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/prom.h>
  29 #include <asm/machdep.h>
  30 #include <asm/cputable.h>
  31 #include <asm/sections.h>
  32 #include <asm/firmware.h>
  33 #include <asm/vdso.h>
  34 #include <asm/vdso_datapage.h>
  35 #include <asm/setup.h>
  36
  37 /* The alignment of the vDSO */
  38 #define VDSO_ALIGNMENT  (1 << 16)
  39
  40 extern char vdso32_start, vdso32_end;
  41 extern char vdso64_start, vdso64_end;
  42
  43 /*
  44  * The vdso data page (aka. systemcfg for old ppc64 fans) is here.
  45  * Once the early boot kernel code no longer needs to muck around
  46  * with it, it will become dynamically allocated
  47  */
  48 static union {
  49         struct vdso_arch_data   data;
  50         u8                      page[PAGE_SIZE];
  51 } vdso_data_store __page_aligned_data;
  52 struct vdso_arch_data *vdso_data = &vdso_data_store.data;
  53
  54 enum vvar_pages {
  55         VVAR_DATA_PAGE_OFFSET,
  56         VVAR_TIMENS_PAGE_OFFSET,
  57         VVAR_NR_PAGES,
  58 };
  59
  60 static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma,
  61                        unsigned long text_size)
  62 {
  63         unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
  64
  65         if (new_size != text_size)
  66                 return -EINVAL;
  67
  68         current->mm->context.vdso = (void __user *)new_vma->vm_start;
  69
  70         return 0;
  71 }
  72
  73 static int vdso32_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
  74 {
  75         return vdso_mremap(sm, new_vma, &vdso32_end - &vdso32_start);
  76 }
  77
  78 static int vdso64_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
  79 {
  80         return vdso_mremap(sm, new_vma, &vdso64_end - &vdso64_start);
  81 }
  82
  83 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
  84                              struct vm_area_struct *vma, struct vm_fault *vmf);
  85
  86 static struct vm_special_mapping vvar_spec __ro_after_init = {
  87         .name = "[vvar]",
  88         .fault = vvar_fault,
  89 };
  90
  91 static struct vm_special_mapping vdso32_spec __ro_after_init = {
  92         .name = "[vdso]",
  93         .mremap = vdso32_mremap,
  94 };
  95
  96 static struct vm_special_mapping vdso64_spec __ro_after_init = {
  97         .name = "[vdso]",
  98         .mremap = vdso64_mremap,
  99 };
 100
 101 #ifdef CONFIG_TIME_NS
 102 struct vdso_data *arch_get_vdso_data(void *vvar_page)
 103 {
 104         return ((struct vdso_arch_data *)vvar_page)->data;
 105 }
 106
 107 /*
 108  * The vvar mapping contains data for a specific time namespace, so when a task
 109  * changes namespace we must unmap its vvar data for the old namespace.
 110  * Subsequent faults will map in data for the new namespace.
 111  *
 112  * For more details see timens_setup_vdso_data().
 113  */
 114 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 115 {
 116         struct mm_struct *mm = task->mm;
 117         struct vm_area_struct *vma;
 118
 119         mmap_read_lock(mm);
 120
 121         for (vma = mm->mmap; vma; vma = vma->vm_next) {
 122                 unsigned long size = vma->vm_end - vma->vm_start;
 123
 124                 if (vma_is_special_mapping(vma, &vvar_spec))
 125                         zap_page_range(vma, vma->vm_start, size);
 126         }
 127
 128         mmap_read_unlock(mm);
 129         return 0;
 130 }
 131
 132 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 133 {
 134         if (likely(vma->vm_mm == current->mm))
 135                 return current->nsproxy->time_ns->vvar_page;
 136
 137         /*
 138          * VM_PFNMAP | VM_IO protect .fault() handler from being called
 139          * through interfaces like /proc/$pid/mem or
 140          * process_vm_{readv,writev}() as long as there's no .access()
 141          * in special_mapping_vmops.
 142          * For more details check_vma_flags() and __access_remote_vm()
 143          */
 144         WARN(1, "vvar_page accessed remotely");
 145
 146         return NULL;
 147 }
 148 #else
 149 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 150 {
 151         return NULL;
 152 }
 153 #endif
 154
 155 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 156                              struct vm_area_struct *vma, struct vm_fault *vmf)
 157 {
 158         struct page *timens_page = find_timens_vvar_page(vma);
 159         unsigned long pfn;
 160
 161         switch (vmf->pgoff) {
 162         case VVAR_DATA_PAGE_OFFSET:
 163                 if (timens_page)
 164                         pfn = page_to_pfn(timens_page);
 165                 else
 166                         pfn = virt_to_pfn(vdso_data);
 167                 break;
 168 #ifdef CONFIG_TIME_NS
 169         case VVAR_TIMENS_PAGE_OFFSET:
 170                 /*
 171                  * If a task belongs to a time namespace then a namespace
 172                  * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 173                  * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 174                  * offset.
