arch/x86/entry/vdso/vma.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright 2007 Andi Kleen, SUSE Labs.
   4  *
   5  * This contains most of the x86 vDSO kernel-side code.
   6  */
   7 #include <linux/mm.h>
   8 #include <linux/err.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/task_stack.h>
  11 #include <linux/slab.h>
  12 #include <linux/init.h>
  13 #include <linux/random.h>
  14 #include <linux/elf.h>
  15 #include <linux/cpu.h>
  16 #include <linux/ptrace.h>
  17 #include <linux/time_namespace.h>
  18
  19 #include <asm/pvclock.h>
  20 #include <asm/vgtod.h>
  21 #include <asm/proto.h>
  22 #include <asm/vdso.h>
  23 #include <asm/vvar.h>
  24 #include <asm/tlb.h>
  25 #include <asm/page.h>
  26 #include <asm/desc.h>
  27 #include <asm/cpufeature.h>
  28 #include <clocksource/hyperv_timer.h>
  29
  30 #undef _ASM_X86_VVAR_H
  31 #define EMIT_VVAR(name, offset) \
  32         const size_t name ## _offset = offset;
  33 #include <asm/vvar.h>
  34
  35 struct vdso_data *arch_get_vdso_data(void *vvar_page)
  36 {
  37         return (struct vdso_data *)(vvar_page + _vdso_data_offset);
  38 }
  39 #undef EMIT_VVAR
  40
  41 unsigned int vclocks_used __read_mostly;
  42
  43 #if defined(CONFIG_X86_64)
  44 unsigned int __read_mostly vdso64_enabled = 1;
  45 #endif
  46
  47 int __init init_vdso_image(const struct vdso_image *image)
  48 {
  49         BUILD_BUG_ON(VDSO_CLOCKMODE_MAX >= 32);
  50         BUG_ON(image->size % PAGE_SIZE != 0);
  51
  52         apply_alternatives((struct alt_instr *)(image->data + image->alt),
  53                            (struct alt_instr *)(image->data + image->alt +
  54                                                 image->alt_len));
  55
  56         return 0;
  57 }
  58
  59 static const struct vm_special_mapping vvar_mapping;
  60 struct linux_binprm;
  61
  62 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
  63                       struct vm_area_struct *vma, struct vm_fault *vmf)
  64 {
  65         const struct vdso_image *image = vma->vm_mm->context.vdso_image;
  66
  67         if (!image || (vmf->pgoff << PAGE_SHIFT) >= image->size)
  68                 return VM_FAULT_SIGBUS;
  69
  70         vmf->page = virt_to_page(image->data + (vmf->pgoff << PAGE_SHIFT));
  71         get_page(vmf->page);
  72         return 0;
  73 }
  74
  75 static void vdso_fix_landing(const struct vdso_image *image,
  76                 struct vm_area_struct *new_vma)
  77 {
  78 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
  79         if (in_ia32_syscall() && image == &vdso_image_32) {
  80                 struct pt_regs *regs = current_pt_regs();
  81                 unsigned long vdso_land = image->sym_int80_landing_pad;
  82                 unsigned long old_land_addr = vdso_land +
  83                         (unsigned long)current->mm->context.vdso;
  84
  85                 /* Fixing userspace landing - look at do_fast_syscall_32 */
  86                 if (regs->ip == old_land_addr)
  87                         regs->ip = new_vma->vm_start + vdso_land;
  88         }
  89 #endif
  90 }
  91
  92 static int vdso_mremap(const struct vm_special_mapping *sm,
  93                 struct vm_area_struct *new_vma)
  94 {
  95         const struct vdso_image *image = current->mm->context.vdso_image;
  96
  97         vdso_fix_landing(image, new_vma);
  98         current->mm->context.vdso = (void __user *)new_vma->vm_start;
  99
 100         return 0;
 101 }
 102
 103 #ifdef CONFIG_TIME_NS
 104 /*
 105  * The vvar page layout depends on whether a task belongs to the root or
 106  * non-root time namespace. Whenever a task changes its namespace, the VVAR
 107  * page tables are cleared and then they will re-faulted with a
 108  * corresponding layout.
 109  * See also the comment near timens_setup_vdso_data() for details.
 110  */
 111 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 112 {
 113         struct mm_struct *mm = task->mm;
 114         struct vm_area_struct *vma;
 115         VMA_ITERATOR(vmi, mm, 0);
 116
 117         mmap_read_lock(mm);
 118         for_each_vma(vmi, vma) {
 119                 if (vma_is_special_mapping(vma, &vvar_mapping))
 120                         zap_vma_pages(vma);
 121         }
 122         mmap_read_unlock(mm);
 123
 124         return 0;
 125 }
 126 #endif
 127
 128 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 129                       struct vm_area_struct *vma, struct vm_fault *vmf)
 130 {
 131         const struct vdso_image *image = vma->vm_mm->context.vdso_image;
 132         unsigned long pfn;
 133         long sym_offset;
 134
 135         if (!image)
 136                 return VM_FAULT_SIGBUS;
 137
 138         sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) +
 139                 image->sym_vvar_start;
 140
 141         /*
 142          * Sanity check: a symbol offset of zero means that the page
 143          * does not exist for this vdso image, not that the page is at
 144          * offset zero relative to the text mapping.  This should be
 145          * impossible here, because sym_offset should only be zero for
 146          * the page past the end of the vvar mapping.
