LXR linux/arch/i386/kernel/sysenter.c

   1/*
   2 * linux/arch/i386/kernel/sysenter.c
   3 *
   4 * (C) Copyright 2002 Linus Torvalds
   5 * Portions based on the vdso-randomization code from exec-shield:
   6 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
   7 *
   8 * This file contains the needed initializations to support sysenter.
   9 */
  10
  11#include <linux/init.h>
  12#include <linux/smp.h>
  13#include <linux/thread_info.h>
  14#include <linux/sched.h>
  15#include <linux/gfp.h>
  16#include <linux/string.h>
  17#include <linux/elf.h>
  18#include <linux/mm.h>
  19#include <linux/module.h>
  20
  21#include <asm/cpufeature.h>
  22#include <asm/msr.h>
  23#include <asm/pgtable.h>
  24#include <asm/unistd.h>
  25#include <asm/elf.h>
  26#include <asm/tlbflush.h>
  27
  28enum {
  29        VDSO_DISABLED = 0,
  30        VDSO_ENABLED = 1,
  31        VDSO_COMPAT = 2,
  32};
  33
  34#ifdef CONFIG_COMPAT_VDSO
  35#define VDSO_DEFAULT    VDSO_COMPAT
  36#else
  37#define VDSO_DEFAULT    VDSO_ENABLED
  38#endif
  39
  40/*
  41 * Should the kernel map a VDSO page into processes and pass its
  42 * address down to glibc upon exec()?
  43 */
  44unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
  45
  46EXPORT_SYMBOL_GPL(vdso_enabled);
  47
  48static int __init vdso_setup(char *s)
  49{
  50        vdso_enabled = simple_strtoul(s, NULL, 0);
  51
  52        return 1;
  53}
  54
  55__setup("vdso=", vdso_setup);
  56
  57extern asmlinkage void sysenter_entry(void);
  58
  59static __init void reloc_symtab(Elf32_Ehdr *ehdr,
  60                                unsigned offset, unsigned size)
  61{
  62        Elf32_Sym *sym = (void *)ehdr + offset;
  63        unsigned nsym = size / sizeof(*sym);
  64        unsigned i;
  65
  66        for(i = 0; i < nsym; i++, sym++) {
  67                if (sym->st_shndx == SHN_UNDEF ||
  68                    sym->st_shndx == SHN_ABS)
  69                        continue;  /* skip */
  70
  71                if (sym->st_shndx > SHN_LORESERVE) {
  72                        printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
  73                               sym->st_shndx);
  74                        continue;
  75                }
  76
  77                switch(ELF_ST_TYPE(sym->st_info)) {
  78                case STT_OBJECT:
  79                case STT_FUNC:
  80                case STT_SECTION:
  81                case STT_FILE:
  82                        sym->st_value += VDSO_HIGH_BASE;
  83                }
  84        }
  85}
  86
  87static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
  88{
  89        Elf32_Dyn *dyn = (void *)ehdr + offset;
  90
  91        for(; dyn->d_tag != DT_NULL; dyn++)
  92                switch(dyn->d_tag) {
  93                case DT_PLTGOT:
  94                case DT_HASH:
  95                case DT_STRTAB:
  96                case DT_SYMTAB:
  97                case DT_RELA:
  98                case DT_INIT:
  99                case DT_FINI:
 100                case DT_REL:
 101                case DT_DEBUG:
 102                case DT_JMPREL:
 103                case DT_VERSYM:
 104                case DT_VERDEF:
 105                case DT_VERNEED:
 106                case DT_ADDRRNGLO ... DT_ADDRRNGHI:
 107                        /* definitely pointers needing relocation */
 108                        dyn->d_un.d_ptr += VDSO_HIGH_BASE;
 109                        break;
 110
 111                case DT_ENCODING ... OLD_DT_LOOS-1:
 112                case DT_LOOS ... DT_HIOS-1:
 113                        /* Tags above DT_ENCODING are pointers if
 114                           they're even */
