linux/arch/x86/vdso/vdso32-setup.c
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   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
  29enum {
  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 */
  57unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
  58
  59static 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
  76EXPORT_SYMBOL_GPL(vdso_enabled);
  77#endif
  78
  79static __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
 107static __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
 159static __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, SELFMAG) != 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
 196static struct page *vdso32_pages[1];
 197
 198#ifdef CONFIG_X86_64
 199
 200#define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SYSENTER32))
 201#define vdso32_syscall()        (boot_cpu_has(X86_FEATURE_SYSCALL32))
 202
 203/* May not be __init: called during resume */
 204void syscall32_cpu_init(void)
 205{
 206        /* Load these always in case some future AMD CPU supports
 207           SYSENTER from compat mode too. */
 208        checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
 209        checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
 210        checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
 211
 212        wrmsrl(MSR_CSTAR, ia32_cstar_target);
 213}
 214
 215#define compat_uses_vma         1
 216
 217static inline void map_compat_vdso(int map)
 218{
 219}
 220
 221#else  /* CONFIG_X86_32 */
 222
 223#define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SEP))
 224#define vdso32_syscall()        (0)
 225
 226void enable_sep_cpu(void)
 227{
 228        int cpu = get_cpu();
 229        struct tss_struct *tss = &per_cpu(init_tss, cpu);
 230
 231        if (!boot_cpu_has(X86_FEATURE_SEP)) {
 232                put_cpu();
 233                return;
 234        }
 235
 236        tss->x86_tss.ss1 = __KERNEL_CS;
 237        tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
 238        wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
 239        wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
 240        wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
 241        put_cpu();      
 242}
 243
 244static struct vm_area_struct gate_vma;
 245
 246static int __init gate_vma_init(void)
 247{
 248        gate_vma.vm_mm = NULL;
 249        gate_vma.vm_start = FIXADDR_USER_START;
 250        gate_vma.vm_end = FIXADDR_USER_END;
 251        gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
 252        gate_vma.vm_page_prot = __P101;
 253        /*
 254         * Make sure the vDSO gets into every core dump.
 255         * Dumping its contents makes post-mortem fully interpretable later
 256         * without matching up the same kernel and hardware config to see
 257         * what PC values meant.
 258         */
 259        gate_vma.vm_flags |= VM_ALWAYSDUMP;
 260        return 0;
 261}
 262
 263#define compat_uses_vma         0
 264
 265static void map_compat_vdso(int map)
 266{
 267        static int vdso_mapped;
 268
 269        if (map == vdso_mapped)
 270                return;
 271
 272        vdso_mapped = map;
 273
 274        __set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
 275                     map ? PAGE_READONLY_EXEC : PAGE_NONE);
 276
 277        /* flush stray tlbs */
 278        flush_tlb_all();
 279}
 280
 281#endif  /* CONFIG_X86_64 */
 282
 283int __init sysenter_setup(void)
 284{
 285        void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 286        const void *vsyscall;
 287        size_t vsyscall_len;
 288
 289        vdso32_pages[0] = virt_to_page(syscall_page);
 290
 291#ifdef CONFIG_X86_32
 292        gate_vma_init();
 293#endif
 294
 295        if (vdso32_syscall()) {
 296                vsyscall = &vdso32_syscall_start;
 297                vsyscall_len = &vdso32_syscall_end - &vdso32_syscall_start;
 298        } else if (vdso32_sysenter()){
 299                vsyscall = &vdso32_sysenter_start;
 300                vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
 301        } else {
 302                vsyscall = &vdso32_int80_start;
 303                vsyscall_len = &vdso32_int80_end - &vdso32_int80_start;
 304        }
 305
 306        memcpy(syscall_page, vsyscall, vsyscall_len);
 307        relocate_vdso(syscall_page);
 308
 309        return 0;
 310}
 311
 312/* Setup a VMA at program startup for the vsyscall page */
 313int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
 314{
 315        struct mm_struct *mm = current->mm;
 316        unsigned long addr;
 317        int ret = 0;
 318        bool compat;
 319
 320        if (vdso_enabled == VDSO_DISABLED)
 321                return 0;
 322
 323        down_write(&mm->mmap_sem);
 324
 325        /* Test compat mode once here, in case someone
 326           changes it via sysctl */
 327        compat = (vdso_enabled == VDSO_COMPAT);
 328
 329        map_compat_vdso(compat);
 330
 331        if (compat)
 332                addr = VDSO_HIGH_BASE;
 333        else {
 334                addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 335                if (IS_ERR_VALUE(addr)) {
 336                        ret = addr;
 337                        goto up_fail;
 338                }
 339        }
 340
 341        if (compat_uses_vma || !compat) {
 342                /*
 343                 * MAYWRITE to allow gdb to COW and set breakpoints
 344                 *
 345                 * Make sure the vDSO gets into every core dump.
 346                 * Dumping its contents makes post-mortem fully
 347                 * interpretable later without matching up the same
 348                 * kernel and hardware config to see what PC values
 349                 * meant.
 350                 */
 351                ret = install_special_mapping(mm, addr, PAGE_SIZE,
 352                                              VM_READ|VM_EXEC|
 353                                              VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
 354                                              VM_ALWAYSDUMP,
 355                                              vdso32_pages);
 356
 357                if (ret)
 358                        goto up_fail;
 359        }
 360
 361        current->mm->context.vdso = (void *)addr;
 362        current_thread_info()->sysenter_return =
 363                VDSO32_SYMBOL(addr, SYSENTER_RETURN);
 364
 365  up_fail:
 366        up_write(&mm->mmap_sem);
 367
 368        return ret;
 369}
 370
 371#ifdef CONFIG_X86_64
 372
 373__initcall(sysenter_setup);
 374
 375#ifdef CONFIG_SYSCTL
 376/* Register vsyscall32 into the ABI table */
 377#include <linux/sysctl.h>
 378
 379static ctl_table abi_table2[] = {
 380        {
 381                .procname       = "vsyscall32",
 382                .data           = &sysctl_vsyscall32,
 383                .maxlen         = sizeof(int),
 384                .mode           = 0644,
 385                .proc_handler   = proc_dointvec
 386        },
 387        {}
 388};
 389
 390static ctl_table abi_root_table2[] = {
 391        {
 392                .ctl_name = CTL_ABI,
 393                .procname = "abi",
 394                .mode = 0555,
 395                .child = abi_table2
 396        },
 397        {}
 398};
 399
 400static __init int ia32_binfmt_init(void)
 401{
 402        register_sysctl_table(abi_root_table2);
 403        return 0;
 404}
 405__initcall(ia32_binfmt_init);
 406#endif
 407
 408#else  /* CONFIG_X86_32 */
 409
 410const char *arch_vma_name(struct vm_area_struct *vma)
 411{
 412        if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 413                return "[vdso]";
 414        return NULL;
 415}
 416
 417struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 418{
 419        struct mm_struct *mm = tsk->mm;
 420
 421        /* Check to see if this task was created in compat vdso mode */
 422        if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
 423                return &gate_vma;
 424        return NULL;
 425}
 426
 427int in_gate_area(struct task_struct *task, unsigned long addr)
 428{
 429        const struct vm_area_struct *vma = get_gate_vma(task);
 430
 431        return vma && addr >= vma->vm_start && addr < vma->vm_end;
 432}
 433
 434int in_gate_area_no_task(unsigned long addr)
 435{
 436        return 0;
 437}
 438
 439#endif  /* CONFIG_X86_64 */
 440