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                 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
 215                         use_sysenter = 1;
 216                 if (boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR)
 217                         use_sysenter = 1;
 218         }
 219
 220         /* Load these always in case some future AMD CPU supports
 221            SYSENTER from compat mode too. */
 222         checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
 223         checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
 224         checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
 225
 226         wrmsrl(MSR_CSTAR, ia32_cstar_target);
 227 }
 228
 229 #define compat_uses_vma         1
 230
 231 static inline void map_compat_vdso(int map)
 232 {
 233 }
 234
 235 #else  /* CONFIG_X86_32 */
 236
 237 #define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SEP))
 238
 239 void enable_sep_cpu(void)
 240 {
 241         int cpu = get_cpu();
 242         struct tss_struct *tss = &per_cpu(init_tss, cpu);
 243
 244         if (!boot_cpu_has(X86_FEATURE_SEP)) {
 245                 put_cpu();
 246                 return;
 247         }
 248
 249         tss->x86_tss.ss1 = __KERNEL_CS;
 250         tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
 251         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
 252         wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
 253         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
 254         put_cpu();
 255 }
 256
 257 static struct vm_area_struct gate_vma;
 258
 259 static int __init gate_vma_init(void)
 260 {
 261         gate_vma.vm_mm = NULL;
 262         gate_vma.vm_start = FIXADDR_USER_START;
 263         gate_vma.vm_end = FIXADDR_USER_END;
 264         gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
 265         gate_vma.vm_page_prot = __P101;
 266         /*
 267          * Make sure the vDSO gets into every core dump.
 268          * Dumping its contents makes post-mortem fully interpretable later
 269          * without matching up the same kernel and hardware config to see
 270          * what PC values meant.
 271          */
 272         gate_vma.vm_flags |= VM_ALWAYSDUMP;
 273         return 0;
 274 }
 275
 276 #define compat_uses_vma         0
 277
 278 static void map_compat_vdso(int map)
 279 {
 280         static int vdso_mapped;
 281
 282         if (map == vdso_mapped)
 283                 return;
 284
 285         vdso_mapped = map;
 286
 287         __set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
 288                      map ? PAGE_READONLY_EXEC : PAGE_NONE);
 289
 290         /* flush stray tlbs */
 291         flush_tlb_all();
 292 }
 293
 294 #endif  /* CONFIG_X86_64 */
 295
 296 int __init sysenter_setup(void)
 297 {
 298         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 299         const void *vsyscall;
 300         size_t vsyscall_len;
 301
 302         vdso32_pages[0] = virt_to_page(syscall_page);
 303
 304 #ifdef CONFIG_X86_32
 305         gate_vma_init();
 306
 307         printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
 308 #endif
 309
 310         if (!vdso32_sysenter()) {
 311                 vsyscall = &vdso32_default_start;
 312                 vsyscall_len = &vdso32_default_end - &vdso32_default_start;
 313         } else {
 314                 vsyscall = &vdso32_sysenter_start;
 315                 vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
 316         }
 317
 318         memcpy(syscall_page, vsyscall, vsyscall_len);
 319         relocate_vdso(syscall_page);
 320
 321         return 0;
 322 }
 323
 324 /* Setup a VMA at program startup for the vsyscall page */
 325 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
 326 {
 327         struct mm_struct *mm = current->mm;
 328         unsigned long addr;
 329         int ret = 0;
 330         bool compat;
 331
 332         if (vdso_enabled == VDSO_DISABLED)
 333                 return 0;
 334
 335         down_write(&mm->mmap_sem);
 336
 337         /* Test compat mode once here, in case someone
 338            changes it via sysctl */
 339         compat = (vdso_enabled == VDSO_COMPAT);
 340
 341         map_compat_vdso(compat);
 342
 343         if (compat)
 344                 addr = VDSO_HIGH_BASE;
 345         else {
 346                 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 347                 if (IS_ERR_VALUE(addr)) {
 348                         ret = addr;
 349                         goto up_fail;
 350                 }
 351         }
 352
 353         if (compat_uses_vma || !compat) {
 354                 /*
 355                  * MAYWRITE to allow gdb to COW and set breakpoints
 356                  *
 357                  * Make sure the vDSO gets into every core dump.
 358                  * Dumping its contents makes post-mortem fully
 359                  * interpretable later without matching up the same
 360                  * kernel and hardware config to see what PC values
 361                  * meant.
 362                  */
 363                 ret = install_special_mapping(mm, addr, PAGE_SIZE,
 364                                               VM_READ|VM_EXEC|
 365                                               VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
 366                                               VM_ALWAYSDUMP,
 367                                               vdso32_pages);
 368
 369                 if (ret)
 370                         goto up_fail;
 371         }
 372
 373         current->mm->context.vdso = (void *)addr;
 374         current_thread_info()->sysenter_return =
 375                 VDSO32_SYMBOL(addr, SYSENTER_RETURN);
 376
 377   up_fail:
 378         up_write(&mm->mmap_sem);
 379
 380         return ret;
 381 }
 382
 383 #ifdef CONFIG_X86_64
 384
 385 __initcall(sysenter_setup);
 386
 387 #ifdef CONFIG_SYSCTL
 388 /* Register vsyscall32 into the ABI table */
 389 #include <linux/sysctl.h>
 390
 391 static ctl_table abi_table2[] = {
 392         {
 393                 .procname       = "vsyscall32",
 394                 .data           = &sysctl_vsyscall32,
 395                 .maxlen         = sizeof(int),
 396                 .mode           = 0644,
 397                 .proc_handler   = proc_dointvec
 398         },
 399         {}
 400 };
 401
 402 static ctl_table abi_root_table2[] = {
 403         {
 404                 .ctl_name = CTL_ABI,
 405                 .procname = "abi",
 406                 .mode = 0555,
 407                 .child = abi_table2
 408         },
 409         {}
 410 };
 411
 412 static __init int ia32_binfmt_init(void)
 413 {
 414         register_sysctl_table(abi_root_table2);
 415         return 0;
 416 }
 417 __initcall(ia32_binfmt_init);
 418 #endif
 419
 420 #else  /* CONFIG_X86_32 */
 421
 422 const char *arch_vma_name(struct vm_area_struct *vma)
 423 {
 424         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 425                 return "[vdso]";
 426         return NULL;
 427 }
 428
 429 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 430 {
 431         struct mm_struct *mm = tsk->mm;
 432
 433         /* Check to see if this task was created in compat vdso mode */
 434         if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
 435                 return &gate_vma;
 436         return NULL;
 437 }
 438
 439 int in_gate_area(struct task_struct *task, unsigned long addr)
 440 {
 441         const struct vm_area_struct *vma = get_gate_vma(task);
 442
 443         return vma && addr >= vma->vm_start && addr < vma->vm_end;
 444 }
 445
 446 int in_gate_area_no_task(unsigned long addr)
 447 {
 448         return 0;
 449 }
 450
 451 #endif  /* CONFIG_X86_64 */