 115                        if (dyn->d_tag >= DT_ENCODING &&
 116                            (dyn->d_tag & 1) == 0)
 117                                dyn->d_un.d_ptr += VDSO_HIGH_BASE;
 118                        break;
 119
 120                case DT_VERDEFNUM:
 121                case DT_VERNEEDNUM:
 122                case DT_FLAGS_1:
 123                case DT_RELACOUNT:
 124                case DT_RELCOUNT:
 125                case DT_VALRNGLO ... DT_VALRNGHI:
 126                        /* definitely not pointers */
 127                        break;
 128
 129                case OLD_DT_LOOS ... DT_LOOS-1:
 130                case DT_HIOS ... DT_VALRNGLO-1:
 131                default:
 132                        if (dyn->d_tag > DT_ENCODING)
 133                                printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
 134                                       dyn->d_tag);
 135                        break;
 136                }
 137}
 138
 139static __init void relocate_vdso(Elf32_Ehdr *ehdr)
 140{
 141        Elf32_Phdr *phdr;
 142        Elf32_Shdr *shdr;
 143        int i;
 144
 145        BUG_ON(memcmp(ehdr->e_ident, ELFMAG, 4) != 0 ||
 146               !elf_check_arch(ehdr) ||
 147               ehdr->e_type != ET_DYN);
 148
 149        ehdr->e_entry += VDSO_HIGH_BASE;
 150
 151        /* rebase phdrs */
 152        phdr = (void *)ehdr + ehdr->e_phoff;
 153        for (i = 0; i < ehdr->e_phnum; i++) {
 154                phdr[i].p_vaddr += VDSO_HIGH_BASE;
 155
 156                /* relocate dynamic stuff */
 157                if (phdr[i].p_type == PT_DYNAMIC)
 158                        reloc_dyn(ehdr, phdr[i].p_offset);
 159        }
 160
 161        /* rebase sections */
 162        shdr = (void *)ehdr + ehdr->e_shoff;
 163        for(i = 0; i < ehdr->e_shnum; i++) {
 164                if (!(shdr[i].sh_flags & SHF_ALLOC))
 165                        continue;
 166
 167                shdr[i].sh_addr += VDSO_HIGH_BASE;
 168
 169                if (shdr[i].sh_type == SHT_SYMTAB ||
 170                    shdr[i].sh_type == SHT_DYNSYM)
 171                        reloc_symtab(ehdr, shdr[i].sh_offset,
 172                                     shdr[i].sh_size);
 173        }
 174}
 175
 176void enable_sep_cpu(void)
 177{
 178        int cpu = get_cpu();
 179        struct tss_struct *tss = &per_cpu(init_tss, cpu);
 180
 181        if (!boot_cpu_has(X86_FEATURE_SEP)) {
 182                put_cpu();
 183                return;
 184        }
 185
 186        tss->x86_tss.ss1 = __KERNEL_CS;
 187        tss->x86_tss.esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
 188        wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
 189        wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.esp1, 0);
 190        wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
 191        put_cpu();      
 192}
 193
 194static struct vm_area_struct gate_vma;
 195
 196static int __init gate_vma_init(void)
 197{
 198        gate_vma.vm_mm = NULL;
 199        gate_vma.vm_start = FIXADDR_USER_START;
 200        gate_vma.vm_end = FIXADDR_USER_END;
 201        gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
 202        gate_vma.vm_page_prot = __P101;
 203        /*
 204         * Make sure the vDSO gets into every core dump.
 205         * Dumping its contents makes post-mortem fully interpretable later
 206         * without matching up the same kernel and hardware config to see
 207         * what PC values meant.
 208         */
 209        gate_vma.vm_flags |= VM_ALWAYSDUMP;
 210        return 0;
 211}
 212
 213/*
 214 * These symbols are defined by vsyscall.o to mark the bounds
 215 * of the ELF DSO images included therein.
