kernel/arch/x86/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/vgtod.h>
  16 #include <asm/proto.h>
  17 #include <asm/vdso.h>
  18 #include <asm/vvar.h>
  19 #include <asm/page.h>
  20 #include <asm/hpet.h>
  21 #include <asm/desc.h>
  22
  23 #if defined(CONFIG_X86_64)
  24 unsigned int __read_mostly vdso64_enabled = 1;
  25 #endif
  26
  27 void __init init_vdso_image(const struct vdso_image *image)
  28 {
  29         int i;
  30         int npages = (image->size) / PAGE_SIZE;
  31
  32         BUG_ON(image->size % PAGE_SIZE != 0);
  33         for (i = 0; i < npages; i++)
  34                 image->text_mapping.pages[i] =
  35                         virt_to_page(image->data + i*PAGE_SIZE);
  36
  37         apply_alternatives((struct alt_instr *)(image->data + image->alt),
  38                            (struct alt_instr *)(image->data + image->alt +
  39                                                 image->alt_len));
  40 }
  41
  42 struct linux_binprm;
  43
  44 /*
  45  * Put the vdso above the (randomized) stack with another randomized
  46  * offset.  This way there is no hole in the middle of address space.
  47  * To save memory make sure it is still in the same PTE as the stack
  48  * top.  This doesn't give that many random bits.
  49  *
  50  * Note that this algorithm is imperfect: the distribution of the vdso
  51  * start address within a PMD is biased toward the end.
  52  *
  53  * Only used for the 64-bit and x32 vdsos.
  54  */
  55 static unsigned long vdso_addr(unsigned long start, unsigned len)
  56 {
  57 #ifdef CONFIG_X86_32
  58         return 0;
  59 #else
  60         unsigned long addr, end;
  61         unsigned offset;
  62
  63         /*
  64          * Round up the start address.  It can start out unaligned as a result
  65          * of stack start randomization.
  66          */
  67         start = PAGE_ALIGN(start);
  68
  69         /* Round the lowest possible end address up to a PMD boundary. */
  70         end = (start + len + PMD_SIZE - 1) & PMD_MASK;
  71         if (end >= TASK_SIZE_MAX)
  72                 end = TASK_SIZE_MAX;
  73         end -= len;
  74
  75         if (end > start) {
  76                 offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
  77                 addr = start + (offset << PAGE_SHIFT);
  78         } else {
  79                 addr = start;
  80         }
  81
  82         /*
  83          * Forcibly align the final address in case we have a hardware
  84          * issue that requires alignment for performance reasons.
  85          */
  86         addr = align_vdso_addr(addr);
  87
  88         return addr;
  89 #endif
  90 }
  91
  92 static int map_vdso(const struct vdso_image *image, bool calculate_addr)
  93 {
  94         struct mm_struct *mm = current->mm;
  95         struct vm_area_struct *vma;
  96         unsigned long addr, text_start;
  97         int ret = 0;
  98         static struct page *no_pages[] = {NULL};
  99         static struct vm_special_mapping vvar_mapping = {
 100                 .name = "[vvar]",
 101                 .pages = no_pages,
 102         };
 103
 104         if (calculate_addr) {
 105                 addr = vdso_addr(current->mm->start_stack,
 106                                  image->size - image->sym_vvar_start);
 107         } else {
 108                 addr = 0;
 109         }
 110
 111         down_write(&mm->mmap_sem);
 112
 113         addr = get_unmapped_area(NULL, addr,
 114                                  image->size - image->sym_vvar_start, 0, 0);
 115         if (IS_ERR_VALUE(addr)) {
 116                 ret = addr;
 117                 goto up_fail;
 118         }
 119
 120         text_start = addr - image->sym_vvar_start;
 121         current->mm->context.vdso = (void __user *)text_start;
 122
 123         /*
 124          * MAYWRITE to allow gdb to COW and set breakpoints
 125          */
 126         vma = _install_special_mapping(mm,
 127                                        text_start,
 128                                        image->size,
 129                                        VM_READ|VM_EXEC|
 130                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 131                                        &image->text_mapping);
 132
 133         if (IS_ERR(vma)) {
 134                 ret = PTR_ERR(vma);
 135                 goto up_fail;
 136         }
 137
 138         vma = _install_special_mapping(mm,
 139                                        addr,
 140                                        -image->sym_vvar_start,
 141                                        VM_READ|VM_MAYREAD,
 142                                        &vvar_mapping);
 143
 144         if (IS_ERR(vma)) {
 145                 ret = PTR_ERR(vma);
