arch/powerpc/kernel/vdso.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2
   3 /*
   4  *    Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
   5  *                       <benh@kernel.crashing.org>
   6  */
   7
   8 #include <linux/errno.h>
   9 #include <linux/sched.h>
  10 #include <linux/kernel.h>
  11 #include <linux/mm.h>
  12 #include <linux/smp.h>
  13 #include <linux/stddef.h>
  14 #include <linux/unistd.h>
  15 #include <linux/slab.h>
  16 #include <linux/user.h>
  17 #include <linux/elf.h>
  18 #include <linux/security.h>
  19 #include <linux/memblock.h>
  20 #include <linux/syscalls.h>
  21 #include <linux/time_namespace.h>
  22 #include <vdso/datapage.h>
  23
  24 #include <asm/syscall.h>
  25 #include <asm/processor.h>
  26 #include <asm/mmu.h>
  27 #include <asm/mmu_context.h>
  28 #include <asm/machdep.h>
  29 #include <asm/cputable.h>
  30 #include <asm/sections.h>
  31 #include <asm/firmware.h>
  32 #include <asm/vdso.h>
  33 #include <asm/vdso_datapage.h>
  34 #include <asm/setup.h>
  35
  36 /* The alignment of the vDSO */
  37 #define VDSO_ALIGNMENT  (1 << 16)
  38
  39 extern char vdso32_start, vdso32_end;
  40 extern char vdso64_start, vdso64_end;
  41
  42 long sys_ni_syscall(void);
  43
  44 /*
  45  * The vdso data page (aka. systemcfg for old ppc64 fans) is here.
  46  * Once the early boot kernel code no longer needs to muck around
  47  * with it, it will become dynamically allocated
  48  */
  49 static union {
  50         struct vdso_arch_data   data;
  51         u8                      page[PAGE_SIZE];
  52 } vdso_data_store __page_aligned_data;
  53 struct vdso_arch_data *vdso_data = &vdso_data_store.data;
  54
  55 enum vvar_pages {
  56         VVAR_DATA_PAGE_OFFSET,
  57         VVAR_TIMENS_PAGE_OFFSET,
  58         VVAR_NR_PAGES,
  59 };
  60
  61 static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma,
  62                        unsigned long text_size)
  63 {
  64         unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
  65
  66         if (new_size != text_size)
  67                 return -EINVAL;
  68
  69         current->mm->context.vdso = (void __user *)new_vma->vm_start;
  70
  71         return 0;
  72 }
  73
  74 static int vdso32_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
  75 {
  76         return vdso_mremap(sm, new_vma, &vdso32_end - &vdso32_start);
  77 }
  78
  79 static int vdso64_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
  80 {
  81         return vdso_mremap(sm, new_vma, &vdso64_end - &vdso64_start);
  82 }
  83
  84 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
  85                              struct vm_area_struct *vma, struct vm_fault *vmf);
  86
  87 static struct vm_special_mapping vvar_spec __ro_after_init = {
  88         .name = "[vvar]",
  89         .fault = vvar_fault,
  90 };
  91
  92 static struct vm_special_mapping vdso32_spec __ro_after_init = {
  93         .name = "[vdso]",
  94         .mremap = vdso32_mremap,
  95 };
  96
  97 static struct vm_special_mapping vdso64_spec __ro_after_init = {
  98         .name = "[vdso]",
  99         .mremap = vdso64_mremap,
 100 };
 101
 102 #ifdef CONFIG_TIME_NS
 103 struct vdso_data *arch_get_vdso_data(void *vvar_page)
 104 {
 105         return ((struct vdso_arch_data *)vvar_page)->data;
 106 }
 107
 108 /*
 109  * The vvar mapping contains data for a specific time namespace, so when a task
 110  * changes namespace we must unmap its vvar data for the old namespace.
 111  * Subsequent faults will map in data for the new namespace.
 112  *
 113  * For more details see timens_setup_vdso_data().
 114  */
 115 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 116 {
 117         struct mm_struct *mm = task->mm;
 118         VMA_ITERATOR(vmi, mm, 0);
 119         struct vm_area_struct *vma;
 120
 121         mmap_read_lock(mm);
 122         for_each_vma(vmi, vma) {
 123                 unsigned long size = vma->vm_end - vma->vm_start;
 124
 125                 if (vma_is_special_mapping(vma, &vvar_spec))
 126                         zap_page_range(vma, vma->vm_start, size);
 127         }
 128         mmap_read_unlock(mm);
 129
 130         return 0;
 131 }
 132
 133 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 134 {
 135         if (likely(vma->vm_mm == current->mm))
 136                 return current->nsproxy->time_ns->vvar_page;
 137
 138         /*
 139          * VM_PFNMAP | VM_IO protect .fault() handler from being called
 140          * through interfaces like /proc/$pid/mem or
 141          * process_vm_{readv,writev}() as long as there's no .access()
 142          * in special_mapping_vmops.
