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, 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 */
 200extern const char vdso32_default_start, vdso32_default_end;
 201extern const char vdso32_sysenter_start, vdso32_sysenter_end;
 202static struct page *vdso32_pages[1];
 203
 204#ifdef CONFIG_X86_64
 205
 206static int use_sysenter __read_mostly = -1;
 207
 208#define vdso32_sysenter()       (use_sysenter > 0)
 209
 210/* May not be __init: called during resume */
 211void 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
 227static 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
 235void 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
 253static struct vm_area_struct gate_vma;
 254
 255static 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
 274static 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
 292int __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 */
 321int 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#ifdef CONFIG_SYSCTL
 381/* Register vsyscall32 into the ABI table */
 382#include <linux/sysctl.h>
 383
 384static ctl_table abi_table2[] = {
 385        {
 386                .procname       = "vsyscall32",
 387                .data           = &sysctl_vsyscall32,
 388                .maxlen         = sizeof(int),
 389                .mode           = 0644,
 390                .proc_handler   = proc_dointvec
 391        },
 392        {}
 393};
 394
 395static ctl_table abi_root_table2[] = {
 396        {
 397                .ctl_name = CTL_ABI,
 398                .procname = "abi",
 399                .mode = 0555,
 400                .child = abi_table2
 401        },
 402        {}
 403};
 404
 405static __init int ia32_binfmt_init(void)
 406{
 407        register_sysctl_table(abi_root_table2);
 408        return 0;
 409}
 410__initcall(ia32_binfmt_init);
 411#endif
 412
 413#else  /* CONFIG_X86_32 */
 414
 415const char *arch_vma_name(struct vm_area_struct *vma)
 416{
 417        if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 418                return "[vdso]";
 419        return NULL;
 420}
 421
 422struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 423{
 424        struct mm_struct *mm = tsk->mm;
 425
 426        /* Check to see if this task was created in compat vdso mode */
 427        if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
 428                return &gate_vma;
 429        return NULL;
 430}
 431
 432int in_gate_area(struct task_struct *task, unsigned long addr)
 433{
 434        const struct vm_area_struct *vma = get_gate_vma(task);
 435
 436        return vma && addr >= vma->vm_start && addr < vma->vm_end;
 437}
 438
 439int in_gate_area_no_task(unsigned long addr)
 440{
 441        return 0;
 442}
 443
 444#endif  /* CONFIG_X86_64 */
 445
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