 146                 goto up_fail;
 147         }
 148
 149         if (image->sym_vvar_page)
 150                 ret = remap_pfn_range(vma,
 151                                       text_start + image->sym_vvar_page,
 152                                       __pa_symbol(&__vvar_page) >> PAGE_SHIFT,
 153                                       PAGE_SIZE,
 154                                       PAGE_READONLY);
 155
 156         if (ret)
 157                 goto up_fail;
 158
 159 #ifdef CONFIG_HPET_TIMER
 160         if (hpet_address && image->sym_hpet_page) {
 161                 ret = io_remap_pfn_range(vma,
 162                         text_start + image->sym_hpet_page,
 163                         hpet_address >> PAGE_SHIFT,
 164                         PAGE_SIZE,
 165                         pgprot_noncached(PAGE_READONLY));
 166
 167                 if (ret)
 168                         goto up_fail;
 169         }
 170 #endif
 171
 172 up_fail:
 173         if (ret)
 174                 current->mm->context.vdso = NULL;
 175
 176         up_write(&mm->mmap_sem);
 177         return ret;
 178 }
 179
 180 #if defined(CONFIG_X86_32) || defined(CONFIG_COMPAT)
 181 static int load_vdso32(void)
 182 {
 183         int ret;
 184
 185         if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
 186                 return 0;
 187
 188         ret = map_vdso(selected_vdso32, false);
 189         if (ret)
 190                 return ret;
 191
 192         if (selected_vdso32->sym_VDSO32_SYSENTER_RETURN)
 193                 current_thread_info()->sysenter_return =
 194                         current->mm->context.vdso +
 195                         selected_vdso32->sym_VDSO32_SYSENTER_RETURN;
 196
 197         return 0;
 198 }
 199 #endif
 200
 201 #ifdef CONFIG_X86_64
 202 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 203 {
 204         if (!vdso64_enabled)
 205                 return 0;
 206
 207         return map_vdso(&vdso_image_64, true);
 208 }
 209
 210 #ifdef CONFIG_COMPAT
 211 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 212                                        int uses_interp)
 213 {
 214 #ifdef CONFIG_X86_X32_ABI
 215         if (test_thread_flag(TIF_X32)) {
 216                 if (!vdso64_enabled)
 217                         return 0;
 218
 219                 return map_vdso(&vdso_image_x32, true);
 220         }
 221 #endif
 222
 223         return load_vdso32();
 224 }
 225 #endif
 226 #else
 227 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 228 {
 229         return load_vdso32();
 230 }
 231 #endif
 232
 233 #ifdef CONFIG_X86_64
 234 static __init int vdso_setup(char *s)
 235 {
 236         vdso64_enabled = simple_strtoul(s, NULL, 0);
 237         return 0;
 238 }
 239 __setup("vdso=", vdso_setup);
 240 #endif
 241
 242 #ifdef CONFIG_X86_64
 243 static void vgetcpu_cpu_init(void *arg)
 244 {
 245         int cpu = smp_processor_id();
 246         struct desc_struct d = { };
 247         unsigned long node = 0;
 248 #ifdef CONFIG_NUMA
 249         node = cpu_to_node(cpu);
 250 #endif
 251         if (cpu_has(&cpu_data(cpu), X86_FEATURE_RDTSCP))
 252                 write_rdtscp_aux((node << 12) | cpu);
 253
 254         /*
 255          * Store cpu number in limit so that it can be loaded
 256          * quickly in user space in vgetcpu. (12 bits for the CPU
 257          * and 8 bits for the node)
 258          */
 259         d.limit0 = cpu | ((node & 0xf) << 12);
 260         d.limit = node >> 4;
 261         d.type = 5;             /* RO data, expand down, accessed */
 262         d.dpl = 3;              /* Visible to user code */
 263         d.s = 1;                /* Not a system segment */
 264         d.p = 1;                /* Present */
 265         d.d = 1;                /* 32-bit */
 266
 267         write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
 268 }
 269
 270 static int
 271 vgetcpu_cpu_notifier(struct notifier_block *n, unsigned long action, void *arg)
 272 {
 273         long cpu = (long)arg;
 274
 275         if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
 276                 smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);
 277
 278         return NOTIFY_DONE;
 279 }
 280
 281 static int __init init_vdso(void)
 282 {
 283         init_vdso_image(&vdso_image_64);
 284
 285 #ifdef CONFIG_X86_X32_ABI
 286         init_vdso_image(&vdso_image_x32);
 287 #endif
 288
 289         cpu_notifier_register_begin();
 290
 291         on_each_cpu(vgetcpu_cpu_init, NULL, 1);
 292         /* notifier priority > KVM */
 293         __hotcpu_notifier(vgetcpu_cpu_notifier, 30);
 294
 295         cpu_notifier_register_done();
 296
 297         return 0;
 298 }
 299 subsys_initcall(init_vdso);
 300 #endif /* CONFIG_X86_64 */