 143          * For more details check_vma_flags() and __access_remote_vm()
 144          */
 145         WARN(1, "vvar_page accessed remotely");
 146
 147         return NULL;
 148 }
 149 #else
 150 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 151 {
 152         return NULL;
 153 }
 154 #endif
 155
 156 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 157                              struct vm_area_struct *vma, struct vm_fault *vmf)
 158 {
 159         struct page *timens_page = find_timens_vvar_page(vma);
 160         unsigned long pfn;
 161
 162         switch (vmf->pgoff) {
 163         case VVAR_DATA_PAGE_OFFSET:
 164                 if (timens_page)
 165                         pfn = page_to_pfn(timens_page);
 166                 else
 167                         pfn = virt_to_pfn(vdso_data);
 168                 break;
 169 #ifdef CONFIG_TIME_NS
 170         case VVAR_TIMENS_PAGE_OFFSET:
 171                 /*
 172                  * If a task belongs to a time namespace then a namespace
 173                  * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 174                  * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 175                  * offset.
 176                  * See also the comment near timens_setup_vdso_data().
 177                  */
 178                 if (!timens_page)
 179                         return VM_FAULT_SIGBUS;
 180                 pfn = virt_to_pfn(vdso_data);
 181                 break;
 182 #endif /* CONFIG_TIME_NS */
 183         default:
 184                 return VM_FAULT_SIGBUS;
 185         }
 186
 187         return vmf_insert_pfn(vma, vmf->address, pfn);
 188 }
 189
 190 /*
 191  * This is called from binfmt_elf, we create the special vma for the
 192  * vDSO and insert it into the mm struct tree
 193  */
 194 static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 195 {
 196         unsigned long vdso_size, vdso_base, mappings_size;
 197         struct vm_special_mapping *vdso_spec;
 198         unsigned long vvar_size = VVAR_NR_PAGES * PAGE_SIZE;
 199         struct mm_struct *mm = current->mm;
 200         struct vm_area_struct *vma;
 201
 202         if (is_32bit_task()) {
 203                 vdso_spec = &vdso32_spec;
 204                 vdso_size = &vdso32_end - &vdso32_start;
 205         } else {
 206                 vdso_spec = &vdso64_spec;
 207                 vdso_size = &vdso64_end - &vdso64_start;
 208         }
 209
 210         mappings_size = vdso_size + vvar_size;
 211         mappings_size += (VDSO_ALIGNMENT - 1) & PAGE_MASK;
 212
 213         /*
 214          * Pick a base address for the vDSO in process space.
 215          * Add enough to the size so that the result can be aligned.
 216          */
 217         vdso_base = get_unmapped_area(NULL, 0, mappings_size, 0, 0);
 218         if (IS_ERR_VALUE(vdso_base))
 219                 return vdso_base;
 220
 221         /* Add required alignment. */
 222         vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
 223
 224         /*
 225          * Put vDSO base into mm struct. We need to do this before calling
 226          * install_special_mapping or the perf counter mmap tracking code
 227          * will fail to recognise it as a vDSO.
 228          */
 229         mm->context.vdso = (void __user *)vdso_base + vvar_size;
 230
 231         vma = _install_special_mapping(mm, vdso_base, vvar_size,
 232                                        VM_READ | VM_MAYREAD | VM_IO |
 233                                        VM_DONTDUMP | VM_PFNMAP, &vvar_spec);
 234         if (IS_ERR(vma))
 235                 return PTR_ERR(vma);
 236
 237         /*
 238          * our vma flags don't have VM_WRITE so by default, the process isn't
 239          * allowed to write those pages.
 240          * gdb can break that with ptrace interface, and thus trigger COW on
 241          * those pages but it's then your responsibility to never do that on
 242          * the "data" page of the vDSO or you'll stop getting kernel updates
 243          * and your nice userland gettimeofday will be totally dead.
 244          * It's fine to use that for setting breakpoints in the vDSO code
 245          * pages though.
