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