 175                  * See also the comment near timens_setup_vdso_data().
 176                  */
 177                 if (!timens_page)
 178                         return VM_FAULT_SIGBUS;
 179                 pfn = virt_to_pfn(vdso_data);
 180                 break;
 181 #endif /* CONFIG_TIME_NS */
 182         default:
 183                 return VM_FAULT_SIGBUS;
 184         }
 185
 186         return vmf_insert_pfn(vma, vmf->address, pfn);
 187 }
 188
 189 /*
 190  * This is called from binfmt_elf, we create the special vma for the
 191  * vDSO and insert it into the mm struct tree
 192  */
 193 static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 194 {
 195         unsigned long vdso_size, vdso_base, mappings_size;
 196         struct vm_special_mapping *vdso_spec;
 197         unsigned long vvar_size = VVAR_NR_PAGES * PAGE_SIZE;
 198         struct mm_struct *mm = current->mm;
 199         struct vm_area_struct *vma;
 200
 201         if (is_32bit_task()) {
 202                 vdso_spec = &vdso32_spec;
 203                 vdso_size = &vdso32_end - &vdso32_start;
 204                 vdso_base = VDSO32_MBASE;
 205         } else {
 206                 vdso_spec = &vdso64_spec;
 207                 vdso_size = &vdso64_end - &vdso64_start;
 208                 /*
 209                  * On 64bit we don't have a preferred map address. This
 210                  * allows get_unmapped_area to find an area near other mmaps
 211                  * and most likely share a SLB entry.
 212                  */
 213                 vdso_base = 0;
 214         }
 215
 216         mappings_size = vdso_size + vvar_size;
 217         mappings_size += (VDSO_ALIGNMENT - 1) & PAGE_MASK;
 218
 219         /*
 220          * pick a base address for the vDSO in process space. We try to put it
 221          * at vdso_base which is the "natural" base for it, but we might fail
 222          * and end up putting it elsewhere.
 223          * Add enough to the size so that the result can be aligned.
 224          */
 225         vdso_base = get_unmapped_area(NULL, vdso_base, mappings_size, 0, 0);
 226         if (IS_ERR_VALUE(vdso_base))
 227                 return vdso_base;
 228
 229         /* Add required alignment. */
 230         vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
 231
 232         /*
 233          * Put vDSO base into mm struct. We need to do this before calling
 234          * install_special_mapping or the perf counter mmap tracking code
 235          * will fail to recognise it as a vDSO.
 236          */
 237         mm->context.vdso = (void __user *)vdso_base + vvar_size;
 238
 239         vma = _install_special_mapping(mm, vdso_base, vvar_size,
 240                                        VM_READ | VM_MAYREAD | VM_IO |
 241                                        VM_DONTDUMP | VM_PFNMAP, &vvar_spec);
 242         if (IS_ERR(vma))
 243                 return PTR_ERR(vma);
 244
 245         /*
 246          * our vma flags don't have VM_WRITE so by default, the process isn't
 247          * allowed to write those pages.
 248          * gdb can break that with ptrace interface, and thus trigger COW on
 249          * those pages but it's then your responsibility to never do that on
 250          * the "data" page of the vDSO or you'll stop getting kernel updates
 251          * and your nice userland gettimeofday will be totally dead.
 252          * It's fine to use that for setting breakpoints in the vDSO code
 253          * pages though.