 246          */
 247         vma = _install_special_mapping(mm, vdso_base + vvar_size, vdso_size,
 248                                        VM_READ | VM_EXEC | VM_MAYREAD |
 249                                        VM_MAYWRITE | VM_MAYEXEC, vdso_spec);
 250         if (IS_ERR(vma))
 251                 do_munmap(mm, vdso_base, vvar_size, NULL);
 252
 253         return PTR_ERR_OR_ZERO(vma);
 254 }
 255
 256 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 257 {
 258         struct mm_struct *mm = current->mm;
 259         int rc;
 260
 261         mm->context.vdso = NULL;
 262
 263         if (mmap_write_lock_killable(mm))
 264                 return -EINTR;
 265
 266         rc = __arch_setup_additional_pages(bprm, uses_interp);
 267         if (rc)
 268                 mm->context.vdso = NULL;
 269
 270         mmap_write_unlock(mm);
 271         return rc;
 272 }
 273
 274 #define VDSO_DO_FIXUPS(type, value, bits, sec) do {                                     \
 275         void *__start = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_start);  \
 276         void *__end = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_end);      \
 277                                                                                         \
 278         do_##type##_fixups((value), __start, __end);                                    \
 279 } while (0)
 280
 281 static void __init vdso_fixup_features(void)
 282 {
 283 #ifdef CONFIG_PPC64
 284         VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 64, ftr_fixup);
 285         VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 64, mmu_ftr_fixup);
 286         VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 64, fw_ftr_fixup);
 287         VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 64, lwsync_fixup);
 288 #endif /* CONFIG_PPC64 */
 289
 290 #ifdef CONFIG_VDSO32
 291         VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 32, ftr_fixup);
 292         VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 32, mmu_ftr_fixup);
 293 #ifdef CONFIG_PPC64
 294         VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 32, fw_ftr_fixup);
 295 #endif /* CONFIG_PPC64 */
 296         VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 32, lwsync_fixup);
 297 #endif
 298 }
 299
 300 /*
 301  * Called from setup_arch to initialize the bitmap of available
 302  * syscalls in the systemcfg page
 303  */
 304 static void __init vdso_setup_syscall_map(void)
 305 {
 306         unsigned int i;
 307
 308         for (i = 0; i < NR_syscalls; i++) {
 309                 if (sys_call_table[i] != (void *)&sys_ni_syscall)
 310                         vdso_data->syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 311                 if (IS_ENABLED(CONFIG_COMPAT) &&
 312                     compat_sys_call_table[i] != (void *)&sys_ni_syscall)
 313                         vdso_data->compat_syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 314         }
 315 }
 316
 317 #ifdef CONFIG_PPC64
 318 int vdso_getcpu_init(void)
 319 {
 320         unsigned long cpu, node, val;
 321
 322         /*
 323          * SPRG_VDSO contains the CPU in the bottom 16 bits and the NUMA node
 324          * in the next 16 bits.  The VDSO uses this to implement getcpu().
 325          */
 326         cpu = get_cpu();
 327         WARN_ON_ONCE(cpu > 0xffff);
 328
 329         node = cpu_to_node(cpu);
 330         WARN_ON_ONCE(node > 0xffff);
 331
 332         val = (cpu & 0xffff) | ((node & 0xffff) << 16);
 333         mtspr(SPRN_SPRG_VDSO_WRITE, val);
 334         get_paca()->sprg_vdso = val;
 335
 336         put_cpu();
 337
 338         return 0;
 339 }
 340 /* We need to call this before SMP init */
 341 early_initcall(vdso_getcpu_init);
 342 #endif
 343
 344 static struct page ** __init vdso_setup_pages(void *start, void *end)
 345 {
 346         int i;
 347         struct page **pagelist;
 348         int pages = (end - start) >> PAGE_SHIFT;
 349
 350         pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
 351         if (!pagelist)
 352                 panic("%s: Cannot allocate page list for VDSO", __func__);
 353
 354         for (i = 0; i < pages; i++)
 355                 pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
 356
 357         return pagelist;
 358 }
 359
 360 static int __init vdso_init(void)
 361 {
 362 #ifdef CONFIG_PPC64
 363         /*
 364          * Fill up the "systemcfg" stuff for backward compatibility
 365          */
 366         strcpy((char *)vdso_data->eye_catcher, "SYSTEMCFG:PPC64");
 367         vdso_data->version.major = SYSTEMCFG_MAJOR;
 368         vdso_data->version.minor = SYSTEMCFG_MINOR;
 369         vdso_data->processor = mfspr(SPRN_PVR);
 370         /*
 371          * Fake the old platform number for pSeries and add
 372          * in LPAR bit if necessary
 373          */
 374         vdso_data->platform = 0x100;
 375         if (firmware_has_feature(FW_FEATURE_LPAR))
 376                 vdso_data->platform |= 1;
 377         vdso_data->physicalMemorySize = memblock_phys_mem_size();
 378         vdso_data->dcache_size = ppc64_caches.l1d.size;
 379         vdso_data->dcache_line_size = ppc64_caches.l1d.line_size;
 380         vdso_data->icache_size = ppc64_caches.l1i.size;
 381         vdso_data->icache_line_size = ppc64_caches.l1i.line_size;
 382         vdso_data->dcache_block_size = ppc64_caches.l1d.block_size;
 383         vdso_data->icache_block_size = ppc64_caches.l1i.block_size;
 384         vdso_data->dcache_log_block_size = ppc64_caches.l1d.log_block_size;
 385         vdso_data->icache_log_block_size = ppc64_caches.l1i.log_block_size;
 386 #endif /* CONFIG_PPC64 */
 387
 388         vdso_setup_syscall_map();
 389
 390         vdso_fixup_features();
 391
 392         if (IS_ENABLED(CONFIG_VDSO32))
 393                 vdso32_spec.pages = vdso_setup_pages(&vdso32_start, &vdso32_end);
 394
 395         if (IS_ENABLED(CONFIG_PPC64))
 396                 vdso64_spec.pages = vdso_setup_pages(&vdso64_start, &vdso64_end);
 397
 398         smp_wmb();
 399
 400         return 0;
 401 }
 402 arch_initcall(vdso_init);