arch/x86/vdso/vdso32-setup.c

   1 /*
   2  * (C) Copyright 2002 Linus Torvalds
   3  * Portions based on the vdso-randomization code from exec-shield:
   4  * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
   5  *
   6  * This file contains the needed initializations to support sysenter.
   7  */
   8
   9 #include <linux/init.h>
  10 #include <linux/smp.h>
  11 #include <linux/thread_info.h>
  12 #include <linux/sched.h>
  13 #include <linux/gfp.h>
  14 #include <linux/string.h>
  15 #include <linux/elf.h>
  16 #include <linux/mm.h>
  17 #include <linux/err.h>
  18 #include <linux/module.h>
  19
  20 #include <asm/cpufeature.h>
  21 #include <asm/msr.h>
  22 #include <asm/pgtable.h>
  23 #include <asm/unistd.h>
  24 #include <asm/elf.h>
  25 #include <asm/tlbflush.h>
  26 #include <asm/vdso.h>
  27 #include <asm/proto.h>
  28
  29 enum {
  30         VDSO_DISABLED = 0,
  31         VDSO_ENABLED = 1,
  32         VDSO_COMPAT = 2,
  33 };
  34
  35 #ifdef CONFIG_COMPAT_VDSO
  36 #define VDSO_DEFAULT    VDSO_COMPAT
  37 #else
  38 #define VDSO_DEFAULT    VDSO_ENABLED
  39 #endif
  40
  41 #ifdef CONFIG_X86_64
  42 #define vdso_enabled                    sysctl_vsyscall32
  43 #define arch_setup_additional_pages     syscall32_setup_pages
  44 #endif
  45
  46 /*
  47  * This is the difference between the prelinked addresses in the vDSO images
  48  * and the VDSO_HIGH_BASE address where CONFIG_COMPAT_VDSO places the vDSO
  49  * in the user address space.
  50  */
  51 #define VDSO_ADDR_ADJUST        (VDSO_HIGH_BASE - (unsigned long)VDSO32_PRELINK)
  52
  53 /*
  54  * Should the kernel map a VDSO page into processes and pass its
  55  * address down to glibc upon exec()?
  56  */
  57 unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
  58
  59 static int __init vdso_setup(char *s)
  60 {
  61         vdso_enabled = simple_strtoul(s, NULL, 0);
  62
  63         return 1;
  64 }
  65
  66 /*
  67  * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
  68  * behavior on both 64-bit and 32-bit kernels.
  69  * On 32-bit kernels, vdso=[012] means the same thing.
  70  */
  71 __setup("vdso32=", vdso_setup);
  72
  73 #ifdef CONFIG_X86_32
  74 __setup_param("vdso=", vdso32_setup, vdso_setup, 0);
  75
  76 EXPORT_SYMBOL_GPL(vdso_enabled);
  77 #endif
  78
  79 static __init void reloc_symtab(Elf32_Ehdr *ehdr,
  80                                 unsigned offset, unsigned size)
  81 {
  82         Elf32_Sym *sym = (void *)ehdr + offset;
  83         unsigned nsym = size / sizeof(*sym);
  84         unsigned i;
  85
  86         for(i = 0; i < nsym; i++, sym++) {
  87                 if (sym->st_shndx == SHN_UNDEF ||
  88                     sym->st_shndx == SHN_ABS)
  89                         continue;  /* skip */
  90
  91                 if (sym->st_shndx > SHN_LORESERVE) {
  92                         printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
  93                                sym->st_shndx);
  94                         continue;
  95                 }
  96
  97                 switch(ELF_ST_TYPE(sym->st_info)) {
  98                 case STT_OBJECT:
  99                 case STT_FUNC:
 100                 case STT_SECTION:
 101                 case STT_FILE:
 102                         sym->st_value += VDSO_ADDR_ADJUST;
 103                 }
 104         }
 105 }
 106
 107 static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
 108 {
 109         Elf32_Dyn *dyn = (void *)ehdr + offset;
 110
 111         for(; dyn->d_tag != DT_NULL; dyn++)
 112                 switch(dyn->d_tag) {
 113                 case DT_PLTGOT:
 114                 case DT_HASH:
 115                 case DT_STRTAB:
 116                 case DT_SYMTAB:
 117                 case DT_RELA:
 118                 case DT_INIT:
 119                 case DT_FINI:
 120                 case DT_REL:
 121                 case DT_DEBUG:
 122                 case DT_JMPREL:
 123                 case DT_VERSYM:
 124                 case DT_VERDEF:
 125                 case DT_VERNEED:
 126                 case DT_ADDRRNGLO ... DT_ADDRRNGHI:
 127                         /* definitely pointers needing relocation */
 128                         dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
 129                         break;
 130
 131                 case DT_ENCODING ... OLD_DT_LOOS-1:
 132                 case DT_LOOS ... DT_HIOS-1:
 133                         /* Tags above DT_ENCODING are pointers if
 134                            they're even */
 135                         if (dyn->d_tag >= DT_ENCODING &&
