arch/x86/kernel/sysenter_32.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
  27 enum {
  28         VDSO_DISABLED = 0,
  29         VDSO_ENABLED = 1,
  30         VDSO_COMPAT = 2,
  31 };
  32
  33 #ifdef CONFIG_COMPAT_VDSO
  34 #define VDSO_DEFAULT    VDSO_COMPAT
  35 #else
  36 #define VDSO_DEFAULT    VDSO_ENABLED
  37 #endif
  38
  39 /*
  40  * Should the kernel map a VDSO page into processes and pass its
  41  * address down to glibc upon exec()?
  42  */
  43 unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
  44
  45 EXPORT_SYMBOL_GPL(vdso_enabled);
  46
  47 static int __init vdso_setup(char *s)
  48 {
  49         vdso_enabled = simple_strtoul(s, NULL, 0);
  50
  51         return 1;
  52 }
  53
  54 __setup("vdso=", vdso_setup);
  55
  56 extern asmlinkage void sysenter_entry(void);
  57
  58 static __init void reloc_symtab(Elf32_Ehdr *ehdr,
  59                                 unsigned offset, unsigned size)
  60 {
  61         Elf32_Sym *sym = (void *)ehdr + offset;
  62         unsigned nsym = size / sizeof(*sym);
  63         unsigned i;
  64
  65         for(i = 0; i < nsym; i++, sym++) {
  66                 if (sym->st_shndx == SHN_UNDEF ||
  67                     sym->st_shndx == SHN_ABS)
  68                         continue;  /* skip */
  69
  70                 if (sym->st_shndx > SHN_LORESERVE) {
  71                         printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
  72                                sym->st_shndx);
  73                         continue;
  74                 }
  75
  76                 switch(ELF_ST_TYPE(sym->st_info)) {
  77                 case STT_OBJECT:
  78                 case STT_FUNC:
  79                 case STT_SECTION:
  80                 case STT_FILE:
  81                         sym->st_value += VDSO_HIGH_BASE;
  82                 }
  83         }
  84 }
  85
  86 static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
  87 {
  88         Elf32_Dyn *dyn = (void *)ehdr + offset;
  89
  90         for(; dyn->d_tag != DT_NULL; dyn++)
  91                 switch(dyn->d_tag) {
  92                 case DT_PLTGOT:
  93                 case DT_HASH:
  94                 case DT_STRTAB:
  95                 case DT_SYMTAB:
  96                 case DT_RELA:
  97                 case DT_INIT:
  98                 case DT_FINI:
  99                 case DT_REL:
 100                 case DT_DEBUG:
 101                 case DT_JMPREL:
 102                 case DT_VERSYM:
 103                 case DT_VERDEF:
 104                 case DT_VERNEED:
 105                 case DT_ADDRRNGLO ... DT_ADDRRNGHI:
 106                         /* definitely pointers needing relocation */
 107                         dyn->d_un.d_ptr += VDSO_HIGH_BASE;
 108                         break;
 109
 110                 case DT_ENCODING ... OLD_DT_LOOS-1:
 111                 case DT_LOOS ... DT_HIOS-1:
 112                         /* Tags above DT_ENCODING are pointers if
 113                            they're even */
 114                         if (dyn->d_tag >= DT_ENCODING &&
 115                             (dyn->d_tag & 1) == 0)
 116                                 dyn->d_un.d_ptr += VDSO_HIGH_BASE;
 117                         break;
 118
 119                 case DT_VERDEFNUM:
 120                 case DT_VERNEEDNUM:
 121                 case DT_FLAGS_1:
 122                 case DT_RELACOUNT:
 123                 case DT_RELCOUNT:
 124                 case DT_VALRNGLO ... DT_VALRNGHI:
 125                         /* definitely not pointers */
 126                         break;
 127
 128                 case OLD_DT_LOOS ... DT_LOOS-1:
 129                 case DT_HIOS ... DT_VALRNGLO-1:
 130                 default:
 131                         if (dyn->d_tag > DT_ENCODING)
 132                                 printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
 133                                        dyn->d_tag);
 134                         break;
 135                 }
 136 }
 137
 138 static __init void relocate_vdso(Elf32_Ehdr *ehdr)
 139 {
 140         Elf32_Phdr *phdr;
 141         Elf32_Shdr *shdr;
 142         int i;
 143
 144         BUG_ON(memcmp(ehdr->e_ident, ELFMAG, 4) != 0 ||
 145                !elf_check_arch(ehdr) ||
 146                ehdr->e_type != ET_DYN);
 147
 148         ehdr->e_entry += VDSO_HIGH_BASE;
 149
 150         /* rebase phdrs */
 151         phdr = (void *)ehdr + ehdr->e_phoff;
 152         for (i = 0; i < ehdr->e_phnum; i++) {
 153                 phdr[i].p_vaddr += VDSO_HIGH_BASE;
 154
 155                 /* relocate dynamic stuff */
 156                 if (phdr[i].p_type == PT_DYNAMIC)
 157                         reloc_dyn(ehdr, phdr[i].p_offset);
 158         }
 159
 160         /* rebase sections */
 161         shdr = (void *)ehdr + ehdr->e_shoff;
 162         for(i = 0; i < ehdr->e_shnum; i++) {
 163                 if (!(shdr[i].sh_flags & SHF_ALLOC))
 164                         continue;
 165
 166                 shdr[i].sh_addr += VDSO_HIGH_BASE;
 167
 168                 if (shdr[i].sh_type == SHT_SYMTAB ||
 169                     shdr[i].sh_type == SHT_DYNSYM)
 170                         reloc_symtab(ehdr, shdr[i].sh_offset,
 171                                      shdr[i].sh_size);
 172         }
 173 }
 174
 175 void enable_sep_cpu(void)
 176 {
 177         int cpu = get_cpu();
 178         struct tss_struct *tss = &per_cpu(init_tss, cpu);
 179
 180         if (!boot_cpu_has(X86_FEATURE_SEP)) {
 181                 put_cpu();
 182                 return;
 183         }
 184
 185         tss->x86_tss.ss1 = __KERNEL_CS;
 186         tss->x86_tss.esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
 187         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
 188         wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.esp1, 0);
 189         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
 190         put_cpu();
 191 }
 192
 193 static struct vm_area_struct gate_vma;
 194
 195 static int __init gate_vma_init(void)
 196 {
 197         gate_vma.vm_mm = NULL;
 198         gate_vma.vm_start = FIXADDR_USER_START;
 199         gate_vma.vm_end = FIXADDR_USER_END;
 200         gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
 201         gate_vma.vm_page_prot = __P101;
 202         /*
 203          * Make sure the vDSO gets into every core dump.
