arch/riscv/kernel/vdso.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
   4  *                    <[email protected]>
   5  * Copyright (C) 2012 ARM Limited
   6  * Copyright (C) 2015 Regents of the University of California
   7  */
   8
   9 #include <linux/elf.h>
  10 #include <linux/mm.h>
  11 #include <linux/slab.h>
  12 #include <linux/binfmts.h>
  13 #include <linux/err.h>
  14 #include <asm/page.h>
  15 #include <asm/vdso.h>
  16 #include <linux/time_namespace.h>
  17 #include <vdso/datapage.h>
  18
  19 enum vvar_pages {
  20         VVAR_DATA_PAGE_OFFSET,
  21         VVAR_TIMENS_PAGE_OFFSET,
  22         VVAR_NR_PAGES,
  23 };
  24
  25 enum rv_vdso_map {
  26         RV_VDSO_MAP_VVAR,
  27         RV_VDSO_MAP_VDSO,
  28 };
  29
  30 #define VVAR_SIZE  (VVAR_NR_PAGES << PAGE_SHIFT)
  31
  32 /*
  33  * The vDSO data page.
  34  */
  35 static union {
  36         struct vdso_data        data;
  37         u8                      page[PAGE_SIZE];
  38 } vdso_data_store __page_aligned_data;
  39 struct vdso_data *vdso_data = &vdso_data_store.data;
  40
  41 struct __vdso_info {
  42         const char *name;
  43         const char *vdso_code_start;
  44         const char *vdso_code_end;
  45         unsigned long vdso_pages;
  46         /* Data Mapping */
  47         struct vm_special_mapping *dm;
  48         /* Code Mapping */
  49         struct vm_special_mapping *cm;
  50 };
  51
  52 static struct __vdso_info vdso_info;
  53 #ifdef CONFIG_COMPAT
  54 static struct __vdso_info compat_vdso_info;
  55 #endif
  56
  57 static int vdso_mremap(const struct vm_special_mapping *sm,
  58                        struct vm_area_struct *new_vma)
  59 {
  60         current->mm->context.vdso = (void *)new_vma->vm_start;
  61
  62         return 0;
  63 }
  64
  65 static void __init __vdso_init(struct __vdso_info *vdso_info)
  66 {
  67         unsigned int i;
  68         struct page **vdso_pagelist;
  69         unsigned long pfn;
  70
  71         if (memcmp(vdso_info->vdso_code_start, "\177ELF", 4))
  72                 panic("vDSO is not a valid ELF object!\n");
  73
  74         vdso_info->vdso_pages = (
  75                 vdso_info->vdso_code_end -
  76                 vdso_info->vdso_code_start) >>
  77                 PAGE_SHIFT;
  78
  79         vdso_pagelist = kcalloc(vdso_info->vdso_pages,
  80                                 sizeof(struct page *),
  81                                 GFP_KERNEL);
  82         if (vdso_pagelist == NULL)
  83                 panic("vDSO kcalloc failed!\n");
  84
  85         /* Grab the vDSO code pages. */
  86         pfn = sym_to_pfn(vdso_info->vdso_code_start);
  87
  88         for (i = 0; i < vdso_info->vdso_pages; i++)
  89                 vdso_pagelist[i] = pfn_to_page(pfn + i);
  90
  91         vdso_info->cm->pages = vdso_pagelist;
  92 }
  93
  94 #ifdef CONFIG_TIME_NS
  95 struct vdso_data *arch_get_vdso_data(void *vvar_page)
  96 {
  97         return (struct vdso_data *)(vvar_page);
  98 }
  99
 100 /*
 101  * The vvar mapping contains data for a specific time namespace, so when a task
 102  * changes namespace we must unmap its vvar data for the old namespace.
 103  * Subsequent faults will map in data for the new namespace.
 104  *
 105  * For more details see timens_setup_vdso_data().
 106  */
 107 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 108 {
 109         struct mm_struct *mm = task->mm;
 110         struct vm_area_struct *vma;
 111         VMA_ITERATOR(vmi, mm, 0);
 112
 113         mmap_read_lock(mm);
 114
 115         for_each_vma(vmi, vma) {
 116                 if (vma_is_special_mapping(vma, vdso_info.dm))
 117                         zap_vma_pages(vma);
 118 #ifdef CONFIG_COMPAT
 119                 if (vma_is_special_mapping(vma, compat_vdso_info.dm))
 120                         zap_vma_pages(vma);
 121 #endif
 122         }
 123
 124         mmap_read_unlock(mm);
 125         return 0;
 126 }
 127 #endif
 128
 129 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 130                              struct vm_area_struct *vma, struct vm_fault *vmf)
 131 {
 132         struct page *timens_page = find_timens_vvar_page(vma);
 133         unsigned long pfn;
 134
 135         switch (vmf->pgoff) {
 136         case VVAR_DATA_PAGE_OFFSET:
 137                 if (timens_page)
 138                         pfn = page_to_pfn(timens_page);
 139                 else
 140                         pfn = sym_to_pfn(vdso_data);
 141                 break;
 142 #ifdef CONFIG_TIME_NS
 143         case VVAR_TIMENS_PAGE_OFFSET:
 144                 /*
 145                  * If a task belongs to a time namespace then a namespace
 146                  * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 147                  * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 148                  * offset.