 254          */
 255         vma = _install_special_mapping(mm, vdso_base + vvar_size, vdso_size,
 256                                        VM_READ | VM_EXEC | VM_MAYREAD |
 257                                        VM_MAYWRITE | VM_MAYEXEC, vdso_spec);
 258         if (IS_ERR(vma))
 259                 do_munmap(mm, vdso_base, vvar_size, NULL);
 260
 261         return PTR_ERR_OR_ZERO(vma);
 262 }
 263
 264 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 265 {
 266         struct mm_struct *mm = current->mm;
 267         int rc;
 268
 269         mm->context.vdso = NULL;
 270
 271         if (mmap_write_lock_killable(mm))
 272                 return -EINTR;
 273
 274         rc = __arch_setup_additional_pages(bprm, uses_interp);
 275         if (rc)
 276                 mm->context.vdso = NULL;
 277
 278         mmap_write_unlock(mm);
 279         return rc;
 280 }
 281
 282 #define VDSO_DO_FIXUPS(type, value, bits, sec) do {                                     \
 283         void *__start = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_start);  \
 284         void *__end = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_end);      \
 285                                                                                         \
 286         do_##type##_fixups((value), __start, __end);                                    \
 287 } while (0)
 288
 289 static void __init vdso_fixup_features(void)
 290 {
 291 #ifdef CONFIG_PPC64
 292         VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 64, ftr_fixup);
 293         VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 64, mmu_ftr_fixup);
 294         VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 64, fw_ftr_fixup);
 295         VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 64, lwsync_fixup);
 296 #endif /* CONFIG_PPC64 */
 297
 298 #ifdef CONFIG_VDSO32
 299         VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 32, ftr_fixup);
 300         VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 32, mmu_ftr_fixup);
 301 #ifdef CONFIG_PPC64
 302         VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 32, fw_ftr_fixup);
 303 #endif /* CONFIG_PPC64 */
 304         VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 32, lwsync_fixup);
 305 #endif
 306 }
 307
 308 /*
 309  * Called from setup_arch to initialize the bitmap of available
 310  * syscalls in the systemcfg page
 311  */
 312 static void __init vdso_setup_syscall_map(void)
 313 {
 314         unsigned int i;
 315
 316         for (i = 0; i < NR_syscalls; i++) {
 317                 if (sys_call_table[i] != (unsigned long)&sys_ni_syscall)
 318                         vdso_data->syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 319                 if (IS_ENABLED(CONFIG_COMPAT) &&
 320                     compat_sys_call_table[i] != (unsigned long)&sys_ni_syscall)
 321                         vdso_data->compat_syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 322         }
 323 }
 324
 325 #ifdef CONFIG_PPC64
 326 int vdso_getcpu_init(void)
 327 {
 328         unsigned long cpu, node, val;
 329
 330         /*
 331          * SPRG_VDSO contains the CPU in the bottom 16 bits and the NUMA node
 332          * in the next 16 bits.  The VDSO uses this to implement getcpu().
 333          */
 334         cpu = get_cpu();
 335         WARN_ON_ONCE(cpu > 0xffff);
 336
 337         node = cpu_to_node(cpu);
 338         WARN_ON_ONCE(node > 0xffff);
 339
 340         val = (cpu & 0xffff) | ((node & 0xffff) << 16);
 341         mtspr(SPRN_SPRG_VDSO_WRITE, val);
 342         get_paca()->sprg_vdso = val;
 343
 344         put_cpu();
 345
 346         return 0;
 347 }
 348 /* We need to call this before SMP init */
 349 early_initcall(vdso_getcpu_init);
 350 #endif
 351
 352 static struct page ** __init vdso_setup_pages(void *start, void *end)
 353 {
 354         int i;
 355         struct page **pagelist;
 356         int pages = (end - start) >> PAGE_SHIFT;
 357
 358         pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
 359         if (!pagelist)
 360                 panic("%s: Cannot allocate page list for VDSO", __func__);
 361
 362         for (i = 0; i < pages; i++)
 363                 pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
 364
 365         return pagelist;
 366 }
 367
 368 static int __init vdso_init(void)
 369 {
 370 #ifdef CONFIG_PPC64
 371         /*
 372          * Fill up the "systemcfg" stuff for backward compatibility
 373          */
 374         strcpy((char *)vdso_data->eye_catcher, "SYSTEMCFG:PPC64");
 375         vdso_data->version.major = SYSTEMCFG_MAJOR;
 376         vdso_data->version.minor = SYSTEMCFG_MINOR;
 377         vdso_data->processor = mfspr(SPRN_PVR);
 378         /*
 379          * Fake the old platform number for pSeries and add
 380          * in LPAR bit if necessary
 381          */
 382         vdso_data->platform = 0x100;
 383         if (firmware_has_feature(FW_FEATURE_LPAR))
 384                 vdso_data->platform |= 1;
 385         vdso_data->physicalMemorySize = memblock_phys_mem_size();
 386         vdso_data->dcache_size = ppc64_caches.l1d.size;
 387         vdso_data->dcache_line_size = ppc64_caches.l1d.line_size;
 388         vdso_data->icache_size = ppc64_caches.l1i.size;
 389         vdso_data->icache_line_size = ppc64_caches.l1i.line_size;
 390         vdso_data->dcache_block_size = ppc64_caches.l1d.block_size;
 391         vdso_data->icache_block_size = ppc64_caches.l1i.block_size;
 392         vdso_data->dcache_log_block_size = ppc64_caches.l1d.log_block_size;
 393         vdso_data->icache_log_block_size = ppc64_caches.l1i.log_block_size;
 394 #endif /* CONFIG_PPC64 */
 395
 396         vdso_setup_syscall_map();
 397
 398         vdso_fixup_features();
 399
 400         if (IS_ENABLED(CONFIG_VDSO32))
 401                 vdso32_spec.pages = vdso_setup_pages(&vdso32_start, &vdso32_end);
 402
 403         if (IS_ENABLED(CONFIG_PPC64))
 404                 vdso64_spec.pages = vdso_setup_pages(&vdso64_start, &vdso64_end);
 405
 406         smp_wmb();
 407
 408         return 0;
 409 }
 410 arch_initcall(vdso_init);