.h>
  19 #include <linux/time_namespace.h>
  20 #include <linux/random.h>
  21 #include <vdso/datapage.h>
  22 #include <asm/vdso/vsyscall.h>
  23 #include <asm/alternative.h>
  24 #include <asm/vdso.h>
  25
  26 extern char vdso64_start[], vdso64_end[];
  27 extern char vdso32_start[], vdso32_end[];
  28
  29 static struct vm_special_mapping vvar_mapping;
  30
  31 static union vdso_data_store vdso_data_store __page_aligned_data;
  32
  33 struct vdso_data *vdso_data = vdso_data_store.data;
  34
  35 #ifdef CONFIG_TIME_NS
  36 struct vdso_data *arch_get_vdso_data(void *vvar_page)
  37 {
  38         return (struct vdso_data *)(vvar_page);
  39 }
  40
  41 /*
  42  * The VVAR page layout depends on whether a task belongs to the root or
  43  * non-root time namespace. Whenever a task changes its namespace, the VVAR
  44  * page tables are cleared and then they will be re-faulted with a
  45  * corresponding layout.
  46  * See also the comment near timens_setup_vdso_data() for details.
  47  */
  48 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
  49 {
  50         struct mm_struct *mm = task->mm;
  51         VMA_ITERATOR(vmi, mm, 0);
  52         struct vm_area_struct *vma;
  53
  54         mmap_read_lock(mm);
  55         for_each_vma(vmi, vma) {
  56                 if (!vma_is_special_mapping(vma, &vvar_mapping))
  57                         continue;
  58                 zap_vma_pages(vma);
  59                 break;
  60         }
  61         mmap_read_unlock(mm);
  62         return 0;
  63 }
  64 #endif
  65
  66 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
  67                              struct vm_area_struct *vma, struct vm_fault *vmf)
  68 {
  69         struct page *timens_page = find_timens_vvar_page(vma);
  70         unsigned long addr, pfn;
  71         vm_fault_t err;
  72
  73         switch (vmf->pgoff) {
  74         case VVAR_DATA_PAGE_OFFSET:
  75                 pfn = virt_to_pfn(vdso_data);
  76                 if (timens_page) {
  77                         /*
  78                          * Fault in VVAR page too, since it will be accessed
  79                          * to get clock data anyway.
  80                          */
  81                         addr = vmf->address + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE;
  82                         err = vmf_insert_pfn(vma, addr, pfn);
  83                         if (unlikely(err & VM_FAULT_ERROR))
  84                                 return err;
  85                         pfn = page_to_pfn(timens_page);
  86                 }
  87                 break;
  88 #ifdef CONFIG_TIME_NS
  89         case VVAR_TIMENS_PAGE_OFFSET:
  90                 /*
  91                  * If a task belongs to a time namespace then a namespace
  92                  * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
  93                  * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
  94                  * offset.
  95                  * See also the comment near timens_setup_vdso_data().
  96                  */
  97                 if (!timens_page)
  98                         return VM_FAULT_SIGBUS;
  99                 pfn = virt_to_pfn(vdso_data);
 100                 break;
 101 #endif /* CONFIG_TIME_NS */
 102         default:
 103                 return VM_FAULT_SIGBUS;
 104         }
 105         return vmf_insert_pfn(vma, vmf->address, pfn);
 106 }
 107
 108 static int vdso_mremap(const struct vm_special_mapping *sm,
 109                        struct vm_area_struct *vma)
 110 {
 111         current->mm->context.vdso_base = vma->vm_start;
 112         return 0;
 113 }
 114
 115 static struct vm_special_mapping vvar_mapping = {
 116         .name = "[vvar]",
 117         .fault = vvar_fault,
 118 };
 119
 120 static struct vm_special_mapping vdso64_mapping = {
 121         .name = "[vdso]",
 122         .mremap = vdso_mremap,
 123 };
 124
 125 static struct vm_special_mapping vdso32_mapping = {
 126         .name = "[vdso]",
 127         .mremap = vdso_mremap,
 128 };
 129
 130 int vdso_getcpu_init(void)
 131 {
 132         set_tod_programmable_field(smp_processor_id());
 133         return 0;
 134 }
 135 early_initcall(vdso_getcpu_init); /* Must be called before SMP init */
 136
 137 static int map_vdso(unsigned long addr, unsigned long vdso_mapping_len)
 138 {
 139         unsigned long vvar_start, vdso_text_start, vdso_text_len;
 140         struct vm_special_mapping *vdso_mapping;
 141         struct mm_struct *mm = current->mm;
 142         struct vm_area_struct *vma;
 143         int rc;
 144
 145         BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
 146         if (mmap_write_lock_killable(mm))
 147                 return -EINTR;
