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