 149                  * See also the comment near timens_setup_vdso_data().
 150                  */
 151                 if (!timens_page)
 152                         return VM_FAULT_SIGBUS;
 153                 pfn = sym_to_pfn(vdso_data);
 154                 break;
 155 #endif /* CONFIG_TIME_NS */
 156         default:
 157                 return VM_FAULT_SIGBUS;
 158         }
 159
 160         return vmf_insert_pfn(vma, vmf->address, pfn);
 161 }
 162
 163 static struct vm_special_mapping rv_vdso_maps[] __ro_after_init = {
 164         [RV_VDSO_MAP_VVAR] = {
 165                 .name   = "[vvar]",
 166                 .fault = vvar_fault,
 167         },
 168         [RV_VDSO_MAP_VDSO] = {
 169                 .name   = "[vdso]",
 170                 .mremap = vdso_mremap,
 171         },
 172 };
 173
 174 static struct __vdso_info vdso_info __ro_after_init = {
 175         .name = "vdso",
 176         .vdso_code_start = vdso_start,
 177         .vdso_code_end = vdso_end,
 178         .dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR],
 179         .cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO],
 180 };
 181
 182 #ifdef CONFIG_COMPAT
 183 static struct vm_special_mapping rv_compat_vdso_maps[] __ro_after_init = {
 184         [RV_VDSO_MAP_VVAR] = {
 185                 .name   = "[vvar]",
 186                 .fault = vvar_fault,
 187         },
 188         [RV_VDSO_MAP_VDSO] = {
 189                 .name   = "[vdso]",
 190                 .mremap = vdso_mremap,
 191         },
 192 };
 193
 194 static struct __vdso_info compat_vdso_info __ro_after_init = {
 195         .name = "compat_vdso",
 196         .vdso_code_start = compat_vdso_start,
 197         .vdso_code_end = compat_vdso_end,
 198         .dm = &rv_compat_vdso_maps[RV_VDSO_MAP_VVAR],
 199         .cm = &rv_compat_vdso_maps[RV_VDSO_MAP_VDSO],
 200 };
 201 #endif
 202
 203 static int __init vdso_init(void)
 204 {
 205         __vdso_init(&vdso_info);
 206 #ifdef CONFIG_COMPAT
 207         __vdso_init(&compat_vdso_info);
 208 #endif
 209
 210         return 0;
 211 }
 212 arch_initcall(vdso_init);
 213
 214 static int __setup_additional_pages(struct mm_struct *mm,
 215                                     struct linux_binprm *bprm,
 216                                     int uses_interp,
 217                                     struct __vdso_info *vdso_info)
 218 {
 219         unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 220         void *ret;
 221
 222         BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
 223
 224         vdso_text_len = vdso_info->vdso_pages << PAGE_SHIFT;
 225         /* Be sure to map the data page */
 226         vdso_mapping_len = vdso_text_len + VVAR_SIZE;
 227
 228         vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 229         if (IS_ERR_VALUE(vdso_base)) {
 230                 ret = ERR_PTR(vdso_base);
 231                 goto up_fail;
 232         }
 233
 234         ret = _install_special_mapping(mm, vdso_base, VVAR_SIZE,
 235                 (VM_READ | VM_MAYREAD | VM_PFNMAP), vdso_info->dm);
 236         if (IS_ERR(ret))
 237                 goto up_fail;
 238
 239         vdso_base += VVAR_SIZE;
 240         mm->context.vdso = (void *)vdso_base;
 241
 242         ret =
 243            _install_special_mapping(mm, vdso_base, vdso_text_len,
 244                 (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
 245                 vdso_info->cm);
 246
 247         if (IS_ERR(ret))
 248                 goto up_fail;
 249
 250         return 0;
 251
 252 up_fail:
 253         mm->context.vdso = NULL;
 254         return PTR_ERR(ret);
 255 }
 256
 257 #ifdef CONFIG_COMPAT
 258 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 259                                        int uses_interp)
 260 {
 261         struct mm_struct *mm = current->mm;
 262         int ret;
 263
 264         if (mmap_write_lock_killable(mm))
 265                 return -EINTR;
 266
 267         ret = __setup_additional_pages(mm, bprm, uses_interp,
 268                                                         &compat_vdso_info);
 269         mmap_write_unlock(mm);
 270
 271         return ret;
 272 }
 273 #endif
 274
 275 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 276 {
 277         struct mm_struct *mm = current->mm;
 278         int ret;
 279
 280         if (mmap_write_lock_killable(mm))
 281                 return -EINTR;
 282
 283         ret = __setup_additional_pages(mm, bprm, uses_interp, &vdso_info);
 284         mmap_write_unlock(mm);
 285
 286         return ret;
 287 }