 204          * Dumping its contents makes post-mortem fully interpretable later
 205          * without matching up the same kernel and hardware config to see
 206          * what PC values meant.
 207          */
 208         gate_vma.vm_flags |= VM_ALWAYSDUMP;
 209         return 0;
 210 }
 211
 212 /*
 213  * These symbols are defined by vsyscall.o to mark the bounds
 214  * of the ELF DSO images included therein.
 215  */
 216 extern const char vsyscall_int80_start, vsyscall_int80_end;
 217 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
 218 static struct page *syscall_pages[1];
 219
 220 static void map_compat_vdso(int map)
 221 {
 222         static int vdso_mapped;
 223
 224         if (map == vdso_mapped)
 225                 return;
 226
 227         vdso_mapped = map;
 228
 229         __set_fixmap(FIX_VDSO, page_to_pfn(syscall_pages[0]) << PAGE_SHIFT,
 230                      map ? PAGE_READONLY_EXEC : PAGE_NONE);
 231
 232         /* flush stray tlbs */
 233         flush_tlb_all();
 234 }
 235
 236 int __init sysenter_setup(void)
 237 {
 238         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 239         const void *vsyscall;
 240         size_t vsyscall_len;
 241
 242         syscall_pages[0] = virt_to_page(syscall_page);
 243
 244         gate_vma_init();
 245
 246         printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
 247
 248         if (!boot_cpu_has(X86_FEATURE_SEP)) {
 249                 vsyscall = &vsyscall_int80_start;
 250                 vsyscall_len = &vsyscall_int80_end - &vsyscall_int80_start;
 251         } else {
 252                 vsyscall = &vsyscall_sysenter_start;
 253                 vsyscall_len = &vsyscall_sysenter_end - &vsyscall_sysenter_start;
 254         }
 255
 256         memcpy(syscall_page, vsyscall, vsyscall_len);
 257         relocate_vdso(syscall_page);
 258
 259         return 0;
 260 }
 261
 262 /* Defined in vsyscall-sysenter.S */
 263 extern void SYSENTER_RETURN;
 264
 265 /* Setup a VMA at program startup for the vsyscall page */
 266 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
 267 {
 268         struct mm_struct *mm = current->mm;
 269         unsigned long addr;
 270         int ret = 0;
 271         bool compat;
 272
 273         down_write(&mm->mmap_sem);
 274
 275         /* Test compat mode once here, in case someone
 276            changes it via sysctl */
 277         compat = (vdso_enabled == VDSO_COMPAT);
 278
 279         map_compat_vdso(compat);
 280
 281         if (compat)
 282                 addr = VDSO_HIGH_BASE;
 283         else {
 284                 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 285                 if (IS_ERR_VALUE(addr)) {
 286                         ret = addr;
 287                         goto up_fail;
 288                 }
 289
 290                 /*
 291                  * MAYWRITE to allow gdb to COW and set breakpoints
 292                  *
 293                  * Make sure the vDSO gets into every core dump.
 294                  * Dumping its contents makes post-mortem fully
 295                  * interpretable later without matching up the same
 296                  * kernel and hardware config to see what PC values
 297                  * meant.
 298                  */
 299                 ret = install_special_mapping(mm, addr, PAGE_SIZE,
 300                                               VM_READ|VM_EXEC|
 301                                               VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
 302                                               VM_ALWAYSDUMP,
 303                                               syscall_pages);
 304
 305                 if (ret)
 306                         goto up_fail;
 307         }
 308
 309         current->mm->context.vdso = (void *)addr;
 310         current_thread_info()->sysenter_return =
 311                 (void *)VDSO_SYM(&SYSENTER_RETURN);
 312
 313   up_fail:
 314         up_write(&mm->mmap_sem);
 315
 316         return ret;
 317 }
 318
 319 const char *arch_vma_name(struct vm_area_struct *vma)
 320 {
 321         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 322                 return "[vdso]";
 323         return NULL;
 324 }
 325
 326 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 327 {
 328         struct mm_struct *mm = tsk->mm;
 329
 330         /* Check to see if this task was created in compat vdso mode */
 331         if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
 332                 return &gate_vma;
 333         return NULL;
 334 }
 335
 336 int in_gate_area(struct task_struct *task, unsigned long addr)
 337 {
 338         const struct vm_area_struct *vma = get_gate_vma(task);
 339
 340         return vma && addr >= vma->vm_start && addr < vma->vm_end;
 341 }
 342
 343 int in_gate_area_no_task(unsigned long addr)
 344 {
 345         return 0;
 346 }