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 <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);