arch/x86/entry/vdso/vma.c

   1 /*
   2  * Copyright 2007 Andi Kleen, SUSE Labs.
   3  * Subject to the GPL, v.2
   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/slab.h>
  11 #include <linux/init.h>
  12 #include <linux/random.h>
  13 #include <linux/elf.h>
  14 #include <linux/cpu.h>
  15 #include <asm/pvclock.h>
  16 #include <asm/vgtod.h>
  17 #include <asm/proto.h>
  18 #include <asm/vdso.h>
  19 #include <asm/vvar.h>
  20 #include <asm/page.h>
  21 #include <asm/hpet.h>
  22 #include <asm/desc.h>
  23 #include <asm/cpufeature.h>
  24
  25 #if defined(CONFIG_X86_64)
  26 unsigned int __read_mostly vdso64_enabled = 1;
  27 #endif
  28
  29 void __init init_vdso_image(const struct vdso_image *image)
  30 {
  31         int i;
  32         int npages = (image->size) / PAGE_SIZE;
  33
  34         BUG_ON(image->size % PAGE_SIZE != 0);
  35         for (i = 0; i < npages; i++)
  36                 image->text_mapping.pages[i] =
  37                         virt_to_page(image->data + i*PAGE_SIZE);
  38
  39         apply_alternatives((struct alt_instr *)(image->data + image->alt),
  40                            (struct alt_instr *)(image->data + image->alt +
  41                                                 image->alt_len));
  42 }
  43
  44 struct linux_binprm;
  45
  46 /*
  47  * Put the vdso above the (randomized) stack with another randomized
  48  * offset.  This way there is no hole in the middle of address space.
  49  * To save memory make sure it is still in the same PTE as the stack
  50  * top.  This doesn't give that many random bits.
  51  *
  52  * Note that this algorithm is imperfect: the distribution of the vdso
  53  * start address within a PMD is biased toward the end.
  54  *
  55  * Only used for the 64-bit and x32 vdsos.
  56  */
  57 static unsigned long vdso_addr(unsigned long start, unsigned len)
  58 {
  59 #ifdef CONFIG_X86_32
  60         return 0;
  61 #else
  62         unsigned long addr, end;
  63         unsigned offset;
  64
  65         /*
  66          * Round up the start address.  It can start out unaligned as a result
  67          * of stack start randomization.
  68          */
  69         start = PAGE_ALIGN(start);
  70
  71         /* Round the lowest possible end address up to a PMD boundary. */
  72         end = (start + len + PMD_SIZE - 1) & PMD_MASK;
  73         if (end >= TASK_SIZE_MAX)
  74                 end = TASK_SIZE_MAX;
  75         end -= len;
  76
  77         if (end > start) {
  78                 offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
  79                 addr = start + (offset << PAGE_SHIFT);
  80         } else {
  81                 addr = start;
  82         }
  83
  84         /*
  85          * Forcibly align the final address in case we have a hardware
  86          * issue that requires alignment for performance reasons.
  87          */
  88         addr = align_vdso_addr(addr);
  89
  90         return addr;
  91 #endif
  92 }
  93
  94 static int map_vdso(const struct vdso_image *image, bool calculate_addr)
  95 {
  96         struct mm_struct *mm = current->mm;
  97         struct vm_area_struct *vma;
  98         unsigned long addr, text_start;
  99         int ret = 0;
 100         static struct page *no_pages[] = {NULL};
 101         static struct vm_special_mapping vvar_mapping = {
 102                 .name = "[vvar]",
 103                 .pages = no_pages,
 104         };
 105         struct pvclock_vsyscall_time_info *pvti;
 106
 107         if (calculate_addr) {
 108                 addr = vdso_addr(current->mm->start_stack,
 109                                  image->size - image->sym_vvar_start);
 110         } else {
 111                 addr = 0;
 112         }
 113
 114         down_write(&mm->mmap_sem);
 115
 116         addr = get_unmapped_area(NULL, addr,
 117                                  image->size - image->sym_vvar_start, 0, 0);
 118         if (IS_ERR_VALUE(addr)) {
 119                 ret = addr;
 120                 goto up_fail;
 121         }
 122
 123         text_start = addr - image->sym_vvar_start;
 124         current->mm->context.vdso = (void __user *)text_start;
 125
 126         /*
 127          * MAYWRITE to allow gdb to COW and set breakpoints
 128          */
 129         vma = _install_special_mapping(mm,
 130                                        text_start,
 131                                        image->size,
 132                                        VM_READ|VM_EXEC|
 133                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 134                                        &image->text_mapping);
 135
 136         if (IS_ERR(vma)) {
 137                 ret = PTR_ERR(vma);
 138                 goto up_fail;
 139         }
 140
 141         vma = _install_special_mapping(mm,
 142                                        addr,
 143                                        -image->sym_vvar_start,
 144                                        VM_READ|VM_MAYREAD,
 145                                        &vvar_mapping);