 136                             (dyn->d_tag & 1) == 0)
 137                                 dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
 138                         break;
 139
 140                 case DT_VERDEFNUM:
 141                 case DT_VERNEEDNUM:
 142                 case DT_FLAGS_1:
 143                 case DT_RELACOUNT:
 144                 case DT_RELCOUNT:
 145                 case DT_VALRNGLO ... DT_VALRNGHI:
 146                         /* definitely not pointers */
 147                         break;
 148
 149                 case OLD_DT_LOOS ... DT_LOOS-1:
 150                 case DT_HIOS ... DT_VALRNGLO-1:
 151                 default:
 152                         if (dyn->d_tag > DT_ENCODING)
 153                                 printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
 154                                        dyn->d_tag);
 155                         break;
 156                 }
 157 }
 158
 159 static __init void relocate_vdso(Elf32_Ehdr *ehdr)
 160 {
 161         Elf32_Phdr *phdr;
 162         Elf32_Shdr *shdr;
 163         int i;
 164
 165         BUG_ON(memcmp(ehdr->e_ident, ELFMAG, 4) != 0 ||
 166                !elf_check_arch_ia32(ehdr) ||
 167                ehdr->e_type != ET_DYN);
 168
 169         ehdr->e_entry += VDSO_ADDR_ADJUST;
 170
 171         /* rebase phdrs */
 172         phdr = (void *)ehdr + ehdr->e_phoff;
 173         for (i = 0; i < ehdr->e_phnum; i++) {
 174                 phdr[i].p_vaddr += VDSO_ADDR_ADJUST;
 175
 176                 /* relocate dynamic stuff */
 177                 if (phdr[i].p_type == PT_DYNAMIC)
 178                         reloc_dyn(ehdr, phdr[i].p_offset);
 179         }
 180
 181         /* rebase sections */
 182         shdr = (void *)ehdr + ehdr->e_shoff;
 183         for(i = 0; i < ehdr->e_shnum; i++) {
 184                 if (!(shdr[i].sh_flags & SHF_ALLOC))
 185                         continue;
 186
 187                 shdr[i].sh_addr += VDSO_ADDR_ADJUST;
 188
 189                 if (shdr[i].sh_type == SHT_SYMTAB ||
 190                     shdr[i].sh_type == SHT_DYNSYM)
 191                         reloc_symtab(ehdr, shdr[i].sh_offset,
 192                                      shdr[i].sh_size);
 193         }
 194 }
 195
 196 /*
 197  * These symbols are defined by vdso32.S to mark the bounds
 198  * of the ELF DSO images included therein.
 199  */
 200 extern const char vdso32_default_start, vdso32_default_end;
 201 extern const char vdso32_sysenter_start, vdso32_sysenter_end;
 202 static struct page *vdso32_pages[1];
 203
 204 #ifdef CONFIG_X86_64
 205
 206 static int use_sysenter __read_mostly = -1;
 207
 208 #define vdso32_sysenter()       (use_sysenter > 0)
 209
 210 /* May not be __init: called during resume */
 211 void syscall32_cpu_init(void)
 212 {
 213         if (use_sysenter < 0)
 214                 use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
 215
 216         /* Load these always in case some future AMD CPU supports
 217            SYSENTER from compat mode too. */
 218         checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
 219         checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
 220         checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
 221
 222         wrmsrl(MSR_CSTAR, ia32_cstar_target);
 223 }
 224
 225 #define compat_uses_vma         1
 226
 227 static inline void map_compat_vdso(int map)
 228 {
 229 }
 230
 231 #else  /* CONFIG_X86_32 */
 232
 233 #define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SEP))
 234
 235 void enable_sep_cpu(void)
 236 {
 237         int cpu = get_cpu();
 238         struct tss_struct *tss = &per_cpu(init_tss, cpu);
 239
 240         if (!boot_cpu_has(X86_FEATURE_SEP)) {
 241                 put_cpu();
 242                 return;
 243         }
 244
 245         tss->x86_tss.ss1 = __KERNEL_CS;
 246         tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
 247         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
 248         wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
 249         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
 250         put_cpu();
 251 }
 252
 253 static struct vm_area_struct gate_vma;
 254
 255 static int __init gate_vma_init(void)
 256 {
 257         gate_vma.vm_mm = NULL;
 258         gate_vma.vm_start = FIXADDR_USER_START;
 259         gate_vma.vm_end = FIXADDR_USER_END;
 260         gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
 261         gate_vma.vm_page_prot = __P101;
 262         /*
 263          * Make sure the vDSO gets into every core dump.