 147          */
 148         if (sym_offset == 0)
 149                 return VM_FAULT_SIGBUS;
 150
 151         if (sym_offset == image->sym_vvar_page) {
 152                 struct page *timens_page = find_timens_vvar_page(vma);
 153
 154                 pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
 155
 156                 /*
 157                  * If a task belongs to a time namespace then a namespace
 158                  * specific VVAR is mapped with the sym_vvar_page offset and
 159                  * the real VVAR page is mapped with the sym_timens_page
 160                  * offset.
 161                  * See also the comment near timens_setup_vdso_data().
 162                  */
 163                 if (timens_page) {
 164                         unsigned long addr;
 165                         vm_fault_t err;
 166
 167                         /*
 168                          * Optimization: inside time namespace pre-fault
 169                          * VVAR page too. As on timens page there are only
 170                          * offsets for clocks on VVAR, it'll be faulted
 171                          * shortly by VDSO code.
 172                          */
 173                         addr = vmf->address + (image->sym_timens_page - sym_offset);
 174                         err = vmf_insert_pfn(vma, addr, pfn);
 175                         if (unlikely(err & VM_FAULT_ERROR))
 176                                 return err;
 177
 178                         pfn = page_to_pfn(timens_page);
 179                 }
 180
 181                 return vmf_insert_pfn(vma, vmf->address, pfn);
 182         } else if (sym_offset == image->sym_pvclock_page) {
 183                 struct pvclock_vsyscall_time_info *pvti =
 184                         pvclock_get_pvti_cpu0_va();
 185                 if (pvti && vclock_was_used(VDSO_CLOCKMODE_PVCLOCK)) {
 186                         return vmf_insert_pfn_prot(vma, vmf->address,
 187                                         __pa(pvti) >> PAGE_SHIFT,
 188                                         pgprot_decrypted(vma->vm_page_prot));
 189                 }
 190         } else if (sym_offset == image->sym_hvclock_page) {
 191                 pfn = hv_get_tsc_pfn();
 192
 193                 if (pfn && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK))
 194                         return vmf_insert_pfn(vma, vmf->address, pfn);
 195         } else if (sym_offset == image->sym_timens_page) {
 196                 struct page *timens_page = find_timens_vvar_page(vma);
 197
 198                 if (!timens_page)
 199                         return VM_FAULT_SIGBUS;
 200
 201                 pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
 202                 return vmf_insert_pfn(vma, vmf->address, pfn);
 203         }
 204
 205         return VM_FAULT_SIGBUS;
 206 }
 207
 208 static const struct vm_special_mapping vdso_mapping = {
 209         .name = "[vdso]",
 210         .fault = vdso_fault,
 211         .mremap = vdso_mremap,
 212 };
 213 static const struct vm_special_mapping vvar_mapping = {
 214         .name = "[vvar]",
 215         .fault = vvar_fault,
 216 };
 217
 218 /*
 219  * Add vdso and vvar mappings to current process.
 220  * @image          - blob to map
 221  * @addr           - request a specific address (zero to map at free addr)
 222  */
 223 static int map_vdso(const struct vdso_image *image, unsigned long addr)
 224 {
 225         struct mm_struct *mm = current->mm;
 226         struct vm_area_struct *vma;
 227         unsigned long text_start;
 228         int ret = 0;
 229
 230         if (mmap_write_lock_killable(mm))
 231                 return -EINTR;
 232
 233         addr = get_unmapped_area(NULL, addr,
 234                                  image->size - image->sym_vvar_start, 0, 0);
 235         if (IS_ERR_VALUE(addr)) {
 236                 ret = addr;
 237                 goto up_fail;
 238         }
 239
 240         text_start = addr - image->sym_vvar_start;
 241
 242         /*
 243          * MAYWRITE to allow gdb to COW and set breakpoints
 244          */
 245         vma = _install_special_mapping(mm,
 246                                        text_start,
 247                                        image->size,
 248                                        VM_READ|VM_EXEC|
 249                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 250                                        &vdso_mapping);
 251
 252         if (IS_ERR(vma)) {
 253                 ret = PTR_ERR(vma);
 254                 goto up_fail;
 255         }
 256
 257         vma = _install_special_mapping(mm,
 258                                        addr,
 259                                        -image->sym_vvar_start,
 260                                        VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
 261                                        VM_PFNMAP,
 262                                        &vvar_mapping);
 263
 264         if (IS_ERR(vma)) {
 265                 ret = PTR_ERR(vma);
 266                 do_munmap(mm, text_start, image->size, NULL);
 267         } else {
 268                 current->mm->context.vdso = (void __user *)text_start;
 269                 current->mm->context.vdso_image = image;
 270         }
 271
 272 up_fail:
 273         mmap_write_unlock(mm);
 274         return ret;
 275 }
 276
 277 #ifdef CONFIG_X86_64
 278 /*
 279  * Put the vdso above the (randomized) stack with another randomized
 280  * offset.  This way there is no hole in the middle of address space.
