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  *                       <[email protected]>
   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 #endif
 133
 134 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 135                              struct vm_area_struct *vma, struct vm_fault *vmf)
 136 {
 137         struct page *timens_page = find_timens_vvar_page(vma);
 138         unsigned long pfn;
 139
 140         switch (vmf->pgoff) {
 141         case VVAR_DATA_PAGE_OFFSET:
 142                 if (timens_page)
 143                         pfn = page_to_pfn(timens_page);
 144                 else
 145                         pfn = virt_to_pfn(vdso_data);
 146                 break;
 147 #ifdef CONFIG_TIME_NS
 148         case VVAR_TIMENS_PAGE_OFFSET:
 149                 /*
 150                  * If a task belongs to a time namespace then a namespace
 151                  * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 152                  * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 153                  * offset.
 154                  * See also the comment near timens_setup_vdso_data().
 155                  */
 156                 if (!timens_page)
 157                         return VM_FAULT_SIGBUS;
 158                 pfn = virt_to_pfn(vdso_data);
 159                 break;
 160 #endif /* CONFIG_TIME_NS */
 161         default:
 162                 return VM_FAULT_SIGBUS;
 163         }
 164
 165         return vmf_insert_pfn(vma, vmf->address, pfn);
 166 }
 167
 168 /*
 169  * This is called from binfmt_elf, we create the special vma for the
 170  * vDSO and insert it into the mm struct tree
 171  */
 172 static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 173 {
 174         unsigned long vdso_size, vdso_base, mappings_size;
 175         struct vm_special_mapping *vdso_spec;
 176         unsigned long vvar_size = VVAR_NR_PAGES * PAGE_SIZE;
 177         struct mm_struct *mm = current->mm;
 178         struct vm_area_struct *vma;
 179
 180         if (is_32bit_task()) {
 181                 vdso_spec = &vdso32_spec;
 182                 vdso_size = &vdso32_end - &vdso32_start;
 183         } else {
 184                 vdso_spec = &vdso64_spec;
 185                 vdso_size = &vdso64_end - &vdso64_start;
 186         }
 187
 188         mappings_size = vdso_size + vvar_size;
 189         mappings_size += (VDSO_ALIGNMENT - 1) & PAGE_MASK;
 190
 191         /*
 192          * Pick a base address for the vDSO in process space.
 193          * Add enough to the size so that the result can be aligned.
 194          */
 195         vdso_base = get_unmapped_area(NULL, 0, mappings_size, 0, 0);
 196         if (IS_ERR_VALUE(vdso_base))
 197                 return vdso_base;
 198
 199         /* Add required alignment. */
 200         vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
 201
 202         /*
 203          * Put vDSO base into mm struct. We need to do this before calling
 204          * install_special_mapping or the perf counter mmap tracking code
 205          * will fail to recognise it as a vDSO.
 206          */
 207         mm->context.vdso = (void __user *)vdso_base + vvar_size;
 208
 209         vma = _install_special_mapping(mm, vdso_base, vvar_size,
 210                                        VM_READ | VM_MAYREAD | VM_IO |
 211                                        VM_DONTDUMP | VM_PFNMAP, &vvar_spec);
 212         if (IS_ERR(vma))
 213                 return PTR_ERR(vma);
 214
 215         /*
 216          * our vma flags don't have VM_WRITE so by default, the process isn't
 217          * allowed to write those pages.
 218          * gdb can break that with ptrace interface, and thus trigger COW on
 219          * those pages but it's then your responsibility to never do that on
 220          * the "data" page of the vDSO or you'll stop getting kernel updates
 221          * and your nice userland gettimeofday will be totally dead.
 222          * It's fine to use that for setting breakpoints in the vDSO code
 223          * pages though.