 216 */
 217extern const char vsyscall_int80_start, vsyscall_int80_end;
 218extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
 219static struct page *syscall_pages[1];
 220
 221static void map_compat_vdso(int map)
 222{
 223        static int vdso_mapped;
 224
 225        if (map == vdso_mapped)
 226                return;
 227
 228        vdso_mapped = map;
 229
 230        __set_fixmap(FIX_VDSO, page_to_pfn(syscall_pages[0]) << PAGE_SHIFT,
 231                     map ? PAGE_READONLY_EXEC : PAGE_NONE);
 232
 233        /* flush stray tlbs */
 234        flush_tlb_all();
 235}
 236
 237int __init sysenter_setup(void)
 238{
 239        void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 240        const void *vsyscall;
 241        size_t vsyscall_len;
 242
 243        syscall_pages[0] = virt_to_page(syscall_page);
 244
 245        gate_vma_init();
 246
 247        printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
 248
 249        if (!boot_cpu_has(X86_FEATURE_SEP)) {
 250                vsyscall = &vsyscall_int80_start;
 251                vsyscall_len = &vsyscall_int80_end - &vsyscall_int80_start;
 252        } else {
 253                vsyscall = &vsyscall_sysenter_start;
 254                vsyscall_len = &vsyscall_sysenter_end - &vsyscall_sysenter_start;
 255        }
 256
 257        memcpy(syscall_page, vsyscall, vsyscall_len);
 258        relocate_vdso(syscall_page);
 259
 260        return 0;
 261}
 262
 263/* Defined in vsyscall-sysenter.S */
 264extern void SYSENTER_RETURN;
 265
 266/* Setup a VMA at program startup for the vsyscall page */
 267int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
 268{
 269        struct mm_struct *mm = current->mm;
 270        unsigned long addr;
 271        int ret = 0;
 272        bool compat;
 273
 274        down_write(&mm->mmap_sem);
 275
 276        /* Test compat mode once here, in case someone
 277           changes it via sysctl */
 278        compat = (vdso_enabled == VDSO_COMPAT);
 279
 280        map_compat_vdso(compat);
 281
 282        if (compat)
 283                addr = VDSO_HIGH_BASE;
 284        else {
 285                addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 286                if (IS_ERR_VALUE(addr)) {
 287                        ret = addr;
 288                        goto up_fail;
 289                }
 290
 291                /*
 292                 * MAYWRITE to allow gdb to COW and set breakpoints
 293                 *
 294                 * Make sure the vDSO gets into every core dump.
 295                 * Dumping its contents makes post-mortem fully
 296                 * interpretable later without matching up the same
 297                 * kernel and hardware config to see what PC values
 298                 * meant.
 299                 */
 300                ret = install_special_mapping(mm, addr, PAGE_SIZE,
 301                                              VM_READ|VM_EXEC|
 302                                              VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
 303                                              VM_ALWAYSDUMP,
 304                                              syscall_pages);
 305
 306                if (ret)
 307                        goto up_fail;
 308        }
 309
 310        current->mm->context.vdso = (void *)addr;
 311        current_thread_info()->sysenter_return =
 312                (void *)VDSO_SYM(&SYSENTER_RETURN);
 313
 314  up_fail:
 315        up_write(&mm->mmap_sem);
 316
 317        return ret;
 318}
 319
 320const char *arch_vma_name(struct vm_area_struct *vma)
 321{
 322        if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 323                return "[vdso]";
 324        return NULL;
 325}
 326
 327struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 328{
 329        struct mm_struct *mm = tsk->mm;
 330
 331        /* Check to see if this task was created in compat vdso mode */
 332        if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
 333                return &gate_vma;
 334        return NULL;
 335}
 336
 337int in_gate_area(struct task_struct *task, unsigned long addr)
 338{
 339        const struct vm_area_struct *vma = get_gate_vma(task);
 340
 341        return vma && addr >= vma->vm_start && addr < vma->vm_end;
 342}
 343
 344int in_gate_area_no_task(unsigned long addr)
 345{
 346        return 0;
 347}
 348