 281  * To save memory make sure it is still in the same PTE as the stack
 282  * top.  This doesn't give that many random bits.
 283  *
 284  * Note that this algorithm is imperfect: the distribution of the vdso
 285  * start address within a PMD is biased toward the end.
 286  *
 287  * Only used for the 64-bit and x32 vdsos.
 288  */
 289 static unsigned long vdso_addr(unsigned long start, unsigned len)
 290 {
 291         unsigned long addr, end;
 292         unsigned offset;
 293
 294         /*
 295          * Round up the start address.  It can start out unaligned as a result
 296          * of stack start randomization.
 297          */
 298         start = PAGE_ALIGN(start);
 299
 300         /* Round the lowest possible end address up to a PMD boundary. */
 301         end = (start + len + PMD_SIZE - 1) & PMD_MASK;
 302         if (end >= DEFAULT_MAP_WINDOW)
 303                 end = DEFAULT_MAP_WINDOW;
 304         end -= len;
 305
 306         if (end > start) {
 307                 offset = get_random_u32_below(((end - start) >> PAGE_SHIFT) + 1);
 308                 addr = start + (offset << PAGE_SHIFT);
 309         } else {
 310                 addr = start;
 311         }
 312
 313         /*
 314          * Forcibly align the final address in case we have a hardware
 315          * issue that requires alignment for performance reasons.
 316          */
 317         addr = align_vdso_addr(addr);
 318
 319         return addr;
 320 }
 321
 322 static int map_vdso_randomized(const struct vdso_image *image)
 323 {
 324         unsigned long addr = vdso_addr(current->mm->start_stack, image->size-image->sym_vvar_start);
 325
 326         return map_vdso(image, addr);
 327 }
 328 #endif
 329
 330 int map_vdso_once(const struct vdso_image *image, unsigned long addr)
 331 {
 332         struct mm_struct *mm = current->mm;
 333         struct vm_area_struct *vma;
 334         VMA_ITERATOR(vmi, mm, 0);
 335
 336         mmap_write_lock(mm);
 337         /*
 338          * Check if we have already mapped vdso blob - fail to prevent
 339          * abusing from userspace install_special_mapping, which may
 340          * not do accounting and rlimit right.
 341          * We could search vma near context.vdso, but it's a slowpath,
 342          * so let's explicitly check all VMAs to be completely sure.
 343          */
 344         for_each_vma(vmi, vma) {
 345                 if (vma_is_special_mapping(vma, &vdso_mapping) ||
 346                                 vma_is_special_mapping(vma, &vvar_mapping)) {
 347                         mmap_write_unlock(mm);
 348                         return -EEXIST;
 349                 }
 350         }
 351         mmap_write_unlock(mm);
 352
 353         return map_vdso(image, addr);
 354 }
 355
 356 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 357 static int load_vdso32(void)
 358 {
 359         if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
 360                 return 0;
 361
 362         return map_vdso(&vdso_image_32, 0);
 363 }
 364 #endif
 365
 366 #ifdef CONFIG_X86_64
 367 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 368 {
 369         if (!vdso64_enabled)
 370                 return 0;
 371
 372         return map_vdso_randomized(&vdso_image_64);
 373 }
 374
 375 #ifdef CONFIG_COMPAT
 376 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 377                                        int uses_interp, bool x32)
 378 {
 379 #ifdef CONFIG_X86_X32_ABI
 380         if (x32) {
 381                 if (!vdso64_enabled)
 382                         return 0;
 383                 return map_vdso_randomized(&vdso_image_x32);
 384         }
 385 #endif
 386 #ifdef CONFIG_IA32_EMULATION
 387         return load_vdso32();
 388 #else
 389         return 0;
 390 #endif
 391 }
 392 #endif
 393 #else
 394 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 395 {
 396         return load_vdso32();
 397 }
 398 #endif
 399
 400 bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
 401 {
 402 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 403         const struct vdso_image *image = current->mm->context.vdso_image;
 404         unsigned long vdso = (unsigned long) current->mm->context.vdso;
 405
 406         if (in_ia32_syscall() && image == &vdso_image_32) {
 407                 if (regs->ip == vdso + image->sym_vdso32_sigreturn_landing_pad ||
 408                     regs->ip == vdso + image->sym_vdso32_rt_sigreturn_landing_pad)
 409                         return true;
 410         }
 411 #endif
 412         return false;
 413 }
 414
 415 #ifdef CONFIG_X86_64
 416 static __init int vdso_setup(char *s)
 417 {
 418         vdso64_enabled = simple_strtoul(s, NULL, 0);
 419         return 1;
 420 }
 421 __setup("vdso=", vdso_setup);
 422 #endif /* CONFIG_X86_64 */