 264          * Dumping its contents makes post-mortem fully interpretable later
 265          * without matching up the same kernel and hardware config to see
 266          * what PC values meant.
 267          */
 268         gate_vma.vm_flags |= VM_ALWAYSDUMP;
 269         return 0;
 270 }
 271
 272 #define compat_uses_vma         0
 273
 274 static void map_compat_vdso(int map)
 275 {
 276         static int vdso_mapped;
 277
 278         if (map == vdso_mapped)
 279                 return;
 280
 281         vdso_mapped = map;
 282
 283         __set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
 284                      map ? PAGE_READONLY_EXEC : PAGE_NONE);
 285
 286         /* flush stray tlbs */
 287         flush_tlb_all();
 288 }
 289
 290 #endif  /* CONFIG_X86_64 */
 291
 292 int __init sysenter_setup(void)
 293 {
 294         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 295         const void *vsyscall;
 296         size_t vsyscall_len;
 297
 298         vdso32_pages[0] = virt_to_page(syscall_page);
 299
 300 #ifdef CONFIG_X86_32
 301         gate_vma_init();
 302
 303         printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
 304 #endif
 305
 306         if (!vdso32_sysenter()) {
 307                 vsyscall = &vdso32_default_start;
 308                 vsyscall_len = &vdso32_default_end - &vdso32_default_start;
 309         } else {
 310                 vsyscall = &vdso32_sysenter_start;
 311                 vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
 312         }
 313
 314         memcpy(syscall_page, vsyscall, vsyscall_len);
 315         relocate_vdso(syscall_page);
 316
 317         return 0;
 318 }
 319
 320 /* Setup a VMA at program startup for the vsyscall page */
 321 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
 322 {
 323         struct mm_struct *mm = current->mm;
 324         unsigned long addr;
 325         int ret = 0;
 326         bool compat;
 327
 328         down_write(&mm->mmap_sem);
 329
 330         /* Test compat mode once here, in case someone
 331            changes it via sysctl */
 332         compat = (vdso_enabled == VDSO_COMPAT);
 333
 334         map_compat_vdso(compat);
 335
 336         if (compat)
 337                 addr = VDSO_HIGH_BASE;
 338         else {
 339                 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 340                 if (IS_ERR_VALUE(addr)) {
 341                         ret = addr;
 342                         goto up_fail;
 343                 }
 344         }
 345
 346         if (compat_uses_vma || !compat) {
 347                 /*
 348                  * MAYWRITE to allow gdb to COW and set breakpoints
 349                  *
 350                  * Make sure the vDSO gets into every core dump.
 351                  * Dumping its contents makes post-mortem fully
 352                  * interpretable later without matching up the same
 353                  * kernel and hardware config to see what PC values
 354                  * meant.
 355                  */
 356                 ret = install_special_mapping(mm, addr, PAGE_SIZE,
 357                                               VM_READ|VM_EXEC|
 358                                               VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
 359                                               VM_ALWAYSDUMP,
 360                                               vdso32_pages);
 361
 362                 if (ret)
 363                         goto up_fail;
 364         }
 365
 366         current->mm->context.vdso = (void *)addr;
 367         current_thread_info()->sysenter_return =
 368                 VDSO32_SYMBOL(addr, SYSENTER_RETURN);
 369
 370   up_fail:
 371         up_write(&mm->mmap_sem);
 372
 373         return ret;
 374 }
 375
 376 #ifdef CONFIG_X86_64
 377
 378 __initcall(sysenter_setup);
 379
 380 #else  /* CONFIG_X86_32 */
 381
 382 const char *arch_vma_name(struct vm_area_struct *vma)
 383 {
 384         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 385                 return "[vdso]";
 386         return NULL;
 387 }
 388
 389 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 390 {
 391         struct mm_struct *mm = tsk->mm;
 392
 393         /* Check to see if this task was created in compat vdso mode */
 394         if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
 395                 return &gate_vma;
 396         return NULL;
 397 }
 398
 399 int in_gate_area(struct task_struct *task, unsigned long addr)
 400 {
 401         const struct vm_area_struct *vma = get_gate_vma(task);
 402
 403         return vma && addr >= vma->vm_start && addr < vma->vm_end;
 404 }
 405
 406 int in_gate_area_no_task(unsigned long addr)
 407 {
 408         return 0;
 409 }
 410
 411 #endif  /* CONFIG_X86_64 */