 224          */
 225         vma = _install_special_mapping(mm, vdso_base + vvar_size, vdso_size,
 226                                        VM_READ | VM_EXEC | VM_MAYREAD |
 227                                        VM_MAYWRITE | VM_MAYEXEC, vdso_spec);
 228         if (IS_ERR(vma))
 229                 do_munmap(mm, vdso_base, vvar_size, NULL);
 230
 231         return PTR_ERR_OR_ZERO(vma);
 232 }
 233
 234 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 235 {
 236         struct mm_struct *mm = current->mm;
 237         int rc;
 238
 239         mm->context.vdso = NULL;
 240
 241         if (mmap_write_lock_killable(mm))
 242                 return -EINTR;
 243
 244         rc = __arch_setup_additional_pages(bprm, uses_interp);
 245         if (rc)
 246                 mm->context.vdso = NULL;
 247
 248         mmap_write_unlock(mm);
 249         return rc;
 250 }
 251
 252 #define VDSO_DO_FIXUPS(type, value, bits, sec) do {                                     \
 253         void *__start = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_start);  \
 254         void *__end = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_end);      \
 255                                                                                         \
 256         do_##type##_fixups((value), __start, __end);                                    \
 257 } while (0)
 258
 259 static void __init vdso_fixup_features(void)
 260 {
 261 #ifdef CONFIG_PPC64
 262         VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 64, ftr_fixup);
 263         VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 64, mmu_ftr_fixup);
 264         VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 64, fw_ftr_fixup);
 265         VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 64, lwsync_fixup);
 266 #endif /* CONFIG_PPC64 */
 267
 268 #ifdef CONFIG_VDSO32
 269         VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 32, ftr_fixup);
 270         VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 32, mmu_ftr_fixup);
 271 #ifdef CONFIG_PPC64
 272         VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 32, fw_ftr_fixup);
 273 #endif /* CONFIG_PPC64 */
 274         VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 32, lwsync_fixup);
 275 #endif
 276 }
 277
 278 /*
 279  * Called from setup_arch to initialize the bitmap of available
 280  * syscalls in the systemcfg page
 281  */
 282 static void __init vdso_setup_syscall_map(void)
 283 {
 284         unsigned int i;
 285
 286         for (i = 0; i < NR_syscalls; i++) {
 287                 if (sys_call_table[i] != (void *)&sys_ni_syscall)
 288                         vdso_data->syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 289                 if (IS_ENABLED(CONFIG_COMPAT) &&
 290                     compat_sys_call_table[i] != (void *)&sys_ni_syscall)
 291                         vdso_data->compat_syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 292         }
 293 }
 294
 295 #ifdef CONFIG_PPC64
 296 int vdso_getcpu_init(void)
 297 {
 298         unsigned long cpu, node, val;
 299
 300         /*
 301          * SPRG_VDSO contains the CPU in the bottom 16 bits and the NUMA node
 302          * in the next 16 bits.  The VDSO uses this to implement getcpu().
 303          */
 304         cpu = get_cpu();
 305         WARN_ON_ONCE(cpu > 0xffff);
 306
 307         node = cpu_to_node(cpu);
 308         WARN_ON_ONCE(node > 0xffff);
 309
 310         val = (cpu & 0xffff) | ((node & 0xffff) << 16);
 311         mtspr(SPRN_SPRG_VDSO_WRITE, val);
 312         get_paca()->sprg_vdso = val;
 313
 314         put_cpu();
 315
 316         return 0;
 317 }
 318 /* We need to call this before SMP init */
 319 early_initcall(vdso_getcpu_init);
 320 #endif
 321
 322 static struct page ** __init vdso_setup_pages(void *start, void *end)
 323 {
 324         int i;
 325         struct page **pagelist;
 326         int pages = (end - start) >> PAGE_SHIFT;
 327
 328         pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
 329         if (!pagelist)
 330                 panic("%s: Cannot allocate page list for VDSO", __func__);
 331
 332         for (i = 0; i < pages; i++)
 333                 pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
 334
 335         return pagelist;
 336 }
 337
 338 static int __init vdso_init(void)
 339 {
 340 #ifdef CONFIG_PPC64
 341         /*
 342          * Fill up the "systemcfg" stuff for backward compatibility
 343          */
 344         strcpy((char *)vdso_data->eye_catcher, "SYSTEMCFG:PPC64");
 345         vdso_data->version.major = SYSTEMCFG_MAJOR;
 346         vdso_data->version.minor = SYSTEMCFG_MINOR;
 347         vdso_data->processor = mfspr(SPRN_PVR);
 348         /*
 349          * Fake the old platform number for pSeries and add
 350          * in LPAR bit if necessary
 351          */
 352         vdso_data->platform = 0x100;
 353         if (firmware_has_feature(FW_FEATURE_LPAR))
 354                 vdso_data->platform |= 1;
 355         vdso_data->physicalMemorySize = memblock_phys_mem_size();
 356         vdso_data->dcache_size = ppc64_caches.l1d.size;
 357         vdso_data->dcache_line_size = ppc64_caches.l1d.line_size;
 358         vdso_data->icache_size = ppc64_caches.l1i.size;
 359         vdso_data->icache_line_size = ppc64_caches.l1i.line_size;
 360         vdso_data->dcache_block_size = ppc64_caches.l1d.block_size;
 361         vdso_data->icache_block_size = ppc64_caches.l1i.block_size;
 362         vdso_data->dcache_log_block_size = ppc64_caches.l1d.log_block_size;
 363         vdso_data->icache_log_block_size = ppc64_caches.l1i.log_block_size;
 364 #endif /* CONFIG_PPC64 */
 365
 366         vdso_setup_syscall_map();
 367
 368         vdso_fixup_features();
 369
 370         if (IS_ENABLED(CONFIG_VDSO32))
 371                 vdso32_spec.pages = vdso_setup_pages(&vdso32_start, &vdso32_end);
 372
 373         if (IS_ENABLED(CONFIG_PPC64))
 374                 vdso64_spec.pages = vdso_setup_pages(&vdso64_start, &vdso64_end);
 375
 376         smp_wmb();
 377
 378         return 0;
 379 }
 380 arch_initcall(vdso_init);