 148
 149         if (is_compat_task()) {
 150                 vdso_text_len = vdso32_end - vdso32_start;
 151                 vdso_mapping = &vdso32_mapping;
 152         } else {
 153                 vdso_text_len = vdso64_end - vdso64_start;
 154                 vdso_mapping = &vdso64_mapping;
 155         }
 156         vvar_start = get_unmapped_area(NULL, addr, vdso_mapping_len, 0, 0);
 157         rc = vvar_start;
 158         if (IS_ERR_VALUE(vvar_start))
 159                 goto out;
 160         vma = _install_special_mapping(mm, vvar_start, VVAR_NR_PAGES*PAGE_SIZE,
 161                                        VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
 162                                        VM_PFNMAP,
 163                                        &vvar_mapping);
 164         rc = PTR_ERR(vma);
 165         if (IS_ERR(vma))
 166                 goto out;
 167         vdso_text_start = vvar_start + VVAR_NR_PAGES * PAGE_SIZE;
 168         /* VM_MAYWRITE for COW so gdb can set breakpoints */
 169         vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len,
 170                                        VM_READ|VM_EXEC|
 171                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 172                                        vdso_mapping);
 173         if (IS_ERR(vma)) {
 174                 do_munmap(mm, vvar_start, PAGE_SIZE, NULL);
 175                 rc = PTR_ERR(vma);
 176         } else {
 177                 current->mm->context.vdso_base = vdso_text_start;
 178                 rc = 0;
 179         }
 180 out:
 181         mmap_write_unlock(mm);
 182         return rc;
 183 }
 184
 185 static unsigned long vdso_addr(unsigned long start, unsigned long len)
 186 {
 187         unsigned long addr, end, offset;
 188
 189         /*
 190          * Round up the start address. It can start out unaligned as a result
 191          * of stack start randomization.
 192          */
 193         start = PAGE_ALIGN(start);
 194
 195         /* Round the lowest possible end address up to a PMD boundary. */
 196         end = (start + len + PMD_SIZE - 1) & PMD_MASK;
 197         if (end >= VDSO_BASE)
 198                 end = VDSO_BASE;
 199         end -= len;
 200
 201         if (end > start) {
 202                 offset = get_random_u32_below(((end - start) >> PAGE_SHIFT) + 1);
 203                 addr = start + (offset << PAGE_SHIFT);
 204         } else {
 205                 addr = start;
 206         }
 207         return addr;
 208 }
 209
 210 unsigned long vdso_text_size(void)
 211 {
 212         unsigned long size;
 213
 214         if (is_compat_task())
 215                 size = vdso32_end - vdso32_start;
 216         else
 217                 size = vdso64_end - vdso64_start;
 218         return PAGE_ALIGN(size);
 219 }
 220
 221 unsigned long vdso_size(void)
 222 {
 223         return vdso_text_size() + VVAR_NR_PAGES * PAGE_SIZE;
 224 }
 225
 226 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 227 {
 228         unsigned long addr = VDSO_BASE;
 229         unsigned long size = vdso_size();
 230
 231         if (current->flags & PF_RANDOMIZE)
 232                 addr = vdso_addr(current->mm->start_stack + PAGE_SIZE, size);
 233         return map_vdso(addr, size);
 234 }
 235
 236 static struct page ** __init vdso_setup_pages(void *start, void *end)
 237 {
 238         int pages = (end - start) >> PAGE_SHIFT;
 239         struct page **pagelist;
 240         int i;
 241
 242         pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
 243         if (!pagelist)
 244                 panic("%s: Cannot allocate page list for VDSO", __func__);
 245         for (i = 0; i < pages; i++)
 246                 pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
 247         return pagelist;
 248 }
 249
 250 static void vdso_apply_alternatives(void)
 251 {
 252         const struct elf64_shdr *alt, *shdr;
 253         struct alt_instr *start, *end;
 254         const struct elf64_hdr *hdr;
 255
 256         hdr = (struct elf64_hdr *)vdso64_start;
 257         shdr = (void *)hdr + hdr->e_shoff;
 258         alt = find_section(hdr, shdr, ".altinstructions");
 259         if (!alt)
 260                 return;
 261         start = (void *)hdr + alt->sh_offset;
 262         end = (void *)hdr + alt->sh_offset + alt->sh_size;
 263         apply_alternatives(start, end);
 264 }
 265
 266 static int __init vdso_init(void)
 267 {
 268         vdso_apply_alternatives();
 269         vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end);
 270         if (IS_ENABLED(CONFIG_COMPAT))
 271                 vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end);
 272         return 0;
 273 }
 274 arch_initcall(vdso_init);