 146
 147         if (IS_ERR(vma)) {
 148                 ret = PTR_ERR(vma);
 149                 goto up_fail;
 150         }
 151
 152         if (image->sym_vvar_page)
 153                 ret = remap_pfn_range(vma,
 154                                       text_start + image->sym_vvar_page,
 155                                       __pa_symbol(&__vvar_page) >> PAGE_SHIFT,
 156                                       PAGE_SIZE,
 157                                       PAGE_READONLY);
 158
 159         if (ret)
 160                 goto up_fail;
 161
 162 #ifdef CONFIG_HPET_TIMER
 163         if (hpet_address && image->sym_hpet_page) {
 164                 ret = io_remap_pfn_range(vma,
 165                         text_start + image->sym_hpet_page,
 166                         hpet_address >> PAGE_SHIFT,
 167                         PAGE_SIZE,
 168                         pgprot_noncached(PAGE_READONLY));
 169
 170                 if (ret)
 171                         goto up_fail;
 172         }
 173 #endif
 174
 175         pvti = pvclock_pvti_cpu0_va();
 176         if (pvti && image->sym_pvclock_page) {
 177                 ret = remap_pfn_range(vma,
 178                                       text_start + image->sym_pvclock_page,
 179                                       __pa(pvti) >> PAGE_SHIFT,
 180                                       PAGE_SIZE,
 181                                       PAGE_READONLY);
 182
 183                 if (ret)
 184                         goto up_fail;
 185         }
 186
 187 up_fail:
 188         if (ret)
 189                 current->mm->context.vdso = NULL;
 190
 191         up_write(&mm->mmap_sem);
 192         return ret;
 193 }
 194
 195 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 196 static int load_vdso32(void)
 197 {
 198         if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
 199                 return 0;
 200
 201         return map_vdso(&vdso_image_32, false);
 202 }
 203 #endif
 204
 205 #ifdef CONFIG_X86_64
 206 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 207 {
 208         if (!vdso64_enabled)
 209                 return 0;
 210
 211         return map_vdso(&vdso_image_64, true);
 212 }
 213
 214 #ifdef CONFIG_COMPAT
 215 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 216                                        int uses_interp)
 217 {
 218 #ifdef CONFIG_X86_X32_ABI
 219         if (test_thread_flag(TIF_X32)) {
 220                 if (!vdso64_enabled)
 221                         return 0;
 222
 223                 return map_vdso(&vdso_image_x32, true);
 224         }
 225 #endif
 226 #ifdef CONFIG_IA32_EMULATION
 227         return load_vdso32();
 228 #else
 229         return 0;
 230 #endif
 231 }
 232 #endif
 233 #else
 234 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 235 {
 236         return load_vdso32();
 237 }
 238 #endif
 239
 240 #ifdef CONFIG_X86_64
 241 static __init int vdso_setup(char *s)
 242 {
 243         vdso64_enabled = simple_strtoul(s, NULL, 0);
 244         return 0;
 245 }
 246 __setup("vdso=", vdso_setup);
 247 #endif
 248
 249 #ifdef CONFIG_X86_64
 250 static void vgetcpu_cpu_init(void *arg)
 251 {
 252         int cpu = smp_processor_id();
 253         struct desc_struct d = { };
 254         unsigned long node = 0;
 255 #ifdef CONFIG_NUMA
 256         node = cpu_to_node(cpu);
 257 #endif
 258         if (static_cpu_has(X86_FEATURE_RDTSCP))
 259                 write_rdtscp_aux((node << 12) | cpu);
 260
 261         /*
 262          * Store cpu number in limit so that it can be loaded
 263          * quickly in user space in vgetcpu. (12 bits for the CPU
 264          * and 8 bits for the node)
 265          */
 266         d.limit0 = cpu | ((node & 0xf) << 12);
 267         d.limit = node >> 4;
 268         d.type = 5;             /* RO data, expand down, accessed */
 269         d.dpl = 3;              /* Visible to user code */
 270         d.s = 1;                /* Not a system segment */
 271         d.p = 1;                /* Present */
 272         d.d = 1;                /* 32-bit */
 273
 274         write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
 275 }
 276
 277 static int
 278 vgetcpu_cpu_notifier(struct notifier_block *n, unsigned long action, void *arg)
 279 {
 280         long cpu = (long)arg;
 281
 282         if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
 283                 smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);
 284
 285         return NOTIFY_DONE;
 286 }
 287
 288 static int __init init_vdso(void)
 289 {
 290         init_vdso_image(&vdso_image_64);
 291
 292 #ifdef CONFIG_X86_X32_ABI
 293         init_vdso_image(&vdso_image_x32);
 294 #endif
 295
 296         cpu_notifier_register_begin();
 297
 298         on_each_cpu(vgetcpu_cpu_init, NULL, 1);
 299         /* notifier priority > KVM */
 300         __hotcpu_notifier(vgetcpu_cpu_notifier, 30);
 301
 302         cpu_notifier_register_done();
 303
 304         return 0;
 305 }
 306 subsys_initcall(init_vdso);
 307 #endif /* CONFIG_X86_64 */