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